The Journal of Bone and Joint Surgery, Vol 73, Issue 1 93-105, Copyright © 1991 by Journal of Bone and Joint Surgery, Inc
Ingrowth and formation of bone in defects in an uncemented fiber-metal total hip-replacement model in dogs
JD Kang, DJ McKernan, M Kruger, T Mutschler, WH Thompson and HE Rubash
Ferguson Laboratory for Orthopaedic Research, Department of Orthopaedic Surgery, University of Pittsburgh, Pennsylvania 15261.
An osseous defect was created in the acetabulum and femur of twenty dogs,
and then a fiber-metal total hip prosthesis was inserted. A comparison was
made between the effects of leaving the defects unfilled, filling the
defects with an autogenous bone graft, and filling them with a 50:50
mixture of autogenous bone graft and a biphasic ceramic composed of
hydroxyapatite and tricalcium phosphate. The characteristics of formation
of bone within the sites of the defects and the extent of the ingrowth of
bone into the underlying porous surface were analyzed. At six and twelve
weeks after implantation, the dogs in the control group (unfilled defects)
had the least amount of bone in the sites of the defects. In the dogs that
had had an autogenous bone graft and those in which the defects had been
filled with a mixture of autogenous bone graft and biphasic ceramic, there
were excellent osteoconductive properties in the filling of the sites of
the defects with new bone. A comparison was made between the amount of bone
that formed in the osseous defects and the amount that formed in the spaces
of the porous-surfaced fiber-metal components of the prostheses, directly
underlying and adjacent to the defects. At six weeks, the greatest amount
of ingrowth of bone into the spaces of the underlying titanium fiber-metal
acetabular components was seen in the control group (22 per cent of the
porous surface), followed by the group in which the defects had been filled
with a mixture of autogenous bone graft and biphasic ceramic (19 per cent).
The defects that had been filled only with autogenous bone graft had poor
ingrowth of bone into the porous surface (4 per cent) and predominantly
fibrous ingrowth. At twelve weeks, these defects again showed the least
amount of ingrowth of bone (15 per cent) compared with the defects in the
control group (24 per cent) and those that had been filled with a mixture
of autogenous bone graft and biphasic ceramic (24 per cent). No
statistically significant differences were found in the amount of ingrowth
of bone into the defects that had been created in the femur in the three
groups of dogs at either six or twelve weeks. However, the trends appeared
to correlate with the data for the acetabular defects.
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