Windolf Markus, Muths Raphael, Braunstein Volker, Gueorguiev Boyko, Hänni Markus, Schwieger Karsten
AO Research Institute, AO Foundation, Clavadelerstrasse 8, 7270 Davos, Switzerland.
Clin Biomech (Bristol). 2009 Jan;24(1):53-8. doi: 10.1016/j.clinbiomech.2008.09.005. Epub 2008 Nov 13.
Compaction of cancellous bone is believed to prevent cut-out. This in vitro study quantified the compaction in the femoral head due to insertion of a dynamic hip screw-blade with and without predrilling and investigated the resulting implant anchorage under cyclic loading.
Eight pairs of human cadaveric femoral heads were instrumented with a dynamic hip screw-blade made of Polyetheretherketon. Pairwise instrumentation was performed either with or without predrilling the specimens. CT scanning was performed before and after implantation, to measure bone-compaction. Subsequently the implant was removed and a third scan was performed to analyze the relaxation of the bone structure. Commercial implants were reinserted and the specimens were cyclically loaded until onset of cut-out occurred. The bone-implant interface was monitored by means of fluoroscopic imaging throughout the experiment. Paired t-tests were performed to identify differences regarding compaction, relaxation and cycles to failure.
Bone density in the surrounding of the implant increased about 30% for the non-predrilled and 20% for the predrilled group when inserting the implant. After implant removal the predrilled specimens fully relaxed; the non-predrilled group showed about 10% plastic deformation. No differences were found regarding cycles to failure (P=0.32).
Significant bone-compaction due to blade insertion was verified. Even though compaction was lower when predrilling the specimens, mainly elastic deformation was present, which is believed to primarily enhance the implant anchorage. Cyclic loading tests confirmed this thesis. The importance of the implantation technique with regard to predrilling is therefore decreased.
松质骨压实被认为可防止内固定物穿出。本体外研究量化了在有或无预钻孔情况下，动力髋螺钉刀片植入股骨头时的骨压实情况，并研究了在循环加载下产生的植入物锚固情况。
八对人体尸体股骨头安装由聚醚醚酮制成的动力髋螺钉刀片。对标本进行成对安装，一组有预钻孔，一组没有。在植入前后进行CT扫描，以测量骨压实情况。随后取出植入物，进行第三次扫描以分析骨结构的松弛情况。重新插入商用植入物，对标本进行循环加载，直至出现内固定物穿出。在整个实验过程中，通过荧光透视成像监测骨-植入物界面。进行配对t检验以确定在压实、松弛和失效循环方面的差异。
植入植入物时，未预钻孔组植入物周围的骨密度增加约30%，预钻孔组增加约20%。取出植入物后，预钻孔标本完全松弛；未预钻孔组显示约10%的塑性变形。在失效循环方面未发现差异（P = 0.32）。
证实了刀片插入导致显著的骨压实。尽管预钻孔时压实程度较低，但主要存在弹性变形，这被认为主要增强了植入物的锚固。循环加载试验证实了这一论点。因此，预钻孔植入技术的重要性降低。
