Internal Snapping Hip Syndrome: Incidence of Multiple-Tendon Existence and Outcome After Endoscopic Transcapsular Release

Purpose: To report the frequency of presentation of bifid or multiple iliopsoas tendons in patients who underwent endoscopic release for internal snapping hip syndrome (ISHS) and to compare both groups. Methods: A consecutive series of patients with ISHS were treated with endoscopic transcapsular release of the iliopsoas tendon at the central compartment and prospectively followed up. The inclusion criteria were patients with a diagnosis of ISHS with failure of conservative treatment. During the procedure, the presence of a bifid tendon was intentionally looked for. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores were evaluated preoperatively and at last follow-up. Four patients presented with a bifid tendon and one patient had 3 tendons. At a minimum of 12 months' follow-up, the presence of snapping recurrence was evaluated and the WOMAC scores were compared between both groups. Results: Among 279 hip arthroscopies, 28 patients underwent central transcapsular iliopsoas tendon release. The mean age was 29.25 years (range, 16 to 65 years; 6 left and 22 right hips). Group 1 included 5 patients with multiple tendons; the remaining patients formed group 2 (n = 23). None of the patients presented with ISHS recurrence. The mean WOMAC score in group 1 was 39 points (95% confidence interval [CI], 26.2 to 55.4 points) preoperatively and 73.6 points (95% CI, 68.4 to 79.6 points) at last follow-up. In group 2 the mean WOMAC score was 47.21 points (95% CI, 44.4 to 58.2 points) preoperatively and 77.91 points (95% CI, 67.8 to 83.4 points) at last follow-up. We identified a bifid tendon retrospectively on magnetic resonance arthrograms in 3 of the 5 cases that were found to have multiple tendons during surgery. None of these were recognized before the procedures. Conclusions: In this series the surgeon intentionally looked for multiple tendons, which were found in 17.85% of the cases. Clinical results in patients with single-and multiple-tendon snapping seem to be similarly adequate. However, the possibility of a type II error should be considered given the small number of patients.