The Journal of Bone and Joint Surgery, Vol 68, Issue 5 640-646, Copyright © 1986 by Journal of Bone and Joint Surgery, Inc
The CAD hip arthroplasty. Five to ten-year follow-up
BJ Thomas, EA Salvati and RD Small
One hundred and fourteen total hip arthroplasties in 100 patients were
performed using the CAD (computer-assisted design) prosthesis at The
Hospital for Special Surgery between 1975 and 1977. Sixty-one of these
patients (seventy-four hips) have been followed both clinically and
radiographically for a minimum of five years (average, 7.1 years). While no
hip required revision before five years, seven hips were revised between
six and ten years postoperatively. Ten hips had an excellent result;
forty-eight, good; eight, fair; and one, poor. Radiographic analysis
revealed narrowing of the cortex of the bone medially at the region of the
proximal part of the stem in the hips that were operated on as compared
with the contralateral side that was not operated on. Nine hips (12 per
cent) had one to two-millimeter radiolucent lines at the femoral
bone-cement interface, and in five the lines were progressive. Fourteen
hips (19 per cent) had radiolucent lines at the femoral bone-cement
interface with a maximum width of 0.5 millimeter. Thirty-four (42 per cent)
had more than three millimeters of resorption of the calcar or superomedial
cyst formation. Survivorship analysis of the prosthesis predicted a 77 per
cent survival rate at nine years. None of the prosthetic stems fractured
despite the fact that the population was young, active, heavy, and
predominantly male. The incidence of calcar resorption, however, was higher
than in other studies. Thus, while the revision rate compared favorably
with that of similar studies using other stem designs, compromise of the
bone stock of the proximal end of the femur may be a significant
disadvantage of this type of prosthesis.
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