A mechanical model of human spinal motion segments.

A modular mechanical model of the spine was developed which can be adapted to approximate the mechanical properties of various spinal levels and pathologic conditions in single- or multi-segmental forms. The characteristics of the model were compared with those of human L4-5 specimens in flexion and extension, axial rotation and lateral bending. The model showed comparable ranges of motion to those of human specimens in all directions and likewise was characterized by increasing stiffness with increasing load as well as hysteresis. This model can be used as a standard for the comparison of different spine testers. As a substitute for cadaveric specimens in implant testing, these models provide the advantages of availability, consistent properties, and adaptability, and avoid the risks associated with handling human tissue.