TRABECULAR BONE ADAPTATION TO VARIATIONS IN POROUS-COATED IMPLANT TOPOLOGY

Trabecular bone adaptation adjacent to porous-coated platen implants e mbedded within canine distal femoral metaphyses was evaluated followin g 24 weeks of daily compressive loading. The in vivo experimental mode l delivered controlled loads to five different platen implant topologi es with variations in platen shape and porous coating distribution. Ad aptive changes were evaluated based on three-dimensional stereological analyses of trabecular bone architecture underneath each platen and n on-destructive mechanical tests of platen construct stiffness. Fully c oated cylindrical platen designs possessed the highest construct stiff ness in both tension and compression. Changes in local trabecular bone morphology were also found to be significantly influenced by platen i mplant topology. Cylindrical platens with fully coated bottom surfaces were associated with greater decreases in trabecular bone volume and connectivity than cylindrical platens with smooth bottom surfaces or f ully coated conical platens. Comparisons to site-matched contralateral control bone volumes across all platen designs indicated significant decreases in the average bone volume fraction, trabecular plate number , and connectivity within experimental samples, but no change in trabe cular plate thickness. In addition, analyses of microstructural anisot ropy revealed a 20 degrees or 20.2 degrees trabecular reorientation to wards the axis of loading in experimental tissue. This study demonstra tes that trabecular bone adaptation near porous-coated surfaces is inf luenced by variations in local implant topology and provides insight i nto specific mechanisms of implant-mediated microstructural adaptation . Copyright (C) 1996 Elsevier Science Ltd.