Department of Orthopaedics, University of Colorado, School of Medicine, Aurora, CO.
Department of Specialty Medicine, Rocky Vista University, College of Osteopathic Medicine, Parker, CO.
J Orthop Trauma. 2019 Apr;33(4):e137-e142. doi: 10.1097/BOT.0000000000001415.
The conventional AO buttress screw used for fracture fixation relies on a historic buttress thread design, which is prone to stripping at the bone-implant interface. We hypothesized that a new Bone-Screw-Fastener with an innovative interlocking thread design demonstrates increased resistance to torque stripping forces compared with the buttress screw, without compromising pullout strength.
A biomechanical model was established in 6 matched pairs of adult human cadaveric tibiae to test torque resistance between the 3.5 mm Bone-Screw-Fastener and the 3.5 mm cortical AO buttress screw until failure. Uniaxial pullout testing of both screw types was performed as an internal control experiment.
The 3.5 mm Bone-Screw-Fastener had a significantly increased resistance to torque failure compared with the standard 3.5 mm AO buttress screw (P = 0.0145). In contrast to the buttress screws, none of the Bone-Screw-Fasteners stripped from the bone but rather failed at the screwdriver-implant interface in terms of a metal-on-metal failure. The internal control experiments revealed no significant difference in axial pullout strength between the 2 implants (P = 0.47).
These data demonstrate the superiority of the new Bone-Screw-Fastener over the conventional AO buttress screw regarding protection from torque stripping forces. In addition, the new thread design that interlocks to the bone does not sacrifice axial pullout resistance conveyed by the buttress screw. Future controlled trials will have to validate the in vivo relevance of these findings in a clinical setting.
传统的用于骨折固定的 AO 支撑螺钉依赖于历史悠久的支撑螺纹设计，这种设计容易在骨-植入物界面处出现螺纹滑丝。我们假设，一种具有创新性的互锁螺纹设计的新型骨螺钉紧固件在不影响拔出强度的情况下，比支撑螺钉更能抵抗扭矩剥离力。
在 6 对匹配的成人尸体胫骨中建立了生物力学模型，以测试 3.5mm 骨螺钉紧固件和 3.5mm 皮质 AO 支撑螺钉之间的抗扭矩阻力，直到失效。作为内部对照实验，对两种螺钉类型进行了单轴拔出试验。
3.5mm 骨螺钉紧固件与标准 3.5mm AO 支撑螺钉相比，抗扭矩失效的能力显著提高（P=0.0145）。与支撑螺钉不同的是，没有一个骨螺钉紧固件从骨中滑出，而是在螺丝刀-植入物界面处发生金属对金属失效。内部对照实验表明，两种植入物的轴向拔出强度无显著差异（P=0.47）。
这些数据表明，新型骨螺钉紧固件在防止扭矩剥离力方面优于传统的 AO 支撑螺钉。此外，与骨互锁的新型螺纹设计不会牺牲支撑螺钉传递的轴向拔出阻力。未来的对照试验将不得不验证这些发现在临床环境中的实际意义。
