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Study Protocol

Selection criteria in posterior tibialis tendon dysfunction, adult acquired flatfoot and progressive collapsing foot deformity research: a scoping review protocol.

[version 1; peer review: awaiting peer review]
Gabriel Moisan
https://orcid.org/0000-0002-1688-4811
1,2, Aaron Jackson3, Léa Tessiot2,4, Ahmed Dami2,4, Kelly Robb5
Gabriel Moisan
https://orcid.org/0000-0002-1688-4811
1,2, Aaron Jackson3, [...] Léa Tessiot2,4, Ahmed Dami2,4, Kelly Robb5
PUBLISHED 25 Jun 2026
Author details Author details
OPEN PEER REVIEW
REVIEWER STATUS AWAITING PEER REVIEW

Abstract

Introduction

Over the past decades, multiple classification systems have been used to describe a spectrum of painful adult-acquired flatfoot. Among the most widely used classifications and terminology are posterior tibial tendon dysfunction (PTTD), adult-acquired flatfoot deformity (AAFD), and progressive collapsing foot deformity (PCFD). Although classification systems have evolved considerably over time, participant selection criteria have not been standardized across studies. Consequently, substantial heterogeneity exists in how these conditions are defined and operationalized in the literature. This variability limits comparability across studies, contributes to inconsistencies in reported outcomes, and ultimately limits the advancement of this field.

Objectives

The purpose of this scoping review will be to map and characterize the participant selection criteria used in research involving PTTD, AAFD, and PCFD, and to describe the extent of methodological variation across literature.

Inclusion criteria

Eligible studies will include peer-reviewed qualitative, quantitative, and mixed-methods research involving adults diagnosed with PTTD, AAFD, or PCFD. Studies will be excluded if they include asymptomatic flatfoot.

Methods

A comprehensive search will be conducted in MEDLINE (PubMed), SPORTDiscus, CINAHL, Cochrane Library (CENTRAL), Physiotherapy Evidence Database (PEDro), Scopus, and Google Scholar. Two independent reviewers will perform study selection, with disagreements resolved by consensus or a third reviewer. Data will be extracted using a piloted standardized form and will include study characteristics, inclusion and exclusion criteria, and demographic variables. Findings will be synthesized using descriptive numerical summaries and narrative mapping.

Discussion

By systematically mapping participant selection criteria and demographic characteristics across studies, this scoping review will explore the extent of methodological variability in the PTTD, AAFD, and PCFD literature. The findings will inform future efforts aimed at improving standardization of selection criteria, thereby enhancing methodological consistency and comparability across studies investigating this spectrum of painful adult-acquired flatfoot disorders.

Keywords

Foot, Ankle, Lower extremity, Musculoskeletal Disease, Review, Diagnostic criteria, Inclusion criteria, Participant selection

Corresponding author: Gabriel Moisan
Competing interests: No competing interests were disclosed.
Grant information: Gabriel Moisan is supported by the Fonds de Recherche du Québec (#347697; https://doi.org/10.69777/347697), the Canadian Institutes of Health Research (202509PJT-549841) and the Natural Sciences and Engineering Research Council of Canada (RGPIN-2023-05364). The funding agreement ensures the authors’ independence in designing the study, writing, and publishing this article.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Copyright:  © 2026 Moisan G et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
How to cite: Moisan G, Jackson A, Tessiot L et al. Selection criteria in posterior tibialis tendon dysfunction, adult acquired flatfoot and progressive collapsing foot deformity research: a scoping review protocol. [version 1; peer review: awaiting peer review]. F1000Research 2026, 15:1012 (https://doi.org/10.12688/f1000research.183687.1) First published: 25 Jun 2026, 15:1012 (https://doi.org/10.12688/f1000research.183687.1) Latest published: 25 Jun 2026, 15:1012 (https://doi.org/10.12688/f1000research.183687.1)

Introduction

Progressive collapsing foot deformity (PCFD),1 is a disabling progressive and multidimensional deformity involving multiple anatomical structures, including the ankle, hindfoot, midfoot, forefoot, and associated ligamentous and soft tissue structures. Over time, this condition has been described using multiple overlapping terms, including posterior tibial tendon dysfunction (PTTD)2,3 and adult-acquired flatfoot deformity (AAFD),4 reflecting an evolving understanding of its pathoanatomy and clinical presentation. The recent transition toward the PCFD classification represents an important conceptual advancement in foot and ankle medicine, aiming to improve diagnostic consistency and clinical communication across severity stages and phenotypes.

Epidemiologically, PTTD/PCFD/AAFD primarily affects middle-aged and older adults, with an estimated prevalence of approximately 3.3% in women, an incidence nearly twice as high in women compared to men, and reported rates approaching 10% in individuals over 65 years of age.5–7 Recent registry data suggest an incidence of approximately 23 referred cases per 100,000 person-years in the general population.8 The condition is associated with significant functional consequences, including impaired balance, mobility limitations, biomechanical deficits, and reduced strength and endurance.9,10 These deficits contribute to reduced participation in physical and social activities,11 decreased foot-specific function, poorer quality of life, and adverse mental health outcomes.12,13

In 2020, Myerson et al.1 introduced the term “progressive collapsing foot deformity” (PCFD) and proposed a unified classification and nomenclature to improve consistency in describing this complex, three-dimensional deformity. Despite such progress, the evolution of the PCFD framework has not been accompanied by equivalent standardization in research methodology. While the updated classification improves phenotypic precision and supports more refined subgrouping, there remains no consensus on how participants should be selected and reported in research studies. This issue is compounded by pre-existing heterogeneity in inclusion and exclusion criteria within earlier literature, predating the adoption of PCFD terminology.14 As a result, diagnostic labels and selection criteria are often applied without transparent reporting of the clinical, imaging, or functional criteria used to define study populations. This lack of methodological consistency limits comparability across studies and reduces the interpretability and synthesis of evidence in this field.

Therefore, the purpose of this scoping review will be to map and characterize the participant selection criteria used in research involving PTTD, AAFD, and PCFD, and to describe the extent of methodological variation across the literature. While this review focuses on participant selection criteria, these are interpreted as the operationalization of diagnostic criteria within research contexts.

Protocol

Review questions

Based on the PCC framework (Participants, Concept, Context), as recommended by Joanna Briggs Institute (JBI) for scoping reviews,15 this review will aim to address the following primary research question: “What participant inclusion and exclusion criteria have been used to define and recruit individuals with PTTD, AAFD, or PCFD, in research?”

The secondary review questions are as follows:

  • 1. How frequently are specific inclusion and exclusion criteria, diagnostic approaches, and classification systems used across the literature?

  • 2. How have the terminology, conceptualization, and diagnostic criteria applied to PTTD, AAFD, and PCFD within research, evolved over time?

  • 3. How do participant selection criteria vary by study design and clinical context (e.g., surgical vs non-surgical studies)?

  • 4. What demographic and clinical characteristics are most reported to describe study populations?

  • 5. What gaps or inconsistencies exist in the reporting and operationalisation of participant selection criteria?

These questions will guide the review in mapping and describing the available evidence regarding participant selection methodologies in studies involving individuals with PTTD, AAFD, and PCFD.

Selection criteria

Participants. This review will include studies involving adult human participants diagnosed with PTTD, AAFD, or PCFD ( Table 1). No restrictions will be applied regarding the etiology of the condition, including traumatic, rheumatologic, degenerative, inflammatory, or overuse-related presentations. Similarly, studies will not be excluded based on unilateral or bilateral involvement. No restrictions will be applied regarding sex, gender, race, ethnicity, or geographic origin. Studies involving participants with asymptomatic flatfeet will be excluded.

Table 1. Presents the eligibility criteria and characteristics of the evidence sources included in this scoping review.

Element (PCC)Inclusion CriteriaExclusion Criteria
Participants (Population)Studies involving adult human participants defined with posterior tibial tendon dysfunction (PTTD), adult-acquired flatfoot deformity (AAFD), or progressive collapsing foot deformity (PCFD), as defined within the study.
No restrictions on:

  • • Etiology (e.g., degenerative, rheumatologic, traumatic, inflammatory, overuse)

  • • Laterality (unilateral or bilateral)

  • • Sex, gender, ethnicity, or geographic location

  • • Studies involving asymptomatic flatfoot populations

  • • Studies involving non-human or cadaveric participants

ConceptStudies reporting explicit inclusion and/or exclusion criteria used to define participants with PTTD, AAFD, or PCFD.
This includes (but is not limited to):

  • • Clinical signs and symptoms

  • • Imaging findings (Magnetic resonance imaging, ultrasound, radiographs)

  • • Functional assessments

  • • Structural or alignment measures

  • • Classification and staging systems

Studies reporting demographic and clinical descriptors of the sample will also be included.

  • • Studies that do not report participant selection criteria

  • • Studies focused solely on clinical diagnoses in the absence of a clearly defined diagnosis criteria

ContextStudies conducted in any research setting, including:

  • • Clinical environments

  • • Surgical settings

  • • Laboratory or biomechanical settings

  • • Rehabilitation or sports medicine settings

  • • Community-based settings

Studies from all geographic locations.		No explicit exclusions based on context, provided the study involves research application of participant selection criteria.
Types of Evidence Sources

  • • Peer-reviewed quantitative, qualitative, and mixed-methods studies

  • • Studies that include defined participant recruitment criteria

  • • Case reports and case series

  • • Systematic reviews and meta-analyses

  • • Narrative reviews, editorials, and commentaries

  • • Conference abstracts and proceedings

  • • Study protocols

  • • Theses and dissertations

Other Limits

  • • Publications in English or French

  • • Studies published in 2006 or after

Concept. This review will examine the inclusion and exclusion criteria used to define and recruit participants with PTTD, AAFD, or PCFD. Particular attention will be given to diagnostic methods, classification systems, clinical findings, imaging criteria, functional assessments, and other participant selection approaches used across studies. The review will also extract demographic and clinical variables used to characterize the study populations.

Context. This review will consider studies conducted in any context, including clinical settings, laboratory environments, surgical settings, sports medicine environments, rehabilitation settings, and community-based care. Studies from all geographic locations will be considered eligible. Eligible studies must quantitatively and/or qualitatively investigate participants with PTTD, AAFD, or PCFD.

Types of evidence sources. Published, peer-reviewed qualitative, quantitative and mixed methods studies will be considered for inclusion in this scoping review. Research protocols, meta-analyses, narrative editorials and comments, case reports, case series, theses, annals of congresses and conference proceedings and systematic reviews will not be considered in the review.

Methods

The scoping review will be conducted in accordance with the methodological guidance provided by Arksey and O’Malley16 and later revised by Levac and Colquhoun.17 Reporting will be in line with the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols for scoping reviews (PRISMA-ScR)18 guidelines. The protocol is registered with Open Science Framework (10.17605/OSF.IO/5Y3EH).

Search strategy

The search strategy will aim to locate published peer-reviewed original studies, quantitative, qualitative, and mixed method studies ( Table 2). An initial limited search of Scopus was undertaken in June 2026 to confirm the feasibility of this review and pilot our search strategy in identifying studies relevant to our research question. The search strategy for Scopus combined key terminology related to PTTD, AAFD, and PCFD. A proximity operator (W/5) was used to capture variation in terminology describing posterior tibial tendon pathology. The strategy was designed to maximize sensitivity while maintaining specificity and was developed in consultation with a research librarian. This search strategy will be adapted for use across other databases (Supplementary file 1).

Table 2. Search strategy for Scopus.

The modified strategy applied in other databases is outlined in additional material.

Scopus (Elsevier)TITLE-ABS-KEY (PTTD OR “acquired flatfoot” OR AAFD OR “progressive collapsing foot deformity” OR PCFD OR “tibialis posterior dysfunction” OR “tibialis posterior insufficiency” OR ((“posterior tibial” OR “tibialis posterior”) W/5 (dysfunction OR insufficiency OR tendinopathy OR tendinitis)))

Electronic databases to be searched will include Scopus, SPORTDiscus (EBSCO), CINAHL (EBSCO), MEDLINE (EBSCO), Cochrane Library (CENTRAL) and Physiotherapy Evidence Database (PEDro). Additionally, grey literature will be explored using Google Scholar.

Source of evidence selection

Following the search, all identified records will be collated and uploaded into EndNote software version 21.5 (Clarivate Analytics, PA, USA) and duplicates will be removed. Following a pilot test, titles and abstracts will be screened using Rayyan (Rayyan Systems Inc., Qatar), by two independent reviewers (LT and AD) for assessment against the inclusion criteria for the review. Potentially relevant papers will be retrieved in full text and will be assessed in detail against the inclusion criteria by two independent reviewers (LT and AD). Reasons for exclusion of full-text papers that do not meet the inclusion criteria will be recorded and reported in the scoping review. Any disagreements that arise between the reviewers at each stage of the selection process will be resolved through discussion or with a third reviewer (GM). The search results and exclusion rationale will be reported in full in the final scoping review and presented in a PRISMA flow diagram.18

Mapping and data extraction

Data will be extracted from included publications by one reviewer (AJ) using a data extraction tool developed by the research team. Data will be imported into a table created in a Microsoft Excel version 16.79.1 (Microsoft Corporation, WA, USA) sheet (supp table 3). The extracted data will include specific details about the participants, concept, context, study methods, and key variables relevant to the review questions. The following data will be extracted and separated for each terminology (PTTD, AAFD, PCFD):

  • • Study characteristics (journal, authors, year, journal, country where the study was conducted, study design, sample size).

  • • Inclusion criteria

  • • Exclusion criteria

  • • Demographic variables

A draft extraction tool is provided and will be modified and revised as necessary during the process of extracting data from each included paper. Modifications will be detailed in the full scoping review. Authors of papers will be contacted to request missing or additional data, where required. If the corresponding author does not respond, the article will still be included, but problematic results will not be analyzed, and limitations will be mentioned in the discussion.

Data analysis and presentation

The results of the review will be analyzed and displayed in tabular format using charting methods to meet the objectives of this scoping review. The results will be presented in a narrative format. Consistent with scoping review methodology, a formal assessment of methodological quality or risk of bias will not be undertaken, and this will be explicitly acknowledged in the review.

Ethical considerations and dissemination

As this scoping review involves the synthesis and analysis of data from previously published literature, ethical approval is not required. Nevertheless, all included sources will be appropriately referenced. The findings of this review will be disseminated through peer-reviewed publications and presentations at scientific conferences. The review methodology will be conducted and reported in accordance with the PRISMA-ScR guidelines18 to ensure transparency, methodological rigour, and reproducibility.

Study status

The search strategy, including the development of keywords and Medical Subject Headings (MeSH) adapted to each database, has been completed. Literature searching and article screening will begin following peer review of the search strategy.

Discussion

Despite a large body of literature on painful adult-acquired flatfoot disorders, there is still no clear consistency in how these conditions are defined in research. Participant selection criteria vary widely between studies and are often incompletely reported, which limits comparability and makes it difficult to synthesize findings across the literature. In many cases, diagnostic labels are applied without a clear description of the clinical, imaging, or functional criteria used to define study participants. This limits clarity regarding how the results are interpreted and applied across different study designs and clinical contexts.

This scoping review will map and characterize the inclusion and exclusion criteria used in research to define individuals with PTTD, AAFD, and PCFD. The review will also provide a structured overview of how these conditions are defined in practice and how this has evolved over time. It will also describe how these criteria vary across study designs and clinical settings. Overall, this synthesis will help clarify current inconsistencies and highlight areas where standardization is lacking. This will ultimately support the development of more consistent research practices, improving comparability across studies in this disabling musculoskeletal disorder.

Data availability

Underlying data

No data is associated with this article.

Extended data

Open Science Framework: “Selection criteria in posterior tibialis tendon dysfunction, adult acquired flatfoot and progressive collapsing foot deformity research: a scoping review protocol (https://doi.org/10.17605/OSF.IO/5Y3EH).

Reporting guidelines

Open Science Framework: PRISMA-ScR protocol checklist19 for “Selection criteria in posterior tibialis tendon dysfunction, adult acquired flatfoot and progressive collapsing foot deformity research: a scoping review protocol (https://doi.org/10.17605/OSF.IO/5Y3EH).

Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).

Acknowledgements

N.A.

References

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Moisan G, Jackson A, Tessiot L et al. Selection criteria in posterior tibialis tendon dysfunction, adult acquired flatfoot and progressive collapsing foot deformity research: a scoping review protocol. [version 1; peer review: awaiting peer review]. F1000Research 2026, 15:1012 (https://doi.org/10.12688/f1000research.183687.1)
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