Lumbar fusion with and without pedicle screw fixation - Comments on a prospective, randomized study

Study Design. In this Journal Club review, the study design, conduct, and analysis of Zdeblick's prospective, randomized trial comparing instrumented and noninstrumented posterolateral lumbar fusion, "A Prospective, Randomized Study of Lumbar Fusion: Preliminary Results," are examined. Objective. The objective of this paper is to review one of the most frequently cited papers published in Spine, to evaluate and discuss its methods and conclusions, and to understand its significance in light of subsequent research. Summary of Background Data. At the time of publication (1993), there were no published studies comparing the fusion rates and clinical outcomes of noninstrumented and instrumented posterolateral lumbar fusion. Methods. The study protocol and methods were critically examined. The results as originally reported and as verified or modified by the reanalysis are discussed in their original context and based on ensuing studies. Results. The original paper reported a benefit with rigid pedicle screw fixation in both the proportion of patients achieving fusion and clinical outcome in patients with degenerative lumbar disease. The reanalysis demonstrated that the difference between the rigid fixation and noninstrumented groups persisted even after accounting for the postrandomization reassignment of patients. Although the difference in clinical outcome between the rigidly instrumented and noninstrumented groups was statistically significant, a non-validated, physician-based measure was used. Subgroup analyses of fusion did not reach statistical significance. Conclusions. This prospective, randomized trial demonstrated that, compared with noninstrumented posterolateral lumbar fusion, rigid pedicle screw fixation results in an increase in the proportion of patients achieving arthrodesis from 64% to 88%. It is not possible to generalize these results to other patient populations. Subsequent research by other investigators has generally confirmed the beneficial effect of rigid segmental fixation on achieving fusion, but a positive relationship between rigid fixation and clinical outcome has yet to be definitively demonstrated.