Sakai Rina, Takahashi Akiko, Takahira Naonobu, Uchiyama Katsufumi, Yamamoto Takeaki, Uchida Kentaro, Fukushima Kensuke, Moriya Mistutoshi, Takaso Masashi, Itoman Moritoshi, Mabuchi Kiyoshi
Department of Medical Engineering and Technology, School of Allied Health Sciences, Kitasato University, Sagamihara City, Kanagawa - Japan.
Hip Int. 2011 May-Jun;21(3):330-5. doi: 10.5301/HIP.2011.8408. Epub 2011 Jun 13.
During cementless stem fixation, impaction of the stem is occasionally complicated by bony injuries. Small fractures not visible to the eye during surgery or on post-operative radiographs may remain undetected, and the incidence of such injuries may be underestimated. Employing the same techniques as those employed during total hip arthroplasty, we implanted cementless stems into artificial femora, with equivalent mechanical characteristics to living femora. The hammering force applied to the femur and the displacement of the stem and femur were measured using a load sensor and imaging, respectively. The von Mises stress generated in the femur during cementless stem press-fixation was also measured using finite element analysis. Average hammering force under these conditions (9.25 kN) was sufficient to cause damage to the artificial femur. The first two of eight hammer strikes caused most displacement of the stem. The von Mises stresses generated by the first and second hammer strikes were 31 and 68 MPa, respectively. Applying a high average hammering force to the stem after displacement has ceased probably contributes to the generation of intraoperative fractures during cementless stem fixation. Given that two strikes appeared to be sufficient, we believe that hammering force should be reduced to a micro-adjustment level after the second hit.
在非骨水泥型股骨柄固定过程中，股骨柄的敲击偶尔会因骨损伤而变得复杂。手术过程中或术后X光片上肉眼不可见的小骨折可能仍未被发现，此类损伤的发生率可能被低估。我们采用与全髋关节置换术相同的技术，将非骨水泥型股骨柄植入具有与活体股骨等效力学特性的人工股骨中。分别使用载荷传感器和成像技术测量施加在股骨上的敲击力以及股骨柄和股骨的位移。还使用有限元分析测量了非骨水泥型股骨柄压配固定过程中股骨内产生的冯·米塞斯应力。在这些条件下的平均敲击力（9.25 kN）足以对人工股骨造成损伤。八次敲击的前两次导致股骨柄的位移最大。第一次和第二次敲击产生的冯·米塞斯应力分别为31 MPa和68 MPa。在位移停止后对股骨柄施加高平均敲击力可能会导致非骨水泥型股骨柄固定过程中发生术中骨折。鉴于两次敲击似乎就足够了，我们认为在第二次敲击后应将敲击力降低到微调水平。
