Abstract
BackgroundThis study was to evaluate and compare the biomechanical features of multilevel lateral lumbar interbody fusion (LLIF) with or without supplemental instrumentations.MethodsSix human lumbar specimens were tested under multidirectional nondestructive moments (7.5 N·m), with a 6 degree-of-freedom spine simulator. The overall and intervertebral range of motion (ROM) were measured optoelectronically. Each specimen was tested under the following conditions at L2–5 levels: intact; stand-alone; cage supplemented with lateral plate (LP); cage supplemented with unilateral or bilateral pedicle screw/rod (UPS or BPS).ResultsCompared with intact condition, the overall and intersegmental ROM were significantly reduced after multilevel stand-alone LLIF. The ROM was further reduced after using LP instrumentation. In flexion-extension (FE) and axial rotation (AR), pedicle screw/rod demonstrated greater overall ROM reduction compared to LP (P < 0.01), and bilateral greater than unilateral (P < 0.01). In lateral bending (LB), BPS demonstrated greater overall ROM reduction compared to UPS and LP (P < 0.01), however, UPS and LP showed similar reduction (P = 0.245). Intervertebral ROM reductions showed similar trend as the overall ones after using different types of instrumentation. However, at L2/3 (P = 0.57) and L3/4 (P = 0.097) levels, the intervertebral ROM reductions in AR were similar between UPS and LP.ConclusionsThe overall and intervertebral stability increased significantly after multilevel LLIF with or without supplemental instrumentation. BPS provided the greatest stability, followed by UPS and LP. However, in clinical practice, less invasive adjunctive fixation methods including UPS and LP may provide sufficient biomechanical stability for multilevel LLIF.
Highlights
This study was to evaluate and compare the biomechanical features of multilevel lateral lumbar interbody fusion (LLIF) with or without supplemental instrumentations
Compared to stand-alone construct, the overall range of motion (ROM) reduction further increased after lateral plate (LP) fixation in all motion planes (P < 0.01)
In lateral bending (LB) motion, BPS construct demonstrated greater overall reduction compared to unilateral (P < 0.01) and LP (P < 0.01) constructs, UPS construct failed to show significant difference compared to LP construct (P = 0.245)
Summary
This study was to evaluate and compare the biomechanical features of multilevel lateral lumbar interbody fusion (LLIF) with or without supplemental instrumentations. Operative approaches to lumbar interbody fusion include posterior, transforaminal, anterior and more recently lateral transpsoas access [1, 2]. Lateral lumbar interbody fusion (LLIF) is a minimally invasive procedure, which circumvents some of the challenges and morbidity risks of anterior or posterior lumbar interbody fusion techniques, while affords necessarily indirect decompression for the treatment of spinal canal stenosis and places interbody cage without manipulation of neural structure [3]. Mostly biomechanical studies evaluating lateral interbody fusion were usually focused on one or two levels [4, 7, 8]. The effect of supplemental instrumentation in multilevel LLIF procedure, such as pedicle screw/rod or lateral plate, on reducing immediately postoperative range of motion (ROM), was not elucidated clearly
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