Levadnyi Ievgen, Awrejcewicz Jan, Gubaua José Eduardo, Pereira Jucélio Tomás
Lodz University of Technology, Department of Automation, Biomechanics and Mechatronics, 1/15 Stefanowski Str., 90-924 Lodz, Poland.
Lodz University of Technology, Department of Automation, Biomechanics and Mechatronics, 1/15 Stefanowski Str., 90-924 Lodz, Poland; Warsaw University of Technology, Institute of Vehicles, 84 Narbutta Str., 02-524 Warsaw, Poland.
Clin Biomech (Bristol). 2017 Dec;50:122-129. doi: 10.1016/j.clinbiomech.2017.10.015. Epub 2017 Oct 18.
The change in mechanical properties of femoral cortical bone tissue surrounding the stem of the hip endoprosthesis is one of the causes of implant instability. We present an analysis used to determine the best conditions for long-term functioning of the bone-implant system, which will lead to improvement of treatment results.
In the present paper, a finite element method coupled with a bone remodelling model is used to evaluate how different three-dimensional prosthesis models influence distribution of the density of bone tissue. The remodelling process begins after the density field is obtained from a computed tomography scan. Then, an isotropic Stanford model is employed to solve the bone remodelling process and verify bone tissue adaptation in relation to different prosthesis models.
The study results show that the long-stem models tend not to transmit loads to proximal regions of bone, which causes the stress-shielding effect. Short stems or application in the calcar region provide a favourable environment for transfer of loads to the proximal region, which allows for maintenance of bone density and, in some cases, for a positive variation, which causes absence of the aseptic loosening of an implant. In the case of hip resurfacing, bone mineral density changes slightly and is closest to an intact femur.
Installation of an implant modifies density distribution and stress field in the bone. Thus, bone tissue is stimulated in a different way than before total hip replacement, which evidences Wolff's law, according to which bone tissue adapts itself to the loads imposed on it. The results suggest that potential stress shielding in the proximal femur and cortical hypertrophy in the distal femur may, in part, be reduced through the use of shorter stems, instead of long ones, provided stem fixation is adequate.
髋关节假体柄周围股骨皮质骨组织力学性能的变化是植入物不稳定的原因之一。我们提出一种分析方法，用于确定骨-植入物系统长期功能的最佳条件，这将有助于改善治疗效果。
在本文中，采用有限元方法结合骨重塑模型来评估不同的三维假体模型如何影响骨组织密度分布。从计算机断层扫描获得密度场后开始重塑过程。然后，采用各向同性的斯坦福模型来求解骨重塑过程，并验证与不同假体模型相关的骨组织适应性。
研究结果表明，长柄模型往往不会将载荷传递到骨的近端区域，从而导致应力屏蔽效应。短柄或应用于股骨矩区域为将载荷传递到近端区域提供了有利环境，这有助于维持骨密度，在某些情况下还会产生正向变化，从而避免植入物无菌性松动。对于髋关节表面置换，骨矿物质密度变化轻微，最接近完整股骨。
植入物的安装会改变骨内的密度分布和应力场。因此，骨组织受到的刺激方式与全髋关节置换前不同，这证明了沃尔夫定律，即骨组织会根据施加在其上的载荷进行自我调整。结果表明，如果柄固定充分，使用较短的柄而非长柄，可能部分减少股骨近端潜在的应力屏蔽和股骨远端的皮质肥厚。
