Functional outcomes of surgical strategies for foot drop secondary to common peroneal nerve injury: A systematic review and meta-analysis

Study design

This study was conducted in accordance with established standards for systematic reviews, following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines^[7] and the recommendations of the Cochrane Handbook.^[8] The protocol was prospectively registered with PROSPERO (CRD420261380937) to ensure methodological transparency.

Eligibility criteria

Search strategy

An extensive literature search was conducted in MEDLINE (via PubMed), Embase, and LILACS from database inception through April 11, 2026. The search strategy [Supplementary Table 1] combined controlled vocabulary terms (e.g., MeSH and Emtree) and free-text terms related to foot drop, peroneal nerve injury, tendon transfer, and nerve reconstruction techniques. Studies were considered irrespective of publication language.

Study selection

Two independent reviewers screened titles, abstracts, and full texts. Disagreements were resolved by consensus.

Data extraction

Data were independently extracted using a standardized form that included study characteristics, patient population, interventions, and outcomes.

Risk of bias assessment

Risk of bias was assessed using the risk of bias in non- randomized studies of interventions (ROBINS-I) tool for non-randomized studies^[9] and the Joanna Briggs Institute (JBI) checklist for case series.^[10]

Data synthesis

A narrative synthesis was performed, structured by type of surgical intervention. A meta-analysis of proportions was conducted on studies evaluating tendon transfer procedures, using a random-effects model with a logit transformation. Statistical analyses were performed using R software (version 4.4.1, R Foundation for Statistical Computing, Vienna, Austria) with the meta package. Given the expected clinical heterogeneity, pooling was restricted to studies with comparable outcome definitions. Statistical heterogeneity was assessed using the I² statistic.

Publication bias was assessed using a funnel plot and Egger’s test. Given the limited number of included studies, these analyses were considered exploratory and interpreted with caution.

Of the nine tendon-transfer studies identified, only seven were included in the quantitative synthesis. Two studies were excluded because they evaluated biomechanical performance and comparisons between tendon-transfer techniques rather than reporting functional dorsiflexion recovery as a dichotomous outcome suitable for pooled proportion analysis. [^11,12]

Certainty of evidence

The certainty of the evidence was assessed using the GRADE approach,^[13] grouping studies by intervention type.

Search strategy

The initial search yielded 303 records across all databases (PubMed = 110, Embase = 185, LILACS = 8). After removing 81 duplicates, 222 records were screened by title and abstract. Of these, 38 studies were considered potentially eligible and selected for full-text assessment.

After full-text assessment, 19 studies fulfilled the predefined eligibility criteria [Figure 1]. Studies were excluded at this stage mainly because they did not evaluate surgical interventions, corresponded to case reports or small case series, involved animal or cadaveric models, or did not specifically address foot drop secondary to CPN injury.

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Figure 1: Preferred Reporting Items for Systematic Reviews and Meta-analyses 2020 flow diagram of study selection.

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Characteristics of included studies

The 19 included studies comprised predominantly retrospective cohort designs, with a smaller number of prospective cohort and case series [Table 1].^{[11,12,14-30]} Sample sizes ranged from 10 to 45 patients, and most studies included adult populations with foot drop secondary to traumatic, compressive, or iatrogenic CPN injury.^{[14-18,22-26]}

Interventions were categorized into four main groups: Neurolysis and nerve repair procedures, nerve transfer techniques, tendon transfer procedures, and combined surgical strategies.^{[11,12,14-30]} Outcomes were primarily reported using the MRC muscle strength scale, functional scores, and measures of gait or dorsiflexion recovery.

Risk of bias

Risk of bias was assessed using the ROBINS-I tool for non- randomized studies [Table 2] and the JBI checklist for case series [Table 3]. Overall, the included studies showed a moderate-to-high risk of bias, mainly due to confounding and non-randomized treatment allocation.

Selection bias was common in retrospective cohort studies, whereas outcome measurement bias was generally low, as most studies used standardized measures such as the MRC scale. Comparative studies were particularly prone to confounding due to a lack of adjustment for baseline differences.

Prospective studies showed relatively lower risk of bias, although still limited by the absence of randomization. Case series studies were associated with a high risk of bias due to the absence of comparator groups.

Studies rated as having a high risk of bias (Horteur et al.,^[17] Tsai et al.,^[21] De Marchi et al.,^[23] Ferraresi et al.,^[29] Ho et al.^[30]) were mainly downgraded because of serious confounding, retrospective participant selection, lack of adjustment for baseline differences, and the absence of comparable control groups. In contrast, studies rated as having moderate risk were primarily limited by residual confounding and non-randomized treatment allocation despite generally standardized outcome assessment.

Neurolysis and nerve repair procedures

Five studies evaluated neurolysis and nerve repair techniques.^[14-18] Overall, these interventions demonstrated moderate to good functional recovery, with approximately 67–81% of patients achieving at least MRC grade ≥3.^[14-18]

Neurolysis showed particularly favorable outcomes in compressive neuropathies, with up to 80% of patients achieving good or excellent results and faster recovery when performed early.^[14,15] Comparative analyses reported no significant differences between neurolysis and direct nerve repair,^[16] suggesting that less invasive procedures may be equally effective in selected cases.

In contrast, nerve grafting was consistently associated with inferior outcomes, with one study reporting no patients achieving MRC ≥4.^[17] More recent approaches incorporating neurorrhaphy combined with nerve transposition and biological augmentation have demonstrated improved functional recovery, with approximately 67.6% of patients achieving MRC ≥3, and superior outcomes with direct repair compared with grafting.^[18]

Nerve transfer techniques

Three studies evaluated nerve transfer strategies.^[19-21] These techniques achieved functional dorsiflexion (MRC ≥3) in approximately 48–83% of patients, depending on the study population and surgical approach.^[19,20]

Double nerve transfer procedures using tibial nerve branches showed moderate success, with nearly half of the patients regaining functional dorsiflexion and significant improvements in range of motion and pain. Outcomes were strongly influenced by timing, with earlier intervention associated with better recovery.^[19]

In contrast, studies combining nerve transfer with neurolysis reported higher success rates, reaching up to 83% functional recovery.^[20] In addition, adjunctive biological therapies, such as acidic fibroblast growth factor, were associated with improved motor outcomes compared to surgery alone, highlighting the potential role of regenerative strategies in enhancing nerve recovery.^[21]

Tendon transfer procedures

Nine studies assessed tendon transfer techniques,^{[11,12,22-28]} representing the most extensively studied intervention. Across studies, tendon transfer consistently resulted in high rates of functional recovery, with approximately 70–90% of patients achieving good or excellent outcomes.^{[22,24,25,28]}

Most patients regained functional dorsiflexion (typically MRC ≥3–4), with significant improvements in gait and independence from orthotic devices.^[11,22-26] However, objective strength recovery remained limited, ranging from 30 to 50% of the contralateral limb in studies reporting quantitative measurements.^{[11,23,24,26]}

Technical variations influenced outcomes. Tendon-to-bone fixation demonstrated superior functional results compared to tendon-to-tendon fixation,^[27] while double and triple- tendon transfer techniques improved toe extension without significantly enhancing ankle dorsiflexion.^[12,28] Despite these variations, tendon transfer procedures consistently provided reliable restoration of functional mobility, even in chronic cases.^[23,24]

Combined surgical strategies

Two studies evaluated combined approaches integrating tendon transfer with nerve repair.^[29,30] These strategies were associated with favorable functional outcomes; however, evidence was limited, and direct comparisons between interventions were scarce.

One study reported that 100% of patients undergoing combined surgery achieved dorsiflexion recovery, compared to only 40% in those treated with tendon transfer alone.^[30] Similarly, another study showed that combined procedures resulted in approximately 72% good functional outcomes, whereas nerve repair alone yielded poor results.^[29]

These findings may suggest a potential synergistic effect, although the limited evidence precludes definitive conclusions.

Synthesis of results

Tendon transfer procedures appeared to demonstrate relatively consistent functional outcomes across studies.^[11,22-26] In contrast, outcomes following neurolysis and nerve repair were more variable and appeared to depend strongly on injury characteristics and timing of intervention.^[14-16]

Nerve transfer techniques showed heterogeneous results, likely reflecting differences in surgical technique, donor nerve selection, and patient selection criteria.^[19-21] Combined surgical strategies were associated with favorable functional outcomes, although evidence was limited.^[29,30]

Importantly, direct comparisons between surgical strategies were scarce, and the available evidence does not allow for definitive conclusions regarding the relative superiority of one technique over another. Therefore, findings should be interpreted as comparative trends rather than causal inferences.

Meta-analysis

A meta-analysis of proportions was conducted for studies evaluating tendon transfer procedures, including seven studies with a total of 139 patients. Using a random-effects model with logit transformation, the pooled proportion of functional dorsiflexion was 76.4% (95% confidence interval [CI] 67.2–83.7%). Statistical heterogeneity was low (I² = 11.6%), indicating a high level of consistency across studies despite differences in surgical techniques and patient characteristics [Figure 2].

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Figure 2: Forest plot of the pooled proportion of functional dorsiflexion following tendon transfer procedures. CI: Confidence intervals.

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Publication bias was explored; however, interpretation was limited because fewer than ten studies were available for quantitative synthesis [Figure 3].

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Figure 3: Funnel plot for assessment of small-study effects in tendon transfer studies.

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Sensitivity analysis

A leave-one-out sensitivity analysis was performed by sequentially excluding each study included in the quantitative synthesis. The pooled proportion of functional dorsiflexion recovery ranged from 73.3% to 78.4%, indicating minimal variation relative to the primary estimate (74.5%; 95% CI, 65.7–81.7%). Exclusion of the high-risk case series did not materially alter the pooled estimate. Overall, no individual study substantially influenced the magnitude or direction of the pooled effect, supporting the robustness and stability of the meta-analytic findings^[28] [Supplementary Figure 1].

Certainty of evidence

The certainty of evidence was assessed using the GRADE approach [Supplementary Table 2]. The assessment was performed by grouping studies according to intervention type. Evidence for tendon transfer procedures was rated as low certainty due to observational study design, risk of bias, and heterogeneity in outcome definitions.