Prognostic Factors of the Posterior Lumbar Interbody Fusion with Expandable Cage

ABSTRACT

OBJECTIVE: The authors performed lumbar arthrodesis with expandable cage at L3-4 to L5-S1 intervertebral space for one year and report the analysis of the factors influencing the successful results. METHODS: The authors included thirty-five patients whose bony fusion had been watched over the 12 month after a posterior interbody fusion procedure with one-level expandable cage. All patients were classified into group A(satisfactory results) and group B(unsatisfactory results) according to their answers to comprehensive low back questionnairies. The intervertebral disc height, segmental lordosis and total lumbar lordosis in the standing neutral lateral radiography were checked and the comparison in the changes of this radiological profiles before and after the surgery was done. RESULTS: Seventeen cases(48.6%) of "excellent" results, and 14 cases(40.0%) of "good" results were included in Group A. In group B, 2 cases(5.7%) of "fair" results and 2 cases(5.7%) of "poor" results were included. Over twelve months after the operation, the mean intervertebral disc height and segmental lordotic angle in group A significantly increased, but those in group B did not significantly increase; however, the improvement of total lumbar lordotic angle could not be observed on both groups. CONCLUSION: The results indicate that the recovery of both intervertebral disc height and segmental lordosis is absolutely essential in order to get a successful result in addition to the solid arthrodesis. However, significant influences of one-level segmental lordotic improvement on the total lumbar lordosis can not be observed after the expandable cage fusion in the lower lumbar spine.