Developing a core outcome set for hand flexor tendon injuries: a systematic review of treatment outcomes

Abstract

This study identifies the outcome domains used in recently published studies on the treatment of hand flexor tendon injuries in adults, in order to inform the development of a core outcome set (COS). Seven databases were searched from January 2013 to March 2023 for randomized and quasi-randomized studies, trial registrations, large observational studies, database studies and systematic reviews. From the 91 eligible original studies/trial registrations, the primary outcome was appropriately identified in only 52% (13/25) of randomized and quasi-randomized controlled trials. We identified 419 author-defined outcomes, further categorized into 147 distinct outcomes and mapped into 72 outcome domains according to the World Health Organization International Classification of Functioning, Disability and Health framework. The large heterogeneity in the outcome domains being assessed/measured across studies highlights the need for a consistent COS to be measured in future clinical research on hand flexor tendon injuries.

Keywords

Core outcome set flexor tendon injuries hand flexor tendons systematic review treatment outcomes

Introduction

Flexor tendon injuries of the hand account for one in 16 cases of hand trauma (Manley et al., 2019). The need for large, high-quality studies of the effectiveness of treatment approaches for surgical repair and postoperative rehabilitation has been highlighted by the James Lind Alliance Priority Setting Partnership on Common Conditions affecting the Hand and Wrist (James Lind Alliance, 2017) and the National Institute for Health and Care Research in the UK, through the recent HTA-commissioned call for repair and rehabilitation of flexor tendon injuries.

There is no consensus on outcomes that are important to patients and the healthcare professionals who treat flexor tendon injury (FTI). The resulting inconsistency in outcomes reported hinders evidence synthesis, contributes to research waste and risks not representing what is important to the patients (Ioannidis et al., 2014; Kirwan et al., 2003). A recent systematic review of outcomes in FTI highlighted the wide variation in reported outcomes and the urgent need to develop a core outcome set (COS) for FTI (Mallina et al., 2022).

A COS is defined as an agreed minimum set of outcomes that should be measured and reported in all clinical trials or research studies for a particular health condition (Williamson et al., 2017). The development of a COS should be based on input from all key stakeholders, including patients, healthcare professionals and researchers (Williamson et al., 2012, 2017). The first step in developing a COS is to conduct a systematic review to identify which outcomes have been measured and reported. These, together with outcomes identified through qualitative interviews with patients with FTI, can then be fed into a consensus-building process.

The aim of this systematic review is to identify outcome domains previously reported in published studies on the management of flexor tendon injuries in adults, map these to the World Health Organization International Classification of Functioning, Disability and Health (WHO ICF) framework (World Health Organization, 2001) and assess selective reporting bias of outcomes in this setting. This longlist of outcome domains will feed into a future multi-stakeholder consensus process to further develop a COS for patients with flexor tendon injuries.

Methods

The design of this systematic review was guided by the Core Outcome Set STAndards for Development (Kirkham et al., 2017). The protocol was prospectively registered in the PROSPERO international prospective register of systematic reviews (CRD42023396266).

Scope and eligibility criteria

Studies of hand flexor tendon injury were defined as those involving adults undergoing primary surgical repair and rehabilitation for injuries to a single or multiple flexor tendons of the hand (zones I–V) and/or secondary procedures (i.e. tenolysis, two-stage tendon reconstruction), whether in an original study, a trial registry or a systematic review.

Study types included randomized controlled trials (RCTs), quasi-randomized controlled trials (qRCTs), trial registrations, observational studies with ≥50 patients and prospectively registered systematic reviews. Detailed inclusion and exclusion criteria are shown in Table 1.

Table 1.

Inclusion and exclusion criteria for studies.

Criteria
Inclusion criteria
Study design
Randomized/quasi-randomized controlled trials
Observational studies (cohort/case control/case series) with ≥50 patients enrolled
Trial registrations
Prospectively registered systematic reviews
Population
Adults who sustained an injury within the scope of the review
Studies of mixed populations (e.g. adults and children, flexor and extensor tendon injuries) were included only if ≥90% of the population were eligible
Intervention
Any primary surgical repair intervention for hand flexor tendon injury or secondary procedures such as tenolysis or two-stage tendon reconstruction
Exclusion criteria
Studies not in English/no English translation published
Biomechanical studies
Cadaveric or animal studies
Reports where only abstract (rather than full report) available (incl. conference abstracts)
Unpublished and ongoing studies, or only protocol available
Studies not assessing treatments (e.g. purely diagnostic/ epidemiological studies)
Purely clinimetric studies (studies only evaluating/vali dating measurement instruments)

Study identification

Search strategies were developed using the key concepts:

anatomical regions of the hand, wrist and forearm;

generic terms for tendons;

specific terms for all flexor tendons of the thumb or fingers;

generic terms for tendon injury or pathology; and

specific terms for flexor tendon injuries.

We combined (1) and (2) with AND, then added them by combining with (3) using OR. The result of this was combined with the summed terms for tendon pathology or injury ((4) OR (5)) using AND.

Relevant free-text terms and subject headings were identified for each database. The databases searched were Ovid MEDLINE, Ovid Embase, Cochrane Central Register of Controlled Trials, PubMed, CINAHL (EBSCO), PEDro and Ovid PsycINFO.

A staged search strategy was conducted as described in the COMET Initiative handbook (Williamson et al., 2017), with the first search conducted on 10 March 2023. An example of the search strategy and descriptions of the staged search method and study selection process are provided in Appendix S1.

Risk of bias assessment

We focused on the outcomes captured by the studies rather than the quantitative outcomes obtained, but also determined whether there was outcome reporting bias, as this could provide insight into which outcomes authors actually prioritize. To assess outcome reporting bias, we used a modified version of an outcome matrix originally developed by Kirkham et al. (2010). This is based on the premise that any outcome reported for inclusion should be reported in the final publication. The modified version is summarized in Table 2 and was used in a previous systematic review of treatment outcomes for hand fractures and joint injuries (Deshmukh et al., 2021).

Table 2.

Modified outcome reporting status categories.

Category	Definition
Not done	No clear reporting of an outcome either through description, a table or figure
Minimal	Outcome reported merely by a summary comment (e.g. ‘there was no significant difference between the intervention arms’) but with no numerical values provided, or if there is such deficiency of information that the reporting is no longer meaningful (e.g. values given but no indication of time point)
Partial	Outcome reported but not at all time points specified elsewhere in the study/registration or lacks sufficient detail to be included in a meta-analysis (e.g. mean value is reported but not variance or p-value for the difference in means between intervention arms)
Complete	Outcome reported at all time points specified elsewhere in the study and with sufficient detail to allow inclusion in a meta-analysis
Unexpected	Outcome reported but was not specified in the study registration or prior to the ‘Results’ section of the study

The primary outcome was considered to be one of the following (in descending order):

the outcome used to calculate sample size of the study;

the primary outcome, if reported in the study; and

the outcome that appeared to be most relevant to the study aim.

If there was no clear primary outcome, all outcomes were considered in the study as secondary outcomes. An independent two-reviewer assessment of the status of outcome reporting was performed (authors SRD, CJH, LM, AF and AS). Generic ‘adverse event’ or ‘complication’ outcomes were excluded from the assessment, except in cases where specific named complications were identified as independent study outcomes.

Data synthesis

All extracted verbatim outcomes were analysed for similarity of meaning through discussion (authors SRD and CJH). A ‘verbatim outcome’ is the literal wording of the outcome. For example, two different ‘verbatim outcomes’ that were similar in meaning and being measured in the same way were reduced into one unique outcome. Verbatim outcomes with similar terminology but different meanings were also split into two unique outcomes if the results for these outcomes could not reasonably be pooled in a meta-analysis. For example, ‘total active motion’ constitutes two unique outcomes if reported in degrees of joint movement in some studies but as a percentage compared with the contralateral limb in others. Unique outcomes were categorized into domains based on the WHO ICF.

Composite outcome measurement instruments were analysed by categorising the individual items and components of each scale into relevant WHO ICF outcome domains, following the principles outlined by Macefield et al. (2014) and also guided by others who have linked WHO ICF domains to composite measures, such as multi-item patient-reported and performance-based outcome measurement instruments (Van de Ven-Stevens et al., 2015; Yong et al., 2022).

Outcome time points are often heterogeneous. For our analysis of outcome time points, we created time point ‘brackets’ and categorized our findings according to these ‘brackets’.

Results

Figure 1 shows the PRISMA study flow diagram (Page et al., 2021). Appendix S2 shows all 98 included studies. Seven studies were systematic reviews; of the remaining 91, most were single-centre (82/91) and based in Asia (45/91) or Europe (22/91) (Table 3). There were 19 trial registrations. There were 24,771 participants in the 72 original studies, of whom 16,412 were from database studies. There were 24 RCTs and one qRCT, with a primary outcome specified in 52% (13/25) of RCTs and qRCTs.

Figure 1.

PRISMA flow diagram.

Table 3.

Study characteristics

Study characteristic	n/N (%)
Type of study
Randomized controlled trial	24/98 (24%)
Quasi-randomized controlled trial	1/98 (1%)
Retrospective observational study (case series; case control; cohort)	35/98 (36%)
Prospective observational study (case series; case control; cohort)	7/98 (7%)
Database/‘big data’ study	5/98 (5%)
Trial registration	19/98 (19%)
Prospectively registered systematic review	7/98 (7%)
Geographic distribution of recruitment
Africa	11/91 (12%)
Asia	45/91 (49%)
Europe	22/91 (24%)
North America	13/91 (14%)
Number of sites
Single-centre	82/91 (90%)
Multi-centre	9/91 (10%)
Number of participants in randomized/quasi-randomized studies (n = 25)
≤50	13/25 (52%)
51–100	10/25 (40%)
>100	2/25 (8%)

Outcomes

There were 419 verbatim outcomes, with the number of outcomes reported per study ranging from 1 to 19 and a median of six outcomes (interquartile range 3 to 8). Verbatim outcomes were reduced and rationalized to 147 unique outcomes. Of these unique outcomes, 61% (89/147) were used in one study, 27% (40/147) were used in two to four studies and 12% (18/147) were used in five or more studies.

There was heterogeneity in the time point ‘bracket’ for outcome assessment as summarized in Table 4. The modal time point ‘bracket’ was 6 weeks to 6 months (35% of verbatim outcomes, 245/701).

Table 4.

Time point brackets of verbatim outcomes

Time point range	n/N (%)
Baseline (pre-intervention)	62/701 (9%)
Immediately post-intervention to 14 days	15/701 (2%)
>14 days to 6 weeks	113/701 (16%)
>6 weeks to 6 months	245/701 (35%)
>6 months to 1 year	68/701 (10%)
>1 year	48/701 (7%)
Final discharge/follow-up	85/701 (12%)
Not stated	65/701 (9%)

Outcome domains

The 147 unique outcomes were mapped into 72 outcome domains using the WHO ICF framework (World Health Organization, 2001). The occurrence of each outcome domain in individual studies was noted; further details are provided in Appendix S3.

While many of the unique outcomes were related to a single WHO ICF domain, some (particulary patient-reported outcome instruments) were related to multiple domains. Some outcomes did not fit the framework at all, the most common being complications/adverse events (65% of studies, 59/91).

Outcomes assessed in systematic reviews

The outcomes reported in the systematic reviews included the themes of function (including strength, range of motion, real-world task completion), return to work, patient satisfaction, quality of life, healthcare resource use, aesthetics and complications/adverse events.

We concluded that the outcome themes of the systematic reviews were sufficiently covered by the WHO ICF domains assessed/measured in the included original research studies. Therefore, we did not consider additional WHO ICF domains.

Outcome reporting bias

Figure 2 shows the reporting status of verbatim outcomes (using the reporting status categories described in Table 2) across original study types, with RCTs/qRCTs subdivided according to trial registration status, reflecting reporting bias for these outcomes. Five of the 25 RCTs/qRCTs were prospectively registered. About 40% of outcomes were ‘completely’ reported across all study types. There were ‘unexpected’ outcomes in all study types except for unregistered RCTs/qRCTs, which logically would have a lower bar for this metric than registered trials, as unregistered trials do not pre-specify the outcomes they will assess/measure.

Figure 2.

Cumulative bar chart showing percentage and number of outcomes within each reporting status category across study types.

Discussion

Our review identified extensive heterogeneity in the outcome domains, outcome time points and outcome measurement instruments reported for FTI treatments. The most commonly reported outcome domain within the WHO ICF impairment of ‘body structures’ and ‘body functions’ categories was mobility of joint functions (b710), followed by muscle power functions (b730) and sensations of pain (b280). Although mobility of joint function was consistently reported, there was considerable variation in the use of different classification systems to calculate total active motion, with a lack of details on the methods used to measure joint angles, which joints were included and whether assessors were blinded.

A large proportion of studies used patient-reported outcome measures (PROMs), which also include items focused on domains in the ‘activities and participation’ category of the WHO ICF, such as the DASH (Hudak et al., 1996), QuickDASH (Beaton et al., 2005) and Michigan Hand Questionnaire (Chung et al., 1998). These PROMs consist of multiple items that are summed into a single composite score that corresponds to several domains within the WHO ICF. Hand and arm use (d445) and return to work (d850 renumerative employment) were the most commonly reported outcome domains.

Our findings of heterogeneity and poor quality in outcome reporting are consistent with those of the systematic review of Mallina et al. (2022). Similarly, Shaw et al. (2022) conducted a systematic review of outcome measurement instruments (OMIs) and found a large number of different OMIs being used to report on the same outcome domains, further highlighting the need for a multi-stakeholder consensus process, in order to agree on both ‘what’ to measure and ‘how’ measure it. Our review extends the previous reviews in several ways: firstly its aim goes beyond evidence synthesis and provides the basis for a large multi-phase study to develop consensus on which outcomes to measure and how. Secondly, previous reviews have not attempted to categorize outcomes or outcome measures into categories that map onto the WHO ICF, thus reducing multiple outcomes that may be named differently in the literature but are in fact the same. Third, our review includes recently published studies and prospectively registered clinical trials that have not yet been reported.

Our review goes further than those of Mallina et al. (2022) and Shaw et al. (2021) by reporting on outcome reporting bias in the included studies and mapping the outcome domains to the WHO ICF. This is a unified coding framework that uses standardized linking rules (Cieza et al., 2002, 2005), as recommended for COS development by COS-STAD (Kirkham et al., 2017), rather than an arbitrary taxonomy of outcome categories.

The WHO ICF, however, does not include all reported outcomes, namely those that focus on the patient or healthcare provider experience, such as patient or surgeon satisfaction, use of health resources or costs and complications or adverse events. The latter is an essential safety endpoint and mandatory for all prospective clinical trials. We found that a wide range of complications were reported, including the incidence of reoperation, such as tenolysis. Reoperation incidence may be a poor proxy measure for the incidence of complications, as not all patients with adhesions that limit joint motion may accept an offer of further surgery.

This review has limitations. Non-English language publications were excluded, which resulted in some studies not being included at the full-text screening stage (n = 8, Figure 1). However, studies with an English publication were included from several of the countries of origin affected by the non-English exclusion criteria, so these countries were still represented to some extent in the final review. For five studies (Figure 1) it was not possible to obtain the full-text article, despite attempts by all review authors to contact their respective institutional libraries. However, based on assessment of the abstracts for these studies, it does not appear that novel outcome domains were assessed in these studies. A potential limitation is the date range of our search. However, a staged search strategy was followed in accordance with the COMET Initiative handbook guidance for COS development (Williamson et al., 2017). We analysed the last 8 years of published literature and then performed a check to confirm that there were no new WHO ICF domains in the 2 year period immediately preceding the 8 year period initially analysed. We therefore did not extend our search further back in time.

A COS for flexor tendon injuries will improve the evidence base for this injury by ensuring a rigorous and patient-centred approach to outcome assessment of these injuries. As recommended by COMET, this review has identified 72 WHO ICF outcome domains, which will be used to develop a longlist of outcome domains for an FTI COS. The next steps are to conduct in-depth interviews with patients undergoing treatment for FTIs. Information from this process will feed into the multi-stakeholder consensus process to develop the final COS.

Supplemental Material

sj-pdf-1-jhs-10.1177_17531934251342732 - Supplemental material for Developing a core outcome set for hand flexor tendon injuries: a systematic review of treatment outcomes

Supplemental material, sj-pdf-1-jhs-10.1177_17531934251342732 for Developing a core outcome set for hand flexor tendon injuries: a systematic review of treatment outcomes by Sandeep Rajiv Deshmukh, Christina Jerosch-Herold, Leanne Miller, Amy Fuller, Abbas See, Paul Leighton and Alexia Karantana in Journal of Hand Surgery (European Volume)

Supplemental Material

sj-pdf-2-jhs-10.1177_17531934251342732 - Supplemental material for Developing a core outcome set for hand flexor tendon injuries: a systematic review of treatment outcomes

Supplemental material, sj-pdf-2-jhs-10.1177_17531934251342732 for Developing a core outcome set for hand flexor tendon injuries: a systematic review of treatment outcomes by Sandeep Rajiv Deshmukh, Christina Jerosch-Herold, Leanne Miller, Amy Fuller, Abbas See, Paul Leighton and Alexia Karantana in Journal of Hand Surgery (European Volume)

Supplemental Material

sj-pdf-3-jhs-10.1177_17531934251342732 - Supplemental material for Developing a core outcome set for hand flexor tendon injuries: a systematic review of treatment outcomes

Supplemental material, sj-pdf-3-jhs-10.1177_17531934251342732 for Developing a core outcome set for hand flexor tendon injuries: a systematic review of treatment outcomes by Sandeep Rajiv Deshmukh, Christina Jerosch-Herold, Leanne Miller, Amy Fuller, Abbas See, Paul Leighton and Alexia Karantana in Journal of Hand Surgery (European Volume)

Footnotes

Declaration of conflicting interests

The author(s) declare no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ethical approval

Not applicable.

Funding

This project is funded by the NIHR (Research for Patient Benefit, NIHR204122F). The views expressed are those of the author(s) and not necessarily those of the NIHR or the Department of Health and Social Care.

Informed consent

Not applicable.

ORCID iDs

Sandeep Rajiv Deshmukh

Alexia Karantana

Supplementary material

Supplemental material for this article is available online.

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