The Journal of Bone and Joint Surgery, Vol 73, Issue 9 1331-1337, Copyright © 1991 by Journal of Bone and Joint Surgery, Inc
Ingrowth of bone in failed fixation of porous-coated femoral components
M Jasty, CR Bragdon, WJ Maloney, T Haire and WH Harris
Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston 02114.
In five straight-stemmed, proximally porous-coated femoral components that
were retrieved at revision arthroplasty from patients who had radiographic
and clinical evidence of loosening, there was growth of bone into the
porous coating. The components had been inserted during a primary
arthroplasty in one woman and four men. The patients ranged in age from
thirty-seven to sixty-seven years. Three patients were heavy, and all five
were active. All patients had had an excellent early result from the
initial arthroplasty; at the one-year follow-up, the mean Harris hip score
had been 91 points. Pain in the hip developed in all of the patients,
between one and three years after the index procedure. Initial radiographs
had revealed excellent position and fixation of the prosthetic components,
but the components then subsided between one and three and one-half years
after the index procedure. All of the femoral components were found to be
grossly loose at the revision operation. Nevertheless, all of the
prosthetic components demonstrated growth of bone into 4 to 44 per cent
(mean, 24 per cent) of the pore spaces available for ingrowth. Woven bone
and fracture callus were found in the curettings from the proximal part of
the femur. The findings in these five patients suggest that late failure of
uncemented porous-surfaced femoral components can occur despite the
presence of extensive ingrowth of bone. These failures may be the result of
fatigue fractures of the trabeculae of the osseous ingrowth into the porous
surfaces. Caution is warranted in the liberal use of these prosthetic
components in heavy, active patients.
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