Assessment of pre- and post-operative biomechanical changes at adjacent levels induced by muscle damage following spondylolisthesis fusion: musculoskeletal modeling of open <i>vs.</i> minimally invasive surgery

This study compared biomechanical impacts of conventional open surgery (COS) and minimally invasive surgery (MIS) for spondylolisthesis using a musculoskeletal model with in-vivo data from 31 patients undergoing L4-L5 fusion. Pre- and post-operative conditions with simulated muscle injury were analyzed, focusing on kinematics, muscle forces, and adjacent segment loading. Both methods altered lumbosacral parameters, but COS caused greater lumbar-pelvic rhythm reduction (60% vs. 14%), largely due to decreased trunk flexion. MIS showed increased multifidus contribution and reduced adjacent loading, though it raised upper segment passive moment and compression. Findings suggest MIS better preserves stability and favorable biomechanics than COS.