MICROSCOPIC STUDIES OF HUMAN PRESS-FIT TITANIUM HIP PROSTHESES

Seven cementless, press fit, rectangular cross section, titanium alloy femoral prostheses were implanted for the treatment of displaced subc apital hip fractures in elderly patients and retrieved postmortem for microscopic evaluation. The mean patient age was 88 years (range, 66-1 03 years), and prostheses were in situ an average of 29 months (range, 6-45 months). Microscopic examination of the specimens revealed regio ns of bone to prosthesis contact without interposed connective tissue, and all were considered stably osseointegrated. The mean microscopic bone to prosthesis contact for five cross sections was 28%. Implantati on of this prosthesis achieved satisfactory primary stability in endos teal cortical bone in these elderly patients, Secondary stabilization was apparent, as evidenced by new, viable bone formation and remodelin g in apposition to the prosthesis.