Biomechanical changes in lumbar intervertebral discs after percutaneous endoscopic transforaminal discectomy surgery...

Percutaneous Endoscopic Transforaminal Discectomy (PETD) is recognized as the leading surgical intervention for lumbar disc herniation (LDH). Moreover, Body Mass Index (BMI) has been established as an independent risk factor for disc reherniation post-PETD. Furthermore, there is a lack of studies investigating the biomechanical changes in the disc post-PETD in relation to diverse BMI levels.

A three-dimensional nonlinear finite element model was developed to simulate the L3-S1 lumbar spine, and a surgical model of the lumbar 4/5 right PETD was also constructed. Forces of 392 N (BMI 20.76 kg/m²), 457 N (24.22 kg/m²), 523 N (27.68 kg/m²), 588 N (31.14 kg/m²) and 653 N (34.6 kg/m²) were applied from the superior edge of the L3 vertebrae. The equivalent von Mises stresses and maximum deformation of the L4/5 nucleus pulposus were observed in normal group and PETD surgery group.

We established normal and PETD surgery model with different BMIs, contributes to understand the equivalent von Mises stresses and maximum deformation of the L4/5 nucleus pulposus with different BMI. The results indicated that the rise in BMI correlates with heightened equivalent von Mises stresses and maximum deformation within the L4/5 nucleus pulposus in both in normal group and PETD surgery group. Besides, the von Mises stress and maximum deformation of the NP in flexion loading are significantly higher than in other loading conditions under the same BMI condition. These values, alongside the occurrence of high-stress areas, display fluctuations across distinct postures, under the influence of BMI. Furthermore, a discernible accumulation of stress was noted within the compromised regions of the nucleus pulposus.

The study suggested that patients who undergone PETD surgery should refrain from engaging in strenuous activities especially flexion during early rehabilitation through finite element analysis. For patients with a high BMI, it is advisable to scientifically reduce weight before and after the surgery in order to maintain appropriate stress on the intervertebral disc.