Snapping hip, also known as coxa saltans, is characterized by an audible snapping sound or sensation felt when the hip is in motion, and may be associated with pain1). Of different types, external snapping hip is accompanied by popping noise when the posterior border of the iliotibial band slides over the greater trochanter as the hip is flexed or extended, and confirmed a positive Ober's test2). Although snapping hip is usually painless, this syndrome may be painful when greater trochanteric bursitis is associated. For most cases, conservative and medical treatment showed good treatment response.

When symptoms persist despite different conservative treatment, surgical intervention is considered. Surgical treatment options are N-plasty with trochanteric bursectomy, Z-plasty and others. Although these invasive methods are effective in improving pain and snapping sound, skin incision leaves a large scar and the Trendelenburg gait may follow as a complication3,4,5,6,7,8,9,10). Ilizaliturri et al.5) obtained comparable clinical results compared to open surgical techniques by performing arthroscopic iliotibial band release in 10 patients (11 cases). Arthroscopy is increasingly performed in Korea. However, no literature has been reported on evaluating clinical results of arthroscopy for snapping hip. Therefore, this study aimed to indentify benefits of arthroscopic treatment by evaluating clinical results of iliotibial band release and gluteal sling release performed arthroscopically and comparing the results with those of previous studies.

The VAS decreased from 6.8 (range, 6-9) preoperatively to 0.2 (range, 0-2) postoperatively, and the mHHS improved from 68.2 (range, 43-73) to 94.8 (range, 89-100) after surgery. Of 7 patients, 6 were pain-free at final follow-up, but a patient complained of mild pain at about VAS score of 2. Hip adduction angles improved from 40° and 30°, respectively, to 0°in two patients with adduction difficulty. Moreover, they were able to cross one leg over the other in a sitting position. All patients had a negative Trendelenburg's test on the sixth postoperative week, and no patient had limping at the last follow-up. All patients were satisfied with scar aesthetically, and there was no recurrence of snapping sound.

External snapping hip commonly occurs due to contracture and tension of the iliotibial band, which results in a positive Ober's test. The Ober's test is performed to identify tightness of the illiotibial band, and can be indicative for adduction difficulty when putting legs down suddenly after knee flexion at 90° and hip abduction in a lateral position. However, snapping sound can rarely occur due to contracture and tension of multiple fibrous bands of the gluteus maximus. In this case, Ober's test is negative3,9,11). Although snapping hip is usually painless, this syndrome may be painful when greater trochanteric bursitis is associated. The greater trochanteric bursa is located between the greater trochanter, belonging to insertion of the gluteus medius and origin of the vastus lateralis, and iliotibial band, and pain can be generated from inflammatory response caused by snapping12). Most patients with snapping hip show good results with stretching exercise, antiinflammatory analgesic use, or greater trochanteric bursa injection3,4,5,8,13,14). However, patients may be unable to sit cross-legged or adduct both legs in a sitting position due to pain like those with adduction difficulty in this study. When pain and discomfort persist despite conservative treatment, surgical intervention is unavoidable. Although a wide range of surgical techniques have been reported in previous literature, open surgical approaches have been most commonly introduced3,4,9,15,16). After Ilizaliturri et al.5) have addressed the result of arthroscopic treatment, successive results have been continuously reported in international studies1,8). The surgical results of previous studies varied according to authors. Although surgical management of external snapping hip showed relatively favorable results, snapping or pain persisted postoperatively in some cases requiring reoperation3,4,5,6,7,15)(Table 1). With an average of 19-month follow-up after arthroscopic surgery, snapping symptom was fully recovered with good aesthetic results in this study. Pain was improved in 90% (9 out of 10) patients. Although a patient (1 case) complained of mild pain at about VAS score of 2, the patient had no physical limitations in activities of daily living. Although specific hip arthroscopic instruments should be available to treat intra-articular pathologies, knee or shoulder-length arthroscopic tools can be used to treat snapping hip. Compared to an open Z-plasty release, arthroscopy has a disadvantage of expensive cost. Although not happened in this study, a defect which was created during iliotibial band release and not reconstructed posteoperatively had a risk of abduction weakness or depression on the surface of the thigh1).

Limitations of this study were the relatively small sample size and short follow-up period and a retrospective study design. Since snapping hip improves with conservative management in most patients, only a few patients are eligible to receive surgical treatment and it is difficult to include a large number of subjects7). However, the long-term follow-up is anticipated to be favorable in identifying relapse of symptoms and the risk of complications in order to prove the effectiveness of arthroscopic intervention. Another limitation was that this study did not measure hip abductor muscle strength between the affected and healthy sides before and after the surgery. Since the iliotibial band acts as a static stabilizer of the hip, a diamond-shaped release of the iliotibial band weakens abductor muscle strength of the affected side. As a result, abductor muscle strength of the healthy side can be overloaded1). Therefore, measuring abductor muscle strength of both sides pre- and post-operatively is thought to be helpful in analyzing the effect of iliotibial band release on changes in abductor muscle strength. However, this study was able to measure changes in muscle strength indirectly by regularly examining ambulation impairment caused by weakened abductor muscle strength by performing the Trendelenburg test on the sixth postoperative week and third postoperative month.

Patients with external snapping hip recalcitrant to conservative management underwent arthroscopic treatment. Despite a short mean follow-up of 19 months, all patients were highly satisfied with both clinical and cosmetic results. We anticipate the successful treatment of patients with adduction difficulty due to contracture and tension of the gluteus maximus.