Injection of Botulinum toxin A into unilateral paraspinal muscles to establish scoliosis model in imma?鄄ture bipedal rats

English Keywords:Scoliosis  Botulinum toxin A  Injection into paraspinal muscles  Bipedal rats  Model

English Abstract:

  【Abstract】 Objectives: To discuss the feasibility and efficacy of injection of Botulinum toxin A into unilateral paraspinal muscles to establish scoliosis model in immature bipedal rats. Methods: 56 4-week old female SD rats were divided into 7 groups randomly. All rats underwent amputations of forelimbs under anesthesia and were kept in height-regulated cages. Group A-F received different concentrations of BTX-A respectively(100U, 50U, 25U, 12.5U, 6.25U, 3.125U, all in 0.5ml). Group G only received an injection of same amount of normal saline. 2 weeks after injection, AP X-rays were obtained under anesthesia. The rats were cut off the skin on the back. Naked-eye observations were taken. Morphological changes of paravertebral muscles were detected under light microscope. Results: The rats were observed to be able to stand bipedally immediately after the amputations of forelimbs. After BTX-A injection, the rats in group A-D were all dead, while all rats in group E, F and G survived. 2 weeks after injection, AP X-rays showed that all survived rats had developed scoliosis in group E and F, and all curves had convex towards right side. The mean Cobb angle in group E was (41.9±3.4)° at 2 weeks after injection, and the mean Cobb angle in group F and G was (33.1±3.2)° and (2.9±6.8)° respectively. Naked-eye observations showed muscle atrophy on the convex side. The histological findings revealed the same as naked-eye observation. Those were not observed in group G. Conclusions: Scoliosis model can be created by 6.25U or 3.125U BTX-A injection in immature bipedal rats, which indicates that paravertebral muscle imbalance can induce scoliosis.