Using Lordotic Cages at the L5-S1 Level Does Not Guarantee the Improvement of Sagittal Alignment in Patients Who Underwent Posterior Lumbar Interbody Fusion.

ABSTRACT

STUDY DESIGN: Retrospective comparative study. PURPOSE: This study aimed to investigate the effects of the lordotic angle of cages on sagittal alignment in patients who underwent 1- or 2-level posterior lumbar interbody fusion (PLIF), including the L5-S1 level. OVERVIEW OF LITERATURE Few studies have addressed the effects of the lordotic angle of cages on regional and global sagittal balance in patients undergoing PLIF at the L5-S1 level. METHODS: Sixty-one patients who underwent 1- or 2-level PLIF, including the L5-S1 level, were divided into two groups based on the lordotic angle of cages (4° and 8° in 41 and 20 patients, respectively). Clinical and radiological parameters were compared. Correlation analyzes were performed to reveal the effect of flexibility and position of cages on the regional sagittal parameters. RESULTS: Pre- and postoperative clinical and radiological parameters were not different between the two groups. Although clinical outcomes improved postoperatively, sagittal parameters did not improve postoperatively in both groups. Patients who underwent 1-level PLIF at the L5-S1 level with the use of 8° cages showed no postoperative improvement (segmental angle 16.1°-15.9°, p =0.140; lumbar lordosis 44.8°-47.8°, p =0.740) of regional sagittal parameters. The degree of anterior location of cages showed a positive correlation with the postoperative restoration of the segmental angle (p =0.012 and p =0.050 at 1 and 2 years postoperatively, respectively). CONCLUSIONS: Clinical and radiological outcomes based on the lordotic angle of cages were not different. Even with the use of 8° cages and regardless of the more anterior position of cages, sagittal alignment did not improve in cases involving the L5-S1 level. PLIF at the L5-S1 level should be used with caution because improvement in sagittal alignment did not occur.