טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentDavid Or
SubjectMinimally Invasive, Motion Preserving Artifical Spinal
Intervertebal Disc
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Moshe Shoham


Abstract

Artificial spinal discs are used for several decades to surgically treat spinal disorders while allowing motion in the treated level.  While existing devices preserve the natural range of motion, they fail to preserve the entire kinematic behaviour, characterized by the screw motion while maintaining the natural stiffness of the disc joint.  Differences in vertebral motion cause pain and increase loading on the adjacent levels, and therefore should be avoided.  Moreover, artificial discs are implanted using largely invasive surgical approaches, with a high risk of infections and complications. 

This work presents two novel concepts of a motion preserving compliant artificial disc that uses the desired screw motion and the desired spatial stiffness as a design input - a passive Stewart-Gough platform with compressible links, and an array of parallel springs.  A novel optimization approach to the design method is established and tested for several cases.  This method proves an improved, feasible, motion preserving artificial spinal disc.  The Stewart-Gough platform’s links stiffnesses and platforms geometry are optimized, while with the spring array disc spring diameters are optimized.

A minimally invasive implantation method is also discussed, tested, and proven feasible.

This work establishes the first milestones of transforming biological joint kinematics from an evaluation tool to a design tool.  Although additional work is required in order to turn the presented concepts into physical, implantable devices, those concepts were shown to have advantages over existing artificial discs in terms of natural motion preservation.