Risk factors for adjacent-segment failure following lumbar fixation with rigid instrumentation for degenerative instability.
OBJECTIVE
The authors performed a retrospective analysis of 125 consecutive patients in whom instrumentation was placed to promote lumbar fusion for the treatment of degenerative instability. All procedures were performed by a single surgeon. The authors sought to determine the risk factors for next-segment degeneration after lumbar spinal fusion with rigid instrumentation.


METHODS
Thirty-one of 125 fusion procedures were performed in women who were postmenopausal. A total of 18 of 125 patients developed symptomatic next-segment degeneration at a previously asymptomatic level; 15 were postmenopausal women. Data were obtained in patients with next-segment failure based on radiographic studies, neurological assessment, demographic factors, and sequential follow-up examinations. The mean follow-up period for this group was 44.8 months. All women were postmenopausal, and 53% received biphosphonate drugs and calcium supplementation preoperatively for osteopenia. Twenty percent of all patients with next-segment failure were cigarette smokers. Next-segment diseases included spondylolisthesis (39%), spinal canal stenosis due to disc herniation and/or facet hypertrophy (33%), stress fracture of the adjacent vertebral body (28%), and scoliosis (17%). Patients frequently had more than one degenerative process at the next segment.


CONCLUSIONS
The risk of adjacent-segment failure is clearly higher for patients in whom lumbar fusion with rigid instrumentation is performed to treat degenerative instability. This risk appears to be especially high in postmenopausal women.
Etebar
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Division of Neurological Surgery, University of South Florida, Tampa, USA.
Cahill
D W
DW
D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000601:surgery*; D007796:Laminectomy; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009192:Myelography; D009984:Orthopedic Fixation Devices; D017698:Postmenopause / Q000502:physiology; D012189:Retrospective Studies; D012307:Risk Factors; D013122:Spinal Diseases / Q000209:etiology*; D013123:Spinal Fusion / Q000009:adverse effects*; D017211:Treatment Failure