The Journal of Bone and Joint Surgery, Vol 66, Issue 6 888-898, Copyright © 1984 by Journal of Bone and Joint Surgery, Inc
Total hip arthroplasty with a low-modulus porous-coated femoral component
HS Tullos, BL McCaskill, R Dickey and J Davidson
Fifty-seven patients had sixty-three total hip replacements, performed
using a femoral stem with a soft, low-modulus porous coating of Proplast
and a conventional acrylic-cemented acetabular component. Forty-seven of
the hips were followed for an average of thirty-seven months. Seventeen (36
per cent) of the forty-seven hips were judged to be clinical failures, and
five of the failures were revised by inserting a new femoral component and
fixing it with acrylic cement. The prostheses were thought to have failed
because they had inadequate support, due to deficiencies in the design of
the stem and in the fit of the implant in the femur. The five retrieved
prostheses were found to have fibrous-tissue ingrowth into the coating,
which had failed by shear within its substance. Therefore, we concluded
that the coating had insufficient strength to withstand normal
weight-bearing loads. To improve performance, a more stable prosthesis with
a stronger porous coating is needed. In addition, a posterior surgical
approach through a transtrochanteric osteotomy may give better exposure of
the femoral canal and facilitate the use of longer-stem (140 to
153-millimeter) designs, which are less likely to be inserted in a varus
position.