A rare cause of hip pain characterized by an inability to walk or bear weight

TEACHING POINTS

■ ITOH has no known etiology and is a diagnosis of exclusion.

■ Most persons with ITOH present with disabling hip pain and no known trauma. Groin pain radiating to the knee is also common. Pain worsens with weight bearing and range of motion of the hip and is often relieved by rest.

■ Diagnosis is confirmed by MRI, as plain radiographs and laboratory testing are typically inconclusive.

■ Treatment is with NSAIDs as well as limited weight bearing with supervised physical therapy to maintain joint range of motion and flexibility.

CASE


The patient was a 58-year-old male with a chief complaint of pain in the left hip and buttock for the past 8 weeks. He denied any trauma or injury to the area. His primary care physician had previously treated him with methylprednisolone (Medrol DOSEPAK) and an intra-articular hip injection, neither of which provided any relief. An MRI was then ordered, and he was referred to the orthopedics and sports medicine department at our clinic.


When he presented to the clinic, the patient was alert and oriented times 3 and claimed the pain in his hip was so severe it felt as if his leg was about to "give way." He rated the pain a 9 out of 10 after activity. Gradually worsening 
pain was also present in his groin and buttock. Other activities that produced significant discomfort included walking; getting out of the car; and playing golf, which he had given up because twisting his hip to swing during the game hurt too much. Rest helped to relieve most of the pain. The patient denied any previous back problems, numbness or tingling, or changes in bowel or bladder function. No fever, chills, nausea, or vomiting had occurred.


Physical examination The patient was sitting in a slouched position, in obvious discomfort, with his left hip and knee extended. Body habitus was normal, and BP measured 120/75 mm Hg. Inspection of the hip revealed no swelling or erythema. No tenderness was present on palpation of the greater trochanter. Active and passive range of motion was limited with hip flexion, abduction, and internal/external rotation. Results of a FABER 
(F  lexion, Abduction, and External Rotation) test were positive. He had one-fifth strength with muscle testing of his left lower extremity secondary to breakaway pain. Sensation, deep tendon reflexes, and knee and ankle examination results were normal. He had an antalgic gait.


Imaging studies and testing Findings from standing anteroposterior and lateral radiographs of the pelvis and left hip were negative for any fracture, osteopenia, arthritis, or malignancy (Figure 1). Both T1- and T2-weighted short inversion-time inversion-recovery (STIR) MRIs revealed an extensive abnormal signal focus involving the left femoral head and neck that extended halfway down the posterior aspect of the femoral neck (Figure 2). Laboratory testing demonstrated a WBC count of 6,300/μL. The ESR using the Westergren method was 4 mm/h; the C-reactive protein level measured 0.2 mg/dL. A diagnosis of idiopathic transient osteoporosis of the hip (ITOH) was considered after ruling out arthritis, infection, avascular necrosis (AVN), and cancer. Based on the negative laboratory results for infection or cancer, negative plain radiographs for fracture or arthritis, and positive findings of bone marrow edema on MRI, ITOH was confirmed.