Murphy T P, Hill C M, Kapatkin A S, Radin A, Shofer F S, Smith G K
Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, 3900 Delancey Street, Philadelphia, PA 19104-6010, USA.
Vet Surg. 2001 May-Jun;30(3):253-60. doi: 10.1053/jvet.2001.23344.
OBJECTIVES--To compare the pullout properties of 3.5-mm AO/ASIF self-tapping screws (STS) to corresponding standard cortex screws (CS) in a uniform synthetic test material and in canine femoral bone. The influence of screw-insertion technique, test material, and test-material thickness were also assessed. STUDY DESIGN--In vitro experimental study. SAMPLE POPULATION--Two independent studies: a uniform synthetic test material and paired femurs from mature dogs. METHODS-Mechanical testing was performed in accordance with standards established by the American Society for Testing and Materials for determination of axial pullout strength of medical bone screws. Completely inserted STS, completely inserted CS, and incompletely inserted STS were tested in 3 groups of 10 test specimens each in 4.96-mm and 6.8-mm thick sheets of synthetic material. In the bone study, group 1 consisted of 24 completely inserted STS compared with 24 completely inserted CS, and group 2 consisted of 24 incompletely inserted STS versus 24 completely inserted CS. Comparisons were made between paired femurs at corresponding insertion sites. Pullout data were normalized, thereby eliminating the effect of test-material thickness on pullout properties. Mean values were compared using 2-way ANOVA. Statistical significance was set at P <.05. RESULTS--In both the 4.96-mm and 6.8-mm synthetic material, pullout testing of the completely inserted STS demonstrated significantly greater yield strength and ultimate strength than completely inserted CS. There was no significant difference between incompletely inserted STS and completely inserted STS. The 6.8-mm test material significantly increased yield strength and ultimate strength for all test groups compared with the 4.96-mm test material. In canine bone, there was no significant difference in yield strength of completely inserted STS and completely inserted CS. Yield strength of completely inserted STS and completely inserted CS were significantly greater than incompletely inserted STS. CONCLUSIONS--Pullout properties of completely inserted STS were significantly greater than corresponding CS in a uniform test material. In canine bone, the pullout strength of STS and CS were not different. Incomplete STS insertion resulted in an 18% reduction in holding power as compared with completely inserted CS and STS in canine bone. CLINICAL RELEVANCE--The length of STS used in canine bone should be such that the cutting flutes extend beyond the trans cortex to maximize pullout strength.
目的——在均匀的合成测试材料和犬股骨中，比较3.5毫米AO/ASIF自攻螺钉（STS）与相应标准皮质骨螺钉（CS）的拔出性能。还评估了螺钉植入技术、测试材料和测试材料厚度的影响。研究设计——体外实验研究。样本群体——两项独立研究：一种均匀的合成测试材料和来自成年犬的配对股骨。方法——按照美国材料与试验协会制定的标准进行力学测试，以确定医用骨螺钉的轴向拔出强度。在4.96毫米和6.8毫米厚的合成材料片上，对每组10个测试样本的完全植入的STS、完全植入的CS和未完全植入的STS进行测试。在骨骼研究中，第1组由24个完全植入的STS与24个完全植入的CS组成，第2组由24个未完全植入的STS与24个完全植入的CS组成。在配对股骨的相应植入部位进行比较。对拔出数据进行归一化处理，从而消除测试材料厚度对拔出性能的影响。使用双向方差分析比较平均值。统计学显著性设定为P<0.05。结果——在4.96毫米和6.8毫米的合成材料中，完全植入的STS的拔出测试显示出比完全植入的CS显著更高的屈服强度和极限强度。未完全植入的STS与完全植入的STS之间没有显著差异。与4.96毫米测试材料相比，6.8毫米测试材料显著提高了所有测试组的屈服强度和极限强度。在犬骨中，完全植入的STS和完全植入的CS的屈服强度没有显著差异。完全植入的STS和完全植入的CS的屈服强度显著高于未完全植入的STS。结论——在均匀测试材料中，完全植入的STS的拔出性能显著高于相应的CS。在犬骨中，STS和CS的拔出强度没有差异。与犬骨中完全植入的CS和STS相比，未完全植入的STS导致固定力降低18%。临床意义——在犬骨中使用的STS长度应使切削槽延伸至皮质骨外，以最大化拔出强度。
