Radiation-induced femoral head necrosis.

There are very few cases of radiation-induced femoral head necrosis described in the literature, therefore, this case will add new knowledge and highlights important aspects in the diagnosis and management of this uncommon condition. Our patient was 74 years old and presented with left hip and groin pain for 8 months, with no previous history of trauma or osteoarthritis. However, he had been treated for metastatic prostate cancer, to the pelvis and roof of the left acetabulum, with androgen ablation, and radiotherapy 5 years before presentation. Examination of the left hip revealed painful movements, but no restriction in the range of motion. Initial X-rays did not show any abnormalities, but MRI scan revealed a suspicious lesion in the roof of the left acetabulum, with no indication of secondary weakening of the femoral neck. The patient was therefore referred to the oncologists to consider radiotherapy, but they were not convinced it was metastatic, because he had no new urinary symptoms, and the PSA remained normal throughout this period. He was subsequently referred for a bone scan to look for possible secondary lesions (from the prostate gland), but this did not reveal any abnormal increased uptake. Three months later, he was reviewed in the clinic with a repeat X-ray of the pelvis which revealed complete destruction of the left femoral head and the acetabular roof, but CT-guided biopsy revealed no evidence of malignancy in the left hip. However, in view of the persistent pain and radiological evidence of left hip destruction, the patient had left Total Hip Replacement (THR), and excellent post-operative recovery. He mobilised fully, and was discharged on day five. Histology of the femoral head and hip capsule, revealed no evidence of metastasis from the prostate cancer, but confirmed osteonecrosis of the femoral head, presumably caused by the previous radiotherapy. MRI of the spine was clear and he was discharged to the oncologists and urologists for follow up.