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Novel Experimental Scoliosis Model in Immature Rat Using Nickel-Titanium Coil Spring

Zhang, Hengyan MD; Wang, Chu MD; Wang, Wei MD; Wu, Zhihong MD; Qiu, Guixing MD

doi: 10.1097/BRS.0b013e3182999757
Basic Science

Study Design. Follow-up of animals after surgically initiated scoliosis.

Objective. To develop quantitatively asymmetric loads on rat lumbar to create scoliosis.

Summary of Background Data. 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.

Conclusion. 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.

Level of Evidence: N/A

Asymmetric load induced by gravity is a critical factor in aggravating scoliosis. Existing scoliosis animal models with rigid or flexible posterior asymmetric tethers cannot efficiently imitate the gravity imposing on lumbar. Nickel-titanium coil springs simulate the asymmetric load that mimics the load on human scoliotic lumbar spines at erect posture.

From the Department of Orthopaedics, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College (CAMS & PUMC), Beijing, China.

Address correspondence and reprint requests to Guixing Qiu, MD, Department of Orthopaedics, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College (CAMS & PUMC), 1 Shuaifuyuan, Wangfujing, Dongcheng District, Beijing 100730, China; E-mail:

Acknowledgment date: November 26, 2012. First revision date: March 7, 2013. Second revision date: April 24, 2013. Acceptance date: April 29, 2013.

The manuscript submitted does not contain information about medical device(s)/drug(s).

National Natural Science Foundation of China (No. 81000817) grant funds were received in support of this work.

No relevant financial activities outside the submitted work.

© 2013 by Lippincott Williams & Wilkins