Department of Orthopedics, The Second Xiangya Hospital of Central South University, Changsha, Hunan 410011, China; College of Mechanical and Vehicle Engineering, Hunan University, Changsha, Hunan 410082, China.
Department of Orthopedics, Shenzhen Hospital of Integrated Traditional Chinese and Western Medicine, Guangzhou University of Chinese Medicine, Shenzhen 518000, China.
Comput Methods Programs Biomed. 2023 May;233:107479. doi: 10.1016/j.cmpb.2023.107479. Epub 2023 Mar 12.
The current trend of laminoplasty is developing toward the goal of muscle preservation and minimum tissue damage. Given this, muscle-preserving techniques in cervical single-door laminoplasty have been modified with protecting the spinous processes at the sites of C2 and/or C7 muscle attachment and reconstruct the posterior musculature in recent years. To date, no study has reported the effect of preserving the posterior musculature during the reconstruction. The purpose of this study is to quantitatively evaluate the biomechanical effect of multiple modified single-door laminoplasty procedures for restoring stability and reducing response level on the cervical spine.
Different cervical laminoplasty models were established for evaluating kinematics and response simulations based on a detailed finite element (FE) head-neck active model (HNAM), including ① C3 - C7 laminoplasty (LP_C37), ② C3 - C6 laminoplasty with C7 spinous process preservation (LP_C36), ③ C3 laminectomy hybrid decompression with C4 - C6 laminoplasty (LT_C3 + LP_C46) and ④ C3 - C7 laminoplasty with unilateral musculature preservation (LP_C37 + UMP). The laminoplasty model was validated by the global range of motion (ROM) and percentage changes relative to the intact state. The C2 - T1 ROM, axial muscle tensile force, and stress/strain levels of functional spinal units were compared among the different laminoplasty groups. The obtained effects were further analysed by comparison with a review of clinical data on cervical laminoplasty scenarios.
Analysis of the locations of concentration of muscle load showed that the C2 muscle attachment sustained more tensile loading than the C7 muscle attachment, primarily in flexion-extension (FE) and in lateral bending (LB) and axial rotation (AR), respectively. Simulated results further quantified that LP_C36 primarily produced 10% decreases in LB and AR modes relative to LP_C37. Compared with LP_C36, LT_C3 + LP_C46 resulted in approximately 30% decreases in FE motion; LP C37 + UMP also showed a similar trend. Additionally, when compared to LP_C37, LT_C3 + LP_C46 and LP C37 + UMP reduced the peak stress level at the intervertebral disc by at most 2-fold as well as the peak strain level of the facet joint capsule by 2-3-fold. All these findings were well correlated with the result of clinical studies comparing modified laminoplasty and classic laminoplasty.
Modified muscle-preserving laminoplasty is superior to classic laminoplasty due to the biomechanical effect of the posterior musculature reconstruction, with a retained postoperative ROM and loading response levels of the functional spinal units. More motion-sparing is beneficial for increasing cervical stability, which probably accelerates the recovery of postoperative neck movement and reduces the risk of the complication for eventual kyphosis and axial pain. Surgeons are encouraged to make every effort to preserve the attachment of the C2 whenever feasible in laminoplasty.
目前，颈椎单开门椎管扩大成形术的发展趋势是朝着保护肌肉和最小化组织损伤的目标进行。近年来，为了达到这一目标，对颈椎单开门椎管扩大成形术中的保肌技术进行了改良，即在 C2 和/或 C7 肌肉附着处的棘突处进行保护，并重建后部肌肉。迄今为止，尚无研究报道在重建过程中保护后部肌肉的效果。本研究的目的是定量评估多种改良的颈椎单开门椎管扩大成形术对颈椎稳定性和降低反应水平的恢复效果。
基于详细的头颈部主动有限元（FE）模型（HNAM），建立了不同的颈椎椎管扩大成形术模型，用于评估运动学和响应模拟，包括①C3-C7 椎管扩大成形术（LP_C37），②C3-C6 椎管扩大成形术伴 C7 棘突保留（LP_C36），③C3 椎板切除术混合减压伴 C4-C6 椎管扩大成形术（LT_C3+LP_C46）和④C3-C7 椎管扩大成形术伴单侧肌肉保留（LP_C37+UMP）。通过与完整状态的全局运动范围（ROM）和百分比变化相比，对椎管扩大成形术模型进行了验证。比较了不同椎管扩大成形术组之间 C2-T1 的 ROM、轴向肌肉拉伸力以及功能单位的应力/应变水平。通过与颈椎椎管扩大成形术临床数据的回顾进行比较，进一步分析了所获得的效果。
对肌肉负荷集中位置的分析表明，C2 肌肉附着处承受的拉伸负荷大于 C7 肌肉附着处，主要在屈伸（FE）和侧屈（LB）和轴向旋转（AR）中。模拟结果进一步量化表明，LP_C36 相对于 LP_C37，LB 和 AR 模式下的降幅约为 10%。与 LP_C36 相比，LT_C3+LP_C46 导致 FE 运动减少约 30%；LP_C37+UMP 也表现出类似的趋势。此外，与 LP_C37 相比，LT_C3+LP_C46 和 LP_C37+UMP 使椎间盘的峰值应力水平降低了最高 2 倍，使小关节囊的峰值应变水平降低了 2-3 倍。所有这些发现都与比较改良椎管扩大成形术和经典椎管扩大成形术的临床研究结果很好地相关。
由于后部肌肉重建的生物力学效果，改良的保肌椎管扩大成形术优于经典的椎管扩大成形术，保留了术后 ROM 和功能单位的加载反应水平。更多的运动保留有利于增加颈椎的稳定性，这可能会加速术后颈部运动的恢复，并降低最终发生后凸畸形和轴向疼痛的风险。鼓励外科医生在可行的情况下尽最大努力保留 C2 的附着处。
