The regional blood flow measurement (RBFM)of lenghtened limb with a peripheral circulation mesuremnt system was carried ou t in 20 rabbits after their tibia was lengthened in different lengthening rates.It was found that whenever a limb was lengthened with a rate over 1 mm/day,the RBFM of the lengthened limb decreased rapidly and returned to preoperative level 8 hours later.It is believed that the vascular and muscular tissues of a limb possess good adaptive capcity to the lengthening rate of 1 mm/day,When the lengthening rate exceeds 1 mm/day,it is liable to result in a significant re-duct of regional blood flow,and then atrophy and weakening of the muscles will occur.

The histological changes in tibial lengthening with metaphyseal osteotomy were observed in 30 goats.It was found that (1) slow lengthening rate of 1 mm/day could enable the tissues to adapt the mechanical traction,and consequently the limitation of elongation could be increased;(2) the new bone formed in the lengthened region might be the result of a combined osteogenesis from endochondral,intramembranous,and fibrous tissue ossification;and (3)the osteogenetic process could be distinguished into 3 stages of hemorrhage and organization of the hematocele,callus formaton,and remodelling of the new bones.