Relationship between New Osteoporotic Vertebral Fracture and Instrumented Lumbar Arthrodesis

STUDY DESIGN Retrospective study. PURPOSE To evaluate the relationship between a new osteoporotic vertebral fracture and instrumented lumbar arthrodesis. OVERVIEW OF LITERATURE In contrast to the growing recognition of the importance of adjacent segment disease after lumbar arthrodesis, relatively little attention has been paid to the relationship between osteoporotic vertebral fractures and instrumented lumbar arthrodesis. METHODS Twenty five patients with a thoracolumbar vertebral fracture following instrumented arthrodesis for degenerative lumbar disorders (study group) were investigated. The influence of instrumented lumbar arthrodesis was examined by comparing the bone mineral density (BMD) of the femoral neck in the study group with that of 28 patients (control group) who had sustained a simple osteoporotic vertebral fracture. The fracture after instrumented arthrodesis was diagnosed at a mean 47 months (range, 7 to 100 months) after the surgery. RESULTS There was a relatively better BMD in the study group, 0.67 ± 0.12 g/cm(2) compared to the control group, 0.60 ± 0.13 g/cm(2) (p = 0.013). The level of back pain improved from a mean of 7.5 ± 1.0 at the time of the fracture to a mean of 4.9 ± 2.0 at 1 year after the fracture (p = 0.001). However, 12 (48%) patients complained of severe back pain 1 year after the fracture. There was negative correlation between the BMD of the femoral neck and back pain at the last follow up (r = - 0.455, p = 0.022). CONCLUSIONS Osteoporotic vertebral fractures after instrumented arthrodesis contribute to the aggravation of back pain and the final outcome of degenerative lumbar disorders. Therefore, it is important to examine the possibility of new osteoporotic vertebral fractures for new-onset back pain after lumbar instrumented arthrodesis.