Abstract
Cementless total knee arthroplasty (TKA) components have rough and porous surface coatings which can enhance bone ingrowth and stability at the bone-implant. To achieve primary stability in the postoperative period where no apposition is formed, the resistance against motions between bone and implant is optimized by increasing the friction at the interface. This is necessary, as excessive relative motions can inhibit bone ingrowth, which might result in loosening and pain. In this research, it was found that the friction can be predicted by measuring the surface morphology of rough implants, and calculating the corresponding perpendicular and lateral contact area parameters. The ratio between these areas, is used to predict the resulting coefficient of friction (COF). This is validated experimentally, by analysing the tribological behaviour of 2 porous and rough titanium coatings against human cadaveric knee bones using reciprocal friction tests with varying normal loads. The results for 2 different coatings showed similar findings for the predicted COF (0.75 and 0.88) versus the calculated values based on the measurement (0.82 and 0.86) proving the feasibility of the approach.
Highlights
Total knee arthroplasty (TKA) is a frequently performed orthopaedic surgical procedure (Wood, 2007)
From a mechanical point of view, a stable fixation can be achieved by optimizing the compressive and frictional forces acting on the boneimplant interface that is created by a press-fit
In this case the shear strength of the bone, which is commonly larger than the interfacial shear strength, will define the resulting friction force (Goddard and Wilman, 1961; Sin et al, 1979; Xie and Williams, 1996) Increasing the surface roughness of the implant will be beneficial, as it is expected to increase the friction at the interface with the bone
Summary
Total knee arthroplasty (TKA) is a frequently performed orthopaedic surgical procedure (Wood, 2007). From a mechanical point of view, a stable fixation can be achieved by optimizing the compressive and frictional forces acting on the boneimplant interface that is created by a press-fit. This is achieved by the difference in dimensions between implant and bone. Increase of the total friction can be achieved by creating hard, rough surfaces where the roughness peaks will scratch through the soft bone surface In this case the shear strength of the bone, which is commonly larger than the interfacial shear strength, will define the resulting friction force (Goddard and Wilman, 1961; Sin et al, 1979; Xie and Williams, 1996) Increasing the surface roughness of the implant will be beneficial, as it is expected to increase the friction at the interface with the bone. Texture and hardness of the bone samples and of the two implant coatings were measured with confocal microscopy and nano indentation
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