The menisci play a decisive role within the healthy knee joint by increasing the contact area and thereby reducing contact pressure on the articulating cartilage. Although increased signs of wear could be observed after meniscus injury and/or (sub-) total meniscectomy , only little research has been performed to examine the importance of the menisci in low-friction motion. Therefore, the aim of this study was to investigate the influence of meniscectomy on overall friction in the knee joint.
Materials And Methods
Six ovine knee joints were ordered from a local butcher and tested within a customized pendulum friction test setup under simulated stance- (axial load: FN ˜ 1kN, initial deflection: d =5°) and swing phase (FN ˜ 250N, d =12°) conditions. To investigate the influence of menisci on knee friction, each joint was consecutively dissected and tested in 3 steps: intact, resection of medial posterior meniscal attachment and meniscectomy. After initially deflecting the joint, the resultant pendulum oscillation was recorded via a motion-capturing system (OptiTrack, NaturalPoint Inc., USA). To evaluate the joint friction, two mathematical models analysing the decay in flexion-extension angle were used [2,3]. While the linear model (µlin) of STANTON assumes an energy loss due to friction, the CRISCO-model additionally considers the time-dependency of viscoelastic materials by a damping coefficient (c). Differences in friction between the knee joint conditions were compared with ach loading condition and mathematical model using 1-way ANOVA.
Meniscectomized joints showed significantly lower friction coefficients during swing phase than intact joints when analysed via STANTON, while the CIRSCO-model revealed no significant differences in friction but a significant decrease in the damping properties c. During stance phase, only an increasing tendency for µlin and c were found between the three dissection steps. However, the overall recorded kinematics showed a notable increase in tibial rotation up to 100% after resection of the posterior meniscal attachment and meniscectomy, especially during swing phase conditions.
For the first time, frictional behaviour of large intact and meniscectomized animal joints was determined. However, the obtained friction coefficient of intact joints was generally higher compared to previous studies [4,5], which might be due to the difference in size and loading conditions . Nevertheless, no major influence of the menisci on the knee joint friction could be observed expect during swing phase using the Stanton-model. However, an increased tibial rotation after resecting the posterior meniscal attachment and meniscectomy was identified. Therefore, further studies should not only consider motion in flexion-extension but also include the overall joint movement.
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