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.

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.