Gwinner Clemens, Märdian Sven, Dröge Tobias, Schulze Martin, Raschke Michael J, Stange Richard
Centre for Musculoskeletal Surgery, Charité - University Medicine Berlin, Augustenburger Platz 1, 13353, Berlin, Germany,
Int Orthop. 2015 Sep;39(9):1749-55. doi: 10.1007/s00264-015-2787-6. Epub 2015 May 7.
The incidence of periprosthetic fractures is inevitably increasing. Sufficient stabilisation and proper screw placement next to large-volume implants remains difficult. Modern locking plates allow polyaxial, thus bicortical, screw placement around a prosthetic stem. This study analysed the biomechanical properties of different screw configurations in a locking plate construct of a periprosthetic femoral fracture model.
A total of 20 Sawbones were used to stabilise a Vancouver-B1 femoral fracture with a locking plate using either four monocortical screws or three bicortical screws for proximal fixation. These were loaded with an increasing axial compression until failure.
Bicortical screw purchase was significantly superior to monocortical regarding load to failure (1,510 N ± 284 N versus 2,350 N ± 212 N, p < 0.001) and maximal number of cycles (6803 ± 760 versus 4041 ± 923, p < 0.001). However, the mode of failure in the bicortical group was a severe comminuted fracture pattern as opposed to the monocortical group in which a pull-out of the screws without further damage to the bone was observed.
Bicortical screw placement enhances the primary stability in treating periprosthetic femoral fractures. Notably, the mode of failure may limit the salvage options in case of revision surgery.
人工关节周围骨折的发生率必然在增加。在大容量植入物旁实现充分稳定和正确的螺钉置入仍然很困难。现代锁定钢板允许多轴，从而实现双皮质螺钉在假体柄周围的置入。本研究分析了人工关节周围股骨骨折模型锁定钢板结构中不同螺钉配置的生物力学特性。
总共使用20个Sawbones标本，用锁定钢板固定温哥华B1型股骨骨折，近端固定采用4枚单皮质螺钉或3枚双皮质螺钉。对这些标本施加逐渐增加的轴向压缩直至失效。
在失效载荷（1510 N±284 N对2350 N±212 N，p<0.001）和最大循环次数（6803±760对4041±923，p<0.001）方面，双皮质螺钉固定明显优于单皮质螺钉固定。然而，双皮质螺钉组的失效模式是严重粉碎性骨折，而单皮质螺钉组观察到螺钉拔出而没有对骨造成进一步损伤。
双皮质螺钉置入可增强人工关节周围股骨骨折治疗的初始稳定性。值得注意的是，失效模式可能会限制翻修手术时的挽救选择。
