The Journal of Bone and Joint Surgery, Vol 70, Issue 5 728-737, Copyright © 1988 by Journal of Bone and Joint Surgery, Inc
The enhancement of fixation of a porous-coated femoral component by autograft and allograft in the dog
DJ McDonald, RH Fitzgerald and EY Chao
Department of Orthopedics, Mayo Clinic, Rochester, Minnesota 55905.
Revision total arthroplasty of the hip, without cement, was done in dogs to
compare the abilities of autologous grafts and allografts of bone to
enhance histological ingrowth of bone and biomechanical strength. Six weeks
after primary total hip arthroplasty with cement, the femoral component was
revised to a titanium fiber-metal prosthesis. On the basis of the type of
graft that was impacted into the voids around the ingrowth surface at
revision, three study groups were created: no graft (control), four dogs;
fresh autograft, six dogs; and frozen allograft, six dogs. Twelve weeks
after revision, histological analysis revealed the greatest amount of
ingrowth proximally in the grafted specimens. A mean of 22.3 per cent
ingrowth was observed in the dogs that had an autograft; this was not
significantly different from the mean of 17.5 per cent in those that had an
allograft. The non-grafted specimens showed little ingrowth, the values
being significantly less than those for the grafted specimens. Push-out
testing showed greater ultimate shear strength proximally than distally in
the grafted specimens, and at the proximal level there was a significant
difference between the group that had an autograft and the control group
(mean, 4.03 and 1.22 megapascals, respectively). Ultimate strength
correlated positively with ingrowth of bone (r = 0.82). Radiographically,
subsidence of the components and lucent lines were observed more frequently
in the nongrafted specimens, and if both were present, significantly less
ingrowth of bone and strength were observed.
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