Alterations in Disc Height, Foraminal Height and Foraminal Width Following One and Two Level AxiaLIF ? A Radiological Analysis

Abstract

Design: Retrospective linear radiological analysis study. Objective: To investigate the effects of AxiaLIF® on anterior disc height (ADH), posterior disc height (PDH), foraminal height (FH) and foraminal width (FW) and demonstrate that AxiaLIF® is an effective minimally-invasive surgery technique for indirect decompression and restoration of disc height. Background: Degenerative changes of the lumbar motion segment often lead to stenosis of the spinal canal or neuroforamen. AxiaLIF® is intended to indirectly increase and stabilize foraminal dimensions by restoring disc height in patients with degenerative disc disease, thereby relieving the axial and radicular pain. Method: Retrospective study of patients who underwent a 360Eš lumbar interbody fusion at L4-5 and L5-S1 with AxiaLIF® between November 2008 and May 2010. Digital radiographs were analyzed on Kodak® computer software. ADH, PDH, FH, and FW, were measured. The anterior vertebral height of L5 vertebra was used to calibrate distance and eliminate potential magnification error for each radiograph. Results: Our study exhibited a mean increase in PDH and ADH at L4-5 and L5-S1 with 2-level AxiaLIF®. Similarly, a mean increase was observed in FH at L5-S1 and FW at L4-5 and L5-S1 with 2-level AxiaLIF®. All changes were statistically significant. The change in FW and FH were even more pronounced with 1-level AxiaLIF®, with a comparable change in posterior and anterior disc height (DH). Conclusion: AxiaLIF® acts to reduce instability by decreasing motion and fusing segments, thus reducing the dynamic compression of nerve roots and cauda equina. We conclude that AxiaLIF® is comparable to anterior lumbar interbody fusion (ALIF) and transforaminal lumbar interbody fusion (TLIF) in terms of indirect decompression and increased DH, with the added benefit of preserving the annulus, anterior longitudinal ligament, and posterior longitudinal ligament. Further observations are required to accurately assess whether AxiaLIF® maintains fusion and preserves disc and foraminal area long term.