BONE DIFFERENTIATION IN POROUS HYDROXYAPATITE IN BABOONS IS REGULATEDBY THE GEOMETRY OF THE SUBSTRATUM - IMPLICATIONS FOR RECONSTRUCTIVE CRANIOFACIAL SURGERY
Sp. Vaneeden et U. Ripamonti, BONE DIFFERENTIATION IN POROUS HYDROXYAPATITE IN BABOONS IS REGULATEDBY THE GEOMETRY OF THE SUBSTRATUM - IMPLICATIONS FOR RECONSTRUCTIVE CRANIOFACIAL SURGERY, Plastic and reconstructive surgery, 93(5), 1994, pp. 959-966
Previous studies have shown the morphogenesis of bone in a porous hydr
oxyapatite substratum when implanted intramuscularly in baboons. This
hydroxyapatite-induced osteogenesis model was used to study the effect
of geometry and pore size of the substratum on bone differentiation.
Two distinct geometric configurations of porous hydroxyapatite of diff
erent pore size were obtained after hydrothermal conversion of the cal
cium carbonate exoskeleton of corals (genera Porites and Goniopora). S
ubstrata were blocks of hydroxyapatite in rod configuration of 200- an
d 500-mum pore size and granular hydroxyapatite (400 to 620 mum in dia
meter) of 200- and 500-mum pore size. A total of 64 granular hydroxyap
atite implants and 32 hydroxyapatite rods were implanted intramuscular
ly in 8 subadult male baboons (Papio ursinus). Specimens were harveste
d on days 60 and 90 and subjected to histologic and histomorphometric
analysis. With the exception of an island of bone that formed in two i
mplants of granular hydroxyapatite of 500-mum pore size, bone differen
tiation occurred only in blocks of hydroxyapatite in rod configuration
of either pore size at both observation periods. The lack of bone for
mation in the granular hydroxyapatite indicates the critical role of g
eometry of the substratum in bone differentiation. These results in pr
imates may have implications for the appropriate selection of porous b
one substitutes for reconstructive craniofacial surgery in humans.