1 Introduction

Peroneal tendon disorders represent a wide spectrum of conditions affecting the lateral ankle and hindfoot, including tendinopathy, subluxation, dislocation, and tear.¹ Patients commonly present with recurrent posterolateral ankle pain and reduced participation in sporting activities.^2–4 The diagnosis of peroneal tendon disorders remains challenging, with only 60 % of patients initially receiving an accurate diagnosis during clinical examination.³ This can be attributed to the low index of suspicion on initial presentation in the community setting and variable sensitivity of magnetic resonance imaging (MRI) in detecting pathology within the substance of the tendon. First line treatment consists of conservative treatment which includes activity modification, footwear changes, temporary immobilization, and corticosteroid injection.^4,5 However, success rates following conservative management are variable.

If conservative treatment fails, surgical intervention is warranted. Historically, traditional open surgery was the mainstay treatment option for peroneal tendon disorders. However, numerous limitations are associated with these procedures, including wound complications, infection, postoperative tendon stenosis, and protracted period of immobilization, with protracted times to return to work and sporting activity. Considering the disadvantages associated with these open procedures, minimally invasive modalities, such as peroneal tendoscopy have been developed.^2,6–8 Peroneal tendoscopy has both diagnostic and therapeutic capabilities. It permits visualization of the tendon to assess for tenosynovitis, tears, adhesions, and provides assessment of the morphology of retromalleolar groove. Additionally, peroneal tendoscopy facilitates concomitant treatment of any of these pathologies while minimizing trauma to the soft tissue envelope.^8,9 However, there is no consensus on the clinical outcomes and complications following peroneal tendoscopy for the treatment of peroneal tendon disorders.

The purpose of this systematic review is to evaluate the outcomes following the use of peroneal tendoscopy for the treatment of peroneal tendon disorders. We also sought to evaluate the level and quality of current available evidence.

2 Methods

3 Results

The search generated 341 studies, and 8 studies met the inclusion and exclusion criteria (Fig. 1).

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Fig. 1 PRISMA flow chart.

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3.1

3.1 Study characteristics & patient demographics

Study characteristics and patient demographics are listed in Table 1. Across 8 studies, there were 190 patients undergoing 195 ankle procedures. The pooled mean age was 32 years (95 % CI 25.0–39.0 years, I² = 96 %), and the pooled mean follow-up time was 30.3 months (95 % CI 20.8–39.8 months, I² = 98 %). The sex distribution was available for 7 studies (n = 167 patients) and showed an overall female predominance (105/167). Traumatic etiology was cited in 71 % of ankles (133/195). Based on the level of evidence (LOE), the studies comprised of one LOE III study¹⁴ and seven LOE IV studies.^4,15–20 The JBI Critical appraisal toolkit was used to assess the risk of bias as demonstrated in Fig. 2. Taken together, the evidence base consisted of 1 study with a high risk of bias,⁴ and 7 studies with a low risk of bias.^14–20

Table 1 Study characteristics and patient demographics.

Author	LOE	Study type	Patients/ankles (n)	Follow-up (mo)	Age (yrs)	Sex (M/F)	Traumatic etiology
Scholten et al., 2006(6)	4	Case series	23/23	24	n/r	n/r	11
Vega et al., 2011	4	Case series	6/6	18.3 ± 2.5	23.5 ± 3.8	3/3	4
Vega et al., 2013	4	Case series	7/7	15.4 ± 4.3	26.4 ± 2.8	4/3	7
Kennedy et al., 2016(5)	4	Case series	23/23	33 ± 7.3	34 ± 8.8	10/13	11
Guelfi et al., 2018(4)	4	Case series	18/18	45 ± 14	29 ± 7.3	11/7	18
Urguden et al., 2019(7)	4	Case series	18/20	24	46.8 ± 11	5/13	20
Nishimura et al., 2020(1)	3	Retrospective cohort study	13/14	24.1 ± 7.9	23.9 ± 11.2	12/1	14
Bojanic et al., 2021(3)	4	Case series	82/84	47 ± 21	46 ± 13	20/62	53

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Fig. 2 Risk of bias assessment using Joanna Briggs Institute Critical Appraisal Tools.

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3.3

3.3 Clinical outcomes

Subjective clinical outcomes are shown in Table 3. Four different patient reported outcome measures (PROMs) were reported in the included studies and included the American Orthopaedic Foot and Ankle Society (AOFAS), Foot and Ankle outcome score (FAOS), Short Form-12 health survey (SF-12) and Japanese Society for Surgery of the Foot (JSSF) hind foot scale.

Table 3 Reported outcome measures.

Author	Patients/ankles (n)	PROM Preop	PROM Postop	Return to sport/activity	Preop Index test performance vs tendoscopy
Scholten et al., 2006	23/23	n/r	VAS 0	n/r	n/r
Vega et al., 2011	6/6	AOFAS 79 ± 3.8VAS 7.7 ± 0.5	AOFAS 99 ± 0.8VAS 0.3 ± 0.5	All returned to daily activity	n/r
Vega et al., 2013	7/7	AOFAS 75 ± 5.8	AOFAS 93 ± 4.3	14.8 ± 2.0wks	n/r
Kennedy et al., 2016	23/23	FAOS 57 ± 14SF-12 54 ± 14.4	FAOS 86 ± 8.4SF-12 81 ± 7.8	22/23 returned to daily activity/sport	Sensitivity∗ 0.90 (95 % CI 0.82–0.95)Specificity∗ 0.72 (95 % CI 0.68–0.83)
Guelfi et al., 2018	18/18	AOFAS 76.8 ± 6.6	AOFAS 97.1 ± 3.9	All returned to daily activity by 12 wks	n/r
Urguden et al., 2019	18/20	AOFAS 76 ± 7.8	AOFAS 96 ± 7.3	n/r	n/r
Nishimura et al., 2020	13/14	JSSF 82.6 ± 5.3	JSSF 99.1 ± 3.5	12.2 ± 0.6wks	n/r
Bojanic et al., 2021	82/84	n/r	n/r	n/r	Sensitivity∗∗ 0.76Specificity∗∗ 0.97

Four studies^15–17,19 reported AOFAS scores, with the forest plots shown in Figs. 3 and 4. The pooled mean postoperative AOFAS score was 96.6 points (95 % CI 94.3 to 99.0 points, I² = 84 %) at latest follow-up. The pooled mean improvement from preoperative to latest postoperative AOFAS score was 19.8 points (95 % CI 18.5 to 21.2 points, I² = 0 %). Nishimura et al. reported JSSF scores, which improved from 82.6 ± 5.3 to 99.1 ± 3.5 points (p < 0.05). Kennedy et al. reported FAOS and SF-12 scores. The mean FAOS score was 57 ± 14.0 and improved to 86 ± 7.8 points (p < 0.01) and the mean SF-12 scores improved from 54 ± 14.4 to 86 ± 8.4 points (p < 0.01).

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Fig. 3 Forest plot of postoperative clinical outcome scores.

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Fig. 4 Forest plot of improvement from preoperative to latest follow-up clinical outcome scores.

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Five studies^14–18 reported return to sport or activity, however only two studies reported specific values in units of time.^14,16 Vega et al., 2013 reported a mean return to sport of 14.8 ± 2.0 weeks,¹⁶ Nishimura et al. reported a return to sport of 12.2 ± 0.6 weeks.¹⁴ The pooled mean return to sport time was 13.3 weeks (95 % CI 10.6–16.0 weeks, I² = 92 %). Vega et al., 2011 reported that all patients returned to daily activity,¹⁵ but did not mention a specific time. Guelfi et al. reported that all patients return to daily activities by 12 weeks,¹⁷ and Kennedy et al. reports that only 1 patient failed to return to their sport.¹⁸

Kennedy et al. reported that MRI demonstrated high agreement with tendoscopic findings, with an overall sensitivity of 0.90 (95 % CI 0.82–0.95) and overall specificity of 0.72 (95 % CI 0.62–0.80). Additionally, Kennedy reported good sensitivity and specificity across several specific peroneal pathologies: peroneus brevis tear (sensitivity 0.77, specificity 0.9), peroneus longus tear (sensitivity 0.8, specificity 1.0), tenosynovitis (sensitivity 1.0, specificity 0.9), and tendinopathy (sensitivity 0.88, specificity 1.0). However, MRI showed poor performance for diagnosing stenosis with a sensitivity of 0.33 and specificity of 0.66.¹⁸ In Bojanić et al.‘s study, the overall preoperative diagnosis, comprised of clinical examination and imaging, compared with tendoscopy yielded overall sensitivity of 0.76 and overall specificity of 0.97. Furthermore, the sensitivity and specificity for specific conditions was as follows: peroneus brevis tear (0.85 and 0.86), LLPB (0.52 and 1.0). The authors found that LLPB was frequently missed or misclassified preoperatively, most often as PB tear or tenosynovitis, only to be later confirmed at tendoscopy.

Sensitivity analyses stratified by study sample size (<15 vs ≥ 15 patients) demonstrated comparable postoperative outcome scores and improvements across subgroups. For postoperative clinical scores, pooled means were 97.41 (95 % CI 94.72–100.11) in smaller studies and 96.84 (95 % CI 95.27–98.41) in larger studies, with no significant subgroup difference (p = 0.72). Similarly, mean improvement from preoperative to latest follow-up was 18.23 points (95 % CI 15.89–20.58) in smaller studies and 20.19 points (95 % CI 18.20–22.19) in larger studies, without evidence of subgroup differences (p = 0.21). Smaller studies exhibited greater heterogeneity, whereas larger studies demonstrated consistent effects with minimal heterogeneity.

4 Complications, failures and secondary surgical procedures

Complications, failures and secondary surgical procedures are listed in Table 4. There were 13 complications reported among 173 ankles, corresponding to a pooled complication rate of 7 % (95 % CI 1–16 %). The most common complication was persistent ankle pain reported in 8 cases (62 % of complications), followed by wound complications in 3 cases (23 % of complications) defined either as delayed healing or wound infection, and one case of hypertrophic scarring and one case of transient sural neuritis.

Sensitivity analysis stratified by study size demonstrated numerically higher complication rates in smaller studies (n < 15) compared with larger cohorts (17 % vs 5 %), however confidence intervals overlapped and subgroup difference were not statistically significant (p = 0.078), indicating the overall pooled estimate was not driven by small studies.

In total there were 3 failures (1.5 % of total cases), which were defined as persistent symptoms for over a year after surgery or persistent symptoms requiring repeat surgery. Bojanic et al. reported the need for 2 revision surgeries (1 % of total cases), with 1 patient requiring peroneal tendon debridement due to persistent pain and swelling, and another patient requiring further resection of a low-lying muscle belly of the PB tendon.²⁰

5 Discussion

The most important finding of this systematic review is that peroneal tendoscopy, across heterogeneous indications, produces improvements in patient-reported outcomes with good return to sport and a low rate of complications and reoperations. Peroneal tendoscopy may also function as a reliable diagnostic-therapeutic modality when preoperative imaging is equivocal. However, the results must be interpreted with caution due to the heterogeneity between the studies included and the lack of comparative studies.

Peroneal tendon physiology enables hindfoot eversion and dynamic lateral ankle stability through the peroneus brevis and longus coursing within the retromalleolar groove. The pathophysiology of peroneal tendon disorders typically involves crowding and altered tendon tracking due to SOL like LLPB muscle belly or PQ, intrasheath subluxation, tenosynovitis, longitudinal tearing, or frank recurrent dislocation with superior peroneal retinaculum (SPR) incompetence.²¹ The diverse presentations pose significant diagnostic challenges during clinical examination and through imaging techniques such as MRI and ultrasound.^3,9,14,22 Surgery is indicated for persistent posterolateral ankle pain, snapping, or instability refractory to structured nonoperative care.²¹ Open surgery was the standard for peroneal tendon disorders, but relatively high complication rates and only modest improvements in patient-reported outcomes^6,14 prompted a shift toward minimally invasive techniques designed to address these limitations. Peroneal tendoscopy emerged to address these limitations, offering reduced surgical morbidity and pain, dynamic intraoperative diagnosis, and targeted treatment through small portals.²³ Compared with open approaches, tendoscopy minimizes soft-tissue morbidity, facilitates targeted treatment, and supports faster rehabilitation.^6,14

The present study shows that PROMs consistently improved. The pooled mean postoperative AOFAS score was 96.6 points (95 % CI 94.3–99.0, I² = 84 %) at latest follow-up, with the pooled mean AOFAS improvement from baseline being +19.8 points (95 % CI 18.5–21.2, I² = 0 %). Chen et al. reported minimally clinical important differences (MCID) for AOFAS ranging from 5.8 to 18.4 points.²⁴ The present study's pooled AOFAS improvement exceeds the upper bound of Chen et al.‘s findings, supporting that the observed gains are not only statistically significant but also clinically meaningful. Consistent with these findings, Nishimura et al. reported statistically significant improvement in JSSF scores improving from 82.6 ± 5.3 to 99.1 ± 3.5 (p < 0.05),¹⁴ and Kennedy et al. reported statistically significant improvements in FOAS (57 ± 14 to 86 ± 8.4 p < 0.01) and SF-12 scores (53 ± 14 to 81 ± 7.8, p < 0.01).¹⁸ Return to sport or activity was favorable across the studies. For instability procedures, the return to sport was within 12 weeks, with tendoscopic SPR repair allowing for slightly earlier return than open repair (12.2 ± 0.6 weeks for tendoscopic vs 13.4 ± 1.5 weeks for open).¹⁴ After tendoscopic groove deepening, the mean return to sport was 14.8 ± 2 weeks.¹⁶ Other studies reported good rates of return to unrestricted daily and recreational activity without a specified timeline.^15,17 One of the main proposed advantages of tendoscopic repair is reduced tissue damage during instrumentation. Higher quality studies are required to assess the return to sport or activity compared to open or alternative procedures.

Across studies, the most common clinical indication leading to tendoscopy was persistent lateral ankle pain and “snapping” with tenosynovitis and intrasheath subluxation. In mixed series, tenosynovitis was the single most frequent intraoperative finding, and tendoscopy was used across a broad spectrum of procedures, including synovectomy, SOL excision, fibular groove deepening, mini-open repair of tendon tears, and tendoscopic SPR repair. Preoperative imaging appears to perform well for tenosynovitis and tendon tears but is less reliable for stenosis and low-lying muscle bellies (LLMB).^18,20 Kennedy et al. showed high overall agreement between MRI and tendoscopy yet variable lesion-level performance and known pitfalls, such as the magic angle effect, aligning with weaker reliability for stenosis.¹⁸ Urgüden et al. also demonstrated MRI–tendoscope mismatches in individual cases.¹⁹ Bojanić et al. showed that LLMB was common intraoperatively and frequently missed or misclassified preoperatively. When LLMB was suspected, specificity was high, but sensitivity was only around 52 %.^18,20 The dynamic nature of the peroneal tendons, as they glide around the lateral malleolus and peroneal tubercle²¹ makes accurate diagnosis challenging with MRI due to the magic angle effect.^25–28 This effect occurs when tendons have their fibers oriented at approximately 55° to the magnetic field, causing an artificially high signal intensity on MRI in the absence of pathology.²¹ Peroneal tendoscopy reduces such diagnostic errors by offering a real-time assessment of tendon tear size and the degree of tenosynovitis. Tendoscopy therefore has a low threshold as both a confirmatory diagnostic and definitive therapeutic step when symptoms persist despite nondiagnostic studies. In-office needle tendoscopy (IONT) may extend these advantages to the clinic setting.²⁹ IONT has been performed in peroneal tendon disorders with several techniques published.^29–32 It allows for a wide-awake local anesthesia technique with dynamic evaluation and immediate minimally invasive treatment.^29,31 IONT has been reported in the setting of other foot and ankle tendon pathologies, including posterior tibial,³³ and Achilles tendons,³⁴ as well as for plantar fascia release.³⁵ In a retrospective case series of 12 patients with chronic Achilles tendinopathy, Butler et al. demonstrated statistically significant improvements in both Victoria Institute of Sports Assessment–Achilles (VISA-A) scores and visual analogue scale (VAS) scores at a mean follow-up of 26 months, with an average return to work time of 5.9 weeks.³⁶ Early data on peroneal IONT suggests high patient acceptability, good diagnostic ability, and early return to work in peroneal tendon pathology,³⁷ however, more studies are needed to report on long-term outcomes, complication and reoperation rates, and comparative effectiveness versus standard tendoscopy and open surgery to ascertain its true clinical impact. Despite the limited peroneal-specific evidence, IONT remains promising given its favorable performance in other foot-and-ankle pathologies, where it has demonstrated high patient acceptability, useful diagnostic yield, and rapid functional recovery. The potential translatable benefits that merit confirmation in peroneal tendon cohorts.

The present systematic review reports a low complication rate of 7.6 % (13 complications) across the eight included studies. The most frequent complication was persistent ankle pain in 62 % of complications (8/13 cases), followed up by wound healing issues in 23 % of complications (3/13 cases), and a single case of hypertrophic scarring and transient sural neuritis. The low complication rate likely reflects the minimal soft-tissue dissection and small portal approach of tendoscopy, along with direct visualization that reduces inadvertent iatrogenic injury and limits the extent of bony and soft-tissue work to what is necessary. Failures occurred in 1.5 % of all cases and were defined as persistent symptoms beyond one year or symptoms necessitating repeat surgery. Only two revision operations (1 % of all cases) were required, and were both reported in the case series by Bojanić et al. One patient underwent peroneal tendon debridement for ongoing pain and swelling and the other required further resection of LLPB muscle belly.²⁰ The low failure rate is plausibly related to the tendoscopy's diagnostic-therapeutic nature, whereby it allows for real-time confirmation of the pain etiology and definitive treatment at the same time. This reduces residual pathology and the need for staged procedures.

To the authors’ knowledge, this is the first systematic review of peroneal tendoscopy that includes a focused synthesis across the principal clinical indications for peroneal tendoscopy, integration of functional outcomes, return-to-sport timelines, diagnostic accuracy considerations, and procedural complication profiles. This systematic review is constrained by the underlying evidence base, which is dominated by small case series and only one retrospective cohort study, which introduces selection bias and limits causal inference. Reporting was heterogenous across indications, techniques and outcome instruments. Five studies reported PROMs, however only four reported the same metric, limiting the feasibility of robust pooling. The follow-up was mostly short to mid-term, and therefore this review is unable to comment on long-term adverse events or late recurrence of peroneal tendon pathologies. These limitations temper confidence in effect sizes and generalizability and underscore the need for prospective controlled studies with standardized outcomes and longer follow-up. The present study mitigated heterogeneity by pre-specifying outcomes, using per-ankle denominators where appropriate, stratifying analyses by indication and procedure where possible, and pooling only when outcome measures were aligned. Although several included studies had small sample sizes, sensitivity analyses stratified by cohort size did not demonstrate significant differences in pooled postoperative scores, magnitude of improvement, or complication rates. Importantly, smaller studies did not systematically overestimate treatment effects, supporting the robustness of the observed findings while acknowledging reduced precision and greater heterogeneity in smaller cohorts.

Future work should prioritize prospective, comparative designs with standardized outcome measures (including sport-specific function and time-loss metrics), longer follow-up, and explicit reporting of imaging–arthroscopy concordance to better define patient selection and the incremental value of tendoscopy and IONT.

6 Conclusion

The most important finding of this systematic review is that peroneal tendoscopy across heterogeneous indications consistently improves patient-reported outcomes, facilitates reliable return to activity, and carries a low rate of complications and reoperations. Across the available literature, postoperative PROMs were consistently high with clinically meaningful improvements, although the precision of pooled estimates is limited by small sample sizes in several studies. Return to sport clustered around three months, and overall complication and failure rates were 7.6 % and 1.5 %, respectively. In parallel, tendoscopy functioned as a useful diagnostic–therapeutic step when preoperative imaging was equivocal, particularly for stenosis and SOLs LLMB and PQ.

Informed consent statement

Not applicable.

Location of work performed

Foot and Ankle Division, Department of Orthopaedic Surgery, 645 Madison Avenue, 4th Floor, New York, NY, 10022, NYU Langone Health, New York City, USA.

Institutional review board statement

Not applicable.

Author contributions

Conceptualization: A Tham, R Rajivan; Methodology A Tham, R Rajivan, J Rubin, JJ Butler; Formal analysis: A Tham, R Rajivan, J Rubin.

Data curation: A Tham, R Rajivan, J Rubin, JJ Butler, M Pianka, A Nair, H Campbell, N Rynecki, M Roof.

Writing – original draft preparation: A Tham, R Rajivan, J Rubin, JJ Butler, M Pianka, A Nair, H Campbell, N Rynecki, M Roof.

Writing – review and editing: A Tham, R Rajivan, J Rubin, JG Kennedy; Project administration: JG Kennedy.

All authors have read and agreed to the published version of the manuscript.

Funding

There was no funding for this study.