Abstract
Total knee arthroplasty aims at restoring the function of the native knee. An important aspect at this point are the knee kinematics, as it can be assumed that following TKA surgery these should resemble the native conditions. The use of cadaveric testing is since long an important step in the development and validation of implant designs and surgical techniques. However, this cadaveric testing has primarily focused on squatting under load bearing conditions. The main research question of this paper is therefore to evaluate the impact of TKA surgery on the knee kinematics under a range of boundary conditions.
A set of five cadaveric knees have been tested in a newly developed and validated knee simulator at Ghent University. In contrast to other simulators, this simulator allows simulating a wide range of conditions as it facilitates a controlled movement of the ankle in the sagittal plane under continuously variable hamstring and quadriceps loading. In the framework of this study, two different motion patterns have been studied. First, the knees were subjected to a traditional squatting motion maintaining constant quadriceps loading. Second, the knees were tested while performing a cycling movement with a highly variable quadriceps load during the extension phase. For both cases, the studied motion patterns have been repeated five times. Following the evaluation of the native knee kinematics, TKA surgery was performed using a single radius implant. During surgery, the implant alignment has been controlled using computer navigation. Subsequently, the same boundary conditions have been applied and the kinematics again recorded.
Focusing on the native knee, the measured kinematic patterns for the squatting motion significantly differ from the ones observed for the cycling movement for similar flexion angles. This is attributed to a difference in quadriceps loading. However, following TKA surgery, the kinematic patterns are remarkably comparable between the squatting and cycling experiments. These observations suggest that the TKA design considered in this study displays a highly constrained behavior. More specifically, the design appears to favor the squatting behavior. Further study is however required to thoroughly evaluate this observation for other implant designs and a wider range of motion patterns.
