The affinity of bone to hydroxyapatite and alumina in experimentally induced osteoporosis

The authors studied how bone reacts to hydroxyapatite (HAP) and alumina (Al2O3) in osteoporosis experimentally induced in a rat animal model by resection of the sciatic nerve. Sixteen and 32 weeks after resection of the sciatic nerve, implants of HAP and Al2O3 were inserted into rat tibias. The reaction of bone to HAP was compared with its reaction to Al2O3, which is bioinert, as a control. The results were analyzed using the affinity index (the length of bone directly opposed to the implant without an intervening fibrous membrane/total length of the bone-implant interface x 100%). In the rats left for 16 weeks after resection of the sciatic nerve the index values 24 weeks after insertion of HAP and Al2O3 were 96.9 +/- 2.4% (N = 8) and 75.2 +/- 22.2% (N = 8), respectively. The index value of HAP was 97.2 +/- 2.6% (N = 12) and of Al2O3 was 86.9 +/- 15.4% (N = 12) at 24 weeks after insertion, when the rats were first left for 32 weeks, after sciatic nerve resection. Bone was demonstrated to have a superior affinity to HAP, compared with Al2O3 (P less than .05).