title: Novel experimental scoliosis model in immature rat using nickel-titanium coil spring.
abstract: METHODS
  Follow-up of animals after surgically initiated scoliosis.
  
  
  OBJECTIVE
  To develop quantitatively asymmetric loads on rat lumbar to create scoliosis.
  
  
  BACKGROUND
  Current animal models for scoliosis use mostly rigid or flexible posterior asymmetric tethers. The curve progression can only be expected for the growth potential, leading to insufficient growth potential for validation of corrective techniques.
  
  
  METHODS
  Scoliosis was induced in 55 five-week-old female Sprague-Dawley rats using a nickel-titanium coil spring. The experimental rats were randomly divided into 2 groups: in group A (n = 15), the nickel-titanium coil spring was not removed until these rats reached physical maturity (age, 12 wk). Group B (n = 40) was further randomly subdivided into 5 subgroups (n = 8 for each subgroup): removal of the spring after 1 week (group B1), 2 weeks (group B2), 3 weeks (group B3), 4 weeks (group B4), and 5 weeks (group B5). All rats were followed for a 7-week period with serial radiographs to document change of the deformity.
  
  
  RESULTS
  All experimental animals of group A developed progressive, structural scoliotic curves convex to the left in the lumbar segment. In group B, the deformity of the lumbar progressed after the spring load was applied and regressed after the spring was removed. The scoliosis in group B1-B3 (the spring removed before sexual maturity) regressed after spring removal until the rats reached sexual maturity (4 wk after spring implant surgery). The scoliosis in group B4-B5 (the spring removed after sexual maturity) regressed only during the first week after spring removal surgery. The average coronal Cobb angle was 7.8° ± 1.3° (range: 6.0° -10.2°) in group B1 at the final follow-up, and there was only 1 experimental rat that maintained a curve more than 108. The models of group B2-B5 maintained stable scoliotic curves (coronal Cobb angle of L2-L5 > 10°) convex to the left in the lumbar segment at the final follow-up.
  
  
  CONCLUSIONS
  This study establishes a rat lumbar scoliosis model via asymmetric load. This method develops lumbar scoliosis in a short time and maintains the essential elements along the curve. It is suitable for the investigation of scoliosis.
authors: From the Department of Orthopaedics, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College (CAMS & PUMC), Beijing, China.
authors: Hengyan
authors: H
authors: Zhang
authors: Chu
authors: C
authors: Wang
authors: Wei
authors: W
authors: Wang
authors: Zhihong
authors: Z
authors: Wu
authors: Guixing
authors: G
authors: Qiu
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D009532:Nickel / Q000008:administration & dosage*; D011859:Radiography; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012600:Scoliosis / Q000000981:diagnostic imaging* / Q000601:surgery*; D053831:Surgical Fixation Devices; D014025:Titanium / Q000008:administration & dosage*
chemical_list: C040654:titanium nickelide; D009532:Nickel; D014025:Titanium