Sandriesser Sabrina, Rupp Markus, Greinwald Markus, Heiss Christian, Augat Peter, Alt Volker
Institute of Biomechanics, Trauma Centre Murnau, Murnau, Germany; Institute of Biomechanics, Paracelsus Medical University Salzburg, Salzburg, Austria.
Department of Trauma, Hand and Reconstructive Surgery, University Hospital Giessen-Marburg, Campus Giessen, Germany.
Injury. 2018 Jun;49 Suppl 1:S61-S65. doi: 10.1016/S0020-1383(18)30306-1.
The seizing of locking screws is a frequently encountered clinical problem during implant removal of locking compression plates (LCP) after completion of fracture healing. The aim of this study was to investigate the effect of two different locking mechanisms on the seizing of locking screws. Specifically, the removal torques before and after cyclic dynamic loading were assessed for screws inserted at the manufacturer-recommended torque or at an increased insertion torque. The seizing of 3.5-mm angular stable screws was assessed as a function of insertion torque for two different locking mechanisms (Thread & Conus and Thread Only). Locking screws (n=10 for each configuration) were inserted either according to the manufacturer-recommended torque or at an increased torque of 150% to simulate an over-insertion of the screw. Half of the screws were removed directly after insertion and the remaining half was removed after a dynamic load protocol of 100,000 cycles. The removal torques of locking screws exceeded the insertion torques for all tested conditions confirming the adequacy of the test setup in mimicking screw seizing in locked plating. Screw seizing was more pronounced for Thread Only design (+37%) compared to Thread & Conus design (+14%; P<0.0001). Cyclic loading of the locking construct consistently resulted in an increased seizing of the locking screws (P<0.0001). Clinical observations from patients treated with the Thread & Conus locking design confirm the biomechanical findings of reduction in seizing effect by using a Thread & Conus design. In conclusion, both over-tightening and cyclic loading are potential causes for screw seizing in locking plate implants. Both effects were found to be less pronounced in the Thread & Conus design as compared to the traditional Thread Only design.
在骨折愈合完成后取出锁定加压钢板（LCP）时，锁定螺钉的卡滞是临床上经常遇到的问题。本研究的目的是探讨两种不同锁定机制对锁定螺钉卡滞的影响。具体而言，评估了以制造商推荐扭矩或增加的插入扭矩插入的螺钉在循环动态加载前后的取出扭矩。对于两种不同的锁定机制（螺纹与圆锥面和仅螺纹），评估了3.5毫米角度稳定螺钉的卡滞情况与插入扭矩的关系。锁定螺钉（每种配置10枚）要么按照制造商推荐的扭矩插入，要么以增加150%的扭矩插入，以模拟螺钉过度插入的情况。一半的螺钉在插入后直接取出，其余的在经过100,000次循环的动态加载协议后取出。在所有测试条件下，锁定螺钉的取出扭矩均超过插入扭矩，这证实了测试设置在模拟锁定钢板中螺钉卡滞方面的充分性。与螺纹与圆锥面设计（增加14%；P<0.0001）相比，仅螺纹设计的螺钉卡滞更为明显（增加37%）。锁定结构的循环加载始终导致锁定螺钉的卡滞增加（P<0.0001）。采用螺纹与圆锥面锁定设计治疗的患者的临床观察结果证实了使用螺纹与圆锥面设计可减少卡滞效应的生物力学研究结果。总之，过度拧紧和循环加载都是锁定钢板植入物中螺钉卡滞的潜在原因。与传统的仅螺纹设计相比，这两种效应在螺纹与圆锥面设计中均不太明显。
