Koh Il-Hyun, Kang Ho-Jung, Kim Ji-Sup, Park Seong-Jin, Choi Yun-Rak
Department of Orthopaedic Surgery, Severance Hospital, Yonsei University College of Medicine, Seoul, South Korea.
Department of Orthopaedic Surgery, Severance Hospital, Yonsei University College of Medicine, Seoul, South Korea.
Injury. 2015 Apr;46(4):638-42. doi: 10.1016/j.injury.2015.01.018. Epub 2015 Jan 20.
An interpositional wedge bone graft is a procedure performed to restore carpal height and scaphoid length for displaced scaphoid nonunions with carpal instability. The purpose of this study was to investigate which headless screw design (threadless central shaft screw or fully threaded variable pitch compression screw) is biomechanically preferred when an interpositional bone graft is needed.
A total of 24 cadaveric scaphoid interpositional bone grafts were divided into three groups and fixed with HCS 3.0, Herbert-Whipple or Acutrak mini-screws, and the relative biochemical stability of each was measured. The specimens were tested using an Instron tensile testing machine to calculate stiffness and load to failure. To measure compression forces at different interfragmentary gaps, 30 interpositional polyurethane bone graft models were generated with three pieces of cancellous sawbone block, and two custom-made load-cells were inserted in each gap. The models were then divided into three groups and fixed with the above screw types. The compression forces at different interfragmentary gaps were measured immediately and 30 min after screw fixation.
The average stiffness and load to failure were similar among the three groups (p>0.05). The average compression force measured at each interfragmentary gap was highest in the HCS 3.0 fixation group, followed by the Herbert-Whipple and Acutrak mini-screw fixation groups both immediately after screw fixation and after 30 min (at which time there were significant decreases in force). The compression forces measured at different interfragmentary gaps were almost identical in the HCS 3.0 and Herbert-Whipple screw fixation groups; however, the force measured at the leading side was significantly lower than that measured at the trailing side in the Acutrak mini-screw fixation group.
The threadless central shaft screw design is biomechanically preferred over the fully threaded variable pitch screw design because it achieves higher and identical compression forces at different interfragmentary gaps with similar stiffness and load to failure.
间置楔形骨移植术是一种用于恢复腕骨高度和舟骨长度的手术，适用于伴有腕骨不稳的移位性舟骨不愈合。本研究的目的是探讨在需要进行间置骨移植时，哪种无头螺钉设计（无螺纹中心轴螺钉或全螺纹变螺距加压螺钉）在生物力学上更具优势。
将24个尸体舟骨间置骨移植标本分为三组，分别用HCS 3.0、Herbert-Whipple或Acutrak微型螺钉固定，并测量每组的相对生物化学稳定性。使用Instron拉伸试验机对标本进行测试，以计算刚度和破坏载荷。为了测量不同骨折块间隙处的压缩力，用三块松质骨锯骨块制作了30个间置聚氨酯骨移植模型，并在每个间隙中插入两个定制的测力传感器。然后将模型分为三组，并用上述螺钉类型固定。在螺钉固定后立即和30分钟后测量不同骨折块间隙处的压缩力。
三组之间的平均刚度和破坏载荷相似（p>0.05）。在螺钉固定后立即以及30分钟后（此时力有显著下降），HCS 3.0固定组在每个骨折块间隙处测得的平均压缩力最高，其次是Herbert-Whipple和Acutrak微型螺钉固定组。HCS 3.0和Herbert-Whipple螺钉固定组在不同骨折块间隙处测得的压缩力几乎相同；然而，在Acutrak微型螺钉固定组中，在前侧测得的力明显低于在后侧测得的力。
无螺纹中心轴螺钉设计在生物力学上优于全螺纹变螺距螺钉设计，因为它在不同骨折块间隙处能实现更高且相同的压缩力，同时具有相似的刚度和破坏载荷。
