Avulsion fracture of the ischial tuberosity: Is the current evidence sufficient to resolve the challenges of treatment selection?

Abstract

Avulsion fracture of the ischial tuberosity (AFIT) is a clinically rare injury that primarily occurs in adolescents participating in competitive sports. AFIT can be challenging to diagnose and manage due to its subtle presentation and the potential for misdiagnosis. Selecting an appropriate treatment method remains challenging due to the lack of universally accepted, evidence-based treatment guidelines for optimal management. A review of the relevant literature indicated that AFIT exhibits more complex healing patterns than other pelvic avulsion fractures with conservative management, and also that the outcomes of AFIT following the surgical treatment of chronic cases are often not as favorable as those of acute cases. Therefore, clinicians should increase their awareness of this type of fracture and consider aggressive surgical intervention in patients with displaced AFIT to ensure optimal outcomes and expedite their return to pre-injury athletic performance levels.

Key Words: Avulsion fracture of the ischial tuberosity; Treatment selection; Conservative management; Surgical intervention; Pelvic avulsion fracture

Core Tip: Avulsion fracture of the ischial tuberosity (AFIT) is a clinically rare injury mainly incurred by adolescents during competitive sports. AFIT is frequently misdiagnosed as a tendon tear or muscle strain and selecting an appropriate treatment method remains challenging due to the absence of evidence-based treatment guidelines. A literature review indicated that AFIT exhibits more complex healing patterns than other pelvic avulsion fractures under conservative management. Clinicians should increase their awareness of this type of injury. Aggressive surgical intervention is suggested for patients with displaced AFIT to ensure optimal outcomes and expedite their return to pre-injury athletic performance levels.

INTRODUCTION

Avulsion fracture of the ischial tuberosity (AFIT) is a rare injury that predominantly occurs in adolescent athletes participating in competitive sports[1]. AFIT accounts for approximately 12% of all pelvic avulsion fractures, and the mean age of patients is about 15 years[1,2]. This type of injury typically occurs due to a sudden and forceful contraction of muscles attached to the ischial tuberosity apophysis, resulting in its avulsion[2]. While the hamstrings are the main muscles associated with AFIT, some cases also involve the adductors; these muscles experience intense traction during sports such as football, sprinting, and gymnastics[1]. An immediate plain pelvic radiograph following trauma helps diagnose AFIT[2]. In atypical cases, such as stress fractures with negligible displacement that may not be discernible on standard radiographs, advanced imaging techniques such as computed tomography or magnetic resonance imaging can help differentiate these injuries from tendon tears or muscle strains[3]. Chronic injuries constitute nearly half of the reported cases of AFIT, and often result from delayed presentation, misdiagnosis, or inadequate initial management, primarily due to insufficient awareness of these injuries and inappropriate treatment[1]. AFIT treatment is challenging largely due to the lack of universally accepted evidence-based treatment guidelines for its optimal management[4]. As a general guideline, treatment choices should depend on fragment size and the degree of displacement[5]; however, the diverse physical capabilities of patients and their functional demands must also be considered. This opinion review proposes a modified framework for managing AFIT based on relevant key case series, case reports, retrospective studies, and reviews from databases such as PubMed and Web of Science, thereby aiming to resolve the challenges associated with the treatment of AFIT.

CURRENT MANAGEMENT OF AFIT

Current treatment options for acute cases of AFIT

Pelvic apophyseal avulsion fractures generally exhibit favorable healing[6]. Conservative management is often sufficient for acute AFIT characterized by minimal displacements or small fragments. A regimen involving rest, analgesics, physical therapy, and immobilization lasting approximately 4-6 weeks, followed by progressive rehabilitation, typically produces satisfactory recovery outcomes in most patients[6,7]. Schuett et al[6] conducted a retrospective study of 225 patients with pelvic avulsion fractures; 97% of the patients were managed conservatively with excellent overall results. Notably, 25 patients (11%) were classified as AFIT, and of these, 3 (16%) with initial displacements exceeding 2 cm eventually developed a nonunion. Therefore, a 2-cm displacement was proposed as a threshold for surgical intervention due to the significantly increased risk of nonunion following conservative care[6,8,9]. However, there is no consensus on a precise fragment displacement threshold that warrants surgical intervention. Ferlic et al[10] also conducted a retrospective study of 13 patients with AFIT; 5 of the patients with displaced fragments over 15 mm underwent surgical procedures and 8 received conservative treatment. Notably, among the surgically treated patients, four with acute AFIT achieved excellent outcomes, while one initially subjected to conservative treatment experienced persistent pain and developed pseudoarthrosis. This patient was treated surgically with positive results, but had to discontinue sports activities. Among the eight patients treated conservatively, four had a fragment displacement less than 15 mm and exhibited excellent outcomes, whereas the other four had a displacement exceeding 15 mm and developed pseudoarthrosis. These findings underscore the importance of early surgical intervention in physically active patients with an AFIT displacement of more than 15 mm. The 15-mm displacement threshold has also been proposed by Nauta et al[5], Eberbach et al[11], and Best et al[12] for selecting operative treatment for AFIT. However, Gidwani and Bircher[13] recommended AFIT with fragment displacement over 1 cm as an indication for early surgical fixation to avoid chronic symptoms (Table 1). The optimal cut-off value for fragment displacement appears to be unresolved, with differing recommendations potentially due to variables such as patient cohorts, treatment methods, rehabilitation programs, follow-up durations, or outcome measures across studies. For example, in the cohort of a study by Schuett et al[6], many patients had a follow-up period of 3 months or less, which may have limited the assessment of fracture healing changes and related symptoms. Given the inherent limitations of reported studies on AFIT, such as small sample sizes, retrospective bias, and lack of randomization, a large-scale prospective control study is needed to determine the optimal cut-off value for fragment displacement, although conducting such research presents significant challenges due to the low frequency of AFIT and variability among individual patient conditions. However, in the author’s opinion, considering the operative trauma and costs associated with surgical treatment, initial conservative management may be prudent for AFIT with minor displacements under 1 cm. If radiographic evaluations indicate no signs of healing or progressive displacement during follow-up at approximately 1 month, surgical intervention is warranted, which may also yield favorable outcomes that are comparable to those of immediate surgery post-injury[5,13]. In AFIT patients with fragment displacement exceeding 1.5 cm, operative treatment should be prioritized to prevent the risk of nonunion and other complications. Treatment of patients with displacements ranging from 1.0 cm to 1.5 cm should be individualized based on physical requirements of the patient; in particular, surgical treatment is suitable for those desiring a rapid recovery and satisfactory functional results (Figure 1).

Figure 1 A management flowchart suggested for avulsion fracture of the ischial tuberosity. CT: Computed tomography; MRI: Magnetic resonance imaging.

Table 1 Thresholds for surgical intervention of avulsion fracture of the ischial tuberosity suggested in the literature.

Threshold for surgery	Ref.	Cohort size and fragment displacement	Treatment methods; duration between trauma and surgery; internal fixation	Rehabilitation methods	Follow-up duration; outcome measures	Reported results
20 mm	Schuett et al[6], 2015	25; 9.5 ± 11.6 mm	Conservative treatment	Protected weight-bearing for 4 weeks to 6 weeks, followed by physical therapy	Mean 151 days of radiographic follow-up; mean 292 days of clinical follow-up	1 with fracture displacement of 6 mm developed a symptomatic nonunion, 3 with displacement over 20 mm resulting in an asymptomatic nonunion
20 mm	Biedert[9], 2015	3; > 20 mm	Surgical treatment; 2-22 weeks; biodegradable suture anchors	Patients fitted with harness device to hold the knee at 90 degrees of flexion for 4-6 weeks; specific postoperative rehabilitation regime	12-24 months; subjective and objective functional results	Good subjective and objective functional results obtained in 3 patients, with all returning to their preinjury sports activities, although one patient underwent a reoperation due to suture loosening
15 mm	Ferlic et al[10], 2014	13; 4 cases < 15 mm and 9 cases > 15 mm	Conservative treatment in 8 patients and surgical treatment in 5 patients; duration not specified; cannulated compression screws	Partial weight-bearing for 6 weeks followed by physical therapy and then eccentric and concentric training for conservative management of patients; partial weight-bearing with light training for 6 weeks in surgically treated patients followed by sports activities	At least 24 months; clinical assessment including strength testing of the hamstring and adductor muscles, range of motion, neurologic examinations, subjective complaints, modified Harris Hip Score, surgical complication, and radiological assessment	4 cases with < 15 mm displacement exhibited excellent outcomes with conservative treatment, 4 cases > 15 mm displacement achieved excellent outcomes with surgical treatment, but 2/4 cases > 15 mm displacement developed pseudoarthrosis with conservative treatment, and another patient who developed pseudoarthrosis following initial conservative treatment obtained good results with surgical intervention but stopped playing soccer
15 mm	Best et al[12], 2021	11; 3.3 cm (mean)	Surgical treatment; mean 14.8 weeks and median within 3 weeks; screws or anchors, excision of bony fragment and suture anchor repair of the tendons, or suture of the tendinous scary bridge	Standardized rehabilitation program	Mean 18.2 months; Hamstring injury-specific Perth Hamstring Assessment Tool, return to sports	Surgery led to very good functional results, with a Perth Hamstring Assessment Tool score mean of 86.9 and high return to sports (10/11)
10 mm	Gidwani and Bircher[13], 2007	6; 1 case no displacement, 1 case 2 cm, 3 cases ≥ 3 cm, 1 case 3 cm chronic avulsion	2 cases non-operative management and 4 cases operative management; 3-month delay in 1 case and ≥ 30 months delay in 3 cases, unknown delay duration in 2 cases; reconstructive plate with or without bone graft	Not specified	Not specified	All patients obtained good outcomes

Diverse surgical methods tailored to individual cases of acute AFIT are presented in the literature. The predominant surgical approach involves open reduction and fixation using devices that include cancellous screws, lag screws, resorbable screws, suture anchors, and reconstruction plates, depending on the location and size of the fragment. Nearly all previously reported surgically treated cases have demonstrated excellent outcomes[5,9,12] of healed fractures, compared to 18% nonunions in non-operative cases, based on the extent of fracture displacement[5]. These outcomes underscore the superior results associated with operative management of these injuries.

Treatment options in chronic cases of AFIT

In chronic cases of AFIT, bone healing potential is often impaired due to sclerosis of the fracture ends or vascular compromise. Nonunion frequently occurs in these cases, along with hamstring syndrome, characterized by persistent pain, muscle weakness, impaired sports performance, and potential sciatic nerve entrapment, all of which increase treatment complexity[14,15]. Furthermore, in chronic cases, conservative treatment such as symptomatic therapy, physical therapy, and functional exercise has yielded minimal to no significant results[15,16]. Therefore, surgical intervention is the only viable option for achieving favorable outcomes in patients with chronic AFIT.

The primary approach to surgery in chronic cases of AFIT involves open reduction and internal fixation of displaced fragments that can be adequately mobilized. Prior to fixation, freshening the fracture ends is crucial to promote healing[10]. If a fracture is not reducible, excision of the fragment followed by attachment of the tendons either to surrounding tissues or to a bridge of scar tissue may be an alternative[15]. If symptoms suggest sciatic nerve involvement, an additional neurolysis procedure is warranted[13]. Chronic cases following surgery can also achieve satisfactory outcomes, with relieved pain and improved function[5,10,12,17]. However, a lower rate of full return to sports has been noted[10,12,17]. Jorgensen et al[18] reported successful outcomes using ultrasound-guided surgical fenestration combined with rehabilitation for sport-related nonunions of AFIT; however, this approach is primarily appropriate in cases with minimal displacement.

FUTURE PERSPECTIVES

A review of the literature indicated that AFIT is associated with more complex healing processes than other types of pelvic avulsion fractures. This is likely due to the need to stringently maintain the posture required for successful healing, which is characterized by hip extension and knee flexion that reduces hamstring stress during conservative treatment. This posture also restricts sitting and standing on the affected leg for several weeks, which is typically difficult for patients to manage. Consequently, the continued stretching stress from the hamstring on the bony fragment increases the risk of displacement and subsequent nonunion. Notably, studies have reported that nonunion occurred after several months of rest and conservative management in AFIT patients with fragment displacement of less than 1 cm[6,15,17,19]. One study reported that the initial fragment displacement of 12 mm in an AFIT patient increased to 23 mm after 11 months of conservative therapy, ultimately requiring surgical intervention for fracture healing[16]. Furthermore, prolonged immobilization, such as the use of splints to maintain a special position, may result in hamstring musculature retraction, hindering the return to previous levels of sports activity[20]. Given the potential complications of fracture nonunion and hamstring syndrome associated with conservative management of acute AFIT cases, and considering that outcomes in operatively treated chronic cases are not as favorable as those in acute cases[10,12,17], the author recommended that physically active patients and athletes with displaced AFIT undergo minimally invasive surgical intervention using screws under navigational guidance to stabilize the fractures at the time of diagnosis, minimizing the risk of developing nonunions. This would facilitate early active functional rehabilitation while preserving the strength of the involved musculature, thereby expediting return to pre-injury athletic performance levels. Due to a lack of high-level evidence such as prospective or randomized trials, treatment decisions for individuals should be based on suitable thresholds for surgical intervention.

CONCLUSION

While the current evidence remains insufficient to fully resolve the challenges of treatment decisions associated with AFIT, a review of the relevant literature suggests that AFIT exhibits more complex healing patterns than other types of pelvic avulsion fractures. Therefore, clinicians should increase their awareness of these injuries and consider a more aggressive surgical approach in cases of displaced fractures to optimize outcomes and facilitate a prompt return to pre-injury athletic performance levels.