Bilateral septic arthritis of the hips associated with radiotherapy to the pelvis: A case report.

We present a case of polyarticular septic arthritis associated with radiotherapy to the pelvis. This led to rapid bilateral destruction of the hip joints. Post-irradiation osteonecrosis of the femoral head is rare with only six cases reported in the literature since 1970. The femoral head, with its tenuous blood supply, is susceptible to necrosis if its microvasculature is damaged by radiation, which can also damage osteoblasts and osteoclasts. Necrotic bone is susceptible to infection and this can lead to septic arthritis or osteitis. In November 1997 he presented to his general practitioner complaining of fever, malaise, night sweats, bilateral hip pain, a rash over his thighs and a weight loss of 6 kg over the previous two months. On examination he was noted to have an erythematous rash over his thighs and hepatosplenomegally. His hips were painful on both active and passive movement, but the range of movement was normal. He was found to have Hb 8.4g%, WCC 12.2x109/l and CRP 196. Virology screen was normal. Bone scan showed mildly increased uptake in the region of the right hip joint. X-rays demonstrated mild bilateral degeneration of the hip joints (Fig. 1). MRI scan showed reduced joint space in both hips with a mild effusion on the right. Attempted ultrasonically guided aspiration of this effusion failed. His symptoms of rash, malaise, fever and loss of weight settled spontaneously and he was discharged home. His hip pain gradually worsened and three months later he was referred to the Orthopaedic Surgery Department. He had a markedly restricted and painful range of movement in both hips with marked wasting of the quadriceps mechanism bilaterally. Xrays (Fig. 2) and computerised tomography (Fig 3, 4 & 5) revealed massive destruction of the femoral heads and acetabulae. The right hip was aspirated under image intensifier. The aspirate contained group G betahaemolytic streptococci. CASE REPORT