Boudreau Bianca, Benamou Jérôme, von Pfeil Dirsko J F, Guillou Reunan P, Beckett Clifford, Déjardin Loïc M
Collaborative Orthopaedic Investigations Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA.
Vet Surg. 2013 Jun;42(5):535-43. doi: 10.1111/j.1532-950X.2013.12023.x. Epub 2013 May 7.
To evaluate the effect of screw insertion torque on the mechanical properties of four 3.5 mm locking systems: New Generation Devices (NGD), Securos (PAX), Synthes (SYN), and Veterinary Orthopedic Implants (VOI).
In vitro mechanical study.
Screws were inserted at 1.5 Nm, 2.5 Nm, and 3.5 Nm torques, using dedicated drill guides and a calibrated torque screwdriver. Locking mechanisms were tested under shear loading conditions using a custom-design probe. Tests were conducted under displacement control until failure. Load to failure and interface stiffness were compared between and within groups using a two-factor ANOVA (P < .05). Failure modes were described.
The SYN group had significantly greater mechanical properties compared to all other groups at any given insertion torque. Insertion torque had a significant effect on the PAX group, increasing the load to failure by 126% when increasing the insertion torque from 1.5 Nm to 3.5 Nm. Insertion torque had no significant effect on the mechanical properties of the VOI group and limited effect on the NGD and SYN groups. Single failure mode, by screw head decoupling or screw shaft fracture, occurred in the SYN and VOI groups, respectively. In contrast, NGD and PAX systems failed through a combination of screw decoupling and/or bending.
Regardless of insertion torque, the SYN locking mechanism showed the highest failure loads, interfacial stiffness as well as consistent failure mode. These findings highlight the dependability of this system. When using the PAX system an insertion torque of at least 2.5 Nm should be recommended.
评估螺钉插入扭矩对四种3.5毫米锁定系统（新一代装置（NGD）、Securos（PAX）、Synthes（SYN）和兽医骨科植入物（VOI））力学性能的影响。
体外力学研究。
使用专用钻孔导向器和校准扭矩螺丝刀，以1.5牛米、2.5牛米和3.5牛米的扭矩插入螺钉。使用定制设计的探头在剪切载荷条件下测试锁定机制。在位移控制下进行测试直至失效。使用双因素方差分析（P < 0.05）比较组间和组内的失效载荷和界面刚度。描述失效模式。
在任何给定的插入扭矩下，SYN组的力学性能均显著优于所有其他组。插入扭矩对PAX组有显著影响，当插入扭矩从1.5牛米增加到3.5牛米时，失效载荷增加了126%。插入扭矩对VOI组的力学性能无显著影响，对NGD组和SYN组的影响有限。SYN组和VOI组分别出现了单一失效模式，即螺钉头部脱开或螺钉轴断裂。相比之下，NGD和PAX系统通过螺钉脱开和/或弯曲的组合失效。
无论插入扭矩如何，SYN锁定机制均显示出最高的失效载荷、界面刚度以及一致的失效模式。这些发现突出了该系统的可靠性。使用PAX系统时，建议插入扭矩至少为2.5牛米。
