Design of cervical spine mechanical emulator for rotation-traction manipulation drills

The cervical spine rotation-traction manipulation is an important therapeutic technique for cervical spondylosis in the Chinese Traditional Medicine (TCM). However, incidence of medical malpractice is relatively high in the rotation-traction therapy when the unfledged internship physicians give the therapy. Thus, it is crucial to build a cervical spine mechanical emulator to evaluate how well one performs the rotation-traction manipulation and also to indicate the faults. In this paper, the in vivo and in vitro measurements are performed to acquire the biomechanical properties and parameters of the rotation-traction manipulation. According to these measurements and physiological structure of human cervical spine, a mass-spring-damper system with electromagnetic clutch, in which the spring is nonlinear, and can be compressed and expanded rectilinearly, is used to replicate the biodynamical properties of the rotation-traction manipulation, and a virtual model of the mass-spring-damper system is built in ADAMS to verify the fitness of the mass-spring-damper model to the in vivo and in vitro measurements and to optimize the model parameters. Then, the rectilinear nonlinear spring is designed with the desired stiffness variation, and the structure of mechanical emulator is given. Finally, a design example of the nonlinear spring and the numerical computations with the designed nonlinear spring and parameters are presented. In addition, a simplified mechanical emulator is fabricated to test whether the mass-spring-damper system with electromagnetic clutch can replicate the observed rapid acceleration change in the rotation-traction manipulation, which lays a sound foundation for putting the drill system into practice.