(Kiosk 2) An Unusual Presentation of Bilateral Idiopathic Hip Avascular Necrosis: A Case Report

Case Diagnosis: A 64 year old woman with rapidly worsening, abnormal gait is diagnosed with bilateral hip avascular necrosis.

Case Description or Program Description: The patient presented to their primary care provider with symptoms of acutely worsening stiffness over the course of one month in the setting of chronic low back pain resulting in new onset gait dysfunction requiring a cane for ambulation. Lumbar MRI revealed degenerative changes and the patient was prescribed physical therapy and a steroid taper. Upon follow-up, the patient’s ambulation worsened and required a walker. The patient was referred to the physiatry clinic and was found to have strikingly abnormal gait and markedly reduced passive rotation of both hips on exam.

Setting: Outpatient care clinic

Assessment/Results: Hip x-ray and MRI were ordered to evaluate for underlying musculoskeletal pathology. MRI of bilateral hips showed marrow edema with depressed insufficiency fractures, avascular necrosis (AVN), and degenerative changes. Given the absence of risk factors, the patient was diagnosed with idiopathic AVN. The patient underwent pre-rehabilitation before having bilateral total hip replacements. The patient returned for follow-up, no longer requiring assistive devices for ambulation.

Discussion (relevance): Commonly, patients visit the physiatry clinic with acute gait abnormality in the setting of spinal pathology, peripheral neuropathy, neurologic or traumatic causes. A diagnosis of hip AVN is relatively uncommon, with an incidence of 10,000 to 20,000 new cases in the US per year with 30-40% of cases being idiopathic. Bilateral idiopathic hip AVN is even less common, although more research is needed to determine its incidence.

Conclusions: This case highlights the importance of maintaining a broad differential when evaluating a patient for acute, abnormal gait and not overlooking other musculoskeletal pathologies.