[Extensometry and primary anchorage of femur implants. Study of the upper metaphyseal intracortical support of the B.P.R cement-less implant].

This study uses extensometry to compare the distribution of strain on a fresh femur before and after implantation of various titanium prostheses: one is a cementless implant with metaphyseal endosteal support; the second is a cemented prosthesis with and without calcar collar contact; the last is a titanium implant with fixation by screens. The precision of the measurements have been improved particularly in the proximal metaphyseal area using bidirectional gauges. The system of loading permits comparison of the different implants and the results obtained with the B.P.R. prosthesis compared with the cemented implant without calcar contact are very close. The effect of the collar appears very limited despite the optimal conditions of the in vivo implantation that improve the calcar-collar contact. The screw implant increases the stress shielding of the proximal area of the femur. The different steps of the experiment illustrate the strain distribution in relation to the implantation of the devices and the contact bone prosthesis. The significant endosteal fixation of the B.P.R. prosthesis in the proximal metaphyseal area allows a better primary anchorage which increases distribution of the stress and therefore results in better secondary fixation by bony ingrowth.