Background: Posterolateral lumbar fusion (PLF) is the most popular technique for stabilizing the lumbar spine. Biomechanically, PLF decreases segmental motion in the posterior column, which presumably reduces facet joint pain. Posterior lumbar interbody fusion (PLIF) may decompress nerve roots by distracting the collapsed disc space, and achieving optimal fusion in relation to load-bearing capacity. The purpose of the study was to examine the role of interbody fixation vs pedicle fixation in transverse lumbar fusion and to assess treated and adjacent disc space height changes over time.

Methods: One hundred patients who underwent PLIF and noninstrumented transverse process fusion (n = 55) or instrumented PLF (n = 45) between 1996 and 1998 were evaluated retrospectively. Outpatient charts and follow-up films were reviewed. Bone fusion was determined using Brantigan and Steffee's classification and clinical outcome by the Prolo scale. Disc space heights at the fusion and adjacent levels were measured. Analysis of variance and chi(2) statistical techniques were used for data analysis.

Results: Disc space height was increased and better maintained in PLIF patients. PLIF resulted in a nonsignificant tendency toward higher fusion rates. No differences in clinical and functional outcomes were found between the groups. There was no correlation between preservation of disc space height and clinical outcome.

Conclusions: Disc space height does not seem to impact clinical outcome in lumbar fusion, and efforts to maintain it may be unwarranted.