Department of Orthopaedic Surgery, Medical College of Wisconsin, Milwaukee, WI.
Orthopaedic and Rehabilitation Engineering Center, Marquette University, Milwaukee, WI.
J Orthop Trauma. 2019 Jun;33(6):e240-e245. doi: 10.1097/BOT.0000000000001447.
This study aimed to investigate the stability and strength of tension band wire fixation using headless compression screws versus headed screws for transverse patella fractures.
Six matched pairs of fresh-frozen cadaveric knees with transverse osteotomies created at the midpoint of the patella were surgically fixed, with one knee randomly receiving fixation with headless screws (Acumed Acutrak 4/5) and the other with headed screws (Synthes 4.0 partially threaded cannulated screws). The specimens were mounted onto a servohydraulic load frame in a 45-degree flexed position and loaded through the quadriceps tendon. Interfragmentary movement was recorded with a motion analysis system. The initial fixation stiffness, range of interfragmentary motion, and strength of the headless screw construct were compared with the headed screw construct. Failure was defined as either a sudden drop in applied tendon force or 2 mm of separation on the anterior surface of the patella (ie, clinical failure), whichever occurred first.
Mean primary interfragmentary motion was 0.31 ± 0.28 degrees for the headed screws and 0.10 ± 0.06 degrees for headless screws under 150 N load (P = 0.03). Mean construct stiffness was 277 ± 243 N/degrees for the headed screws and 510 ± 362 N/degrees for the headless screws (P = 0.03). None of the constructs from either group displayed structural failure before reaching the clinical failure gap of 2 mm. The mean clinical failure strength was 808 ± 183 N for the headless screws construct and 520 ± 241 N for the headed screws construct (P = 0.03).
Headless screw tension band fixation demonstrated superior biomechanical behaviors over standard headed screw fixation with higher construct rigidity, smaller interfragmentary motion, and greater fixation strength.
本研究旨在探讨无头加压螺钉与带螺纹头螺钉固定横断髌骨骨折的稳定性和强度。
对 6 对新鲜冷冻尸体膝关节进行手术固定，在髌骨中点处制作横断骨切开术，其中一只膝关节随机接受无头螺钉（Acumed Acutrak 4/5）固定，另一只膝关节接受带螺纹头螺钉（Synthes 4.0 部分螺纹空心螺钉）固定。将标本安装在 45 度弯曲位置的伺服液压加载架上，并通过股四头肌肌腱加载。使用运动分析系统记录骨折间的运动。比较无头螺钉与带螺纹头螺钉的初始固定刚度、骨折间运动范围和无头螺钉结构的强度。失效定义为施加在肌腱上的力突然下降或髌骨前表面分离 2 毫米（即临床失效），以先发生的为准。
在 150 N 载荷下，带螺纹头螺钉的平均初始骨折间运动为 0.31±0.28 度，无头螺钉为 0.10±0.06 度（P=0.03）。带螺纹头螺钉的结构刚度为 277±243 N/度，无头螺钉为 510±362 N/度（P=0.03）。在达到 2 毫米的临床失效间隙之前，两组的任何一种结构都没有显示出结构失效。无头螺钉结构的平均临床失效强度为 808±183 N，带螺纹头螺钉结构为 520±241 N（P=0.03）。
无头螺钉张力带固定在生物力学性能方面优于标准带螺纹头螺钉固定，具有更高的结构刚性、更小的骨折间运动和更大的固定强度。
