Department of Mechanical Engineering, Ecole Polytechnique de Montréal, Montreal, Quebec, Canada.
Spine (Phila Pa 1976). 2013 Jan 15;38(2):E73-83. doi: 10.1097/BRS.0b013e31827a641e.
Biomechanical analysis of vertebral derotation techniques for the surgical correction of thoracic scoliosis.
To model and analyze vertebral derotation maneuvers biomechanically to maximize the tridimensional correction of scoliosis and minimize the implant-vertebra forces.
Vertebral derotation techniques were recently developed to improve the correction of scoliotic deformities in the transverse plane. Those techniques consist in applying a combination of moments and forces using a vertebral derotation device, cohesively linked to the thoracic apical pedicle screws, to derotate the spine and the rib cage. However, many variations of the technique exist and the correction mechanisms are not fully understood to achieve an optimal correction of scoliosis.
A biomechanical model was developed to simulate the instrumentation surgery numerically of 4 Lenke type 1 patients with scoliosis, instrumented using a vertebral derotation device and vertebral derotation maneuvers as major correction technique. Then, for each case, 32 additional instrumentation surgical procedures were simulated to better understand the biomechanics of the vertebral derotation technique, varying the implant type and density, the number of derotation levels, the vertebral derotation angle and the posteriorly oriented force applied during the maneuver.
On average, among 32 additional simulations, there was an important variability of the resulting apical vertebral rotation (15°) and the mean resultant implant-vertebra force (205 N) but little variability for the main thoracic Cobb angle (6°) and the thoracic kyphosis (4°). The implant type, the implant density and the vertebral derotation angle were the parameters that most influenced the correction of scoliosis. The correction in the coronal and transverse planes was improved using monoaxial pedicle screw density of 2 and a bilateral vertebral derotation maneuver on 3 levels at the apex of the thoracic curve, with an extra 15° applied on the vertebral derotation device. When reducing the implant density by 50%, it was possible to reduce the mean implant-vertebra forces while keeping a good correction.
Biomechanically, it is possible to significantly improve the correction of thoracic scoliotic deformities, particularly in the transverse plane, when using vertebral derotation maneuvers.
用于胸弯脊柱侧凸手术矫正的椎体旋转技术的生物力学分析。
对椎体旋转手法进行建模和分析，以最大限度地实现脊柱侧凸的三维矫正，并最小化植入物-椎体的力。
椎体旋转技术最近被开发出来，以改善在横断面上矫正脊柱侧凸畸形。这些技术包括使用与胸顶椎弓根螺钉紧密相连的椎体旋转装置施加组合的力和力矩，以旋转脊柱和肋骨笼。然而，该技术存在许多变化，其矫正机制尚未完全了解，以实现脊柱侧凸的最佳矫正。
建立了一个生物力学模型来数值模拟 4 例 Lenke 1 型脊柱侧凸患者的器械手术，使用椎体旋转装置和椎体旋转手法作为主要矫正技术进行器械手术。然后，对于每个病例，模拟了 32 个额外的器械手术过程，以更好地理解椎体旋转技术的生物力学，改变植入物类型和密度、旋转水平的数量、椎体旋转角度和在操作过程中施加的向后力。
在 32 次额外模拟中，平均而言，椎体旋转的最终结果（15°）和平均最终植入物-椎体力（205N）存在很大的可变性，但主要胸椎 Cobb 角（6°）和胸椎后凸（4°）的可变性很小。植入物类型、植入物密度和椎体旋转角度是影响脊柱侧凸矫正的主要参数。使用 2 个单轴椎弓根螺钉密度和在胸弯顶点的 3 个水平进行双侧椎体旋转操作，在椎体旋转装置上施加额外的 15°，可以改善冠状面和横断面上的矫正。当将植入物密度降低 50%时，在保持良好矫正的同时，也可以降低平均植入物-椎体的力。
从生物力学的角度来看，使用椎体旋转手法可以显著改善胸弯脊柱侧凸的矫正，特别是在横断面上。
