A multi-directional wear apparatus was developed to simulate the kinematic motion of diarthrodial joints. A comprehensive evaluation including biotribological and biomechanical characterization of articular surfaces was performed with concomitant translational and oscillating rotational motion similar to that experienced in vivo. Various system parameters were evaluated in the designed experiments including normal load magnitude (high/low), surface quality (defect/no defect), and wear pattern (with/without rotation). Biomechanical charactdynamic cyclical testing. Quasi-linear viscoelastic theory was used to curve-fit the stress relaxation data, while the dynamic data was used to determine the dynamic properties through Fast Fourier Transform analysis and verify the assumptions posed with the QLV theory.

Overall tissue compression was significantly dependent on load magnitude (p<0.0001). Loss of tissue was significantly affected by load magnitude (p<0.0012) and wear pattern (p<0.014). μ_static was significantly dependent on surface quality (p<0.0034) and the interaction of wear pattern and surface quality (p<0.024), while μ_initial was significantly dependent on both surface quality (p<0.013) and wear pattern (p<0.021).

Comparisons of the curve-fit parameters showed a significant decrease in pre- vs postwear elastic response, A, and viscous response, c. In addition, the short term relaxation response, τ₁, showed a significant decrease between no defect (0.801±0.13 sec) and a defect (0.679±0.16 sec). lGl_post-wear/lGl_pre-wear < 1 revealed a decrease in overall dynamic stiffness due to wear. The loss, tan δ, was generally greater while lGl was less for those specimens experiencing rotation. Qualitatively, SEM photographs revealed the mechanical degradation o f the tissue surface due to wear. Surfaces with a defect had increased wear debris, which ultimately contributes to third body wear. Surfaces without a defect had preferentially aligned abrasions, while those surfaces outside the wear path showed no signs of wear.

Significant correlation was detected between the μ_static and μ_initial for both the nonlinear viscous response, B (p<0.049 and p<0.052), and the long term relaxation constant, τ₂ (p<0.013 and p<0.062). Thus, the comprehensive evaluation of biomechanical and biotribological characteristics suggests the new wear regime and standardization of analysis techniques will aid in the development of functional articular repair and clinical repair techniques.