Abstract
INTRODUCTION An advantage of lateral lumbar interbody fusion (LLIF) surgery is the indirect decompression of the neural elements that occurs because of the resulting disc height restoration, spinal realignment, and ligamentotaxis. The degree to which indirect decompression occurs varies; no method exists for effectively predicting which patients will respond. METHODS We performed a retrospective evaluation of prospectively collected consecutive patients at a single institution who were treated with LLIF without direct decompression. MRI was used to grade canal stenosis, and three-dimensional reconstructions were used to measure changes in the central canal area (CCA). Multivariate regression was used to identify predictive variables of increases in CCA. RESULTS 110 levels were treated in 66 patients; mean age was 68 years. Preoperatively, 19 patients had moderate stenosis (29%), 18 had severe stenosis (27%), and the remainder had mild or no stenosis. Of these 37 patients, only 4 still had severe stenosis postoperatively, 4 had moderate stenosis, and 29 (78%) improved to mild or no stenosis. CCA increased 41% from a mean of 1.09 cm2 to a mean of 1.55 cm2 (P < .001). Increases in anterior disc height (73%), posterior disc height (81%), spondylolisthesis (66%), right (26%) and left (22%) foraminal heights, and right (12%) and left (18%) foraminal widths (all P < .001) were noted. No significant differences were noted by level or indication (p>0.05). Multivariate regression identified that preoperative spondylolisthesis (P = .002), the presence of intradiscal vacuum phenomenon (P = .049), and preoperative segmental lordosis (P = .009) were independently associated with increase in CCA. CONCLUSION LLIF successfully achieves indirect decompression of the central canal area radiographically with a mean increase of 41%. Preoperative spondylolisthesis on standing films, the presence of intradiscal vacuum phenomenon on computed tomography, and preoperative segmental lordosis were independent predictive factors for increase in central canal area.