Abstract: Eighteen healthy hybrid pups weighing 0.8 to 1.2kg at the age of 21 to 28 days old were divided randomly into three groups as follows ：① Operative group : under general anaesthesia, the broadest muscle of back, greater Pectoral muscle and external oblique muscle of abdomen were subjected to overlapping suture at one truncal side and shortened by 2.5 to 3cm. The spine became scoliosis after operation and the concave side was at operation side. Two months after operation , the suture was loose and the scoliosis was disappeared gradually.② Forced lateral position group ： the dogs were fixed and made it lateral position at the sand bag for 4 to 8 weeks. The muscle of compressed region were suffered from niyoischeimia, degeneration, adhesion and cicatricial contracture. The spine became fixed scoliosis and convex to the other side (cobb's 17°- 33°) and ③ Control group ： the dogs were freely lived during the experiment. All the dogs of this group were without scoliosis. The results showed that the forced lateral position for certain time can make the pups to muscle contracture scoliosis. The characteristics of scoliosis and the cytological changes of muscle in compression region were the same as human idiopathic scoliosis. It indicated that the aetiology of idopathic scoliosis has a close relation with forced lateral positon during infantile period.

Key words: Forced lateral position, Muscle contracture scoliosis, Canine