Abstract
It is impossible to determine the effect of a single parameter in clinical or in-vitro knee research. There are also parameters which can not or hardly be determined. These disadvantages can be overcome with a model. The objective of this study was to create a dynamic FE model of a human knee joint after TKA which is applicable to a variety of research question.
The knee model consisted of a femur, tibia and patella, collateral ligaments and a PCL, combined with a CKS cruciate retaining total knee prosthesis. The patella was not resurfaced. An axialload of 150 N and a quadriceps-force of 81N was applied. The model was validated by the model prediction of joint laxities at different flexion-angles and the calculation of the knee kinematics during flexion-extension.
The predicted varus-valgus laxity at different flexion angles was in between 0 and 6.3 degrees. Laxity values decreased towards extension and towards 90 degrees of flexion. The AP test at 20, 30 and 90 degrees of flexion showed a anterior laxity of 3.1, 4.3 and 2 mm, respectively. The posterior laxity was 5.7 mm, but could only be determined at 90 degrees. The model predicted reasonable kinematics, which were identical for two consecutive flexion-extension movements.
The model predictions were well in agreement with reported values, which were measured experimentally. Differences could be well explained by ligament structures which were (still) omitted with in the model. This dynamic model, in which ligaments were actually modelled as bands, combined all major structures within the knee joint. It was well able to predict laxities and kinematics and turned out to be very stable, mathematically. With this model we will be able to address effects of prosthetic and surgical parameters on the stability and kinematics of the knee joint.
(presenting author)
Correspondence should be addressed to Richard Komistek, PhD, International Society for Technology in Arthroplasty, PO Box 6564, Auburn, CA 95604, USA. E-mail: ista@pacbell.net
