Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Keelung Rd, No. 43, Sec. 4, Taipei, 106, Taiwan, Republic of China.
Department of Surgery, Cheng-Hsin General Hospital, Taipei, Taiwan.
BMC Musculoskelet Disord. 2022 Jun 27;23(1):612. doi: 10.1186/s12891-022-05477-5.
Many studies have been conducted to compare traditional trajectory (TT) and cortical bone trajectory (CBT) screws; however, how screw parameters affect the biomechanical properties of TT and CBT screws, and so their efficacy remains to be investigated.
A finite element model was used to simulate screws with different trajectories, diameters, and lengths. Responses for implant and tissues at the adjacent and fixed segments were used as the comparison indices. The contact lengths and spanning areas of the inserted screws were defined and compared across the varieties.
The trajectory and diameter had a greater impact on the responses from the implant and tissues than the length. The CBT has shorter length than the TT; however, the contact length and supporting area of the CBT within the cortical bone were 19.6%. and 14.5% higher than those of the TT, respectively. Overall, the TT and CBT were equally effective at stabilizing the instrumented segment, except for bending and rotation. The CBT experienced less adjacent segment compensations than the TT. With the same diameter and length, the TT was considerably less stressed than the CBT, especially for flexion and extension.
The CBT may provide less stress at adjacent segments compared with the TT. The CBT may provide more stiffer in osteoporotic segments than the TT due to greater contact with cortical bone and a wider supporting base between the paired screws. However, both entry point and insertion trajectory of the CBT should be carefully executed to avoid vertebral breach and ensure a stable cone-screw purchase.
已有许多研究比较了传统轨迹（TT）和皮质骨轨迹（CBT）螺钉；然而，螺钉参数如何影响 TT 和 CBT 螺钉的生物力学特性及其疗效仍有待研究。
采用有限元模型模拟不同轨迹、直径和长度的螺钉。将植入物和相邻固定节段的组织的响应作为比较指标。定义并比较了各种情况下插入螺钉的接触长度和跨越面积。
轨迹和直径对植入物和组织的响应影响大于长度。CBT 的长度比 TT 短；然而，CBT 在皮质骨内的接触长度和支撑面积分别比 TT 高 19.6%和 14.5%。总体而言，TT 和 CBT 在稳定仪器节段方面同样有效，除了弯曲和旋转。CBT 经历的相邻节段补偿比 TT 少。在相同直径和长度的情况下，TT 的应力明显小于 CBT，尤其是在弯曲和伸展时。
与 TT 相比，CBT 可能在相邻节段产生的应力更小。由于与皮质骨的接触更多以及配对螺钉之间的支撑基础更宽，CBT 在骨质疏松节段可能提供更大的刚度。然而，CBT 的进钉点和插入轨迹都应仔细执行，以避免椎骨破裂并确保稳定的圆锥-螺钉固定。
