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  • v.11(1); 2022

Outcomes of managing healthcare services using the Theory of Constraints: A systematic review

Gustavo m. bacelar-silva.

a Department of Community Medicine, Information and Health Decision Sciences, Faculty of Medicine (MEDCIDS-FMUP), University of Porto, Porto, Portugal

b Center for Health Technology and Services Research (CINTESIS), Porto, Portugal

c Department of Distance Learning, Bahiana School of Medicine and Public Health, Salvador, Brazil

James F. Cox, III

d Management Department, Terry College of Business, University of Georgia, Athens, GA, USA

Pedro Pereira Rodrigues

Associated data.

Despite ever-increasing resources devoted to healthcare, lack of capacity and timeliness are still chronic problems worldwide. This systematic review aims to present an overview of the Theory of Constraints (TOC) implementations in healthcare services and their outcomes. We analysed 42 TOC implementations (15 full-text articles, 12 video proceedings, and 2 theses/disserations) from major scientific electronic databases and TOC International Certification Organization Conferences. All implementations reported positive outcomes, both tangible and intangible. The two main improvements reported by authors were in productivity (98%; n = 41) – more patients treated – and in the timeliness of care (83%; n = 35). Furthermore, the selected studies reported dramatic improvements: 50% mean reductions in patient waiting time; 38% reduction in patient length of stay; 43% mean increase in operating room productivity and 34% mean increase in throughput. TOC implementations attained positive results in all levels of the health and social care chain. Most TOC recommendations and changes showed almost immediate results and required little or no additional cost to implement. Evidence supports TOC as a promising solution for the chronic healthcare problem, improving quality and timeliness, both necessary conditions for providing effective healthcare.

1. Introduction

Healthcare has evolved dramatically in the last century but managing it has become a conundrum. The 20th century was the stage of extremely relevant discoveries in medicine that affected health conditions all over the world, e.g., penicillin, the pacemaker. After those discoveries, we are living longer, and the population is growing. However, these improvements led to a higher and rising demand for healthcare services.

Medicine continues to evolve at an impressive rate, and so is its increasing costs. Healthcare consumes an average of 10% of a country’s gross domestic product (GDP), and its costs are rising faster than economies are growing (Halim, 2019 ); in the USA this reached 18% of GDP in 2017 (Sisko et al., 2019 ). Despite this unprecedented investment in healthcare, lack of capacity and timeliness are still problems affecting every country, even the wealthier (World Health Organization, 2010 , 2019 ). Long wait lists for appointments (Ryu & Lee, 2017 ), emergency departments crowding (Morley et al., 2018 ), shortages of hospital beds (Song & Ferris, 2018 ), and cancellations of elective surgeries (Al Talalwah & McIltrot, 2019 ) are some examples of chronic problems. The delay of care is a significant issue, a persistent and undesirable characteristic of current healthcare systems (Murray & Berwick, 2003 ; Ryu & Lee, 2017 ). When patients must wait for medical assistance, serious consequences happen (Corley, 2016 ; Ryu & Lee, 2017 ). Long waits before care delivery have emotional consequences (e.g., anxiety, despair) and contribute to worsening clinical conditions, developing avoidable complications, and even death. There are also financial consequences, treating patients in more advanced conditions requires more specialised care resources, which are more costly.

Healthcare services are under pressure to deliver better healthcare outcomes to an increasing population, with higher quality care, in less time, and at a stable (or lower) cost. However, current management methods are not providing an effective solution to this chronic problem. Traditional solutions to address this problem often require investment to add more capacity to the system, but without a proper analysis to improve throughput using existing resources, it has the potential to make the situation even worse (Han et al., 2007 ).

Over the last century, some disruptive management philosophies emerged and had considerably improved quality and reduced lead times of manufacturing and services. As a natural consequence, researchers considered the adoption of these management philosophies in the healthcare environment to improve care delivery (Kim et al., 2006 ; Young et al., 2004 ). Potential solutions – like Lean and Six Sigma – provide limited benefits, and they both encounter the same problems: involve high investments and long implementation time (Chiarini & Bracci, 2013 ; D’Andreamatteo et al., 2015 ; Poksinska et al., 2017 ).

The Theory of Constraints (TOC) is also one of those disruptive management philosophies that emerged late in the last century. Originally developed by Dr Goldratt to solve manufacturing issues, TOC today is considered a holistic management philosophy that views every organisation as a system composed of many interacting resources. These interdependent resources work together towards achieving the system goal; however, at least one resource limits the capacity of the whole system; otherwise, its throughput would be infinite. This limiting resource is the constraint, and it is the most important resource of any organisation since it determines the performance of the whole system (Goldratt & Cox, 2004 ; Goldratt, 1999 ).

Acknowledging the existence of a constraint creates a whole new management paradigm. Instead of considering any new improvement idea anywhere as an improvement for the organisation, improvement efforts should focus on the constraint. If an organisation was able to identify and increase throughput at its constraint, more effectively exploit the constraint, or better subordinate other resources to the constraint, then the organisation would achieve more of its goal. For instance, if the organisation loses a minute at the constraint, this is a minute lost for the whole organisation; but if any other resource loses a minute, it will not dramatically affect the organisation because it has protective capacity to recover the flow (Goldratt & Cox, 2004 ). Furthermore, to assure overall performance, the organisation must plan and synchronise its productive flow according to the constraint and protect it from uncertainty. Since most healthcare academics and practitioners are unfamiliar with TOC, a brief overview is provided here with a more detailed description provided in the appendix for those interested.

1.1. TOC overview

In contrast to both the traditional management philosophy’s and lean (reduce waste) philosophy’s emphasis on cost reduction everywhere, TOC focuses on achieving the organisation goal (e.g., providing excellent and timely healthcare effectively). Its primary focus is on increasing throughput (the number of properly treated patients), although maintaining or reducing operating expenses are very common consequences. TOC also strives for a systems perspective of the environment examining all stakeholders’ perspectives in searching for a win-win solution to satisfy the different stakeholders (the objective is to meet the stakeholders' necessary conditions without compromising the goal achievement). The organisation goal is achieved by implementing three processes of ongoing improvement (POOGI) to align, schedule and execute the organisation’s processes to achieve its goal: 1. five focusing steps (5FS) (Cox et al., 2012 ; Goldratt & Cox, 2004 ); 2. buffer management (BM) (Cox et al., 2012 ; Goldratt, 1986 ); and 3. change question sequence (CQS) (Cox et al., 2012 ; Goldratt, 1994 ).

First, we define the organisation’s goal and supporting measures. Next, we apply the 5 focusing steps (5FS) (Goldratt & Cox, 2004 ), which starts by step 1: identifying the constraint; then step 2: deciding how to exploit the constraint – how to make maximum use of its available capacity. Since all other resources have more capacity, the constraint governs both the throughput and inventory in the system, (therefore the need for step 3, which means that all non-constraint resources must work accordingly to support the previous decisions. If the constraint remains, now it is time to invest money, (step 4: elevating the constraint and eliminating it. However, this is a process of ongoing improvement (POOGI), thus step 5: we must not allow inertia to become the system’s constraint, we must go back to step 1 and start again.

Remember that TOC has two other POOGI’s. Buffer management (BM) is a mechanism used in both the planning and execution phases of TOC applications that controls the constraint’s protection against uncertainty based on the amount of time or stock (in healthcare, e.g., patients or beds) remaining until it is idle. A simple colour-coding system similar to a traffic light’s colours is used to determine when to take action. Green means everything is running smoothly, do what you are doing; yellow means an imminent threat to patient flow or constraint utilisation is approaching, plan accordingly to eliminate the threat; and red means enact the plan. This proactive control system eliminates most disruptions to the constraint and to patient flow.

The change question sequence (CQS) is comprised of five-interrelated questions that are answered with a set of logic diagrams (Cox et al., 2012 ; Goldratt, 1986 , 1994 ). This POOGI provides a gap analysis of system characteristics (question 1: why change?), a logical analysis starting with the current system problems (called undesirable effects, UDEs in TOC terminology) and ending with the identification of the system’s underlying core problem(s) and its assumptions (question 2: What to change?). Based on the causal network constructed in answering the preceding question, the search for and development of a holistic win-win solution to the system’s core problem(s) and related problems is in response to question 3 (what to change to?). Answering question 4 (how to cause the change?) results in the construction of an effective implementation plan. In answering question 5 (how to measure and sustain the change?), one establishes procedures for measuring and sustaining system results. The application of the 5FS to a healthcare environment is provided in the supplementary material as are more detailed applications of BM and CQS.

The adoption of TOC in business environments started in manufacturing and has spread to other areas, such as logistics, distribution, project management, and sales and marketing (Ronen, 2005 ). In 1998, Mabin and Balderstone ( 2003 ) conducted a literature review to assess the outcomes provided by TOC applications. This study involved 77 different companies across many different purposes (for-profit, not-for-profit, and government), industries, and sizes, including giant multinational corporations (e.g., Boeing and GM), military organisations (e.g., US Air Force), and even a small-town bakery. Their analysis of reported changes presented positive results, though many companies achieved with only partial implementations:

  • Lead-time reduction of 69%;
  • Cycle-times reduction of 66%;
  • Due-date-performance improvement of 60%;
  • Inventory levels reduction of 50%;
  • Revenue increase of 60% (excluding one outlier, a 600% increase at Lucent Technologies achieved within one year).

These significant results support the investigation of TOC as a potentially effective solution for the chronic healthcare problem. However, the application of TOC still has few case studies published in refereed academic journals (Mabin & Mirzaei, 2016 ; Ronen, 2005 ), particularly in healthcare. Since academic papers do not entirely reflect the adoption of TOC in healthcare yet, answers to this subject may be covered in grey literature.

The widely accepted definition of grey literature is known as “that which is produced on all levels of governmental, academics, business and industry in print and electronic formats, but which is not controlled by commercial publishers” (Auger, 1998 ). Examples of grey literature include conference abstracts and proceedings, research reports, dissertations, government documents, personal correspondence, among others. The inclusion of grey literature in systematic reviews is not as common as it should be, because of the cost in time and resources needed to search for it. However, including grey literature is a valuable and recommended practice, since it helps to reduce the publication lag time between a manuscript submission and its publication, and enriches the findings of a study (Paez, 2017 ; Shamseer et al., 2015 ).

A typical path in conducting research is to move from the grey literature to the academic literature. A degree-seeking candidate conducts and defends a thesis or dissertation (reviewed by an examining committee). Then, she submits and presents an updated version of the research as a presentation at a conference (and again receives critiques from reviewers and the audience). Finally, she submits the “improved” research to an academic journal for formal peer review and publication.

Therefore, to minimise the publication bias and provide a more balanced view of the evidence, we decided to include in this systematic review a major source of TOC knowledge: the annual conference video proceedings of the Theory of Constraints International Certification Organization (TOCICO) Conferences (2004–2020). The TOCICO is a global not-for-profit certification organisation for TOC practitioners, consultants, and academics formed to develop and administer certification standards, and facilitate the exchange of the latest developments in the TOC body of knowledge (TOCICO, 2018 ).

Our motivation for this systematic review is two-fold. First, to assess the adoption of TOC as a potentially effective solution for the chronic healthcare problem. Second, to gather existing TOC academic literature, and expand it with TOC experts’ knowledge available in grey literature.

The aim of this systematic review is to present an overview of TOC implementations in healthcare services and their effects. To this end, the proposed study will answer the following four questions:

  • What are the outcomes of applying the TOC in healthcare services?
  • What is the diffusion of TOC in healthcare so far (e.g., primary care or hospital, public or private practice)?
  • Are there common problems – also called undesirable effects (UDEs) in TOC terminology – faced by healthcare services and was TOC able to address all of them?
  • What are the methods and tools commonly used to apply TOC in healthcare services?

The first question aims to give a preliminary answer to whether TOC has improved healthcare services. This question tries to describe the outcomes achieved after implementing TOC in a healthcare service considering a wide range of effects, for instance, the number of surgeries performed, provider utilisation, the waiting time (direct and indirect) of patients for an appointment, the number of patients treated, the length of stay (LOS) in a hospital, the financial results, the quality or timeliness of healthcare, the patient no-show rate, etc.

The second question presents the details of the healthcare services where TOC implementations occurred. This question intends to reveal to what extent TOC has been implemented in healthcare. For that purpose, we described the country of the implementation, level of care (e.g., primary care), nature of service (e.g., for profit, government), its setting (e.g., hospital, clinic), and a brief service description (e.g., operating room, emergency department).

Question three aims to unveil whether healthcare services face common or unique UDEs and core problems and if TOC was able to address them. In cases of successful outcomes, can these case studies help to provide a generic template to guide other healthcare organisations around the globe facing the same problems in their search for a successful path of improvement?

The last question aims to present the methods and tools used to support the implementations. In addition to the three POOGI, TOC has a number of other methods and tools (such as throughput accounting, critical chain project management) used in other organisations to improve performance. To what extent are these tools used in healthcare?

This systematic review followed the guidelines proposed by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement (Shamseer et al., 2015 ), with some exceptions detailed below. We imposed these exceptions to take account of the variety of research approaches and consequent methodologies, as well as different traditions of research (social sciences and health sciences).

2.1. Data sources, eligibility criteria and data extraction

This systematic review used three scientific databases and four grey literature databases. We performed an automated literature search on the scientific (academic) electronic databases – PubMed, Web of Science (WoS) and Scopus – to identify relevant articles published in peer-reviewed journals. We obtained an annotated bibliography (citations and abstracts) of TOCICO Conference video proceedings related to TOC applied in a healthcare environment. Moreover, we performed an automated literature search on a set of theses and dissertations electronic databases – The Networked Digital Library of Theses and Dissertations (NDLTD), Open Access Theses and Dissertations (OATD), and OpenThesis (OT) – to identify relevant studies unpublished in peer-reviewed journals.

TOCICO has its short-, and long-abstracts vetted by TOC experts and slides are reviewed and critiqued as a second stage of the review process. Other sources of TOC implementations are consultant websites, but we chose not to use these sources because they were not vetted. Likewise, we decided to include theses and dissertations because they are previously assessed by an academic committee (generally considered experts in that topic) and may contain knowledge unpublished in scientific journals (due to lead time between submission and publishing, and acceptance issues) (Paez, 2017 ).

This systematic review of TOC in healthcare included all relevant empirical studies, as described by Brandão de Souza ( 2009 ). In each selected study, the authors describe at least one actual implementation of TOC in a healthcare service, which must describe the application of TOC principles and methods to improve patient flow followed by its outcomes (regardless of geographical location, and languages of publication).

We excluded studies that did not meet the following criteria:

  • Do not report at least one implementation of TOC in healthcare.
  • No further details besides an abstract.
  • Papers with no abstract available.
  • Interviews, editorials, letters to the editor, simulations, books, tutorials, other systematic reviews, and theoretical papers. Here we consider theoretical papers those that focus on reflections and explanations on methodologies or specific issues within TOC in healthcare.
  • Studies that report implementations of TOC combined with any other management methodology, such as Lean, Six-Sigma, or Total Quality Management. Exceptions for this are those cases where TOC was the leading methodology and a different methodology was used secondarily (e.g., to describe the process flows using a value stream mapping).
  • Studies primarily focused on support services, such as information technology processes, meal delivery, and financial services in a healthcare environment.

Two researchers searched for relevant papers on electronic databases using a search strategy calibrated in Scopus database, which combines the terms described in Table 1 (searching article title, abstract and keywords).

Search strategy including TOC terms and healthcare terms

We managed details of retrieved references in EndNote and used an online spreadsheet (Google Sheets). The two reviewers independently screened the titles and abstracts to assess which studies met the eligibility criteria.

We extracted data by using a standardised data extraction sheet (Google Sheets) directly from the included studies. Besides general study data (e.g., title, authors, year of publication, country where study was performed, publication source, and number of implementations described in each study), we collected information needed to perform the analysis minimising the risk of bias, and to answer each one of our four research questions.

The bias analysis consisted of 8 items. Each item captures a step of a TOC implementation and contains a statement and a 4-point scale (0-strongly disagree to 3-strongly agree). Whenever we were not able to classify an item given the content of the document, this item was not considered (up to a maximum of 2 unconsidered items allowed). The evaluation items are below (more information is available as supplementary material):

  • Definition of the goal
  • Definition of global performance measures
  • Why change (Gap analysis and UDEs)
  • Identification of the constraint
  • Definition of how to exploit
  • Subordination of everything else to support the constraint
  • Elevation of the constraint
  • Successfully established continuous improvement

In order to answer the four research questions, we performed a narrative synthesis of the case studies outcomes. Relevant data was extracted and presented in a tabular form and these findings were categorised and synthesised in a narrative summary. The narrative synthesis explores both the relationships and findings within and among the included studies.

Based on the methods described in the previous section, we were able to identify 202 potentially relevant records by searching the scientific databases (last search on 2020–07-23), 64 records in the TOCICO database, and 206 theses/dissertations. We removed 94 duplicates and screened the titles and abstracts of 378 records; 19 articles, 18 videos, and 6 theses/dissertations remained. After performing a full-paper assessment and watching all available video proceedings (with respective presentation slides), we excluded 6 articles, 6 videos, and 4 theses/dissertations. We included 2 articles from the reference lists of scientific studies. The final list included 15 articles from the academic literature, 9 video proceedings, and 2 theses/dissertations. Figure 1 illustrates the flow of information through the different stages of this systematic review.

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Object name is THSS_A_1813056_F0001_B.jpg

Flow of information through the different stages of this systematic review.

Overall, we analysed 42 implementations (cases). Those 15 full-text articles contributed with describing 22 implementations, while those 12 video proceedings described 24 implementations and 2 theses/dissertations described 4 implementations. Some articles (n = 4), video proceedings (n = 4), and theses/dissertations (n = 1) described more than 1 implementation (e.g., Knight et al. ( 2004 ) described 10 implementations). On the other hand, we could also identify a few implementations described in more than one record (e.g., 1 implementation described by 2 articles and 1 video proceeding, and 3 implementations described by 1 article and 1 video proceeding). Table 2 provides a summary of selected studies and bias analysis. Following a discussion of the bias analysis, the four research questions are answered.

Summary of participating studies. Includes publication source, number of implementations, bias analysis (bias score), health service details (e.g., country, setting), results, and UDEs

a Three implementations described in two different sources. b One implementation described in three different sources. c Described in an article and a thesis. d Described in an article and 2 TOCICO videos proceedings. UNC: Uncertain; N/A: Not available.

3.1. Bias analysis

The evaluation system revealed that 83% of assessed implementations are classified as Excellent, 5% as Adequate, and 12% as Marginal. There was no Inadequate implementation among the full-text articles and video proceedings, none was therefore excluded.

All 12 video proceedings (100%) implementations achieved an Excellent classification, whereas 68% of article implementations achieved this classification. All theses/dissertations had an article (and no video proceeding) describing their respective implementations, and for this purpose, they were described together. Only 1 implementation achieved the highest possible score, an average of 3, and it was a video proceeding (Sierraalta-Arganguren, 2015 ).

3.2. Question 1: outcomes of applying the TOC in healthcare services

Before going deeper into the results of TOC implementations, we must consider the goal of the organisations involved in this study. Half of the articles (n = 8) and 2 video proceedings presented problems with the definition of their organisation’s goal. Most of them did not mention the goal within the text, some did not clearly define the goal, and there was one article that the goal seemed to change along with the paper. However, an analysis of those that defined their goal shows 2 frequent characteristics: timeliness and quality of care.

All implementations reported positive outcomes, but they had different documented results, both tangible and intangible. Most of these outcomes did not require an additional cost and, in those that did it, the additional cost was little and always recovered in the very short-term. The two main positive outcomes reported by authors were in productivity (98%; n = 41), which means more patients treated, and in the timeliness of care (83%; n = 35). Other positive results are related to quality of care (48%; n = 20), financial outcomes (29%; n = 12), and staff satisfaction (29%; n = 12). However, since we did not give a survey to the stakeholders of each implementation, these results may underestimate the impact of TOC. Table 3 contains a summary of groups of positive outcomes reported after implementing TOC.

Summary of groups of positive outcomes reported after implementing TOC

Percentages are based on 42 implementations.

Besides the overall positive outcomes, a few implementations also reported neutral results (7%; n = 3) (Gupta & Kline, 2008 ; Kimbrough et al., 2015 ; Lubitsh et al., 2005 ) – no significant change in a measurement – and one reported an UDE (2%). The authors described this UDE as “at times, the growth in the throughput caused congestion on the ward and especially in further treatment at health centres” (Paavola, 2008 ). This occurred because the number of operations per day increased by 50% and changeover times reduced from 54 minutes to 13 minutes – which potentially generated 700 USD k-$800 k savings for the Hospital District and caused a positive impact in staff motivation. The undesirable consequence was the next workstation got congested because of the additional throughput.

Furthermore, we assessed the performance outcomes reported after implementing TOC in healthcare services. The data available ( Table 4 ) was analysed using exploratory data analysis methods, the same methods used by Mabin and Balderstone ( 2003 ).

Summary of performance outcomes related after implementing TOC in healthcare services

a Difference (%) in the percentage of patients meeting the 4-hour target. b We did not use aggregate results from Umble and Umble (Umble & Umble, 2006 ) because Knight et al. (Knight et al., 2004 ) provided more recent results. c Value extracted from a chart. d ORP: operating rooms productivity.

3.2.1. Waiting time (mean reduction: 50%)

We considered the waiting time for appointments, exams, and procedures. Over half of the sample had reductions on waiting time equal or greater than 50%.

3.2.2. Length of stay (mean reduction: 38%)

The LOS included a rich collection of environments (e.g., whole hospitals, specific wards, an emergency department) in different countries. Many studies reported reductions of over 50%.

3.2.3. Accident and Emergency Department 4-hour target (mean improvement: 61%)

Studies from the UK assessed improvements in A&E (Accident and Emergency – equivalent to emergency department) – based on the percentage of patients seen and released within the 4-hour target. It did not allow us to merge these results into length of stay. Results varied between 45% and 73%.

3.2.4. Overtime (mean reduction: 93%)

Those studies that reported overtime achieved a mean reduction of 93%. The reduction of overtime varied between 63% and 100% (most of the cases).

3.2.5. No-show and late-cancellation rate (mean reduction: 72%)

Two implementations focused on reducing no-show and cancellation rate. One implementation was able to reduce those rates at 53%, the other reduced 90%.

3.2.6. Operating room productivity (mean improvement: 43%)

Implementations that focused to improve operating rooms were able to increase the number of surgeries varying from 5% (during peak hours, reducing in 8% after hours) to 100%. In many cases, the improvement continued after the study, which would increase this longer mean if we had considered this longer period.

3.2.7. Changeover time (mean reduction: 41%)

Few studies reported the changeover time between operations, but those who reported experienced a mean reduction of 41%.

3.2.8. Throughput (mean improvement: 34%)

The most frequently reported outcome; throughput in TOC is defined as the rate at which the system generates “goal units” (Cox et al., 2012 ). In this case, we considered throughput as the number of patients adequately processed and we assessed the difference in this measure after implementing TOC. The lowest improvement was a 5% increase in surgery during peak hours (described above), the highest was a 100% increase in cataract surgeries. Nearly half of the cases had an increase of 40% or more.

Almost all organisations had successfully achieved and sustained improvement, but many of them apparently stagnated after that and did not report further improved outcomes. When it comes to continuous improvement, defining its sustainability is difficult since there is no clear definition and guidelines on how to assess it in past research. However, of those organisations that reported the sustainability of the solution (n = 34), 74% (n = 25) reported being successful in achieving and sustaining continuous improvement, i.e., were able to continue to improve beyond their initial improvement along time. The other 26% (n = 9) did not achieve or sustain continuous improvement. The remaining organisations (n = 8) did not provide follow-up on the achievement and sustainability of continuous improvement (uncertain).

3.3. Question 2: diffusion of TOC in healthcare

According to our findings, a typical TOC implementation in healthcare occurred in the Accident and Emergency Department of a United Kingdom (UK) public hospital. Nevertheless, TOC has been implemented in a diverse set of environments and countries.

Most of TOC implementations occurred in the UK or in the United States (USA), 28 out of 41. Although the USA had more published studies (9 studies), the UK took the lead in the total number of implementations (19 implementations in 6 studies). Finland is represented with 3 articles that describe 4 implementations. Other countries described in a single article or proceedings are Israel (3 implementations), Brazil (2 implementations), Netherlands (2 implementations), Italy (1 implementation), New Zealand (1 implementation), and Venezuela (1 implementation).

Considering the levels of care, tertiary care (e.g., hospitalised patients, surgeries) were the most common, contributing 76% (n = 35). Implementations in primary care (e.g., family medicine clinic) and secondary (i.e. speciality care, e.g., ophthalmology, psychiatric rehabilitation) corresponded to 9%; (n = 4) and 15%; (n = 7), respectively. These numbers reflect the fact that hospitals are the most common setting of TOC implementations (86%; n = 36) followed by clinics (7%; n = 3), home care (5%; n = 2), and a health system (2%; n = 1). The same is true considering the nature of services, although there were representatives of all categories, government health services account for the most with 62% (n = 26), followed by for-profit (21%; n = 9), and not-for-profit (17%; n = 7).

The description of the services revealed the diversity of environments where TOC was implemented. Accident and Emergency Departments (33%; n = 14) and operating room (12%; n = 5) stood out as the most common environments. However, the list of services where TOC was implemented includes highly specialised services (e.g., neurosurgery and heart surgery), a government health system run by the U.S. Air Force, a chemotherapy clinic, a family medicine clinic, a home care delivery system, and discharge planning.

We can view the elements that compose the health and social care industry similar to a chain structure. Each link of this health and social care chain corresponds to a different service provided (e.g., general practitioner, inpatient care) and they are organised according to complexity level and need of care (e.g., general practitioner + speciality care + emergency). An overloaded link preventing patients to access treatment in a timely manner may result in an increased demand for the next link of the chain (higher complexity treatment) as the illness progresses. All implementations evaluated had an impact within their respective links of the health and social care chain. However, 57% (n = 24) of the implementations also had an impact between the links. That means the consequences of those 24 TOC implementations reverberated across the health and social care chain, indirectly improving other links (e.g., reducing the time between the emergency department and hospital admission).

While most of the studies analysed only applied TOC in specific environments. the TOCICO video proceedings contained 3 holistic implementations. These holistic implementations included one hospital (for-profit) in Venezuela (Sierraalta-Arganguren, 2015 ) and 2 hospitals in the UK (De Kiewiet, 2012 ; Stratton & West, 2014 ).

3.4. Question 3: common problems (UDEs) faced by healthcare services

The reported problem (the gap) that motivated implementing TOC was identified in each case study and arranged into 4 different categories. The most common problems experienced by healthcare services involved in this systematic review were (1) insufficient productivity (31%; n = 9), usually represented as a pressure to do more and be faster with existing or less resources; followed by (2) inadequate timeliness of care (21%; n = 6), usually patients had to wait for long periods for their treatment, both when scheduling appointments and procedures (indirect waiting) and once in the clinic/hospital (direct waiting); (3) financial problems (21%; n = 6), profits were low or non-existent; and (4) issues in quality of care (e.g., healthcare provided not as good as desired, consumer and provider low satisfaction or dissatisfaction, patients at risk of more complications) (18%; n = 5) complete the list. One article and two proceedings (11%) did not describe clearly the gap between where the organisation was and where it should be with respect to its goal (Buwalda & Gijs, 2013 ; Lubitsh et al., 2005 ; Ronen & Pass, 2011 ).

The median number of UDEs reported was 4, but we found a minimum of 1 (Kimbrough et al., 2015 ; Wadhwa, 2007 ) and a maximum of 115 (Taylor, 2016 ). The latter was a video proceeding that mentioned the existence of 111 UDEs in one of its three implementations but did not described them. One article (Gonçalves et al., 2018 ) and two proceedings (Ronen & Pass, 2011 ; Stratton & West, 2014 ) did not report any UDE. All UDEs reported were analysed and arranged accordingly to their nature, resulting in 8 categories. The authors commonly reported more issues related to productivity (27%; n = 28), followed by financial outcomes (15%; n = 15) and market demand (12%; n = 12). Other UDEs reported were timeliness of care (11%; n = 11), lack of staff (10%; n = 10), logistics (10%; n = 10), staff satisfaction (8%; n = 8), and quality of care (6%; n = 6).

Since not all implementations described their UDEs, we considered only those 37 (88%) that did to assess whether they were able to address their UDEs. Most of the implementations (86%; n = 32) were able to address all their UDEs after TOC implementation, although a few implementations (12%; n = 5) could only partially address their UDEs (Gupta & Kline, 2008 ; Lubitsh et al., 2005 ; Paavola, 2008 ). Lubitsh et al. admitted that their results were biased due to a corporate merger being in process during the TOC implementation (“A frequently occurring complaint from staff was that the merger process was against the spirit of TOC and was undoing all the improvements which had come out of it.”) (Lubitsh et al., 2005 , p. 129).

3.5. Question 4: methods and tools used to apply TOC in healthcare services

The analysis of the TOC implementations sequence revealed many different approaches. The articles and video proceedings used 5 different TOC methods: 5FS, BM, thinking processes (TP), drum-buffer-rope (DBR), and CQS. The most used method reported was the 5FS, accounting for 76% (n = 32), followed by BM (60%; n = 25), TP (54%; n = 22), DBR (40%; n = 17), and CQS (17%; n = 7). Some implementations included more than 1 TOC method. Within the articles, 2 of them reported a maximum of 3 methods: Groop et al. ( 2012 , 2017 )) described the use of 5FS, CQS, and TP; while Cox, Robinson, and Maxwell (Cox et al., 2014 , 2016 ) described the use of 5FS, TP, and BM. The latter implementation described the use of all 5 methods on a video proceeding (Cox & Robinson, 2012 ). More details about each of these TOC methods and their adoption in each study are available as supplementary material.

Among other methods adopted to support the TOC implementations, 4 of them stood out: documented flow analysis (76%; n = 31), TOC training (69%; n = 29), improvement meetings (67%; n = 28) – frequently called buffer management meetings or huddles –, and participation of a TOC champion (64%; n = 27). Articles describe other relevant methods, such as process flowcharting, semi-structured interviews, and non-participant observation, but none of these methods achieved an adoption level of 50%. All methods used are available in Table 5 .

Methods and tools used to apply TOC in healthcare services

* Process flowcharting is very similar to documented flow analysis; we considered the former as a graphical representation of the latter.

4. Discussion

Articles and video proceedings accounted for a similar number of implementations, 22 and 24, respectively. However, the video proceedings had only 12 studies included while there were 15 articles. Only 5 implementations were documented both in articles and in video proceedings. The number of video proceedings would have been even higher if we had included theoretical studies. While the video proceedings represent the grey literature, these results demonstrate the relevance and necessity of including these studies in this review. On the other hand, theses/dissertations accounted for a small sample in this study (n = 2), reporting 4 implementations (also described in articles) (Groop, 2012 ; Lubitsh, 2002 ). This paucity demonstrates the need for academic healthcare researchers to proactively investigate such emerging topics as TOC.

Besides quantity, the quality of TOC implementations in academic studies is still lower than expected. Of course, there are good TOC implementations in academic papers. But, overall, our bias analysis revealed some gaps between academic and grey literature. Our framework assessed the implementations according to their adherence to TOC principles (and revealed when and where it was not achieved). Both academic and grey literature studies had well-described TOC implementations that achieved a high score, but academic studies had a lower mean score. Although the video proceedings provided rich details about the TOC tools and methods, many times they missed providing the implementation sequence. In contrast, academic studies provided a better description of the sequence. The fact that video proceedings were made to an audience familiar with TOC, whereas articles usually make no assumptions might help explain these differences to some extent.

Not surprisingly, most of the severe inconsistencies in applying TOC principles occurred in those studies that had the lowest score, including those studies that reported a few neutral results among their outcomes. Despite such shortcomings, all of them reported overall positive results. Some inconsistencies found involved skipping steps 2 (exploit) and 3 (subordinate) of the 5FS (Gonçalves et al., 2018 ), considering UDEs as bottlenecks (Kimbrough et al., 2015 ), staff not attending TOC committee meetings (Lubitsh, 2002 ; Lubitsh et al., 2005 ), and solutions based on cost accounting (Gupta & Kline, 2008 ), instead of throughput accounting. Throughput accounting is a management accounting method developed by Goldratt that evaluates the impact of any proposed local action on the system as a whole. Throughput accounting addresses the shortcomings of cost accounting on decision making (Budd, 2010 ).

4.1. Outcomes of applying the TOC in healthcare services

A relevant aspect of our findings is that all TOC implementations reported an overall positive outcome. Most implementations resulted in a dramatic improvement, particularly those that achieved higher scores in the bias analysis.

Most TOC recommendations and changes required little or no additional cost to implement and, whenever an investment was necessary, the return on investment (ROI) was usually immediate (or it pays off in the short-term) and much higher than the cost. Other methodologies, like Lean and Six-Sigma, usually demand more time, management attention, and financial resources (Blackmore & Kaplan, 2017 ; Chiarini & Bracci, 2013 ; D’Andreamatteo et al., 2015 ). Lean and Six Sigma implementations take much longer because they try to improve all processes of the system, lacking the focus to improve where it is needed to achieve the organization's goal. The benefits of combining the focusing mechanism of TOC with Lean and Six-Sigma tools to link local improvements to significant organisation results are huge. More importantly is the understanding that many “local improvements” do not translate into positive global results. The successful combination of TOC with other methodologies already exist (Pirasteh & Farah, 2006 ), including in Wadhwa ( 2007 ).

On the light of the outcomes reported, one may question whether the improvement in some measurements, such as an increase in throughput or operations performed and a decrease in LOS, might jeopardise the quality of care delivered. Actually, the quality and timeliness of care increase for two reasons: (1) a TOC implementation alleviates the workload of qualified medical professionals (the constraint) so they can spend more time with patients performing high skill-level tasks; furthermore, (2) as throughput increases and waiting time decreases, healthcare organisations are able to deliver care to more patients on a timely manner, preventing the worsening of clinical conditions (Ryu & Lee, 2017 ). These two aspects are directly related to better value provided and lead to better healthcare outcomes (Porter & Lee, 2013 ).

Sustainability of results is also a relevant concern. Those cases that achieved higher scores were also associated with continuous improvement. Many implementations (61%; n = 25) were able to successfully achieve and sustain continuous improvement. However, any TOC implementation involves a change mindset to build a new paradigm within the organisational culture. For this reason, in order to achieve continuous improvement, one must adopt and continuously use TOC principles to manage.

Like Mabin and Balderstone ( 2003 ), we faced the same concern when assessing the performance outcomes reported after implementing TOC in healthcare services. The existence of so many apparent gaps in the data could indicate that those factors were not improved, or that only a few factors in each case improved. Likewise, there are many valid reasons for those omissions. Many healthcare services adopted TOC with a specific focus, such as to increase throughput, and may have failed to give attention to (or find a need to measure or report) effects outside this focus. Moreover, it was difficult to collect hard data, some studies only presented measurements after implementing TOC (e.g., “elevated enrolment capacity by 800 additional enrolees”, “generated over 1.6 million additional revenue”). Many studies reported results that did not allow us to calculate (e.g., “daily number of operations has increased”). In many, if not all cases, the organisation was constantly fighting fires. Their role was to put out fires not to spend time documenting and measuring their problems.

The findings reported in this study become even more relevant when we realise that only 3 environments did a holistic implementation and only 1 environment reported the adoption of all TOC methods. The outcomes of all other 37 implementations resulted from applying some components of the overall TOC managerial philosophy. These results are only a partial demonstration of the power of TOC, corroborating results of a prior literature search of TOC applications (Mabin & Balderstone, 2003 ).

4.2. Diffusion of TOC in healthcare

Mabin and Balderstone ( 2003 ) stated that a great number of other TOC applications have never been published (and many of them probably never will) because they provide a competitive advantage. The same may be true for TOC applications in healthcare services.

The mean performance outcomes reported after implementing TOC in healthcare services provide good evidence of the adoption of TOC as a potential effective solution for the chronic problems in most, if not every, healthcare environment. The set of studies included in this review, though small, demonstrates that TOC has already attained significant results in all levels of care and many links of the health and social care chain. There are successful examples from general practice (Cox & Robinson, 2012 ; Cox et al., 2014 , 2016 ) to home care (Groop et al., 2017 ), described in 9 countries, on 4 continents. Furthermore, solutions proposed by Groop et al. ( 2017 ), or some variant of them, are now applied in at least 20% of the home care systems operating in Finland. At least 10 hospitals in the UK have already adopted TOC to support their practice (Knight et al., 2004 ). However, we only found a few cases in primary and speciality care.

4.3. Common problems (UDEs) faced by healthcare services

Shortages of hospital beds and workforce are frequently associated as common causes for lack of performance in healthcare services (Crisp & Chen, 2014 ; Song & Ferris, 2018 ). Nevertheless, TOC has proved with several successful cases its capacity to dramatically improve performance using the existing workforce; and, when necessary, usually hired an additional non-constraint, such as a medical assistant, at a reduced cost to leverage the constraint (the much expensive and scarce provider). Furthermore, the shortage of hospital beds did not present as a root cause, but as a symptom. As a matter of fact, the impressive mean reduction of 38% in LOS achieved by TOC also worked providing increased capacity to treat more patients within a given period of time using the same existing beds, as mentioned by Knight et al. ( 2004 ). Examples above and all other TOC outcomes show that healthcare services suffer from similar problems, but usually have a huge amount of protective capacity. These organisations are managing their resources and patient flow based on bad/outdated policies, which focus on improving local efficiency (not assessing its global impact on the organisation). Consequently, existing extra capacity is mismanaged, which leads to undesirable outcomes (e.g., long waiting, increased LOS). TOC demonstrated that it is possible to uncover the hidden capacity and achieve breakthrough results with no or little investment by proper management of critical resources and patient flow.

4.4. Methods and tools used to apply TOC in healthcare services

The three POOGI offered by TOC have proven extremely valuable in healthcare. The path to improving healthcare systems and organisations is described in the 5FS. First, organisations must identify (step 1) where the constraint is currently and where the constraint should strategically be. Next, they need to uncover their hidden potential by making better use of existing resources (steps 2 and 3). Only after achieving their true potential should the organisations consider the need to invest in acquiring more capacity (step 4). But to continue improving, it is essential to remember step 5: do not let inertia become the system constraint.

Many times, however, a policy, procedure, rule, measure or behaviour is blocking patient flow (details explained in the supplementary material). In these cases, the TP and the CQS are quite useful in identifying and addressing these types of problems. Buffer management is extremely useful in hospital environments, where demand is uncertain (for example, in the emergency department where no appointment schedule exists) and where there are thousands of potential processes flows through the various hospital departments. DBR plays an important role once a patient process flow is then identified and frequently updated by the patient’s physician (the drum) to ensure the patient receives appropriate and timely healthcare (Strear & Sirias, 2020 ). Knight’s Pride and Joy ( 2014 ) provides numerous instances of the use of TOC in a healthcare environment. In an outpatient environment, buffer management is extremely useful in proactively managing the rapid treatment of acute patients, pulling patients forward in time to imminent vacant appointment slots, and monitoring overall and specific appointment types backlogs, as explained in a 2-article series where the authors used TOC to address commonly studied appointment scheduling system design and execution problems (Cox, 2019 ; Cox & Boyd, 2018 ).

5. Limitations

Naturally, this work has some limitations and we would like to acknowledge them. First, the number of TOC implementations described in this study is small. Our dilemma in addressing this limitation was the traditional “Rigor versus Relevance” quandary. Do we wait another ten or more years so that enough published academic research is available to conduct statistical tests of significance OR do we conduct an exploratory investigation of what is available today in hopes that other researchers will move forward in learning more about TOC in healthcare and be on the forefront of developing new knowledge instead of the traditional role of academics of just reporting history? We choose the latter.

As an effort to address the above-mentioned limitation, we included grey literature sources, here represented as TOCICO video proceedings and academic theses. As previously stated, TOCICO is a not-for-profit certification and knowledge development and dissemination organisation. Many members are certified in all aspects of TOC; others are on that journey. Most members are consultants and have led dozens to hundreds of TOC implementations. These presentations are vetted by the top TOC experts in the world. Presenters willingly share their successful and failed implementations in hopes of developing better solutions. Similarly, theses and dissertations are vetted by the students’ examination committees.

A lesser limitation is that we tried to analyse each implementation separately, but many times a single article or video presentation reporting multiple cases treated them as one. Furthermore, this review only considered practical implementations directly related to patient flow. There are many other successful case studies in support services, such as logistic service of medical records in a hospital (Aguilar-Escobar et al., 2016 ), hospital inventory management (Wang et al., 2015 ), medical claims processing (Taylor & Sheffield, 2002 ), and developing technical reports for healthcare decision-makers (Patwardhan et al., 2006 ). These healthcare support-services TOC implementations differ little from TOC implementations in other services, so they provide no gain in TOC knowledge in healthcare.

5.1. Recommendations for future work

In the future, it would be of great value to science and management to have a systematic review that includes theoretical papers with proposed solutions, even though never implemented. Other recommendations are (1) a study revealing details of the most common TOC tools and methods used in the healthcare environments, (2) more studies about TOC in primary care and speciality care, (3) TOC combined with other methodologies, and (4) to develop generic templates of various applications based on the literature and successful case studies through theory building for use in implementing TOC in similar environments (theory testing). Cox and Boyd ( 2018 ) provided such a template for outpatient schedule design and Cox ( 2019 ) provided a template for outpatient schedule execution for testing and modification by other researchers.

6. Conclusion

Existing literature has revealed TOC as a potential effective solution to address the chronic healthcare problems. All documented healthcare services that implemented TOC achieved positive results, even those that only used some components or did a marginal implementation. Those organisations that adequately applied TOC were able to rapidly achieve breakthrough improvement, and with no or little investment. Furthermore, recent research shows that combining the focusing mechanism of TOC with other existing methodologies (e.g., Lean, Six-sigma) would provide larger benefits than using the other methodologies alone. TOC provided positive results in many different environments along the health and social care chain, and in many different countries, which leads one to believe they can be used to improve almost any healthcare environment.

Supplementary Material

Acknowledgments.

This work was supported by the FCT – Fundação para a Ciência e a Tecnologia as part of a PhD scholarship [PD/BD/129829/2017]. This PhD scholarship was funded by the European Social Fund and national MCTES funds. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of this manuscript.

Funding Statement

Fundação para a Ciência e a Tecnologia [PD/BD/129829/2017]

Declaration of interest statement

The authors declare no conflict of interest.

Supplementary material

Supplemental data for this article can be accessed here .

  • Aguilar-Escobar, V. G., Garrido-Vega, P., & González-Zamora, M. M. (2016). Applying the theory of constraints to the logistics service of medical records of a hospital . European Research on Management and Business Economics , 22 ( 3 ), 139–146. 10.1016/j.iedee.2015.07.001 [ CrossRef ] [ Google Scholar ]
  • Al Talalwah, N., & McIltrot, K. H. (2019). Cancellation of surgeries: Integrative review . Journal of PeriAnesthesia Nursing , 34 ( 1 ), 86–96. 10.1016/j.jopan.2017.09.012 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Auger, P. (1998). Information sources in grey literature . De Gruyter. [ Google Scholar ]
  • Bacelar, G. (2019). How a doctor implemented TOC and improved his ophthalmology practice over 50% in a few weeks . TOCICO 2019 International Conference Proceedings . TOCICO International Conference: 17th Annual Worldwide Gathering of TOC Professionals. https://www.tocico.org/page/2019Bacelar [ Google Scholar ]
  • Blackmore, C. C., & Kaplan, G. S. (2017). Lean and the perfect patient experience . BMJ Quality & Safety , 26 ( 2 ), 85. 10.1136/bmjqs-2016-005273 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Brandão de Souza, L. (2009). Trends and approaches in lean healthcare . Leadership in Health Services , 22 ( 2 ), 121–139. 10.1108/17511870910953788 [ CrossRef ] [ Google Scholar ]
  • Budd, C. S. (2010). CHAPTER 13: Traditional measures in finance and accounting, problems, literature review, and TOC measures. In Cox, J. F., & Schleier Jr, J. G. (Eds.),  Theory of constraints handbook (pp. 335–371). McGrawHill. [ Google Scholar ]
  • Buwalda, P. E., & Gijs, A. (2013). Increase quality, decrease stress in a hospital . TOCICO International Public Sector Effectiveness Conference Proceedings . TOCICO International Public Sector Effectiveness Conference. [ Google Scholar ]
  • Cattaneo, C., & Bassani, G. (2016). The TOC thinking process: The viability of change . Human Systems Management , 35 ( 4 ), 301–323. 10.3233/HSM-161616 [ CrossRef ] [ Google Scholar ]
  • Chiarini, A., & Bracci, E. (2013). Implementing lean six sigma in healthcare: Issues from Italy . Public Money & Management , 33 ( 5 ), 361–368. 10.1080/09540962.2013.817126 [ CrossRef ] [ Google Scholar ]
  • Corley, J. (2016). The global health care crisis no one is talking about . HuffPost. https://www.huffpost.com/entry/the-global-health-care-cr_b_10074262
  • Cox, J. F. (2019). Using the theory of constraints’ processes of ongoing improvement to address the provider appointment scheduling system execution problem . Health Systems , 1–32. 10.1080/20476965.2019.1646105 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Cox, J. F., & Boyd, L. H. (2018). Using the theory of constraints’ processes of ongoing improvement to address the provider appointment scheduling system design problem . Health Systems , 9 (2), 1–35. 10.1080/20476965.2018.1471439 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Cox, J. F., Boyd, L. H., Sullivan, T. T., Reid, R. A., & Cartier, B. (2012). The theory of constraints international certification organization dictionary (Second Edition) . McGraw-Hill Education. http://www.tocico.org/?page=dictionary [ Google Scholar ]
  • Cox, J. F., & Robinson, T. M. (2012). The use of TOC in a medical appointment scheduling system for family practice . TOCICO Conference 2012: 10th Annual Worldwide Gathering of TOC Professionals , 10. https://www.tocico.org/page/12ConfVid9 [ Google Scholar ]
  • Cox, J. F., Robinson, T. M., & Maxwell, W. (2014). Applying the ‘theory of constraints’ to solve your practice’s most vexing problem . Family Practice Management , 21 ( 5 ), 18–22. https://www.aafp.org/fpm/2014/0900/p18.html [ PubMed ] [ Google Scholar ]
  • Cox, J. F., Robinson, T. M., & Maxwell, W. (2016). Unconstraining a doctor’s office. TOC’s buffer management can help solve core scheduling problems . Industrial Engineer , 48 ( 2 ), 28–33. https://www.iise.org/IndustrialEngineer/details.aspx?id=40935 [ Google Scholar ]
  • Crisp, N., & Chen, L. (2014). Global supply of health professionals . New England Journal of Medicine , 370 ( 10 ), 950–957. 10.1056/NEJMra1111610 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • D’Andreamatteo, A., Ianni, L., Lega, F., & Sargiacomo, M. (2015). Lean in healthcare: A comprehensive review . Health Policy , 119 ( 9 ), 1197–1209. 10.1016/j.healthpol.2015.02.002 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • de Kiewiet, M. (2012). Solid gains throughout an acute hospital . TOCICO Conference 2012: 10th Annual Worldwide Gathering of TOC Professionals , 10 . https://www.tocico.org/page/12ConfVid1 [ Google Scholar ]
  • Goldratt, E. M. (1986). The race . North River Press. [ Google Scholar ]
  • Goldratt, E. M. (1994). It’s not luck . http://catalog.hathitrust.org/api/volumes/oclc/31443609.html
  • Goldratt, E. M. (1999). Theory of constraints: What is this thing called and how should it be implemented? North River Press. [ Google Scholar ]
  • Goldratt, E. M., & Cox, J. (2004). The goal: A process of ongoing improvement . (3., rev. ed., 20. anniversary ed). North River Press. [ Google Scholar ]
  • Gonçalves, A. A., De Castro Silva, S. L. F., Martins, C. H. F., Cheng, C., Barbosa, J. G. P., & De Oliveira, S. B. (2018). Decision Support Systems in Cancer Treatment: A Case Study at Brazilian National Cancer Institute . Studies in Health Technology and Informatics , 251 , 199–202. 10.3233/978-1-61499-880-8-199 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Groop, J. (2012). Theory of Constraints in field service: Factors limiting productivity in home care operations [Doctoral dissertation] . Aalto University. http://lib.tkk.fi/Diss/ [ Google Scholar ]
  • Groop, J., Ketokivi, M., Gupta, M., & Holmström, J. (2017). Improving home care: Knowledge creation through engagement and design . Journal of Operations Management , 53–56 ( 1 ), 9–22. 10.1016/j.jom.2017.11.001 [ CrossRef ] [ Google Scholar ]
  • Gupta, M., & Kline, J. (2008). Managing a community mental health agency: A Theory of Constraints based framework . Total Quality Management and Business Excellence , 19 ( 3 ), 281–294. 10.1080/14783360701601850 [ CrossRef ] [ Google Scholar ]
  • Gupta, M. C., Bridgman, S., & Kaur Sahi, G. (2015). Application of TOC-based framework to improve market orientation in a non-profit organization . Journal of Strategic Marketing , 23 ( 7 ), 579–599. 10.1080/0965254X.2014.1001865 [ CrossRef ] [ Google Scholar ]
  • Halim, S. (2019). Is healthcare on the brink of a global workforce crisis? Health Europa . https://www.healtheuropa.eu/global-workforce-crisis/90846/ [ Google Scholar ]
  • Han, J. H., Zhou, C., France, D. J., Zhong, S., Jones, I., Storrow, A. B., & Aronsky, D. (2007). The effect of emergency department expansion on emergency department overcrowding . Academic Emergency Medicine , 14 ( 4 ), 338–343. 10.1197/j.aem.2006.12.005 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Karvonen, S., Rämö, J., Leijala, M., & Holmström, J. (2004). Productivity improvement in heart surgery—A case study on care process development . Production Planning and Control , 15 ( 3 ), 238–246. 10.1080/09537280410001670322 [ CrossRef ] [ Google Scholar ]
  • Kim, C. S., Spahlinger, D. A., Kin, J. M., & Billi, J. E. (2006). Lean health care: What can hospitals learn from a world-class automaker? Journal of Hospital Medicine , 1 ( 3 ), 191–199. 10.1002/jhm.68 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Kimbrough, C. W., McMasters, K. M., Canary, J., Jackson, L., Farah, I., Boswell, M. V., Kim, D., & Scoggins, C. R. (2015). Improved operating room efficiency via constraint management: Experience of a tertiary-care academic medical center . Journal of the American College of Surgeons , 221 ( 1 ), 154–162. 10.1016/j.jamcollsurg.2015.02.032 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Knight, A. (2014). Pride and joy (1st ed.). Linney Group Ltd. [ Google Scholar ]
  • Knight, A., Schragenheim, E., Gibb, H., & Schragenheim, A. (2004). Making TOC the main way in health and social care . TOCICO Conference 2004: 2nd Annual Worldwide Gathering of TOC Professionals , 2 . https://vimeopro.com/tocico/2004-international-conference-presentations/video/165916359 [ Google Scholar ]
  • Lubitsh, G. (2002). A longitudinal study into the impact of theory of constraints (TOC) on three departments in an NHS trust [Doctoral dissertation] . University of East London. [ Google Scholar ]
  • Lubitsh, G., Doyle, C., & Valentine, J. (2005). The impact of theory of constraints (TOC) in an NHS trust . Journal of Management Development , 24 ( 2 ), 116–131. 10.1108/02621710510579482 [ CrossRef ] [ Google Scholar ]
  • Mabin, V. (2019). Using TOC to improve the delivery of chemotherapy for cancer treatments in a large public hospital . TOCICO 2019 International Conference Proceedings . TOCICO International Conference: 17th Annual Worldwide Gathering of TOC Professionals. https://www.tocico.org/page/2019Mabin2 [ Google Scholar ]
  • Mabin, V. (2020). How TOC dramatically improved the delivery of chemotherapy treatments in a large public hospital . TOCICO 2020 International Conference Proceedings . TOCICO Virtual Conference. [ Google Scholar ]
  • Mabin, V., & Balderstone, S. J. (2003). The performance of the theory of constraints methodology: Analysis and discussion of successful TOC applications . International Journal of Operations & Production Management , 23 ( 6 ), 568–595. 10.1108/01443570310476636 [ CrossRef ] [ Google Scholar ]
  • Mabin, V., & Mirzaei, M. (2016). Expanding the world of theory of constraints . 2016 TOCICO International Video Conference Proceedings . 2016 TOCICO International Conference. [ Google Scholar ]
  • Mabin, V., Yee, J., Babington, S., Caldwell, V., & Moore, R. (2018). Using the theory of constraints to resolve long-standing resource and service issues in a large public hospital . Health Systems , 7 ( 3 ), 230–249. 10.1080/20476965.2017.1403674 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Morley, C., Unwin, M., Peterson, G. M., Stankovich, J., & Kinsman, L. (2018). Emergency department crowding: A systematic review of causes, consequences and solutions . Plos One , 13 ( 8 ), e0203316. 10.1371/journal.pone.0203316 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Murray, M., & Berwick, D. M. (2003). Advanced access: Reducing waiting and delays in primary care . JAMA , 289 ( 8 ), 1035–1040. 10.1001/jama.289.8.1035 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Paavola, T. (2008). Exploiting Process thinking in Health Care . International Journal of Healthcare Information Systems and Informatics (IJHISI) , 3 ( 2 ), 12–20. 10.4018/jhisi.2008040102 [ CrossRef ] [ Google Scholar ]
  • Paez, A. (2017). Gray literature: An important resource in systematic reviews . Journal of Evidence-Based Medicine , 10 ( 3 ), 233–240. 10.1111/jebm.12266 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Patwardhan, M. B., Sarría-Santamera, A., & Matchar, D. B. (2006). Improving the process of developing technical reports for health care decision-makers: Using the theory of constraints in the evidence-based practice centers . International Journal of Technology Assessment in Health Care , 22 ( 1 ), 26–32. Cambridge Core. 10.1017/S026646230605080X [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Pirasteh, R. M., & Farah, K. S. (2006). Continuous improvement trio—the top elements of TOC, lean and six sigma make beautiful music together . APICS Magazine , 16 (5), 31–33. [ Google Scholar ]
  • Poksinska, B. B., Fialkowska-Filipek, M., & Engström, J. (2017). Does Lean healthcare improve patient satisfaction? A mixed-method investigation into primary care . BMJ Quality & Safety , 26 ( 2 ), 95. 10.1136/bmjqs-2015-004290 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Porter, M. E., & Lee, T. H. (2013). The strategy that will fix health care . Harvard Business Review , 90 ( 10 ), 50–70. https://hbr.org/2013/10/the-strategy-that-will-fix-health-care [ Google Scholar ]
  • Ronen, B. (2005). Special issue on the theory of constraints—practice and research . Human Systems Management , 24 (1) , 1–2. https://content.iospress.com/articles/human-systems-management/hsm571 [ Google Scholar ]
  • Ronen, B., & Pass, S. (2011). Throughput enhancement in operating rooms: Doing more with existing resources . TOCICO International Conference: 9th Annual Worldwide Gathering of TOC Professionals , 9 . https://www.tocico.org/page/11ConfVid21 [ Google Scholar ]
  • Ryu, J., & Lee, T. H. (2017). The waiting game—why providers may fail to reduce wait times . New England Journal of Medicine , 376 ( 24 ), 2309–2311. 10.1056/NEJMp1704478 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Shamseer, L., Moher, D., Clarke, M., Ghersi, D., Liberati, A., Petticrew, M., Shekelle, P., & Stewart, L. A., the PRISMA-P Group . (2015). Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015: Elaboration and explanation . BMJ , 349 ( 1 ), g7647. 10.1136/bmj.g7647 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Sierraalta-Arganguren, M. C. (2015). Transformation of the flow of patient-centered care in the emergency room . TOCICO Conference 2015: 13th Annual Worldwide Gathering of TOC Professionals , 13 . https://www.tocico.org/page/15ConfVid37 [ Google Scholar ]
  • Sisko, A. M., Keehan, S. P., Poisal, J. A., Cuckler, G. A., Smith, S. D., Madison, A. J., Rennie, K. E., & Hardesty, J. C. (2019). National health expenditure projections, 2018–27: Economic and demographic trends drive spending and enrollment growth . Health Affairs , 38 ( 3 ), 491–501. 10.1377/hlthaff.2018.05499 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Song, Z., & Ferris, T. G. (2018). Baby boomers and beds: A demographic challenge for the ages . Journal of General Internal Medicine , 33 ( 3 ), 367–369. 10.1007/s11606-017-4257-x [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • Stratton, R., & Knight, A. (2010). Managing patient flow using time buffers . Journal of Manufacturing Technology Management , 21 ( 4 ), 484–498. 10.1108/17410381011046599 [ CrossRef ] [ Google Scholar ]
  • Stratton, R., & West, B. (2014). A holistic solution for community health and social care . TOCICO Conference 2014: 12th Annual Worldwide Gathering of TOC Professionals , 12 . https://www.tocico.org/page/14ConfVid75 [ Google Scholar ]
  • Strear, C., & Sirias, D. (2020). Smash the bottleneck: Fixing patient flow for better care (and a better bottom line) . Health Administration Press. [ Google Scholar ]
  • Taylor, B. (2016). TOC in US healthcare strategy and operations . TOCICO International Conference: 14th Annual Worldwide Gathering of TOC Professionals , 14 . https://www.tocico.org/page/16ConfVid70 [ Google Scholar ]
  • Taylor, L. J., & Sheffield, D. (2002). Goldratt’s thinking process applied to medical claims processing . Hospital Topics , 80 ( 4 ), 13–21. 10.1080/00185860209598005 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • TOCICO . (2018). Theory of constraints international certification organization . https://www.tocico.org/ [ Google Scholar ]
  • Umble, M., & Umble, E. J. (2006). Utilizing buffer management to improve performance in a healthcare environment . European Journal of Operational Research , 174 ( 2 ), 1060–1075. 10.1016/j.ejor.2005.02.059 [ CrossRef ] [ Google Scholar ]
  • Wadhwa, G. (2007). Viable vision: Achievable in healthcare . TOCICO Conference 2007: 5th Annual Worldwide Gathering of TOC Professionals , 5. https://vimeopro.com/tocico/2007-international-conference-presentations/video/165330301 [ Google Scholar ]
  • Wang, L., Cheng, C., Tseng, Y., & Liu, Y. (2015). Demand-pull replenishment model for hospital inventory management: A dynamic buffer-adjustment approach . International Journal of Production Research , 53 ( 24 ), 7533–7546. 10.1080/00207543.2015.1102353 [ CrossRef ] [ Google Scholar ]
  • Womack, D. E., & Flowers, S. (1999). Improving system performance: A case study in the application of the theory of constraints . Journal of Healthcare Management , 44 ( 5 ), 397–407. 10.1097/00115514-199909000-00013 [ PubMed ] [ CrossRef ] [ Google Scholar ]
  • World Health Organization . (2010). The world health report: Health systems financing: The path to universal coverage . World Health Organization. http://www.who.int/whr/2010/en/ [ PMC free article ] [ PubMed ]
  • World Health Organization . (2019). World health statistics 2019: Monitoring health for the SDGs, sustainable development goals . World Health Organization. https://www.who.int/gho/publications/world_health_statistics/2019/en/
  • Young, T., Brailsford, S., Connell, C., Davies, R., Harper, P., & Klein, J. H.. Using industrial processes to improve patient care . (2004). BMJ : British Medical Journal , 328 ( 7432 ), 162–164. PMC. 10.1136/bmj.328.7432.162 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]

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International Journal of Quality & Reliability Management

ISSN : 0265-671X

Article publication date: 26 February 2024

Theory of Constraints (TOC), though a well-established process improvement methodology in manufacturing, is still a novel philosophy for healthcare and an exhaustive review of literature is needed to summarize the key findings of various researchers. Such a review can provide a direction to the researchers and academicians interested in exploring the application of TOC in the healthcare sector. This paper aims to review the existing literature of TOC tools and techniques applied to the healthcare environment, and to investigate motivating factors, benefits and key gaps for identifying directions for future research in the domain of healthcare.

Design/methodology/approach

In this paper, different electronic repositories were searched using multiple keywords. The current study identified 36 articles published between January 1999 to mid-2021 to conceptualize and summarize the research questions used in the study. Descriptive analysis along with pictorial representations have been used for better visualization of work.

This paper presents a thorough literature review of TOC in healthcare and identifies the evolution, current trends, tools used, nature of services chosen for application and research gaps and recommends future direction for research. A variety of motivating factors and benefits of TOC in healthcare are identified. Another key finding of this study is that almost all implementations listed in literature reported positive outcomes and substantial improvements in the performance of the healthcare unit chosen for study.

Practical implications

This paper provides valuable insight to researchers, practitioners and policymakers on the potential of TOC to improve quality of services, flow of patients, revenues, process efficiency and cost reduction in different health care settings. A number of findings and suggestions compiled in the paper from literature study can be used for diagnosing, learning and making substantial changes in healthcare. The methodologies used by different researchers were analysed and combined to propose a generic step by step procedure to apply TOC. This methodology will guide the practising managers about the appropriate tools of TOC for their specific need.

Social implications

Good health is always the first desire of all men and women around the globe. The global aim of healthcare is to quickly cure more patients and ensure healthier population both today and in future. This article will work as a foundation for future applications of TOC in healthcare and guide upcoming applications in the booming healthcare sector. The paper will help the healthcare managers in serving a greater number of patients with limited available resources.

Originality/value

This paper provides original collaborative work compiled by the authors. Since no comprehensive systematic review of TOC in healthcare has been reported earlier, this study would be a valuable asset for researchers in this field. A model has been presented that links various benefits with one another and clarifies the need to focus on process improvement which naturally results in these benefits. Similarly, a model has been presented to guide the users in implementation of TOC in healthcare.

  • Theory of constraints
  • Systematic literature review
  • Quality improvement

Datt, M. , Gupta, A. , Misra, S.K. and Gupta, M. (2024), "Theory of constraints in healthcare: a systematic literature review", International Journal of Quality & Reliability Management , Vol. ahead-of-print No. ahead-of-print. https://doi.org/10.1108/IJQRM-02-2022-0056

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  • © 2021

Literature Reviews

Modern Methods for Investigating Scientific and Technological Knowledge

  • Ana Paula Cardoso Ermel   ORCID: https://orcid.org/0000-0002-3874-9792 0 ,
  • D. P. Lacerda   ORCID: https://orcid.org/0000-0002-8011-3376 1 ,
  • Maria Isabel W. M. Morandi   ORCID: https://orcid.org/0000-0003-1337-1487 2 ,
  • Leandro Gauss   ORCID: https://orcid.org/0000-0001-5708-5912 3

Production and Systems Engineering, Universidade do Vale do Rio dos Sinos, São Leopoldo, Brazil

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  • Offers a new method of reviewing, analysing, and synthesising scientific literature into a systematic review
  • Presents computational tools to aid in this technique
  • Provides several illustrative examples of the methodology in action

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  • Table of contents

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Table of contents (10 chapters)

Front matter, introduction.

Ana Paula Cardoso Ermel, D. P. Lacerda, Maria Isabel W. M. Morandi, Leandro Gauss

Scientific Contributions of Systematic Literature Reviews: Fundamentals in Karl Popper

  • Systematic Literature Review
  • Literature Analysis
  • Literature Synthesis

Literature Grounded Theory (LGT)

Computational tools for literature review, analysis, and synthesis, what to consider in a systematic literature review: three examples from design science research, future perspectives, correction to: literature reviews.

This book begins by introducing the topic of knowledge in literature, including its scientific foundations. Due to the ever-increasing number of scientific publications, literature reviews are becoming more and more essential to stay updated.  Literature Reviews  describes an innovative system for creating systematic literature reviews, through reviewing, analyzing, and synthesizing scientific and technological literature.

It then discusses systematic literature reviews, content analysis, and literature synthesis separately, before presenting the methodology to combine them in one process. It showcases computational tools to aid in this technique and offers examples of the method in action. Finally, the book takes a new of future developments in the subject.

This book is of interest to graduate students, as well as researchers and academics, helping them to deepen insights and improve skills needed to conduct thorough literature reviews.

  • Literature Grounded Theory
  • Content Analysis
  • Meta-Analysis

Ana Paula Cardoso Ermel  holds a Master's degree in Production and Systems Engineering (UNISINOS) and a Bachelor's degree in Mechanical Engineering (URI). She has extensive knowledge in the implementation of quality management systems in the metalworking industry and holds the position of a permanent researcher at the Research Group on Modeling for Learning (GMAP | UNISINOS).

Daniel Pacheco Lacerda  holds a Doctoral degree in Production and Systems Engineering (COPPE/UFRJ) and Master’s and Bachelor’s degree in Business Administration (UNISINOS and SJT). He is a permanent researcher and associate professor in the Graduate Program of Production and Systems Engineering at UNISINOS University. In this same institution, he coordinates the Undergraduate Program of Production and Systems Engineering, and the Research Group on Modeling for Learning (GMAP | UNISINOS). Over the last ten years, he accumulated a list of academic recognitions within and outside Braziland has been recently identified as the 12th most prolific author on the Theory of Constraints worldwide. He has published numerous journal articles and eighteen books.

Maria Isabel Wolf Motta Morandi  holds Doctoral and Master’s degrees in Production and Systems Engineering (UNISINOS), a Bachelor’s degree in Chemistry Engineering (UFRGS), and Specializations in Management and Logistics (FGV). She is a permanent researcher and coordinator at the Research Group on Modeling for Learning (GMAP | UNISINOS) and an associate professor in the Undergraduate Program of Production and Systems Engineering at UNISINOS University. She also has 18 years of experience as an executive in the chemical industry, 13 years of experience in specialized consultancies for multinational companies, as well as extensive knowledge in applied research regarding systems thinking, systems dynamics, discrete-event simulation, and mathematical modeling.

Leandro Gauss  holdsa Master's degree in Production and Systems Engineering (UNISINOS) and a Bachelor's degree in Industrial Design and Mechanical Engineering (ULBRA). For more than seventeen years, he has been working on the design process of capital goods for manufacturing environments within and outside Brazil, and since 2018 integrates the Research Group on Modeling for Learning (GMAP | UNISINOS) as a permanent researcher. He is also an assistant professor in the Undergraduate Program of Production and Systems Engineering at UNISINOS University,  and in the last two years received awards for best article and dissertation at master's level from the two most renowned Production Engineering Associations in Brazil (ANPEPRO and ABEPRO).

Book Title : Literature Reviews

Book Subtitle : Modern Methods for Investigating Scientific and Technological Knowledge

Authors : Ana Paula Cardoso Ermel, D. P. Lacerda, Maria Isabel W. M. Morandi, Leandro Gauss

DOI : https://doi.org/10.1007/978-3-030-75722-9

Publisher : Springer Cham

eBook Packages : Education , Education (R0)

Copyright Information : The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021

Hardcover ISBN : 978-3-030-75721-2 Published: 31 August 2021

Softcover ISBN : 978-3-030-75724-3 Published: 01 September 2022

eBook ISBN : 978-3-030-75722-9 Published: 30 August 2021

Edition Number : 1

Number of Pages : XVII, 202

Number of Illustrations : 18 b/w illustrations, 73 illustrations in colour

Topics : Research Skills , Thesis and Dissertation , Research Methods in Education , Operations Research, Management Science , Operations Management

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Theory of Constraints – A Review

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ABSTRACT: Theory of Constraints is a systematic approach which identifies the weakest links in a system and focuses on its improvement there by improving the efficiency of the company overall. The growth of a company, whether service or production depends on a detailed understanding of its structure to survive global competition. Theory of Constraint plays an important role to withstand global competition as it stresses on efficiency at minimal cost. This literature review does an overall study of Theory of constraint and how it can be theoretically be applicable in any scenario be it Manufacturing or Service sectors

Related Papers

Erkam Guresen

Theory of constraints (TOC) is a technique that produces solutions for every kind of bottleneck in a short time. The philosophy of the theory is to determine the weaker part of the process chain and to eliminate this constraint point by taking action. After improvement, the next weaker part of the process chain is determined, and so on, for continuous improvement. The main goal is to apply improvement actions continuously to reach an excellent system structure. This paper describes how the five main steps of the theory of constraints were applied to eliminate waste at a supplier firm in Turkey..

theory of constraints a literature review

IJESRT Journal

Theory of constraints (TOC) is about thinking in logical and systematic way similar to the Plan do check act (PDCA) learning loop. It is not only about analyzing the causes and effect but also verifying basic assumptions, exploring alternatives and process improvement. The goal of TOC is to maximize the efficiency, profitability, quality of work. This paper includes basic theoretical information about TOC. It basically helps in problem solving & implementing the solution for the same. TOC is majorly applied in manufacturing sector, including distribution, marketing, project management, and accounting. In short, any situation involving change to a system TOC is applied

Management Decision

Togar Simatupang

Abstract: Product quality is merely a necessary condition for a firm to stay in the market. Yet most managers have not accepted this perceived reality. Highlights a self-reflective diagnosis used to uncover the real contribution of TQM in achieving the firm’s global goal. Also introduces the theory of constraints as a powerful tool to guide decision processes that could bring the firm closer to its goal. Keywords: Product quality, Production management, TQM

Tabish S. A.

Today, more than ever, change is inevitable in healthcare organizations to satisfying ever increasing expectations. Consumers expect higher service quality than the price they're willing to pay to acquire those products and services. More than ever, employees expect job security. Shareholders expect that today's investments will yield a higher rate of return over a shorter timeframe. Management is constantly pressured to keep costs under control. In the coming decade, we are likely to see a lot of focus directed towards applying management principles to solutions of complex social issues such as environmental sustainability, energy security, access to healthcare etc. This will also underline the need for increased interdisciplinary interaction and influence on business management. In light of today's competitive pressures and a rapidly changing environment, to not change is to give way to one's competitors. To improve means to change. We know that to improve means we must: provide services that solve customers' problems, release services consistent with market demand, reduce variability in our processes, have measurements that indicate success relative to achieving our goal and reward people for their contribution to change. Many organizations have concluded that a process of ongoing improvement is an absolute necessity. Theory of Constraints (TOC) brings a new dimension to management philosophy and provides an interesting challenge to the traditional ways of looking at an organization's profitability. Adopted within a wide variety of organizations and settings, it appears that organizations using TOC have determined that it can help them achieve a number of management objectives, including continuous improvement. Using TOC should be guided by the purpose or requirements it is necessary to meet. The goal of every organization is the same; optimize profitability by meeting customer requirements better than the competition. The TOC is both descriptive and prescriptive in nature that describes the cause of system constraints and provides guidance on how to resolve them. TOC provides a set of holistic processes and rules, all based on a systems approach that exploits the inherent simplicity within complex systems through focusing on the few "leverage points " as a way to synchronize the parts to achieve ongoing improvement in the performance of the system as a whole. This paper will clarify the concepts on the TOC and will facilitate its successful implementation in organisations with special reference to healthcare institutions.

International Journal of Production Research

Jan Riezebos

Minimizing production cost is a key element of the industry. To use resources efficiently, various concepts of operations management have been developed since the Industrial Revolution such as just in time, total quality control or lean manufacturing. Manufacturing shops –classified broadly as job, batch or flow shop according to process type, standardization level or quantity of production– continue to evolve by applying these various improvement approaches. Synchronous manufacturing and theory of constraints attempt to improve production processes by analyzing operational measures. They emphasize the importance of work in process levels and amend to have short term planning processes organized in accordance with the system constraints. This review tries to highlight the important connections between the drum-buffer-rope scheduling, single piece flow and operations-finance interface. ÜRETİM ÇİZELGELEMEDE DAVUL-TAMPO-İP YÖNTEMİ ÜZERİNE BİR LİTERATÜR İNCELEMESİ ÖZET Endüstride üretim maliyetlerinin minimizasyonu önemli bir yer tutmaktadır. Sanayi Devriminden günümüze dek, kaynakların etkin kullanımı için tam zamanında üretim, toplam kalite kontrolü veya yalın üretim gibi çeşitli üretim yönetimi teknikleri geliştirilmiştir. Üretim süreçlerine göre iş, parti veya akış tipi olarak sınıflandırılabilen atölyeler, bu farklı süreç iyileştirme yaklaşımlarını kullanarak evrilmeye devam etmektedir. Üretim süreçlerini operasyonel ölçütler ile inceleyerek geliştirmeye yönelik bir yaklaşım sunan senkronize üretim ve kısıtlar teorisi, ara stok seviyelerinin önemini vurgularken sistem kısıtları ile uyumlu, ve kısa vadeli planlama süreçlerinin gerekliliğine işaret etmektedir. Bu çalışmada senkronize üretim ve kısıtlar teorisinin çizelgeleme uygulaması olan davul-tampon-ip yöntemine ilişkin bir literatür incelemesi sunulmaktadır. Literatür incelemesi sonuçları davul-tampon-ip yöntemi ve parça akışı arasındaki ilişkiye işaret etmektedir. Anahtar sözcükler: Davul-tampon-ip, kısıtlar teorisi, üretim çizelgeleme

Surendra Patil

Operational Research Society of New Zealand 33rd Annual Conference, Auckland 1998

Vicky Mabin , Steven Balderstone

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Theory of Constraints (TOC)

THE BIG IDEA

What Is the Theory of Constraints?

The Theory of Constraints is a methodology for identifying the most important limiting factor (i.e., constraint) that stands in the way of achieving a goal and then systematically improving that constraint until it is no longer the limiting factor. In manufacturing, the constraint is often referred to as a bottleneck.

The Theory of Constraints takes a scientific approach to improvement. It hypothesizes that every complex system, including manufacturing processes, consists of multiple linked activities, one of which acts as a constraint upon the entire system (i.e., the constraint activity is the “weakest link in the chain”).

So what is the ultimate goal of most manufacturing companies? To make a profit – both in the short term and in the long term. The Theory of Constraints provides a powerful set of tools for helping to achieve that goal, including:

  • The Five Focusing Steps: a methodology for identifying and eliminating constraints
  • The Thinking Processes: tools for analyzing and resolving problems
  • Throughput Accounting: a method for measuring performance and guiding management decisions

Dr. Eliyahu Goldratt conceived the Theory of Constraints (TOC), and introduced it to a wide audience through his bestselling 1984 novel, “The Goal”. Since then, TOC has continued to evolve and develop, and today it is a significant factor within the world of management best practices.

One of the appealing characteristics of the Theory of Constraints is that it inherently prioritizes improvement activities. The top priority is always the current constraint. In environments where there is an urgent need to improve, TOC offers a highly focused methodology for creating rapid improvement.

A successful Theory of Constraints implementation will have the following benefits:

  • Increased Profit: the primary goal of TOC for most companies
  • Fast Improvement: a result of focusing all attention on one critical area – the system constraint
  • Improved Capacity: optimizing the constraint enables more product to be manufactured
  • Reduced Lead Times: optimizing the constraint results in smoother and faster product flow
  • Reduced Inventory: eliminating bottlenecks means there will be less work-in-process

XL HD Run Screen

Basics of TOC

Core concept.

The core concept of the Theory of Constraints is that every process has a single constraint and that total process throughput can only be improved when the constraint is improved. A very important corollary to this is that spending time optimizing non-constraints will not provide significant benefits; only improvements to the constraint will further the goal (achieving more profit).

Thus, TOC seeks to provide precise and sustained focus on improving the current constraint until it no longer limits throughput, at which point the focus moves to the next constraint. The underlying power of TOC flows from its ability to generate a tremendously strong focus towards a single goal (profit) and to removing the principal impediment (the constraint) to achieving more of that goal. In fact, Goldratt considers focus to be the essence of TOC.

The Five Focusing Steps

The Theory of Constraints provides a specific methodology for identifying and eliminating constraints, referred to as the Five Focusing Steps. As shown in the following diagram, it is a cyclical process.

Circle flowchart featuring the Five Focusing Steps of TOC.

The Five Focusing Steps are further described in the following table.

The Thinking Processes

The Theory of Constraints includes a sophisticated problem solving methodology called the Thinking Processes. The Thinking Processes are optimized for complex systems with many interdependencies (e.g., manufacturing lines). They are designed as scientific “cause and effect” tools, which strive to first identify the root causes of undesirable effects (referred to as UDEs), and then remove the UDEs without creating new ones.

The Thinking Processes are used to answer the following three questions, which are essential to TOC:

  • What needs to be changed?
  • What should it be changed to?
  • What actions will cause the change?

Examples of tools that have been formalized as part of the Thinking Processes include:

Throughput Accounting

Throughput Accounting is an alternative accounting methodology that attempts to eliminate harmful distortions introduced from traditional accounting practices – distortions that promote behaviors contrary to the goal of increasing profit in the long term.

In traditional accounting, inventory is an asset (in theory, it can be converted to cash by selling it). This often drives undesirable behavior at companies – manufacturing items that are not truly needed. Accumulating inventory inflates assets and generates a “paper profit” based on inventory that may or may not ever be sold (e.g., due to obsolescence) and that incurs cost as it sits in storage. The Theory of Constraints, on the other hand, considers inventory to be a liability – inventory ties up cash that could be used more productively elsewhere.

In traditional accounting, there is also a very strong emphasis on cutting expenses. The Theory of Constraints, on the other hand, considers cutting expenses to be of much less importance than increasing throughput. Cutting expenses is limited by reaching zero expenses, whereas increasing throughput has no such limitations.

These and other conflicts result in the Theory of Constraints emphasizing Throughput Accounting, which uses as its core measures: Throughput, Investment, and Operating Expense.

In addition, Throughput Accounting has four key derived measures: Net Profit, Return on Investment, Productivity, and Investment Turns.

Net Profit = Throughput − Operating Expenses

Return on Investment = Net Profit / Investment

Productivity = Throughput / Operating Expenses

Investment Turns = Throughput / Investment

In general, management decisions are guided by their effect on achieving the following improvements (in order of priority):

  • Will Throughput be increased?
  • Will Investment be reduced?
  • Will Operating Expenses be reduced?

The strongest emphasis (by far) is on increasing Throughput. In essence, TOC is saying to focus less on cutting expenses (Investment and Operating Expenses) and focus more on building sales (Throughput).

Drum-Buffer-Rope

Drum-Buffer-Rope (DBR) is a method of synchronizing production to the constraint while minimizing inventory and work-in-process.

The “Drum” is the constraint. The speed at which the constraint runs sets the “beat” for the process and determines total throughput.

The “Buffer” is the level of inventory needed to maintain consistent production. It ensures that brief interruptions and fluctuations in non-constraints do not affect the constraint. Buffers represent time; the amount of time (usually measured in hours) that work-in-process should arrive in advance of being used to ensure steady operation of the protected resource. The more variation there is in the process the larger the buffers need to be. An alternative to large buffer inventories is sprint capacity (intentional overcapacity) at non-constraints. Typically, there are two buffers:

  • Constraint Buffer: immediately before the constraint; protects the constraint
  • Customer Buffer: at the very end of the process; protects the shipping schedule

The “Rope” is a signal generated by the constraint indicating that some amount of inventory has been consumed. This in turn triggers an identically sized release of inventory into the process. The role of the rope is to maintain throughput without creating an accumulation of excess inventory.

The Nature of Constraints

What are constraints.

Constraints are anything that prevents the organization from making progress towards its goal. In manufacturing processes, constraints are often referred to as bottlenecks. Interestingly, constraints can take many forms other than equipment. There are differing opinions on how to best categorize constraints; a common approach is shown in the following table.

There are also differing opinions on whether a system can have more than one constraint. The conventional wisdom is that most systems have one constraint, and occasionally a system may have two or three constraints.

In manufacturing plants where a mix of products is produced, it is possible for each product to take a unique manufacturing path and the constraint may “move” depending on the path taken. This environment can be modeled as multiple systems – one for each unique manufacturing path.

Policy Constraints

Policy constraints deserve special mention. It may come as a surprise that the most common form of constraint (by far) is the policy constraint.

Since policy constraints often stem from long-established and widely accepted policies, they can be particularly difficult to identify and even harder to overcome. It is typically much easier for an external party to identify policy constraints, since an external party is less likely to take existing policies for granted.

When a policy constraint is associated with a firmly entrenched paradigm (e.g., “we must always keep our equipment running to lower the manufacturing cost per piece”), a significant investment in training and coaching is likely to be required to change the paradigm and eliminate the constraint.

Policy constraints are not addressed through application of the Five Focusing Steps. Instead, the three questions discussed earlier in the Thinking Processes section are applied:

The Thinking Processes are designed to effectively work through these questions and resolve conflicts that may arise from changing existing policies.

TOC Example

An excellent way to deepen your understanding of the Theory of Constraints is to walk through a simple implementation example. In this example, the Five Focusing Steps are used to identify and eliminate an equipment constraint (i.e., bottleneck) in the manufacturing process.

Step One – Identify the Constraint

In this step, the manufacturing process is reviewed to identify the constraint. A simple but often effective technique is to literally walk through the manufacturing process looking for indications of the constraint.

The deliverable for this step is the identification of the single piece of equipment that is constraining process throughput.

Step Two – Exploit the Constraint

In this step, the objective is to make the most of what you have – maximize throughput of the constraint using currently available resources. The line between exploiting the constraint (this step) and elevating the constraint (the fourth step) is not always clear. This step focuses on quick wins and rapid relief; leaving more complex and substantive changes for later.

The deliverable for this step is improved utilization of the constraint, which in turn will result in improved throughput for the process. If the actions taken in this step “break” the constraint (i.e., the constraint moves) jump ahead to Step Five. Otherwise, continue to Step Three.

Step Three – Subordinate and Synchronize to the Constraint

In this step, the focus is on non-constraint equipment. The primary objective is to support the needs of the constraint (i.e., subordinate to the constraint). Efficiency of non-constraint equipment is a secondary concern as long as constraint operation is not adversely impacted.

By definition, all non-constraint equipment has some degree of excess capacity. This excess capacity is a virtue, as it enables smoother operation of the constraint. The manufacturing process is purposely unbalanced:

Some useful techniques for this step include:

The deliverable for this step is fewer instances of constraint operation being stopped by upstream or downstream equipment, which in turn results in improved throughput for the process. If the actions taken in this step “break” the constraint (i.e., the constraint moves) jump ahead to Step Five. Otherwise, continue to Step Four.

Step Four – Elevate Performance of the Constraint

In this step, more substantive changes are implemented to “break” the constraint. These changes may necessitate a significant investment of time and/or money (e.g., adding equipment or hiring more staff). The key is to ensure that all such investments are evaluated for effectiveness (preferably using Throughput Accounting metrics).

The deliverable for this step is a significant enough performance improvement to break the constraint (i.e., move the constraint elsewhere).

Step Five – Repeat the Process

In this step, the objective is to ensure that the Five Focusing Steps are not implemented as a one-off improvement project. Instead, they should be implemented as a continuous improvement process.

This step also includes a caution…beware of inertia. Remain vigilant and ensure that improvement is ongoing and continuous. The Five Focusing Steps are kind of like “Whac-A-Mole”…pound one constraint down and then move right on to the next!

Integrating with Lean

Contrasting theory of constraints and lean manufacturing.

The Theory of Constraints and Lean Manufacturing are both systematic methods for improving manufacturing effectiveness. However, they have very different approaches:

  • The Theory of Constraints focuses on identifying and removing constraints that limit throughput. Therefore, successful application tends to increase manufacturing capacity.
  • Lean Manufacturing focuses on eliminating waste from the manufacturing process. Therefore, successful application tends to reduce manufacturing costs.

Both methodologies have a strong customer focus and are capable of transforming companies to be faster, stronger, and more agile. Nonetheless, there are significant differences, as highlighted in the following table.

From the perspective of the Theory of Constraints, it is more practical and less expensive to maintain a degree of excess capacity for non-constraints (i.e., an intentionally unbalanced line) than to try to eliminate all sources of variation (which is necessary to efficiently operate a balanced line). Eliminating variation is still desirable in TOC; it is simply given less attention than improving throughput.

Combining Theory of Constraints and Lean Manufacturing

One of the most powerful aspects of the Theory of Constraints is its laser-like focus on improving the constraint. While Lean Manufacturing can be focused, more typically it is implemented as a broad-spectrum tool.

In the real world, there is always a need to compromise, since all companies have finite resources. Not every aspect of every process is truly worth optimizing, and not all waste is truly worth eliminating. In this light, the Theory of Constraints can serve as a highly effective mechanism for prioritizing improvement projects, while Lean Manufacturing can provide a rich toolbox of improvement techniques. The result – manufacturing effectiveness is significantly increased by eliminating waste from the parts of the system that are the largest constraints on opportunity and profitability.

While Lean Manufacturing tools and techniques are primarily applied to the constraint, they can also be applied to equipment that is subordinated to the constraint (e.g., to equipment that starves or blocks the constraint; to post-constraint equipment that causes quality losses).

The remainder of this section describes how to apply a range of Lean Manufacturing tools and techniques to the Five Focusing Steps.

Process chart for applying the Five Focusing Steps of TOC with Lean Manufacturing tools and techniques.

Applying Lean Tools to “Identify the Constraint”

Lean Manufacturing provides an excellent tool for visually mapping the flow of production (Value Stream Mapping) as well as a philosophy that promotes spending time on the plant floor (Gemba).

Applying Lean Tools to “Exploit the Constraint”

Lean Manufacturing strongly supports the idea of making the most of what you have, which is also the underlying theme for exploiting the constraint. For example, lean teaches to organize the work area (5S), to motivate and empower employees (Visual Factory/Andon), to capture best practices (Standardized Work), and to brainstorm incremental ideas for improvement ( Kaizen ).

Applying Lean Tools to “Subordinate to the Constraint”

Lean Manufacturing techniques for regulating flow (Kanban) and synchronizing automated lines (Line Control) can be applied towards subordinating and synchronizing to the constraint.

Applying Lean Tools to “Elevate the Constraint”

Lean Manufacturing techniques for proactively maintaining equipment ( TPM ), dramatically reducing changeover times ( SMED ), building defect detection and prevention into production processes (Poka-Yoke), and partially automating equipment (Jidoka) all have direct application when elevating the constraint. TPM and SMED can also be viewed as exploitation techniques (maximizing throughput using currently available resources); however, they are fairly complex and are likely to benefit from working with outside experts.

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VIDEO

  1. Chapter two

  2. The Theory of constraint

  3. Research Methods

  4. Approaches , Analysis And Sources Of Literature Review ( RESEARCH METHODOLOGY AND IPR)

  5. How To Decide WHAT To Learn (Theory Of Constraints)

  6. What is literature review?

COMMENTS

  1. Theory of Constraints: A Literature Review

    Literature Review Theory of constraints has a wide range of implementation scale. Theory can be applied in production, logistics, supply chain, distribution, project management, accounting, research and development, sales and marketing and so on. As the main idea is that every system has at least one weakest point, in literature there are lots ...

  2. (PDF) Theory of Constraints: A Literature Review

    Purpose Theory of Constraints (TOC), though a well-established process improvement methodology in manufacturing, is still a novel philosophy for healthcare and an exhaustive review of literature ...

  3. Theory of Constraints: A Literature Review

    Theory of Constraints: A systematic review from the management context. The results establish that the investigative tendencies of the TOC in the different productive sectors and its application in business management environments establish that its application increases the efficiency of the process.

  4. Outcomes of managing healthcare services using the Theory of

    ABSTRACT. Despite ever-increasing resources devoted to healthcare, lack of capacity and timeliness are still chronic problems worldwide. This systematic review aims to present an overview of the Theory of Constraints (TOC) implementations in healthcare services and their outcomes. We analysed 42 TOC implementations (15 full-text articles, 12 ...

  5. Systematic Literature Review of Theory of Constraints

    The methodology of systematic literature review was used in the article. Bibliometric research was conducted on the basis of four full-text databases of EBSCO, Emerald, ScienceDirect and SpringerLink from the years 2013-2017. Four main research directions related to the Theory of Limitations have been identified: (1) practical use of the TOC ...

  6. Theory of constraints in healthcare: a systematic literature review

    Purpose. Theory of Constraints (TOC), though a well-established process improvement methodology in manufacturing, is still a novel philosophy for healthcare and an exhaustive review of literature is needed to summarize the key findings of various researchers. Such a review can provide a direction to the researchers and academicians interested ...

  7. Theory of constraints: review and bibliometric analysis

    This paper presents a bibliometric analysis of the Theory of Constraints (TOC) research i.e. a total of 1009 journal articles published since 1984. From a bibliometric point of view, the state of the art was mapped and research gaps in the scientific literature identified, creating opportunities for future research.

  8. (PDF) A Review of Goldratt's Theory of Constraints (TOC) -- lessons

    A Review of Goldratt's Theory of Constraints (TOC) -- lessons from the international literature. September 1998; Authors: Steven J. Balderstone. ... Based on the literature, the authors present ...

  9. [PDF] Theory of Constraints: A systematic review from the management

    The results establish that the investigative tendencies of the TOC in the different productive sectors and its application in business management environments establish that its application increases the efficiency of the process. : The investigations began with the drum-buffer-rope architecture, as the basis of the Theory of Constraints (TOC). Currently, TOC has been applied in various ...

  10. Theory of constraints in healthcare: a systematic literature review

    DOI: 10.1108/ijqrm-02-2022-0056 Corpus ID: 267998661; Theory of constraints in healthcare: a systematic literature review @article{Datt2024TheoryOC, title={Theory of constraints in healthcare: a systematic literature review}, author={Mohit Datt and Ajay Gupta and Sushendra Kumar Misra and Mahesh Gupta}, journal={International Journal of Quality \& Reliability Management}, year={2024}, url ...

  11. PDF Theory of Constraints: A Literature Review

    2. Literature Review. Theory of constraints has a wide range of implementation scale. Theory can be applied in production, logistics, supply chain, distribution, project management, accounting ...

  12. (PDF) Theory of Constraints: A systematic review from the management

    Study design The research is classified as a systematic literature review of the Theory of Constraints, exploratory and descriptive. It is based on a bibliometric (Spinak, 1996, López, 1996, Ferreiro, 1995) and content (Bardin, 2002) analysis. ... Theory of Constraints: A Literature Review. Procedia - Social and Behavioral Sciences, 150, 930 ...

  13. The World of the Theory of Constraints A Review of the ...

    The Theory of Constraints (TOC) - as developed by Dr. Eliyahu Goldratt - has seen a rapid expansion since the publication of his book, The Goal. As with most fast growing areas, you can quickly feel out of touch with new developments. The World of the Theory of Constraints provides a summary of recently published research on TOC. The authors explored databases, and sought out papers and books ...

  14. Theory of constraints in healthcare: a systematic literature review

    Purpose Theory of Constraints (TOC), though a well-established process improvement methodology in manufacturing, is still a novel philosophy for healthcare and an exhaustive review of literature ...

  15. Full article: Using the theory of constraints' processes of ongoing

    Theory of Constraints has been used in many different environments including manufacturing, supply chain, retailing, government, services, military, education, ... In this literature review, the fourteen major problems were identified; four related to schedule design ...

  16. PDF A Review of Goldratt's Theory of Constraints (TOC)

    Hence our mission two years ago was to conduct a literature search to identify recent works (mostly post 1990). This search has culminated in an annotated bibliography, which is to be published shortly by North River Press [23]. Alongside this literature research grew a Masters thesis, pulling all this material together, both the theory and the ...

  17. Literature Reviews: Modern Methods for Investigating Scientific and

    What to Consider in a Systematic Literature Review: Three Examples from Design Science Research. Ana Paula Cardoso Ermel, D. P. Lacerda, Maria Isabel W. M. Morandi, Leandro Gauss; ... academic recognitions within and outside Braziland has been recently identified as the 12th most prolific author on the Theory of Constraints worldwide. He has ...

  18. Outcomes of managing healthcare services using the Theory of

    The Theory of Constraints (TOC) is also one of those disruptive management philosophies that emerged late in the last century. ... In 1998, Mabin and Balderstone (Citation 2003) conducted a literature review to assess the outcomes provided by TOC applications. This study involved 77 different companies across many different purposes (for-profit ...

  19. The World of the Theory of Constraints

    The World of the Theory of Constraints provides a summary of recently published research on TOC. The authors explored databases, and sought out papers and books drawing on as wide a range as possible. Aside from the works by Dr. Goldratt himself, the authors focus on items published since 1990, highlighting the most recent developments in TOC.

  20. (PDF) Theory of Constraints: A systematic review from the management

    The research is classified as a systematic literature review of the Theory of Constraints, exploratory and descriptive. It is based on a bibliometric (Spinak, 1996, López, 1996, F erreiro,

  21. (PDF) Theory of Constraints

    This literature review does an overall study of Theory of constraint and how it can be theoretically be applicable in any scenario be it Manufacturing or Service sectors. ... Theory of Constraints - A Review Dion Chacko1*,V Shantha2,Milan S Kumar3Prajwal M Javli4,Sreenand S5 1,2,3,4,5 Department Of Mechanical Engineering (IEM), Sir M ...

  22. A Review of Goldratt ' s Theory of Constraints ( TOC )

    Abstract The two authors are finalising the first comprehensive bibliography on the Theory of Constraints (TOC)[23] which is to be published by North River Press, the publishers of several works on TOC, most notably Eli Goldratt's seminal works [11-17], such as The Goal, It's Not Luck, and Critical Chain. Based on our extensive search of the literature, this talk will draw on examples of ...

  23. Theory of Constraints (TOC)

    The Theory of Constraints is a methodology for identifying the most important limiting factor (i.e., constraint) that stands in the way of achieving a goal and then systematically improving that constraint until it is no longer the limiting factor. In manufacturing, the constraint is often referred to as a bottleneck.