Abstract: BACKGROUND: The fully visualized foraminoscopy currently serves as a reliable approach for managing lumbar intervertebral space infections. There is still a lack of biomechanical research on lumbar spine stability in patients after transforaminal endoscopic treatment of intervertebral disc infection.
OBJECTIVE: To analyze the biomechanical changes in lumbar stability before and after fully visualized foraminoscopy in patients with lumbar intervertebral space infections, and to determine whether this procedure affects lumbar spine stability and whether secondary rigid internal fixation is necessary to ensure postoperative spinal stability.
METHODS: Preoperative CT images from a patient treated with fully visualized foraminoscopy for intervertebral disc infection and followed up for 2 years later were collected. A preoperative finite element model (M1) of the L4/5 (intervertebral disc infection segment) was established using Mimics, Geomagic, SolidWorks, and Ansys. Based on this model, a postoperative model M2 of the patient who underwent fully visualized foraminoscopy for intervertebral disc infection was reconstructed based on the patient's postoperative CT data and laminar/articular process osteotomy. Identical test stresses were applied to the L4 vertebra in both models, while the L5 vertebra was fixed and supported. The range of motion and peak Von Mises stress of the annulus fibrosus were analyzed under six directions (flexion, extension, left rotation, right rotation, left lateral bending, and right lateral bending).
RESULTS AND CONCLUSION: (1) Compared with M1, M2 exhibited range of motion increases of 0.863° (flexion), 0.326° (extension), 0.580° (left lateral bending), 0.476° (right lateral bending), 0.283° (left rotation), and 0.054° (right rotation). The total range of motion changes remained below 2°, indicating minimal impact on segmental stability. (2) Annulus fibrosus stress analysis revealed peak Von Mises stress increases of 0.290 9 MPa (flexion), 0.407 6 MPa (extension), 0.933 6 MPa (left lateral bending), 0.195 5 MPa (right lateral bending), 0.349 7 MPa (left rotation), and 0.061 5 MPa (right rotation) in M2 compared with M2. The peak Von Mises stress of the annulus fibrosus of the M1 and M2 models under different load states did not change significantly, and were far below the threshold value (2 MPa). (3) It is indicated that postoperative stability of the affected segment in patients with lumbar intervertebral disc infection treated with fully visualized foraminoscopy is minimally altered. After active control of the infection, secondary spinal fixation may not be necessary to ensure spinal stability.

Key words: fully visualized foraminoscopy, lumbar spinal infection, intervertebral space infection, finite element analysis, biomechanics