Comparison of Monosegment Instrumented Posterior Lumbar Interbody Fusion with and without a Metal Cage in Degenerative Spine

Purpose: To compare the radiological and clinical results of a local bone graft with those of a single cage in monosegement instrumented posterior lumbar interbody fusion (PLIF) for a spinal stenosis or low-grade spondylolisthesis at the L4-5 level. Materials and Methods: Eighteen patients underwent PLIF using a local bone block and a chip bone without a cage (no-cage group) and 24 patients underwent PLIF using a local bone graft with a single non-threaded metal cage (cage group). All the patients were followed up for a minimum of 2 years. The disc space height, disc lordosis, bone union and clinical results according to Lin's criteria of both groups were reviewed and compared retrospectively. Results: The disc space heights of the no-cage and cage groups increased by 27% and 44% at the immediate postoperative and 12% and 27% at the latest follow-up, respectively. The cage group showed significantly better restoration of the disc space height (p 0.05). Clinical satisfactory results were obtained in 72% of the no-cage group and 84% of the cage group without a significant difference (p>0.05). Conclusion: Both groups had a significant loss of restored disc space height 3 months after surgery. PLIF using a cage showed better restoration of the disc space height but there was significant loss of disc lordosis during the follow-up. A cage with sufficient height is recommended for restoring the disc space as well as preventing a loss of disc lordosis.