Can we encourage the endoscopic treatment for external snapping hip (ESH)? A systematic review of current concepts

Snapping hip syndrome (SHS), also known as coxa saltans, is a condition characterized by a snapping sensation, sometimes audible and/or associated with pain [1, 2]. Perrin first described this condition in 1859, and it is estimated to affect up to 10% of the general population, with a female prevalence [3]. There are two main forms based on the causes: intra-articular and extra-articular, with the latter being more common [4]. Further categorization among extra-articular forms includes internal hip snap syndrome (ISHS) and external hip snap syndrome (ESHS). ESHS, the most prevalent form, is often linked to repetitive flexion and extension movements seen in certain sports like dancing or running or to predisposing anatomical conditions such as coxa vara, prominent greater trochanter, reduced bi-iliac width, increased distance between the greater trochanters, bone spurs, and trochanteric bursa hyperplasia [5‐9]. Thickening of the posterior part of the iliotibial band (ITB) or focal thickening of the anterior border of the gluteus maximus (GM) muscle can typically cause ESHS [10]. The thickened posterior ITB passes over the greater trochanter (GT), snapping anteriorly during extension and returning to a posterior position during flexion, giving rise to the phenomenon of snapping, corroborated by Ober's test positivity [7, 8, 11]. Asymptomatic snapping should be considered the usual occurrence, occurring in the 5–10% of population [12, 13]. Painful symptoms may occur in some patients due to inflammation of the GT bursa between the gluteus medius and vastus lateralis [11]. First-line treatment for such patients typically involves conservative measures such as physiotherapeutic stretching exercises, anti-inflammatory therapy, or corticosteroid infiltrative therapy targeting the greater trochanteric bursa. Surgery is indicated if conservative treatment fails for at least 6 months [13]. Historically, this surgery has been performed with an open technique with lengthening of the ITB by Z or N-plasty or with resection of a posterior portion of the ITB, elliptical resection, or step-cut procedure [2, 7, 14]. Although these techniques have shown promising results in reducing pain and clicking, they carry all the risks of open surgery, such as hematoma formation, wound complications, slow postoperative recovery, and Trendelenburg gait [15, 16]. In recent years, advancements in arthroscopic techniques have made it possible to perform surgeries such as gluteus major tenotomy and/or ITB release for this condition.

The main techniques reported in literature are ITB band release (diamond-shape defect), GM release, ITB band release (transverse cut) and ITB + GM complex release (fan-like).

ITB diamond-shape defect was developed by Ilizaliturri [17] and it consisted in one longitudinal cut along the ITB over the GT and then two transverse cuts, starting from the center of the first one and directed anteriorly and posteriorly. The resection of the four flaps created on the ITB result in the diamond-shape defect. In 2013 two more techniques have been published: ITB transverse cut and GM release.

The first one [18] is a transverse cut of ITB from anterior to posterior at the level of the snapping assessed before surgery, while the second one [1] is focused on the release of GM insertion on femoral linea aspera. The most recently described technique produces a fan-like release of ITB and GM through a stepwise approach, until the snapping is no more reproducible [19].

This systematic review aims to assess clinical outcomes, time to return to sport, and complications associated with arthroscopic surgery for external snap hip syndrome (ESHS).

The electronic database search yielded 96 articles, of which 43 were selected for systematic review. Among them, 9 articles focused on endoscopic external snap hip (ESH) treatment, including 403 patients and 689 hips, of which 286 were bilateral, and 262 were female patients. All patients underwent ITB release, gluteus maximus tenotomy or a combination of both treatments. The information regarding the studies and patients included can be found in Table 1.

All studies showed failure of conservative treatment, such as physical therapy and/or corticosteroid injections, before surgery [1, 3, 17‐19, 24‐27].

The most important finding of this systematic review is that endoscopic management of EHS offers a safe and effective means of improving functional outcomes and returning patients to pre-injury activity levels.

The primary goal of surgery is to eliminate the snapping by releasing the ITB and along with GT bursectomy to reduce tension and to remove the inflamed tissue. Several authors have described various surgical techniques, including simple release (transverse or cross incision), release with resection, lengthening of the ITB by Z-plasty or repair, diagonal trochanteric osteotomy, cross incision with flaps sutured to the tract, resection of the posterior half of the tract at the insertion of the gluteus maximus, and ellipsoidal resection of the tract over the trochanter [28]. Open surgical approaches have been associated with complications, including recurrent snapping, persistent hip pain, and sensory nerve injury resulting from surgical incisions [29]. A study by Hoskins et al., in which 80 patients (92 hips) with ESH were operated on via an open approach, showed a failure rate of 22% [30]. Therefore, the endoscopic release was introduced to reduce complications, recurrency, and invasivity.

The success of surgery depends on the precise execution of the technique and careful patient selection, taking into account factors such as motivation and emotional stability. Surgery is an appropriate final solution for refractory cases to conservative treatment [17].

This systematic review highlights that endoscopic treatment of ESH produces favorable outcomes in the short to medium term. Endoscopic techniques demonstrate success rates ranging from 75 to 100%, with failure rates ranging from 0 to 25% (including recurrent snapping at 4%-25% and recurrent pain without snapping at 1%25%), as reported in the included studies [1, 3, 17‐19, 24‐27].

The study with the largest cohort (248 patients, 477 hips) reported a 100% success rate with no cases of failure or recurrence over a 2-year follow-up period [26]. Whereas the study with the least favorable outcomes involved the smallest patient sample (8 patients, 9 hips) and reported a 75% success rate with a 25% failure rate after a follow-up period of 2.6 years [1].

This review includes three distinct techniques for treating ESH. Four studies reported a diamond-shaped or transverse cut [17‐19, 25] of the ITB, three studies opted for an isolated tenotomy of the gluteus maximus [1, 3, 27], while two other studies combined both techniques [24, 26].

A noteworthy finding of this review is the high rate of return to pre-injury activity levels among patients [1, 3, 17, 19, 24] (see Table 3). The time required for patients to return to pre-injury activity levels was mentioned in five studies and ranged from 6 weeks to 6 months, depending on the severity of the snapping and the specifics of the rehabilitation program. [1, 18, 24, 26, 27]

Only seven patients experienced recurrence: all but one returned to their pre-injury activity levels without the need for revision. The exceptional patient, a 33-year-old man, experienced a persistent snap and pain that needed a revision procedure, with gluteus maximus release. After a follow-up period of 22 months, the patient remained asymptomatic and snap-free [1].

The oldest study included in this review, conducted by Ilizaliturri et al. in 2006, focused on endoscopic treatment of ESH in a cohort of 10 patients (11 hips). Using the WOMAC Score, a validated joint-specific scale, the study reported a satisfactory success rate of 92 percent. In addition, the authors noted an improvement in WOMAC scores from 81 to 94 over a mean follow-up period of 22 months (range: 12–36 months) [17].

In a recent study by Malinowski et al. in 2024, 27 patients (31 hips) with ESH were evaluated after endoscopic treatment. Significant improvements were observed in the primary outcome measure, iHOT-12, which increased from 46 to 93 after a minimum of 2 years of follow-up. In addition, the study observed a 100% patient satisfaction rate, along with a low incidence of complications and return to previous activity levels within eight weeks [24].

In the most extensive study by Shrestha et al. in 2017, a retrospective evaluation was performed on a substantial cohort of patients undergoing endoscopic transverse ITB release (n = 248 patients, 477 hips). After a 2-year follow-up period, the study reported a remarkable 100% success rate with no intraoperative or postoperative complications [26].

Endoscopic surgical management of the ESH can be performed with minimal risk of recurrence and/or revision. In our systematic review, we observed similarly low incidence rates of recurrence (1.02%) and revision (0.15%).

Zini et al. conducted a retrospective evaluation in 2013 on a series of patients undergoing endoscopic transverse ITB release (n = 15 hips). After a mean follow-up of 34 months (range: 12–84 months), their cohort of patients reported no intraoperative or postoperative complications [19]. Similarly, Yoon et al. in 2014 retrospectively evaluated patients underwent endoscopic ITB release with a diamond-shaped cut with gluteus maximus tenotomy (n = 10 hips). In their cohort, only one patient reported mild pain after a mean follow-up of 19 months (range: 12–33 months) [18].

The endoscopic technique described by Ilizaliturri et al. [17] revealed satisfactory resolution of symptoms in seven of the nine hips. However, the two hips that did not have a resolution of snapping or pain showed contracture and hypotrophy of the gluteus maximus before surgery. This suggests a potentially different biomechanical etiology for these cases of snapping hips, underscoring the importance of a thorough physical examination and attention to the presence of posterior muscle contractures. In certain situations, with the recurrency of intraoperative snapping, releasing both the iliotibial band (ITB) and gluteus maximus (GM) muscles may be necessary [24].

This systematic review presents some limitations that need to be highlighted. First, a few low-quality studies are included in the analysis. Most of them are retrospective. Second, studies are susceptible to many sources of bias in data collection and reporting, participant selection, and unblinded outcomes assessment. Third, various endoscopic surgical techniques are employed. Fourth, a wide variety of follow-ups with 12–204 months were reported in the different studies. A more homogeneous and standardized clinical follow-up could improve the data's validity. However, the data presented in this review allow hypotheses to be made for future high-quality studies.

External snapping hip is a condition better understood over time, but its treatment remains controversial. This systematic review shows that endoscopic treatment of external snap hip (ESH) is a viable option when conservative measures fail, mainly to relieve mechanical impingement and improve symptoms, with a low risk of complications and a high likelihood of returning patients to pre-injury activity levels. This may suggest that endoscopy may be chosen over open techniques. However, further research is essential to evaluate the long-term efficacy and cost-effectiveness of endoscopic treatment of ESH. Large-scale prospective randomized studies with carefully selected control groups are needed to clarify the potential benefits of surgery for refractory cases of ESH.