Vida J T, Pooya Hooman, Vasseur Philip B, Garcia Tanya C, Schulz Kurt, Stover Susan M
Veterinary Medical Teaching Hospital, J.D. Wheat Veterinary Orthopedic Research Laboratory, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Vet Surg. 2005 Sep-Oct;34(5):491-8. doi: 10.1111/j.1532-950X.2005.00074.x.
To compare shear stability of simulated humeral lateral condylar fractures reduced with either a self-compressing pin or cortical bone screw.
In vitro biomechanical tests.
Bilateral cadaveric canine humeri (n=18) without evidence of elbow disease.
Lateral condylar fracture was simulated by standardized osteotomy. Bone fragments were stabilized with a self-compressing pin or a cortical bone screw (2.7 or 3.5 mm) inserted in lag fashion. Specimens were mounted in a materials testing system and the condylar fragment displaced in a proximal direction until failure. Mechanical testing variables derived from load-deformation curves were compared between stabilization methods using a Student's paired t-test.
There were no statistically significant differences for mechanical testing variables between pin and screw stabilized specimens at expected walk and trot loads. Three yield points subjectively coincided with yield of the interfragmentary interface (Y1), bone at the implant interface (Y2), and implant deformation (Y3). Displacements at Y1 were 48-156% greater for pin than screw stabilized specimens. Y2 and Y3 loads were higher for screw than pin stabilized specimens, but likely supraphysiologic for dogs convalescing after surgical repair.
A self-compressing pin or a cortical bone screw inserted in lag fashion both provided adequate strength in applied shear to sustain expected physiologic loads through the repaired canine elbow during postoperative convalescence.
Because self-compressing pins were easy to implant and mechanical properties were not significantly different than cortical screws at expected physiologic loads, pins should be considered for the repair of traumatic humeral condylar fractures.
比较使用自加压针或皮质骨螺钉复位的模拟肱骨外侧髁骨折的剪切稳定性。
体外生物力学试验。
无肘部疾病证据的双侧犬尸体肱骨（n = 18）。
通过标准化截骨术模拟外侧髁骨折。用自加压针或以拉力方式插入的皮质骨螺钉（2.7或3.5毫米）固定骨碎片。将标本安装在材料测试系统中，使髁部碎片向近端移位直至失效。使用学生配对t检验比较不同固定方法之间从载荷-变形曲线得出的力学测试变量。
在预期的行走和小跑载荷下，用针和螺钉固定的标本之间的力学测试变量无统计学显著差异。主观上有三个屈服点与骨折块间界面的屈服（Y1）、植入物界面处的骨（Y2）和植入物变形（Y3）一致。在Y1处，用针固定的标本的位移比用螺钉固定的标本大48% - 156%。用螺钉固定的标本的Y2和Y3载荷高于用针固定的标本，但对于手术修复后正在恢复的犬来说可能超过生理范围。
自加压针或以拉力方式插入的皮质骨螺钉在施加剪切力时均提供了足够的强度，以在术后恢复期间维持通过修复的犬肘部的预期生理载荷。
由于自加压针易于植入，且在预期生理载荷下其力学性能与皮质骨螺钉无显著差异，因此在修复创伤性肱骨髁骨折时应考虑使用针。
