Long-Term Functional Outcome of Pedicle Screw Instrumentation as a Support for Posterolateral Spinal Fusion

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Abstract
A prospective randomized clinical study with a 5-year follow-up. To analyze the long-term effect of supplementary transpedicular screw fixation on reoperation rate and functional outcome. Within the past few years the benefit of supplemental pedicle screw fixation has been questioned as a standard procedure in lumbar spinal fusion surgery. The long-term effect of supplemental pedicle screw fixation is still unknown. From 1992 through 1994 a total of 129 patients with severe chronic low back pain were randomly selected for either supplemental pedicle screw fixation (instrumented) or no pedicle screw instrumentation (noninstrumented) posterolateral spinal fusion. The Dallas Pain Questionnaire, Low Back Pain Rating Scale, and a questionnaire concerning work status assessed the outcome. A 5-year follow-up of 93% showed that the instrumented group had a 25% reoperation rate (removal of instrumentation with and without second fusion) compared with a reoperation rate of 14% in the noninstrumented group (fusion and decompression) (P < 0.03). A total of 51% were capable of working after 5 years compared with 40% before surgery. There was no difference in work capacity between the two groups at any point of observation. Overall, there was no significant difference between the instrumented and noninstrumented groups in regard to functional outcome as measured by both the Dallas Pain Questionnaire and Low Back Pain Rating Scale. When analyzing diagnostic subgroups at the 5-year follow-up, patients with isthmic spondylolisthesis had a significantly better outcome by use of a posterolateral fusion without supplemental instrumentation compared with an instrumented fusion (P < 0.03). However, patients with primary degenerative instability improved significantly more when instrumentation supported the posterolateral spinal fusions (P < 0.02). To the question "was it worth it?" 67% answered "yes" in the instrumented group whereas 70% did so in the noninstrumented groups (not significant). The long-term functional outcome of posterolateral spinal fusion improved significantly for boththose with and without pedicle screw instrumentation, with a global 70% satisfaction reported by the patients. Patients with isthmic spondylolisthesis Grades 1 and 2 with noninstrumented fusion had superior long-term outcomes after posterolateral spinal fusion in comparison with an instrumented fusion. In contrast, patients diagnosed as having primary degenerative instability improved significantly when the posterolateral fusion was supported by instrumentation. In actuality, pedicle screw instrumentation increased reoperation rate compared with noninstrumented posterolateral fusion.