Sangiorgio Sophia N, Borkowski Sean L, Day Matthew J, Ho Nathan C, Knutsen Ashleen, Scaduto Anthony A, Bowen Richard E, Ebramzadeh Edward
J. Vernon Luck Sr, M.D. Orthopaedic Research Center (JVL), Orthopaedic Institute for Children (OIC)/UCLA, Los Angeles, CA, USA.
Lucideon-Healthcare, Raleigh, NC, USA.
Spine Deform. 2020 Aug;8(4):577-584. doi: 10.1007/s43390-020-00061-0. Epub 2020 Feb 5.
Biomechanical simulation of DVR and pure-moment testing on thoracic spines.
Characterize load-deformation response of thoracic spines under DVR maneuvers until failure, and compare to pure-moment testing of same spines. Despite reports of surgical complications, few studies exist on increase in ROM under DVR torque. Biomechanical models predicting increases from surgical releases have consistently used "pure-moments", a standard established for non-destructive measurement of ROM. Yet, DVR torque is not accurately modeled using pure moments and, moreover, magnitudes of torque applied during DVR maneuvers may be substantially higher than pure-moment testing.
Cadaveric thoracic spines (N = 11) were imaged, then prepared. Polyaxial pedicle screws were implanted at T7-T10 after surgical releases. Bilateral facetectomies and Ponte osteotomies were completed at T10-T11. A custom apparatus, mounted into an 8-dof MTS load frame, was used to attach to pedicle screws, allowing simulation of surgical DVR maneuvers. Motions of vertebrae were measured using optical motion tracking. Torque was increased until rupture of the T10-T11 disc or fracture at the pedicle screw sites at any level. The torque-rotation behavior was compared to its behavior under pure-moment testing performed prior to the DVR maneuver.
Under DVR maneuvers, failure of the T10-T11 discs accompanied in most cases by pedicle screw loosening, occurred at 13.7-54.7 Nm torque, increasing axial rotation by 1.4°-8.9°. In contrast, pure-moment testing (4 Nm) increased axial rotation by only 0.0°-0.9°.
DVR resulted in substantially greater correction potential increases compared to pure-moment testing even at the same torque. These results suggest increased flexibility obtained by osteotomies and facetectomies is underestimated using pure-moment testing, misrepresenting clinical expectations. The present study is an important and necessary step toward the establishment of a more accurate and ultimately surgically applied model.
III.
胸段脊柱的DVR生物力学模拟及纯力矩测试。
描述胸段脊柱在DVR操作直至失效时的载荷-变形响应，并与相同脊柱的纯力矩测试进行比较。尽管有手术并发症的报道，但关于DVR扭矩作用下ROM增加的研究很少。预测手术松解后ROM增加的生物力学模型一直使用“纯力矩”，这是一种为ROM的无损测量建立的标准。然而，DVR扭矩不能用纯力矩准确建模，而且，DVR操作期间施加的扭矩大小可能远高于纯力矩测试。
对11具尸体胸段脊柱进行成像，然后进行准备。在手术松解后，于T7-T10植入多轴椎弓根螺钉。在T10-T11完成双侧关节突切除术和 Ponte 截骨术。使用安装在8自由度MTS加载框架中的定制装置连接到椎弓根螺钉，以模拟手术DVR操作。使用光学运动跟踪测量椎体的运动。增加扭矩直至T10-T11椎间盘破裂或任何水平的椎弓根螺钉部位骨折。将扭矩-旋转行为与其在DVR操作之前进行的纯力矩测试下的行为进行比较。
在DVR操作下，T10-T11椎间盘失效，大多数情况下伴有椎弓根螺钉松动，发生在13.7-54.7 Nm扭矩时，轴向旋转增加1.4°-8.9°。相比之下，纯力矩测试（4 Nm）仅使轴向旋转增加0.0°-0.9°。
即使在相同扭矩下，与纯力矩测试相比，DVR导致的矫正潜力增加也显著更大。这些结果表明，使用纯力矩测试低估了截骨术和关节突切除术获得的灵活性，从而错误地反映了临床预期。本研究是朝着建立更准确且最终可用于手术的模型迈出的重要且必要的一步。
III级。
