The influence of lumbar lordosis on spinal fusion and functional outcome after posterolateral spinal fusion with and without pedicle screw instrumentation

The aim of the current study was to examine the correlation between lumbar lordosis, spinal fusion, and functional outcome in patients suffering from severe low back pain, treated by posterolateral spinal fusion with or without pedicle screw instrumentation. One hundred thirty patients were randomly allocated to posterolateral lumbar fusion with or without Cotrel-Dubousset instrumentation. Functional outcome was assessed preoperatively, and 1 and 2 years postoperatively. Lordosis angles of the lumbar spine and fusion rates were assessed at the 1- and 2-year follow-up. No difference in lordosis angle was found between the two groups at any time. Lordosis was unchanged at 2 years compared with preoperative status in both groups. In the instrumented group, nonunion (23%) was followed by a decrease in lordosis at follow-up (p < 0.05). However, in the noninstrumented group, nonunion (14%) resulted in increased lordosis (p < 0.05). No correlation was found between functional outcome and lordosis angle. The current study showed no correlation between functional outcome and lordosis angle either before or after posterolateral spinal fusion. Use of instrumentation did not influence lumbar spinal alignment compared with noninstrumented fusions. The sagittal alignment was stable both 1 and 2 years after solid fusion. The failure mode of instrumented fusions was a reduced degree of lordosis in contrast to an increased degree of lordosis in patients with noninstrumented fusion.