Development of a scoliotic spine model for biomechanical in vitro studies

• A surrogate of scoliotic spines was developed for biomechanical in vitro tests.
• A Cobb angle > 40° could be achieved.
• An axial rotation to the convex side resulted by itself.
• The scoliotic spine is stiffer than the original one.
• The motion behavior showed no significant asymmetry for each loading direction.

BackgroundIn vitro experiments are important to compare surgical treatments. Especially new implants need preclinical evaluation. However, in vitro experiments with scoliotic specimens are impossible because they are not available. The purpose of this study was to develop an in vitro scoliosis model with cadaveric calf spine specimens, which may serve as a surrogate for human scoliotic spines.MethodsSix cadaveric calf spine specimens (T8–L6) were modified in three different steps to create a thoracolumbar scoliosis, convex to the right. First, all intervertebral discs received a nucleotomy. In the second step the cavity was filled with silicone. The silicone hardened in a bend position to obtain an asymmetrical nucleus. Finally, a wedge profile of the vertebral bodies was achieved by unilateral horizontal cuts (T9–L5), followed by spreading and fixation. Flexibility tests in a spine tester were performed in all motion planes with the original spine and after the different steps during the creation of the model.FindingsA Cobb angle > 40° in the frontal plane could be achieved. Additionally, the vertebrae showed an axial rotation to the convex side. The range of motion increased due to the nucleotomy, decreased slightly after replacement with silicone, and decreased below the values of the intact spine after producing the wedge shape of the vertebrae. In each loading direction there was no significant asymmetry in the motion behavior.InterpretationThis study suggests a method to modify a straight spine specimen into a scoliotic one, which can be used for biomechanical in vitro experiments.