Orthopaedics Department, Hannover Medical School (MHH), Germany.
Acta Orthop. 2011 Jun;82(3):339-43. doi: 10.3109/17453674.2011.574564. Epub 2011 Apr 19.
New implant designs have incorporated a single radius instead of a multiple radius to the femoral component in order to improve the mechanical function after TKA. We investigated the amount of quadriceps force required to extend the knee during an isokinetic extension cycle of different total knee designs, focusing on the radius of the femoral component (single vs. multiple).
Human knee specimens (n = 12, median patient age 68 (63-70) years) were tested in a kinematic knee-simulating machine untreated and after implantation of 2 types of knee prosthesis systems, one with a single femoral radius design and one with a multiple femoral radius design. During the test cycle, a hydraulic cylinder, which simulated the quadriceps muscle, applied sufficient force to the quadriceps tendon to produce a constant extension moment of 31 Nm. The quadriceps extension force was measured from 120° to full knee extension.
The shape of the quadriceps force curve was typically sinusoidal before and after TKA, reaching a maximum value of 1,493 N at 110°. With the single femoral radius design, quadriceps force was similar to that of the normal knee: 1,509 N at 110° flexion (p = 0.4). In contrast, the multiple femoral radius design showed an increase in quadriceps extension force relative to the normal knee, with a maximum of 1,721 N at 90° flexion (p = 0.03).
The single femoral radius design showed lower maximum extension forces than the multiple femoral radius design. In addition, with the single femoral radius design maximum quadriceps force needed to extend a constant extension force shifted to higher degrees of knee flexion, representing a more physiological quadriceps force pattern, which could have a positive effect on knee function after TKA.
为了改善 TKA 后的机械功能，新型植入物设计采用了单一半径而不是股骨部件的多个半径。我们研究了不同全膝关节设计在等速伸膝循环中伸展膝关节所需的股四头肌力量，重点是股骨部件的半径（单一与多个）。
在未处理和植入两种膝关节假体系统后，对 12 个人类膝关节标本（中位患者年龄 68（63-70）岁）进行了运动学膝关节模拟机测试，其中一种具有单一股骨半径设计，另一种具有多个股骨半径设计。在测试循环中，液压缸模拟股四头肌，向股四头肌肌腱施加足够的力，以产生 31 Nm 的恒定伸展力矩。从 120°到全膝关节伸展测量股四头肌伸展力。
TKA 前后股四头肌力曲线的形状通常呈正弦形，在 110°处达到 1,493 N 的最大值。在具有单一股骨半径设计的情况下，股四头肌力类似于正常膝关节：在 110°弯曲时为 1,509 N（p = 0.4）。相比之下，多个股骨半径设计显示股四头肌伸展力相对于正常膝关节增加，在 90°弯曲时达到最大值 1,721 N（p = 0.03）。
单一股骨半径设计的最大伸展力低于多个股骨半径设计。此外，具有单一股骨半径设计的最大股四头肌力需要伸展恒定的伸展力，向更高的膝关节弯曲度转移，代表更生理的股四头肌力模式，这可能对 TKA 后膝关节功能产生积极影响。
