Natural coral as bone-defect-filling material

Natural coral (NC) has been studied experimentally and clinically as a bone substitute, but its resorption rate and possible replacement by bone still need to be defined in humans. In this study bicortical bone was harvested from the iliac crest of 10 patients. The defect was filled with a NC block, and changes were monitored by X-rays and quantitative CT scans for a mean of 2.1 years. A biopsy was taken at 1 year. The purpose of the study was to investigate the resorption rate and pattern of NC (Porites) implants and t he replacement, if any, of the implant by new bone. The blocks underwent ce ntripetal resorption, but all the blocks still could be detected by X-rays and CT scans at the end of the follow-up period. The density of the remaini ng block did not change. Seven of the 10 implants were smaller than 50% of their original size at the end of the study. Bone ingrowth could be observe d only in two of seven biopsies. One implant had to be removed after 1.7 ye ars due to infection. The study shows that resorption of natural coral proc eeds centripetally and apparently more rapidly when accompanied by tissue i ngrowth. None of the blocks resorbed completely, and the defect at the ilia c crest had not been restored by the end of the study. (C) 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 51, 117-122, 2000.