Chang Chih-Wei, Chen Yen-Nien, Li Chun-Ting, Chung Chi-Rung, Tseng Chung-Chih, Chang Chih-Han, Peng Yao-Te
Department of BioMedical Engineering, National Cheng Kung University, Tainan City, Taiwan; Department of Orthopedics, College of Medicine, National Cheng Kung University, Tainan City, Taiwan; Department of Orthopedics & Joint Reconstruction Center, National Cheng Kung University Hospital, Collage of Medicine, National Cheng Kung University, Tainan City, Taiwan.
Department of BioMedical Engineering, National Cheng Kung University, Tainan City, Taiwan; Department of Orthopedics, Show-Chwan Memorial Hospital, Changhua City, Taiwan.
Injury. 2019 Feb;50(2):263-271. doi: 10.1016/j.injury.2018.12.004. Epub 2018 Dec 5.
To date, the effects of various screw configurations on the stability of tibial tubercle osteotomy (TTO) are not completely understood. Hence, the first aim of this study is to evaluate the stability of TTO under various screw configurations. The second aim is to evaluate the internal stresses in the bone and the contact forces on the bone fragment that are developed by the tibia and screws in response to the applied load after the equilibrant is revealed.
To calculate the biomechanical responses of the bone and screw under loading, finite element (FE) method was used in this study. Six types of screw configurations were studied in the simulation: two parallel horizontal screws placed at a 20 mm interval, two parallel horizontal screws placed at a 30 mm interval, two parallel upward screws, two parallel downward screws, two trapezoid screws, and two divergent screws. The displacement of the bone fragment, contact forces on the fragment, and the internal stress in the bone were used as indices for comparison.
Among all configurations, the configuration of two parallel downward screws yielded the highest stability with the lowest fragment displacement and gap opening. Although the maximum displacement of the TTO with the configuration of two parallel horizontal screws was slightly higher than that of the downward configuration, the difference was only 0.2 mm. The configuration of two upward screws resulted in the highest fragment displacement and gap deformation between the fragment and tibia. The stress of the osteotomized bone fragment was highest with the configuration of two upward screws.
Based on the present model, the current configuration of two parallel horizontal screws is recommended for TTO. If this is inappropriate in a specific clinical scenario, then the downward screw configuration may be used as an alternative. By contrast, the configuration of two parallel upward screws is least suggested for the fixation of TTO.
迄今为止，各种螺钉配置对胫骨结节截骨术（TTO）稳定性的影响尚未完全明确。因此，本研究的首要目的是评估不同螺钉配置下TTO的稳定性。第二个目的是在揭示平衡力后，评估骨骼中的内应力以及胫骨和螺钉在施加负荷时对骨块产生的接触力。
为计算加载情况下骨骼和螺钉的生物力学响应，本研究采用了有限元（FE）方法。在模拟中研究了六种螺钉配置：两根间隔20毫米的平行水平螺钉、两根间隔30毫米的平行水平螺钉、两根平行向上的螺钉、两根平行向下的螺钉、两根梯形螺钉和两根发散螺钉。骨块的位移、骨块上的接触力以及骨骼中的内应力用作比较指标。
在所有配置中，两根平行向下螺钉的配置产生了最高的稳定性，骨块位移和间隙开口最小。虽然两根平行水平螺钉配置的TTO最大位移略高于向下配置，但差异仅为0.2毫米。两根向上螺钉的配置导致骨块位移最大，且骨块与胫骨之间的间隙变形最大。两根向上螺钉配置时，截骨骨块的应力最高。
基于当前模型，建议TTO采用两根平行水平螺钉的当前配置。如果在特定临床情况下不合适，则可使用向下螺钉配置作为替代方案。相比之下，两根平行向上螺钉的配置最不建议用于TTO的固定。
