척추경 나사못 고정술과 골밀도와의 관계

Abstract

Fifteen patients undergoing posterior decompression and spinal fusion with transpedicular screws for spinal stenosis or spondylolisthesis were studied. The purpose of this study was to evaluate the changes of bone mineral density in the lumbar spine after an instrumented spinal fusion; to discover if there is a relationship between screw loosenings and a decrease in bone mineral density; and to know if problems caused by the screws make any adverse affects to the spinal fusion. There have been several biomechanical reports about relationship between vertebral bone mineral density and pedicular screw loosenings; and it has been known that low bone mineral content makes insufficient mechanical stability in the bone-screw interface. Preoperative assessment of the bone mineral density has been stressed since it is crucial for a successful fusion. The patient were divided into two groups: loosening and non-loosening. Bone mineral density was evaluated up to one year after operation in both groups and fusion rate was compared in both groups. Statistical studies were performed to determine the relationship, if any, between the amount of bone mineral content and loosening of the screws. Fusion was compared in all cases of both groups and there was an improvement of back scores in both groups. Radiographic type of loosening was classified into 4 types: type 1 was 6 screws; type 2, 2; type 3, 12; type 4, 0. Mean bone mineral density of type 3 loosening decreased more than non-loosening screw. There was no correlation between preoperative bone mineral density and severity of screw loosenings (p> 0.0~5); bone mineral density decreased continuously after operation in both groups. The decreasing rate was highter in loosening group, but no statistical significance was noted. There is no direct proof linking low bone mineral density as being the sole cause perpetuating screw failures in the instrumented spinal fusions, and loosening of the transpedicular screws doesnt affect the outcome of spinal fusion. Lumbar spinal fusion with instrumentation can be performed safely on elder patients with low BMD.