APPROPRIATE OSTEOTOMY SITE AND NUMBER IN LIMB LENGTHENING

The effects of the placement of osteotomy site on osteogenesis during monofocal and bifocal lengthening were investigated in 37 immature rab bits allocated to 4 groups according to osteotomy site: (1) monofocal in the proximal diaphysis; (2) monofocal in the distal diaphysis: (3) bifocal in the proximal and distal diaphysis; and (4) bifocal in the p roximal diaphysis, The right tibia was distracted at an overall rate o f 1.0 mm per day for 15 days, These groups were compared by assessment of soft radiograph findings and torsional strength 2 and 6 weeks afte r the end of distraction, Microangiography was done in 5 rabbits in th e bifocal proximal and distal group, The proximal distracted site show ed favorable bone regeneration compared with the distal site, and tors ional strength was significantly greater in the proximal than in the d istal osteotomy group, Less bone formation and lower torsional strengt h were observed in the bifocal proximal diaphysis group, with short in termediate segment, than that in the other bifocal group, with long in termediate segment, The nutrient artery in the latter group was preser ved in the intermediate segment and reanastomosed to the metaphyseal a rteries, These results suggest that the proximal diaphysis is more sui table for the osteotomy site than is the distal diaphysis, In a 2-leve l osteotomy, the inflow site of the nutrient artery should be included within the intermediate segment.