The biomechanical effects of foraminoplasty of different areas under lumbar percutaneous endoscopy on intervertebral discs: A 3D finite element analysis

BACKGROUND: We set out to evaluate the biomechanical influence of foraminoplasty on intervertebral discs in different areas under lumber percutaneous endoscopy through the use of a three-dimensional finite element. METHODS: We established a normal 3D finite element mode of L(3–5), using simulate lumbar percutaneous endoscopy by carrying out cylindrical excision of a bone whose diameter was 7.5 mm on the L(5) superior articular process and the L(4) inferior articular process, respectively. We therefore obtained 3 models. The first was the normal lumbar model, the second the L(4) inferior articular process shaped model, while the third was the L(5) superior articular process shaped model. We compared the biomechanics of discs of L(3/4) and L(4/5) in states of forward flexion, backward extension, left and right flexion as well as left and right rotation. RESULTS: When the L(4) inferior articular process shaped model was in backward extension, left rotation, and right rotation, the stress of the L(4/5) disc was greater than in the normal model, especially in the state of extension. When the L(5) superior articular process shaped model was in left and right rotation, the biggest stress of the L(4/5) disc increased slightly. However, no matter which way the L(5) superior articular process or the L(4) inferior articular process of model was shaped, the stress impact of the L(3/4) disc was small. CONCLUSIONS: There is more biomechanical influence on the L(4/5) disc when carrying out a foraminoplasty on L(4) inferior articular process under a lumber percutaneous endoscopy. In addition, the influence of both types of surgery on the stress of L(3/4) disc is small.