(Kiosk 2) Ischiofemoral Impingement Due to an Undiagnosed Pelvic Avulsion Fracture: A Case Report

Case Diagnosis: Ischiofemoral impingement and ischial bursitis due to heterotopic ossification

Case Description or Program Description: A 26-year-old female graduate student presented with 10 years of posterior right hip pain and decrease in athletic function. Notable history included a hamstring strain while sprinting in 5th grade. Physical exam suggested hamstring tendinopathy and ischiofemoral impingement. MRI revealed a chronic, fragmented, ischial tuberosity apophyseal avulsion with ischial bursitis and edema within the fragmented bone suggesting the development of Heterotopic Ossification (HO). Diagnostic ultrasound revealed additional signs of ischiofemoral impingement, which were not evident on MRI. Ultrasound-guided corticosteroid injections in her ischial bursa and ischiofemoral space provided complete relief. The patient was able to resume her activities of daily living (ADLs) and exercise without pain.

Setting: Outpatient Musculoskeletal Clinic

Assessment/Results: At 6 weeks post-procedure her pain remained a 3/10 with continued progress in ADLs and exercise. She could ride a bike pain-free for up to 60 minutes and attend the entirety of her classes without discomfort.

Discussion (relevance): Ischial tuberosity avulsion fractures are an uncommon cause of injuries in athletes and often occur after forceful hamstring contraction in a lengthened position. Although rare, heterotopic ossification can develop as late sequelae and can be a debilitating cause of pain and dysfunction, such as in this case. Furthermore, this case is unique because it exemplifies the perfect scenario in which point-of-care ultrasound can be more advantageous than MRI as a diagnostic tool due to its dynamic nature and potential for interventions. While corticosteroid injections did provide at least 6 weeks of pain relief and improved function, this patient will likely require surgical management to address the mechanical impingement.

Conclusions: A timely diagnosis and management of pelvic avulsion fractures can help mitigate the risk of rare complications like HO. Additionally, diagnostic and interventional ultrasound can be valuable for yielding clinically relevant information that may be missed on MRI.