Biomechanischer Einfluss der Implantation einer Bandscheibenprothese auf die Kinematik von L5/S1-Segmenten

Background: Lumbar total disc replacement (TDR) is intended to preserve physiological motion and reduce adjacent segment degeneration compared with spinal fusion. However, detailed biomechanical data on its effects at the lumbosacral junction (L5/S1) remain limited. Methods: Human cadaveric L5/S1 motion segments were examined in vitro using a high-precision six-degree-of-freedom measurement system. Kinematics were analyzed during axial rotation, flexion–extension, and lateral bending under controlled axial preload conditions with systematic variation of preload position. Measurements were performed in the intact state and after implantation of a non-compressible ball-and-socket lumbar disc prosthesis (Maverick™). Outcome measures included range of motion (ROM), segmental stiffness, hysteresis behavior, and migration of the instantaneous helical axis (IHA). Results: Disc prosthesis implantation preserved overall segmental mobility but altered motion guidance and load distribution. A ventral shift of the IHA and reduced segmental compressibility were observed. In the mid-range of motion, movement was primarily guided by the prosthetic joint, whereas facet joint coupling increasingly influenced stiffness and motion limitation at motion extremes. Axial preload position significantly affected ROM and stiffness in both intact and implanted conditions. Complete restoration of native segmental biomechanics was not achieved. Conclusions: Lumbar TDR at L5/S1 preserves motion but modifies physiological kinematics. These biomechanical alterations may influence adjacent segment behavior, underscoring the need for careful patient selection and further multi-segmental biomechanical studies.