Influence of porous coating level on proximal femoral remodeling - A postmortem analysis

This study used femurs retrieved at autopsy to compare the extent and locat ion of bone remodeling between four patients implanted with proximally poro us coated femoral prostheses and a matched group of four patients implanted with extensively porous coated femoral prostheses. The femoral components studied were large, cementless, straight, cobalt chrome stems and were iden tical except for the amount of porous coating. The contralateral normal fem ur of each patient also was retrieved, implanted with an identical prosthes is, and used as a control for bone mineral content, Dual energy gray absorp tiometric analysis showed marked loss of bone mineral content in both group s of patients. The extensively coated group had less bone loss on average ( 18.4%) than did the proximally coated group (38.6%). There was no relations hip between the extent of coating and the location of bone mineral loss; sp ecifically, proximal coating did not protect against loss of bone mineral c ontent proximally or distally in the femur. Videodensitometric analysis of cross sections of periprosthetic bone also showed that the extensively coat ed group tended to have less decrease in bone density than did the proximal ly coated group (14.3% versus 28.4%). Although one cannot presume that all proximally fixed stem designs mould produce results similar to those presen ted here, these findings show that decreasing the extent of porous coating alone does not necessarily reduce proximal femoral bone loss.