Abstract
Introduction: No previous cases of avascular necrosis (AVN) of the femoral head have been described in the World Literature, to our knowledge. This paper reports the catastrophic failure of the bony integrity of the hip in three patients (five hips) following prolonged hypotension during spinal surgery for spinal stenosis on a Montreal mattress and offers advice to prevent this complication of spinal surgery. A theory to explain this phenomenon is explored, but we recognize its limitations with such a small sample.
Method: The case notes of all patients undergoing decompressive spinal surgery in our hospitals between March 1997 and December 2001 were examined (168 cases). Three patients had been identified as suffering from AVN following prolonged hypotensive anaesthesia prospectively. No other cases were identified after the notes review. Clinical notes and pre- and post-operative radiographs were studied in an attempt to identify the factors that caused this complication in these three patients.
Results: Between 1997 and 2001, 168 patients underwent surgery for multi-level symptomatic spinal stenosis in our hospitals. Forty percent of the patients had an instrumented fusion as well as a decompression. During this period, three patients had catastrophic AVN of the femoral head requiring total hip arthroplasty soon after their spinal operation. All had some clinical and radiological evidence of hip arthritis at their pre-surgery visit. All subsequently, presented within symptomatic hip AVN within six months of the index operation. In two, histology confirmed the diagnosis of AVN, and typical changes of AVN were well demonstrated on MRI in the third patient.
Conclusions: The development of avascular necrosis of the femoral heads following surgery for spinal stenosis may be due to a femoral head at risk being exposed to hypotensive anesthesia, prone positioning on a Montreal mattress or a combination of the two. Careful intra-operative positioning may reduce the risk of this occurring after spinal surgery. However, close post-operative 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 of this condition.
The abstracts were prepared by Dr Robert Moore. Correspondence should be addressed to him at Spine Society of Australia, c/o the Adelaide Centre for Spinal Research, Institute of Medical and Veterinary Science, PO Box 14, Rundle Mall, Adelaide SA 500, Australia.
