Biomechanical analysis of lateral interbody fusion strategies for adjacent segment degeneration in the lumbar spine

Abstract Background context. Surgical treatment of symptomatic adjacent segment disease (ASD) typically involves extension of previous instrumentation to include the newly-affected level(s). Disruption of the incision-site can present challenges and increases the risk of complication. Lateral-based interbody fusion techniques may provide a viable surgical alternative that avoids these risks. This study is the first to analyze the biomechanical effect of adding a lateral-based construct to an existing fusion. Purpose. To determine whether a minimally-invasive lateral interbody device, with and without supplemental instrumentation, can effectively stabilize the rostral segment adjacent to a two-level fusion when compared to a traditional posterior revision approach. Study Design/Setting. A cadaveric biomechanical study of lateral-based interbody strategies as add-on techniques to an existing fusion for the treatment of ASD. Methods. Twelve lumbosacral specimens were non-destructively loaded in flexion, extension, lateral bending, and torsion. Sequentially, the tested conditions were: intact, two-level TLIF (L3-L5), followed by LLIF (lateral lumbar interbody fusion) procedures at L2-L3 including: interbody alone, a supplemental lateral plate, a supplemental spinous process plate, and then either cortical screw or pedicle screw fixation. A three-level TLIF was the final instrumented condition. In all conditions, three-dimensional kinematics were tracked and range of motion (ROM) calculated for comparisons. Institutional funds (