Effect of posterior lumbar interbody fusion on the lumbar sagittal spinal profile
Objective: To determine the effect of different cage geometries and posterior instrumentation on the sagittal spinal profile after monosegmental lumbar interbody fusion.
Methods: The study is based on a retrospective analysis of 119 patients with segmental instability, who were surgically managed by monosegmental PLIF with PEEK-Cages and dorsal instrumentation.
Results: At radiographic follow-up after surgery we found a significant improvement of the lumbar sagittal spinal profile, independent of the cage geometry utilised. A marked discrepancy between 0 degrees -standard and 4 degrees -trapezoid implants concerning the radiographic parameters lumbar lordosis, disc height, correction of spondylolisthesis and sacral inclination was not found. With the use of 4 degrees optimised cages in segment L4/5 slightly better results for segmental lordosis were obtained. Reliability of the radiographic evaluation, expressed as intra-observer error, was satisfactory. Cage geometry did not have an effect on the clinical result. By combining interbody fusion with pedicular instrumentation the reposition of slipped vertebra and distraction of the interbody space could more effectively be achieved. Patients without dorsal instrumentation had a higher rate of pseudarthrosis as well as a less satisfactory clinical outcome.
Conclusions: These results show that normal sagittal alignment after single-level lumbar fusion can be achieved with rectangular and 4 degrees -wedged cages. Although results after utilization of 4 degrees -wedged cages do not significantly differ, these implants offer the surgeon one more sizing variation with which physiological lumbar lordosis may be attained. The combination of intersomatic implants with dorsal instrumentation achieves a more precise realignment and has a lower rate of cage-associated complications. It therefore seems prudent that an interbody fusion for the surgical management of lumbar segmental instability should be combined with pedicular instrumentation.