Diagnostic Validity of Ultrasound Imaging After Injection Into the Peroneal Tendon Sheath for Detecting Pseudo-Pouch Formation in Recurrent Peroneal Tendon Dislocation.

BACKGROUND

Recurrent peroneal tendon dislocation (RPTD) can be difficult to diagnose when tendon dislocation cannot be reproduced clinically. Most cases are associated with pseudo-pouch formation due to incomplete healing of the superior peroneal retinaculum/fibrocartilaginous ridge complex. We evaluated ultrasound-guided intrasheath fluid injection (US-I) for detecting pseudo-pouch formation and compared it with magnetic resonance imaging (MRI).

METHODS

In this small retrospective diagnostic case-control study, 23 ankles with surgically confirmed RPTD and 11 symptomatic ankles without RPTD underwent MRI and US-I. Pseudo-pouch formation was independently assessed by 3 foot and ankle surgeons. Intraoperative findings served as the reference standard in the RPTD group. For the primary endpoint, sensitivity, specificity, and interobserver agreement for pseudo-pouch detection were calculated for both modalities. As an exploratory analysis, we also assessed the sensitivity of pseudo-pouch positivity on US-I for surgically confirmed RPTD.

RESULTS

The study included 23 RPTD ankles (mean age, 29.9 ± 18.1 years) and 11 control ankles (mean age, 38.8 ± 17.3 years). Twenty-one of 23 RPTD cases had an intraoperative pseudo-pouch, all detected by US-I; the remaining 2 had no pseudo-pouch on US-I or at surgery. For pseudo-pouch detection, US-I showed 100% sensitivity (95% CI, 83.9%-100.0%) and 100% specificity (95% CI, 75.3%-100.0%), whereas MRI showed 38.1% sensitivity (95% CI, 18.1%-61.6%) and 100.0% specificity (95% CI, 75.3%-100.0%). In the exploratory RPTD analysis, US-I identified 21 of 23 RPTD ankles (91.3% sensitivity).

CONCLUSION

In this small retrospective cohort, US-I may improve visualization of pseudo-pouch morphology compared with routine MRI in selected patients with suspected RPTD. This technique may provide clinically useful diagnostic information, particularly when tendon dislocation cannot be reproduced during physical examination. Prospective validation in a consecutive suspected-RPTD cohort is needed.

LEVEL OF EVIDENCE: Level III, diagnostic study.