Long-term clinical outcomes following the use of synthetic hydroxyapatite and bone graft in impaction in revision hip arthroplasty.

Impaction grafting using morsellised allograft bone restores bone stock, but carries the potential for transmission of infection. Synthetic bone graft substitutes can eliminate this risk but may, however, influence outcome. In this study we tested the hypothesis that a 50/50 mix of hydroxyapatite and allograft does not affect long-term function, survival or radiological outcome. Sixty-five patients had revision hip arthroplasty using impaction grafting with either pure allograft (42 patients) or a 50/50 mixture of allograft and solid particulate hydroxyapatite. Harris hip scores were assessed pre-operatively and annual intervals thereafter. Function was analyzed using multilevel modeling, the Kaplan-Meier method used for survival analysis and graft incorporation was assessed radiologically. The hip score improved in both groups but showed a small annual decline (average 1.2/year, p<0.01). This decline was higher for females (average 3.4, p=0.025) and significantly related to pre-op scores (p<0.001). After adjusting for these, allograft patients had marginally higher scores (difference=3.1, p=0.3). The majority of revisions were for aseptic loosening. At 13 years survival in the allograft group was 84%, and 82% in the mixture group (p=0.96, log rank test). Radiologically the graft incorporation was similar in both groups (p=0.62). We conclude that long-term prosthesis survival and function following revision arthroplasty with a 50/50 mixture of allograft and hydroxyapatite are comparable to allograft alone.