Heidemann W, Gerlach K L, Gröbel K H, Köllner H G
Klinik für Mund-, Kiefer- und Gesichtschirurgie, Otto-von-Guericke Universität, Magdeburg.
Mund Kiefer Gesichtschir. 1998 May;2(3):136-40. doi: 10.1007/s100060050048.
The standard drill size for most osteosynthesis screws is about 75% of the screw's external diameter. When screws are inserted in thick cortical bone, a small pilot hole size can result in high torsional stress, leading to screw fracturing. The aim of this study was to enlarge the drill size up to a critical pilot hole size, exceeding of which leads to a rapid decrease of the screw's holding power. Titanium screws of diameter 1.5 and 2 mm were inserted in discs of PVC, wood and porcine mandibular bone with different thickness between 2 to 4 mm, using pilot hole sizes of 66-95% of the screw's external diameter. The maximum torque was recorded and pull-out tests were performed. Ten trials were conducted for each screw-pilot hole size-material combination, yielding a total of 1560 tests. A multiphase regression analysis was performed to calculate the critical pilot hole size (CPHS). In torque measurements, the CPHS of microscrews were between 83% and 85% of screw outer diameter (SOD) and the CPHS of miniscrews were between 80% and 90% of SOD. In pull-out analysis the CPHS of microscrews were between 83% and 89% of SOD and the CPHS of miniscrews were between 79% and 91% of SOD. The CPHS was thus found to be around 85% of the screw's external diameter. Up to this critical point the pilot hole size may be increased without affecting the holding power of the screws.
大多数骨固定螺钉的标准钻孔尺寸约为螺钉外径的75%。当螺钉插入较厚的皮质骨时，较小的引导孔尺寸会导致高扭转应力，从而导致螺钉断裂。本研究的目的是将钻孔尺寸扩大到临界引导孔尺寸，超过该尺寸会导致螺钉固定力迅速下降。将直径为1.5毫米和2毫米的钛螺钉插入厚度在2至4毫米之间的聚氯乙烯、木材和猪下颌骨圆盘，使用的引导孔尺寸为螺钉外径的66%至95%。记录最大扭矩并进行拔出试验。对每种螺钉-引导孔尺寸-材料组合进行了10次试验，总共进行了1560次试验。进行多阶段回归分析以计算临界引导孔尺寸（CPHS）。在扭矩测量中，微型螺钉的CPHS在螺钉外径（SOD）的83%至85%之间，小型螺钉的CPHS在SOD的80%至90%之间。在拔出分析中，微型螺钉的CPHS在SOD的83%至89%之间，小型螺钉的CPHS在SOD的79%至91%之间。因此发现CPHS约为螺钉外径的85%。在达到这个临界点之前，可以增加引导孔尺寸而不影响螺钉的固定力。
