To evaluate the possibility of using porous beta-calcium pyrophosphate (beta-CPP) as a bone graft substitute by comparing its osteoconduction and degradation with porous hydroxyapatite (HA).

Porous HA and porous beta-CPP were implanted in the proximal tibia of 7 dogs. Two animals were sacrificed at 8weeks and 5 animals were sacrificed at 20 weeks after surgery. Radiographs and histologic sections were evaluated.

The mean period required for the radiolucent zone to disappear was 7.1±1.1 weeks in HA and 6.4±1.1 weeks in beta-CPP. By serial radiography, resorption was more prominent in porous beta-CPP than in porous HA at 8 weeks (p=0.04) and at 20 weeks. The proportion of bony tissue in the pore was 16.8% in HA and 29.7% in -CPP. The proportion of pores with bony tissue was 70.2% in HA and 62.5% in beta-CPP at 8 weeks.

In beta-CPP, the new bone growth was as vigorous as in HA, but the degradation was more rapid than in HA. These results suggest that beta-CPP is a more ideal new bone graft substitute.