The biomechanical effect of the relevant segments after facet-disectomy in different diameters under posterior lumbar percutaneous endoscopes: a three-dimensional finite element analysis.

OBJECTIVE To evaluate the biomechanical influence after percutaneous endoscopic lumbar facetectomy in different diameters on segmental range of motion (ROM) and intradiscal pressure (IDP) of the relevant segments by establishing three dimensional finite element (FE) model. METHODS An intact L3-5 model was successfully constructed from the CT of a healthy volunteer as Model A (MA). The Model B (MB), Model C (MC) and Model D (MD) were obtained through facetectomy on L4 inferior facet in diameters 7.5 mm, 10 mm and 15 mm on MA for simulation. The ROM and IDP of L3/4 and L4/5 of four models were all compared in forward flexion, backward extension, left and right bending, left and right rotation. RESULTS Compared with MA, the ROM of L4/5 of MB, MC and MD all increased. MD changed more significantly than MB and MC in backward extension, right bending and right rotation. But that of MB and MC on L3/4 had no prominent change, while MD had a slight increase in backward extension. The IDP of MB and MC on L4/5 in six states was similar to MA, yet MD increased obviously in backward extension, right bending, left and right rotation. The IDP on L3/4 of MB and MC was resemble to MA in six conditions, nevertheless MD increased slightly only in backward extension. CONCLUSION Compared with the facetectomy in diameters 7.5 mm and 10 mm, the mechanical effect brought by facetectomy in diameter 15 mm on the operating segment changed more significantly, and had a corresponding effect on the adjacent segments.