Abstract
BackgroundReduction of lumbar spondylolisthesis during spinal fusion surgery is important for improving the fusion rate and restoring the sagittal alignment. Despite the variety of reduction methods, the fundamental mechanics of lumbar spondylolisthesis reduction remain unclear. This study aimed to investigate the biomechanical behavior while performing spondylolisthesis reduction with the anterior and posterior lever reduction method.MethodsWe developed an L4–L5 spondylolisthesis model using sawbones. Two spine surgeons performed the simulated reduction with a customized Cobb elevator. The following data were collected: the torque and angular motion of Cobb, displacement of vertebral bodies, change of lordotic angle between L4 and L5, total axial force and torque applied on the model, and force received by adjacent disc.ResultsLess torque value (116 N-cm vs. 155 N-cm) and greater angular motion (53o vs. 38o) of Cobb elevator were observed in anterior lever reduction. Moreover, the total axial force received by the entire model was greater in the posterior lever method than that in the anterior lever method (40.8 N vs. 16.38 N). Besides, the displacement of both vertebral bodies was greater in the anterior lever method.ConclusionsThe anterior lever reduction is a more effort-saving method than the posterior lever reduction method. The existing evidence supports the biomechanical advantage of the anterior reduction method, which might be one of the contributing factors to successfully treating high-grade lumbar spondylolisthesis with short-segment instrumentation.
Highlights
Reduction of lumbar spondylolisthesis during spinal fusion surgery is important for improving the fusion rate and restoring the sagittal alignment
The posterior approach can be used in instrumented interbody fusion techniques, such as posterior lumbar interbody fusion (PLIF) or transforaminal lumbar interbody fusion (TLIF), which leads to a satisfactory outcome in patients with spondylolisthesis [9]
6.74 ± 0.97 0.87 ± 0.25 − 4.88 ± 1.94 40.8 ± 4.54 12 ± 5.1 p Value anterior lever reduction had greater angular motion compared with posterior lever reduction (53o vs. 38o, p < 0.001, Table 1, Fig. 4b)
Summary
Reduction of lumbar spondylolisthesis during spinal fusion surgery is important for improving the fusion rate and restoring the sagittal alignment. This study aimed to investigate the biomechanical behavior while performing spondylolisthesis reduction with the anterior and posterior lever reduction method. In patients with high-grade spondylolisthesis with abnormal posture, reduction and realignment procedures should be performed to restore the global spinopelvic balance [5, 7, 8]. The anterior approach of the lumbar spine, which can be used in instrumented interbody fusion technique of anterior interbody fusion (ALIF), can facilitate access to the intervertebral space without passing through the spinal canal with retraction of the nerve roots and cauda equina, reducing the potential risk of nerve injury and dural tear [10]
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