Avascular necrosis of the femoral head after surgery for lumbar spinal stenosis.

Study Design: Case report.

Objective: To report a previously undescribed complication of lumbar spinal surgery under prolonged hypotensive anesthesia.

Background Data: Avascular necrosis of bone most commonly affects the femoral head. The etiology of the condition is understood in only 75% of cases. There have been no prior reports of this condition following lumbar spine surgery carried out under hypotensive anesthetic.

Methods: Notes review, clinical examination, plain radiographs, and magnetic resonance imaging diagnosed three patients who developed avascular necrosis of the femoral heads (five joints in total) after surgery for lumbar spinal stenosis. All three were treated with total hip replacement (five joints), and the diagnosis of avascular necrosis was confirmed in two by histopathological examination.

Results: All three patients have recovered full mobility following hip replacement surgery. None had any residual symptoms of lumbar spinal stenosis or hip disease, and none of them had shown any clinical evidence of avascular necrosis in any other bone.

Conclusions: The development of avascular necrosis of the femoral heads following surgery for spinal stenosis may be due to hypotensive anesthesia, prone positioning on a Montreal mattress, or a combination of the two. Careful intraoperative positioning may reduce the risk of this occurring after spinal surgery. However, close postoperative surveillance and a high index of suspicion of worsening hip pathology in patients who appear to mobilize poorly after lumbar spinal surgery may be the only method of early detection and treatment for this condition.