1 Introduction

This Element focuses on Lean, one of the most widely used improvement approaches.Reference Henrique and Filho¹ The term ‘Lean’ was first coined in 1988 by KrafcikReference Krafcik² to explain the success of the Toyota Production System in simultaneously achieving high levels of productivity and quality in Japanese car production. Womack et al.’s 1990 book The Machine That Changed the WorldReference Womack, Jones and Roos³ is often seen as having popularised Lean. Womack and Jones’ text Lean Thinking,Reference Womack and Jones⁴ published in 1996, was particularly influential in emphasising that a key feature of Lean is a focus on eliminating waste – defined as any part of a process that adds time, effort or cost, but no direct value. Lean Thinking proposed five key principles (Box 1), based on the underlying assumption that organisations are made up of processes, and that using these principles in a stepwise and sequential way can add value, reduce waste, and continuously improve in an ever-repeating process.Reference Radnor, Holweg and Waring⁵

A large volume of academic and practitioner writing has emerged since the 1990s, but – despite its widespread use – no single consensus on a definition of Lean has emerged.Reference Shah and Ward^6, Reference Samuel, Found and Williams⁷ Generally speaking, however, Lean comprises a ‘philosophy’ of ideas and principles and a set of tools, techniques, and practices aimed at reconfiguring organisational processes to reduce waste and enhance productivity. It involves the systematic and rigorous application of a range of specialist improvement tools, techniques, and frameworks,Reference Radnor^8, Reference Ogden and Moncy^9, Reference Hines and Harrison¹⁰ coupled with a culture of continuous improvement.Reference Langley, Nolan, Norman and Provost¹¹ Accordingly, one useful definition is:

Blended approaches that combine Lean with other improvement approaches have also appeared. Among the most popular of these is Lean Six Sigma:Reference Henrique and Filho^1, Reference Vaishnavi and Suresh^12, Reference Kuiper, Lee and van Ham¹³ a hybrid of Lean and Six Sigma. Six Sigma is a business process improvement methodology, characterised by a set of statistical and management tools (e.g. cause-and-effect diagrams, Pareto analysis, process maps, and data collection). A prominent feature of Six Sigma is its use of ‘projects’, typically using a methodology known as DMAIC (Define, Measure, Analyse, Improve, and Control). It has been argued that combining Lean and Six Sigma offers a powerful means of improving productivity and efficiency by reducing waste and variation.Reference George¹⁴

2 Lean in Action

Lean has been widely used in healthcare, particularly in acute care (hospitals), to address issues such as waiting times, workflow,Reference Hynes, Murray and Murra^29, Reference Godley and Jenkins³⁰ and operational efficiencies.Reference Samanta and Gurumurthy^31, Reference Devi, Shukla and Bhat^32, Reference Molla, Warren and Stewart³³ Examples of Lean Six Sigma are also reported in the literature,Reference Samanta and Gurumurthy³¹ motivated by concerns such as improving patient safety, increasing operational efficiency, and reducing financial costs.Reference McDermott, Antony and Bhat³⁴

In this section, we offer two case studies of attempts to implement Lean at scale in the National Health Service (NHS) in the UK: the Productive Ward Programme and the Virginia Mason Production System.

3 Implementing Lean

Despite the enthusiasm for Lean, it is clear that its implementation in healthcare is not straightforward.^{Reference Parkhi54–}Reference Deblois and Lepanto⁶³ One challenge for Lean is that its terminology, including Japanese terms for concepts such as muda (waste) and gemba (real place), is not always easy to grasp. A deeper problem, perhaps, is the potential for dissonance between the world of manufacturing, based on highly repetitive, automated production of repeatable items, and the human-centred world of healthcare.Reference Spear⁶⁴ Also challenging is the perceived link between Lean and efforts to reduce resources and staff,Reference Adler, Goldoftas and Levine⁶⁵ leading to some reluctance to use the term Lean. There has also been a corresponding emergence of other terms, such as Model of Improvement and Virginia Mason Production System, that often share much in common with Lean but are not called Lean.

A second challenge is that implementing Lean may need long-term organisational policies and strategic planning; a switch from a hierarchical culture to an improvement culture that supports workforce stability, team leadership and decentralised decision-making; and recognition of the socio-technical nature of healthcare work.Reference Marsilio^61, Reference Spear⁶⁴ The available evidence suggests that Lean in healthcare needs to integrate technical elements (such as tools and workplace layout) and social elements (such as teamwork, organisational culture, employee learning, and participation).Reference Marsilio⁶¹ Sustainability also requires Lean to be viewed as more than a set of projects, but instead as an ongoing way of approaching work and thinking about systems.Reference Radnor, Holweg and Waring^5, Reference Young and McClean^66, Reference Joosten, Bongers and Janssen⁶⁷

In practice, there is a tendency to give significant attention to Lean tools and techniquesReference Marsilio^61, Reference Reed and Card⁶⁸ but reducing Lean to a toolbox risks reducing recognition of the need for the cultural change and leadership behaviours required to deliver improvement.Reference Camuffo and Fabrizio⁶⁹ Many would argue that the tools and techniques have dominated the implementation discussion over the important aspect of behavioural and culture change.^{Reference Stone70–}Reference Radnor and Osborne⁷³ Joosten et al.,Reference Joosten, Bongers and Janssen⁶⁷ for example, report that when the emphasis is process-oriented, little attention may be given to context and the human side of improvement. Even when the emphasis is on tools and techniques, fidelity of implementation is often problematic.Reference Radnor and Osborne⁷³

A further challenge lies in the level of senior leadership and management commitment required to support the strategic alignment of organisations with Lean practices and philosophies, as illustrated by both the Productive Ward and Virginia Mason case studies. It is noted by van Elp et al.Reference Van Elp, Roemeling and Aij²⁵ that the role of management is a key ingredient for improvement in healthcare, but, while the concept of Lean leadership is discussed in the literature,Reference Ward, Liker, Cristiano and Sobeck⁷⁴ understanding of how different leadership styles impact on Lean and improvement more generally is limited, especially in relation to leadership behaviours.Reference Poksinska⁷⁵ A multi-case, multi-methods study in the Netherlands found that a hybrid leadership approach is likely to be required in order for Lean implementation to be successful. This approach combines leadership behaviours that are transactional (based on extrinsic rewards and give-and-take relationships) and transformational (inspiring others to buy in to a strategic vision and go beyond self-interest) and appeared to promote the improvement capability of teams.Reference Walley and Jennison-Phillips¹⁸

Further, as the two case studies demonstrate, Lean and other improvement approaches rely heavily on staff involvement and commitment.Reference Tlapa, Zepeda-Lugo and Tortorella^76, Reference Hines, Taylor and Walsh⁷⁷ Disengagement of staff has been reported as the biggest reason for Lean failure,Reference Albanese, Aaby and Platchek⁷⁸ but monitoring and enhancing of Lean team experience and satisfaction are often overlooked.Reference Stone⁷⁰ McCann et al.’s three-year studyReference Albanese, Aaby and Platchek⁷⁸ of the introduction of Lean in a large UK hospital found initial enthusiasm for the approach, especially at ward level, but scepticism and reservations about the approach later appeared. Practical barriers included heavy workloads, insufficient resources, and not being able to take staff away from their clinical duties to attend meetings and training. Many of the improvement interventions were superficial, both in relation to their impact and their connection to Lean, and there was sporadic use of improvement tools that were labelled as Lean but might not have been. Limited progress ‘led to Lean appearing weak, pliable and superficial’.Reference McCann, Hassard, Granter and Hyde⁷⁹

A further challenge for Lean implementation is the tendency for efforts to focus on specific departments (e.g. accident and emergency) rather than the entire healthcare organisation.Reference Tlapa, Zepeda-Lugo and Tortorella^76, Reference Sommer and Blumenthal⁸⁰ Small, localised improvements may help organisations to maintain momentum, but there is a risk of sub-optimising other parts of the wider health and social care system.Reference Ronen, Pliskin and Pass⁸¹ Even within single organisations, failing to take a systems improvement approach may mean that an improvement in one area can simply move an issue (e.g. waiting times) elsewhere.Reference Leite, Williams, Radnor and Bateman⁸²

Linked to these kinds of challenges, Lean and other improvement approaches may be adopted in healthcare in a piecemeal fashion before being abandoned in favour of the latest initiative without allowing time to embed.Reference Proudlove, Moxham and Boaden^83, Reference Jabbal⁸⁴ The ‘readiness’ of the organisation not only to implement but also to maintain their adopted approach is crucial.Reference Leite, Bateman and Radnor^85, Reference Williams and Radnor⁸⁶ Some scholars advocate that understanding the local context is crucial when implementing Lean in healthcare.Reference Parkhi^54, Reference Chassin⁸⁷ Yet important attributes of context are often poorly defined, and current knowledge of the role of contextual factors in implementing new practices and methods such as Lean is limited.Reference Burgess and Richmond^49, Reference Rangachari^88, Reference Reponen, Rundall and Shortell⁸⁹

4 Critiques of Lean in Healthcare

Lean is widely discussed and deployed in health services globally and enjoys widespread engagement, belief, support, and commitment. However, it is also clear that it faces a number of challenges. Some of these relate to the lack of a robust evidence base for Lean. By 2009, Brandão de Souza’s reviewReference De Souza L⁹⁰ had identified over 90 academic articles from ten different countries, which classified studies into three areas:

• Manufacturing-type cases – improvements to manufacturing or process environments, such as radiology or pharmacy.

• Support services cases – improvements in areas such as IT, human resources, and finance.

• Patient flow cases – improvements to length of stay and waiting list initiatives.

This review identified reports of improvements in areas such as waiting times and reduction of errors and costs,Reference Silvester, Lendon, Bevan, Steyn and Walley⁹¹ as well as intangible benefits such as increased employee motivation.Reference Radnor, Holweg and Waring⁵ Other studies since then have documented the continued popularity of Lean in healthcare,Reference Jiang, Sousa, Moreira and Amaro⁹² in areas as diverse as surgery, emergency departments, mental health, and pharmacy. Some reviews continue to report improvements arising from the use of Lean,Reference Kotter⁴³ including reductions in errors or defects and variability, better physical layout, and the optimisation of resource allocation and inventory.Reference Santos, Reis and Souza^62, Reference Abdallah and Alkhaldi⁹³ Reduction in time (e.g. length of stay and release of test results) is the most reported benefit.Reference Mousavi Isfahani, Tourani and Seyedin^94, Reference Vest and Gamm^95, Reference Woodnutt⁹⁶

However, much of the research on Lean in health settings is characterised by poor quality study designs. There appears to be an overreliance on single site, pathways, or service case studies. Robust and well-structured evaluations are rare, tending to be missing altogether or done too early. Moraros et al.’s reviewReference Moraros, Lemstra and Nwankwo⁵⁷ of 22 articles found that none used high-quality experimental study designs such as randomised control trials or quasi-experimental study designs (e.g. prospective longitudinal cohorts). Only four reported on health outcomes, and just one of these found a statistically significant impact of implementing Lean. A total of fifteen studies focusing on process outcomes covered areas such as waiting times, patient flow, and workplace engagement, but only two found a statistically significant positive effect of Lean. None of the 22 studies reported on the financial costs.

The lack of longitudinal studies has further limited insight.Reference Mazzocato, Thor and Backman^97, Reference Stentoft and Freytag⁹⁸ Lean interventions are often reviewed over a period of 1–2 years,Reference Fillingham⁹⁹ potentially offering little understanding of the impact and sustainability of Lean over the longer term.Reference Jabbal^84, Reference Mazzocato, Thor and Backman^97, Reference Hallam^100, Reference Roemeling, Land and Ahaus¹⁰¹ As the Productive Ward case study illustrates, many organisations report short-term gains when implementing Lean, but more widespread and sustained improvements may be elusive. Similarly, a review of Lean Six Sigma studies showed that only 20 per cent of studies reported on the long-term (1–3 years) effects of the improvement. To help evidence the sustainability of these studies, a longitudinal post-intervention period is required.Reference Samanta and Gurumurthy³¹ There is a clear need to use methods other than single-case studies, such as pre- and post-interventions and ethnographic studies.Reference Santos, Reis and Souza⁶²

The ability to show the strategic and whole-systems impact of Lean and Lean Six SigmaReference Samanta and Gurumurthy³¹ has been especially lacking, linked to the tendency for implementation to be pragmatic, patchy, and fragmented.Reference Young and McClean⁶⁶ A Lean healthcare system should operate as a cohesive and well-connected system rather than as a collection of independent facilities.Reference Graban¹⁰² However, Burgess and Radnor’sReference Burgess and Radnor²² evaluation of Lean in English NHS trusts found that implementation tended to be isolated rather than system-wide, leading to a disjointed approach. The problems stem from how healthcare organisations are functionally organised, often characterised by fragmentation,Reference Bateman, Lethbridge, Bell, Warren and Schroeder¹⁰³ but also how implementation tends to be approached.

A perhaps fundamental challenge regarding the evidence base is that, although understanding the value of the ‘customer’ (patient) is central to the principles of Lean in healthcare, there is limited research to show how the value or the voice of the customer/patientReference Found and Harrison¹⁰⁴ is captured and used within Lean and associated approaches,Reference Radnor and Osborne⁷³ and evidence of direct benefit for patients has been slow to appear. Similarly, how Lean integrates with the person-centred and co-production agenda is also unclear. Although both synergies and divergences have been noted between Lean Six Sigma and person-centred care,Reference Teeling, Dewing and Baldie¹⁰⁵ further research is required to identify where and how Lean and associated techniques can enhance patient care and transform person-centred cultures.

More well-designed, applied studies using the principles of evidence-based medicine are needed to assure the quality and credibility of the evidence base for Lean. Bateman reminds us that interdisciplinary research can strengthen most fields of enquiry, especially in improving and managing healthcare quality, but also emphasises the need for an appreciation of the idiosyncrasies of the sector, including professional dynamics.Reference Bateman¹⁰⁶ Learning from other disciplines outside healthcare will help us to continue to progress understanding of healthcare improvement. Theory-based evaluations are likely to be helpful, as illustrated by an evaluation of a six-year single Lean case study that used Programme Theory to help understand and capture cultural, individual, and team influences on the Lean interventions.Reference Lindsay and Aitken¹⁰⁷ Well-designed studies should also clearly identify what adaptations are needed to accommodate the nuances and intricacies of our healthcare systems. These studies would benefit from the discipline of operations management but also other theoretical lenses (such as psychology, sociology, and design science) to understand the complexity and interdependence of healthcare settings. Longitudinal studies, especially post-intervention, are needed to evidence the sustainability of improvements achieved and to identify when outcomes start to wane. Approaches such as simulationReference Hallam¹⁰⁰ may help in developing systems-level evaluation. Benefits realisation frameworks based on quality, time, and costReference Graban¹⁰² would help to create the evidence base and give confidence in the healthcare improvements achieved through utilising a Lean-based approach, as many healthcare professionals make a diagnosis through data.

Finally, much of the Lean and the Lean Six Sigma literature focuses on hospitals and acute healthcare. More studies are needed to evidence how Lean and Lean Six Sigma are implemented within community and primary care settings. Further research into Lean and associated techniques is also needed for integrated networks that include social care.

5 Conclusions

In this Element, we have both acknowledged the popularity of Lean in healthcare and reported on its mixed results using case studies and the broader literature. It is clear that a strong evidence base of well-designed studies is imperative to advance the implementation of Lean and associated process improvement techniques in healthcare. Future research should use study designs that are regarded as powerful from the perspective of evidence-based medicine (e.g. including well-designed observational, experimental, and quasi-experimental designs with a longitudinal emphasis). However, research should also draw more widely on other disciplines (such as psychology, sociology, medicine), as well as industrial and operational management, given the need to investigate the sociotechnical elements required for the implementation of Lean and to develop the necessary conceptual model for further testing.Reference Santos, Reis and Souza⁶² This should also extend to research into how Lean and Lean Six Sigma can be used with new emerging trends and technologies (such as artificial intelligence, automation, and robotics) as they are introduced and embedded within our healthcare systems.Reference McDermott, Antony and Bhat³⁴ Similarly, recognising how Lean can be integrated with other established improvement models, approaches, and frameworks would be useful. Learning from the negative impacts of implementing Lean also needs to be analysed and reported to advance our understanding of Lean in healthcare.Reference Santos, Reis and Souza⁶²

6 Further Reading

• GrabanReference Graban¹⁰² – provides a practical insight to the implementation of Lean in a hospital setting.

• BichenoReference Bicheno¹⁰⁸ – explains how various Lean tools can be used within service organisations.

• RadnorReference Radnor⁸– compares key approaches, such as Lean and Six Sigma.

• Radnor et al.Reference Radnor, Bateman and Esain¹⁰⁹ – provide case chapters on various aspects of improving healthcare operations, including a Lean case study.