Obesity Induced Intradiscal Stress Amplification Following Lumbar Foraminoplasty: Implications for Reherniation Risk

: Recurrent lumbar disc herniation after endoscopic lumbar surgery remains a concern, particularly in patients with elevated body mass index (BMI). Although foraminoplasty relieves neural foraminal compression, partial facet resection may alter postoperative load transmission and intradiscal stress. This study assessed the biomechanical influence of BMI-derived axial loading on intradiscal stress distribution in the post-foraminoplasty L4–L5 segment and its potential implication for reherniation risk.

A three-dimensional L4–L5 finite element model was reconstructed from CT images of a healthy adult male. Foraminoplasty was simulated by partial resection of the L5 superior articular process. Five BMI-derived axial loads (394.65–794.98 N) were combined with 10 N·m moments during flexion, extension, lateral bending, and axial rotation. Maximum von Mises stress was evaluated separately in the annulus fibrosus and nucleus pulposus using descriptive quantitative comparisons.

Nucleus pulposus stress generally increased with loading. During flexion, it rose from 0.4165 to 0.5843 MPa, representing a 40.29% increase, and flexion produced the highest nucleus pulposus stress under all loads. Annulus fibrosus stress also showed an overall load-dependent increase, although the motion producing the maximum value varied. During flexion, it increased from 1.9450 to 2.4420 MPa (25.55%). The overall maximum annulus fibrosus stress was 2.6613 MPa during left lateral bending at 794.98 N. Stress localized predominantly posteriorly in the nucleus pulposus and anterolaterally or posterolaterally in the annulus fibrosus.

These compartment-specific responses indicate that postoperative disc mechanics are jointly influenced by axial load magnitude and motion direction, potentially increasing mechanical vulnerability under elevated loading.

BMI-related loading should be considered in surgical planning and postoperative rehabilitation to minimize unfavorable disc stress and potential reherniation risk after foraminoplasty.