Keywords
Rehabilitation, Intervention, Complexity, Complex adaptive system, Service delivery, Scoping review, Study protocol
Complexity is used to describe patient characteristics, service delivery challenges, and system-level factors, yet there is limited clarity regarding how it is defined, conceptualised, operationalised, and applied across rehabilitation contexts. This lack of conceptual coherence presents challenges for the design, organisation, and delivery of rehabilitation services within increasingly integrated health and social care systems.
This review aims to examine how complexity is conceptualised, defined, and operationalised in the international rehabilitation literature at the level of the person, service, and health and social care system. It will also explore how varying conceptualisations of complexity influence the design, delivery, organisation, and resourcing of rehabilitation services, pathways, and models of care.
A scoping review methodology will be employed to map the breadth and nature of the evidence. Studies published in English since 2015 examining complexity in rehabilitation populations, services, or systems will be included. Eligible sources will include any study design, population, and setting. Studies must explicitly conceptualise, define, or operationalise complexity at the level of the person, service, or health and social care system. The search will cover five academic databases and grey literature sources. The review will follow updated Joanna Briggs Institute guidance, aligned with the PRISMA-ScR framework. Data will be charted and synthesised to identify patterns across contexts and levels.
The review will map the extent and scope of conceptualisations of complexity and examine how these shape rehabilitation service delivery and organisation. It will also identify gaps in the literature, particularly in relation to multi-level understandings of complexity.
Findings will contribute to greater conceptual clarity and inform future research, policy, and practice in the development of responsive, integrated rehabilitation systems.
Rehabilitation, Intervention, Complexity, Complex adaptive system, Service delivery, Scoping review, Study protocol
Rehabilitation services around the world, in response to population demographic change, are increasingly challenged by complex care needs, patients whose medical, psychological, and social circumstances require tailored, multidisciplinary, and resource-intensive responses.1 Rehabilitation is defined as a multimodal, person-centred, and collaborative process, delivered through a coordinated set of interventions designed to optimise functioning and reduce disability in individuals with health conditions, injury, age-related changes, or other factors affecting functioning, in interaction with their environment, across the continuum of care.2,3 As complexity increases, the optimisation of functioning necessarily requires coordination across disciplines, organisations, and sectors. Rehabilitation, therefore, plays a critical role within integrated care systems, where the care of people with complex needs typically spans acute, post-acute, community, and social care services.
Rehabilitation is framed as interventions targeting body structures, functions, activities/participation, and contextual factors, all with the explicit goal of optimising functioning rather than only treating disease or symptoms.3,4 Rehabilitation is an adaptive, iterative and relational process characterised by shared decision-making, feedback loops and co-evolving goals. Complexity is widely acknowledged in rehabilitation policy and practice but inconsistently defined. Sometimes it is linked to multimorbidity or dependency, but in other contexts it reflects psychosocial, systemic, or relational factors. One conceptualisation of complexity presents clinical, social and system complexity.5 This lack of clarity complicates planning, commissioning, and delivery. A particular challenge is the distinction between specialist rehabilitation and complex specialist rehabilitation, which is variably interpreted across systems.6 Understanding and operationalising complexity is therefore essential not only for service categorisation but also for aligning rehabilitation within broader integrated care reforms, such as Sláintecare in Ireland.7 There is some limited understanding of complexity in the context of rehabilitation, but because of inconsistent use of terminology and lack of agreement around the definition of complexity in this context, the scope of what is already known is not clearly mapped.8 This evidence review aims to scope what is currently known internationally. Clarifying how complexity is understood and operationalised across rehabilitation domains will strengthen Ireland’s capacity to deliver coordinated, needs-based, and sustainable rehabilitation care.
The primary aim of this scoping review is to examine how complexity is conceptualised, defined, and operationalised in the international rehabilitation literature at the level of the person, the service, and the health and social care system.
We will also examine how do varying conceptualisations of complexity shape the design, delivery, organisation, and resourcing of rehabilitation services, pathways, and models of care.
The specific objectives of the review are:
1) To determine the extent and scope of the definition, conceptualisation, and operationalisation of complexity in the international rehabilitation literature.
2) To chart how the various conceptualisations of complexity shape the design, delivery, organisation and resourcing of rehabilitation services, pathways and models of care.
3) To identify gaps in the literature for future research.
Scoping reviews are used to review health research evidence and identify gaps in the existing literature. Scoping reviews are specifically designed to map the breadth and nature of evidence in areas where concepts are still emerging and where study designs, populations, and outcomes are heterogeneous.8–10 A scoping review is the most appropriate methodological approach for this topic because the concept of complexity in rehabilitation is broad, multifaceted, and inconsistently defined across the literature.
This approach will allow us to clarify how complexity is conceptualised and operationalised in rehabilitation, to describe the range of study designs and settings, and to identify gaps in knowledge that may warrant more focused systematic reviews.11
In line with established scoping review guidance and reporting standards, this review will provide a comprehensive map of existing evidence rather than a narrowly focused effectiveness synthesis, which is better suited to systematic review methodology.10 Given these characteristics of the topic and the current state of the literature, a scoping review offers the most suitable and rigorous method for informing future research priorities, conceptual development, and practice in rehabilitation.
This scoping review was registered with the Open Science Framework (10.17605/OSF.IO/WUAVS) and it will be conducted in accordance with the updated Joanna Briggs Institute (JBI) methodological guidance,10 which is now aligned with the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews) framework.12
A scoping review will be conducted to explore the following questions:
Primary Review Question:
How is complexity conceptualised, defined, and operationalised in the international rehabilitation literature at the level of the person, the service, and the health and social care system?
Secondary Review Question:
How do varying conceptualisations of complexity shape the design, delivery, organisation, and resourcing of rehabilitation services, pathways, and models of care?
The initial search strategy was developed by the research team with the guidance of a University Librarian in December 2025. The strategy was piloted, refined and finalised in January 2026 (see Table 1. Search strategy).
The strategy was subsequently adapted for each electronic databases by modifying controlled vocabulary, search syntax, and indexing terms as appropriate for each database (see Table 2 Search Strategy for Medline and CINAHL as an example).
A grey literature search will be undertaken to supplement the evidence identified through database searching and to ensure that relevant non-indexed materials are captured. The approach to grey literature will be iterative and may be refined following the preliminary assessment of results from the main database searches.
The grey literature search will initially target materials likely to contain policy or practice-related information relevant to complexity and rehabilitation. This may include:
- professional guidelines, position statements, and practice standards from recognised clinical or rehabilitation bodies;
- government or statutory reports;
- policy frameworks and official documents from national or international health agencies;
- reports or publications produced by research institutes, NGOs, or professional associations;
- selected targeted repositories (e.g., CADTH’s grey literature checklist subsets, OpenGrey, government portals).
Reference lists of included studies and documents will also be manually searched to identify additional literature that meets the eligibility criteria.
Titles and documents identified through the grey literature search will be screened using the same inclusion criteria as the academic literature.
A set of eligibility criteria was developed in December 2025 using the PCC (Population, Concept, Context) framework recommended for scoping reviews. The criteria were pilot tested through independent dual screening of an initial sample of 100 records to ensure shared understanding and consistency in interpretation. Following this calibration exercise, each reviewer independently screened a further 500 records. Eligibility criteria were refined iteratively through discussion during this process to enhance clarity and reduce ambiguity prior to full screening.13
INCLUSION CRITERIA:
Any population receiving/planned to receive rehabilitation, including:
- Adults, including older people, children and young people
- Those receiving physical, cognitive, psychosocial, and mental health rehabilitation
- People living with all health conditions (illness, injury, congenital, ageing, stress, pregnancy, genetic predisposition)
- Families or carers of people receiving/planned to receive rehabilitation
- People who are reported as not fitting within standardised pathways of rehabilitation
EXCLUSION CRITERIA
Any population not receiving/planned to receive rehabilitation services.
Population receiving/planned to receive pre-rehab.
INCLUSION CRITERIA
Studies focused on complexity in rehabilitation, specifically:
- Conceptualisations and definitions of complexity
- Frameworks, models, and classifications
- Operationalisations (how complexity is measured, used, or assumed).
- Complexity must relate to how rehabilitation services, pathways, or systems are organised, delivered, coordinated, or governed.
Studies focused on applications of complexity in:
- service design
- pathway structures
- workforce configurations
- commissioning and funding
- transitions and integrated care arrangements
Studies including explicit attention to three layers of complexity:
- Person-level complexity: clinical complexity, acuity, multimorbidity, psychosocial/environmental risk, behavioural/cognitive needs
- Process/service-level complexity: intensity, interdisciplinarity, multimodality, coordination requirements
- System-level complexity: commissioning, governance, organisational arrangements, cross-sector transitions, degree of integration
EXCLUSION CRITERIA
Studies where complexity is limited to clinical or biomedical characteristics, such as disease severity, impairment, lesion characteristics, or references to “complex” surgery, fractures, or pathology, without reference to rehabilitation service organisation or delivery.
Studies examining complex rehabilitation interventions where complexity relates only to intervention components and not to rehabilitation service organisation, pathways, or system arrangements.
Studies where there is no service, pathway, or system dimension evident.
Studies describing complex interventions where complexity is not analysed, defined, or discussed as a conceptual or organisational construct. Studies focused on effectiveness, not understanding complexity.
Studies where complexity is included as a background rhetoric only: complexity appears only in the introduction or conclusion, there is no analytical engagement with complexity, and information about complexity could be removed without changing the paper’s argument.
INCLUSION CRITERIA
Rehabilitation services, programmes, pathways, and systems operating within health and integrated care structures.
- All care settings (acute, post-acute, tertiary/specialist, community, home, virtual, private and public).
EXCLUSION CRITERIA
Non-rehabilitation contexts, for example where the focus is on acute care, surgery, diagnostics, or prevention; long-term care or social care only, without rehab component; mental health only (without rehabilitation focus).
Focus on assessment or discharge only without a close link to rehabilitation.
Studies focused exclusively on pre-rehabilitation or prehabilitation without a rehabilitation service component.
In relation to the type of evidence, the following criteria will apply:
INCLUSION CRITERIA
Any study design, including qualitative, quantitative and mixed-methods designs, reviews, guidelines, editorials/commentaries (for conceptual papers), dissertations/theses.
Published in English in the last 10 years (since 01/01/2015). This timeframe was selected to capture contemporary conceptualisations of complexity in rehabilitation services and systems, reflecting recent developments in integrated care, multidisciplinary rehabilitation models, and health and care system organisation. Earlier literature will be considered through reference list screening where relevant conceptual contributions are identified.
EXCLUSION CRITERIA
Study protocols, single cases, books.
Titles and abstracts returned from the searches will be examined to determine whether they align with the review’s eligibility criteria. Full texts will then be obtained for any records that appear potentially relevant, and these will be assessed in detail against the same criteria. Only studies that meet all eligibility requirements will be included.
At each stage of screening (title, abstract, and full text), a proportion of the sample (to be determined based on sample size) will be screened independently by two reviewers. Decisions will then be compared, and any disagreements will be resolved through discussion. Where consensus cannot be reached, a third reviewer will make the final decision. Once full agreement and clarity regarding the screening process have been established, the remaining records will be screened by a single reviewer.
Studies that do not meet the inclusion criteria will be excluded, and the reasons for exclusion will be documented and reported in the review. The overall screening and selection process will be summarised using a PRISMA-ScR flow diagram,12 accompanied by a narrative explanation of each stage. A software application will be used to document each stage of the screening process and enable blind decision-making.
Data charting will be carried out to systematically extract and organise information relevant to the conceptualisation and operationalisation of “complexity” in rehabilitation across the person, service, and system levels. The charting process will allow comparison across studies and support the development of a descriptive map and narrative synthesis aligned with the primary and secondary review questions.
Data will be charted using a structured extraction form developed for this review. The form will be iteratively refined as familiarity with the evidence base increases, consistent with JBI guidance.10
Data will be charted using a structured form that captures the following categories:
1. General study characteristics (author, year, country, study type, population, setting)
2. How complexity is conceptualised (primary question)
‐ Level of the person (for example, level of individual complexity, biopsychosocial, behavioural, cognitive, emotional, multimorbidity, social determinants of health)
‐ Level of the service (for example, how rehabilitation services describe “rehabilitation complexity”, what are the caseload management implications)
‐ Level of the health and social care system (for example, how systems conceptualise complexity, e.g., multimorbidity burden, social vulnerability, resource intensity)
3. How complexity is operationalised
4. Implications of complexity for rehabilitation delivery (secondary question)
5. Outputs, tools, frameworks, and recommendations.
Data charting will be carried out initially by one reviewer. A second reviewer will verify a sample to ensure consistency, after which both reviewers will discuss any discrepancies and refine the charting tool as needed through an iterative process. Any modifications made will be documented and included as an appendix. Where disagreements persist, a third reviewer will examine the issue.
Where disagreements relate to the interpretation of conceptual meaning rather than data extraction accuracy, reviewers will discuss the theoretical framing until consensus is reached, with involvement of a third reviewer where necessary.
The findings of the review will be presented in accordance with the PRISMA-ScR reporting framework,12 with results displayed in tables alongside a descriptive narrative. The narrative synthesis will draw on the themes that emerge from the charted data, providing an organised summary of the evidence.
This protocol outlines the planned approach for a scoping review examining complexity within rehabilitation contexts. It sets out the review objectives, methodological framework, eligibility criteria, data extraction processes, and plans for reporting findings. Publishing the protocol helps to reduce the risk of reporting bias and may also serve as a useful reference for researchers developing evidence synthesis projects related to rehabilitation needs or practice.
Understanding how complexity is conceptualised and operationalised within rehabilitation is essential for advancing both practice and policy. At present, definitions of complexity vary widely across clinical disciplines, services, and health systems, creating inconsistencies in assessment, care planning, resource allocation, and service design. This lack of conceptual clarity can lead to fragmented care, inequitable access to rehabilitation, and challenges in commissioning or evaluating services for populations with complex needs. By systematically mapping the evidence on how complexity is defined at the level of the person, the service, and the broader system, this review will provide a comprehensive overview of existing approaches and highlight areas of convergence and divergence in the international literature. Identifying how these conceptualisations shape the delivery and organisation of rehabilitation will support the development of more coherent models of care, inform workforce planning, and guide the design of services better aligned with patient needs.
This protocol outlines our plans for a scoping review that will contribute to the evidence base on understanding complexity in rehabilitation. It describes the background and research methodology underpinning the scoping review process. We anticipate that the findings of this review will inform the development of evidence-based, high-quality rehabilitation services and support policymakers, clinicians, and researchers in identifying gaps in the current evidence base. This, in turn, will help inform future research priorities and the development of clearer, more consistent definitions and operational frameworks. Overall, this scoping review aims to provide an important foundation for improving the quality, efficiency, and equity of rehabilitation for individuals with complex health and social needs.
The study commenced in December 2025, and the protocol was finalised in February 2025, with the scoping review expected to be completed by May 2026.
We intend to disseminate the results through publication in a peer-reviewed journal and a final report.
No primary data were generated or analysed in this study. This scoping review is based on data extracted from published literature, all of which are cited within the article.
The data supporting the findings of this review are available within the article and its supplementary materials (including extraction tables), as well as from the original published sources.
All underlying materials are also available on the Open Science Framework (OSF): https://doi.org/10.17605/OSF.IO/WUAVS.14 The repository includes the full study materials, including search strategies, screening decisions, and data extraction processes relevant to this scoping review.
Is the rationale for, and objectives of, the study clearly described?
Yes
Is the study design appropriate for the research question?
Yes
Are sufficient details of the methods provided to allow replication by others?
Partly
Are the datasets clearly presented in a useable and accessible format?
Partly
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: rehabilitation, service delivery
Alongside their report, reviewers assign a status to the article:
| Invited Reviewers | |
|---|---|
| 1 | |
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Version 1 16 Jun 26 |
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