Biomechanical response of decompression alone in lower grade lumbar degenerative spondylolisthesis--A finite element analysis

Background: Previous studies have demonstrated the clinical efficacy of decompression alone in lower-grade spondylolisthesis. A higher rate of surgical revision and a lower rate of back pain relief was also observed. However, there is a lack of relevant biomechanical evidence after decompression alone for lower-grade spondylolisthesis.

Purpose: Evaluating the biomechanical characteristics of total laminectomy, hemilaminectomy, and facetectomy for lower-grade spondylolisthesis by analyzing the range of motion (ROM), intradiscal pressure (IDP), annulus fibrosus stress (AFS), facet joints contact force (FJCF), and isthmus stress (IS).

Methods: Firstly, we utilized finite element tools to develop a normal lumbar model and subsequently constructed a spondylolisthesis model based on the normal model. We then performed total laminectomy, hemilaminectomy, and one-third facetectomy in the normal model and spondylolisthesis model, respectively. Finally, we analyzed parameters, such as ROM, IDP, AFS, FJCF, and IS, for all the models under the same concentrate force and moment.

Results: The intact spondylolisthesis model showed a significant increase in the relative parameters, including ROM, AFS, FJCF, and IS, compared to the intact normal lumbar model. Hemilaminectomy and one-third facetectomy in both spondylolisthesis and normal lumbar models did not result in an obvious change in ROM, IDP, AFS, FJCF, and IS compared to the pre-operative state. Moreover, there was no significant difference in the degree of parameter changes between the spondylolisthesis and normal lumbar models after undergoing the same surgical procedures. However, total laminectomy significantly increased ROM, AFS, and IS and decreased the FJCF in both normal lumbar models and spondylolisthesis models.

Conclusion: Hemilaminectomy and one-third facetectomy did not have a significant impact on the segment stability of lower-grade spondylolisthesis; however, patients with LDS undergoing hemilaminectomy and one-third facetectomy may experience higher isthmus stress on the surgical side during rotation. In addition, total laminectomy changes the biomechanics in both normal lumbar models and spondylolisthesis models.