The Journal of Bone and Joint Surgery, Vol 68, Issue 9 1396-1409, Copyright © 1986 by Journal of Bone and Joint Surgery, Inc
A comparative study of porous coatings in a weight-bearing total hip-arthroplasty model
TM Turner, DR Sumner, RM Urban, DP Rivero and JO Galante
The purposes of this study were to compare ingrowth of bone into three
types of porous coating and to determine the effect of the type of porous
coating and the degree of coverage of the stem on the remodeling of bone on
the femoral side in cementless hip arthroplasty. A left total hip
arthroplasty was performed in forty dogs. Thirty of the dogs had a
titanium-alloy femoral prosthesis that had had one of three types of
commercially pure titanium porous material applied along the length of the
anterior and posterior surfaces of the stem: ten with sintered fiber-metal,
ten with sintered beads, and ten with plasma flame-spray coating. The
remaining ten dogs had a femoral component that was circumferentially
coated with commercially pure titanium that was plasma flame-sprayed along
the length of the stem. In each group, five animals were killed at one
month and five were killed at six months. Ingrowth of bone into all three
types of porous coating was observed, indicating secure fixation of all
components. By six months, there was more ingrowth of bone and new
medullary bone adjacent to the proximal and distal aspects of the stems
compared with the middle level of the stems in all groups. No significant
difference in ingrowth of bone was observed in the beaded surface (25.2 per
cent) and the fiber-metal surface (16.6 per cent) at one month, but at six
months there was significantly less ingrowth into the beaded surface (23.3
per cent) than into the fiber-metal surface (37.3 per cent). In all groups,
a proximal-to-distal gradient of loss of cortical bone was observed by six
months. The group of dogs that had the stem with the circumferential
coating experienced more severe loss of bone than did the three groups that
had a stem with a partial coating. The magnitude of loss of bone was
dependent on the extent rather than the type of porous coating.