Bone remodelling around cementless composite acetabular components: the effects of implant geometry and implant-bone interfacial conditions.

Recent developments in acetabular implants suggest flexible, alternative bearing material that may reduce wear and peri-prosthetic bone resorption. The goal of this study was to investigate the deviations in load transfer and the extent of bone remodelling around composite acetabular components having different geometries, material properties and implant-bone interface conditions, using 3-D FE analysis and bone remodelling algorithm. Variation in prosthesis type and implant-bone interface conditions affected peri-prosthetic strain distribution and bone remodelling. Strain shielding was considerably higher for bonded implant-bone interface condition as compared to debonded implant-bone interface condition. The average bone deformation (0.133mm) for horseshoe-shaped CFR-PEEK (resembling MITCH PCR(TM) cup) was very close to that of the intact acetabulum (0.135mm) at comparable locations. A reduction in bone density of 21-50% was predicted within the acetabulum for the implant resembling Cambridge cup, having bonded interface. For debonded interface condition, bone density increase of ~55% was observed in the supero-posterior part of acetabulum, whereas bone density reductions were low (1-20%) in other locations. Bone density reductions were considerably less (2-4%) for horseshoe-shaped CFR-PEEK component. Moreover, an increase in bone density of 1-87% was predicted around the acetabulum. Compared to the horseshoe-shaped design, the hemispherical design exacerbated bone resorption. Results indicated that the thickness of the acetabular component played a crucial role in the implant induced bone adaptation. The horseshoe-shaped CFR-PEEK component of 3mm thickness seemed a better alternative bearing surface than other designs, with regard to strain shielding, bone deformation and bone remodelling.