Spine Structure Mechanics

1. Spine Structure Mechanics J. Marcus Hollis Sudhakar G. Madanagopal, M.D. A.E. Engin, Ph.D. Sreenivasulu Kolakanuru,M.S. University of South Alabama

2. Thanks toSCIB Funding • Initiate robotic Spine testing • Train graduate students that are now full time staff with industrial support • Additional Industrial Support for Robotic Spine testing in the Biomechanics Lab

3. Objective Develop Method for Determining Spine motion segment and substructure mechanical properties efficiently* *Maximum amount of data per specimen

4. Winkelstein & MyersJournal of Biomechanical Engineering OCTOBER 2002, Vol. 124 ’ 511

5. 6 D.O.F. Testing Robot Essential a 6 D.O.F. Actuator Allows for simultaneous control of motion in all three translations and three rotations. When used with a 6 D.O.F, load cell and appropriate software allows for control of all six loading components on a structure or a combination of Force Control D.O.F.s and Position Control D.O.F.s

6. Original Robot Tester Development - Knees J Biomech. 1996 Forces and moments in six-DOF at the human knee joint: mathematical description for control.･Fujie H, Livesay GA, Fujita M, Woo SL.Department of Biomedical Engineering, School of Medicine, Kitasato University, Kanagawa, Japan. J Biomech Eng. 1995 A six-degree-of-freedom test system for the study of joint mechanics and ligament forces.･Hollis JM.Orthopaedic Biomechanics Laboratory. University of Arkansas for Medical Sciences, Little Rock, 72205, USA.

7. A robot is an electro-mechanical or bio-mechanical device or group of devices that can perform autonomous or preprogrammed tasks. Wikipedia

8. Adapt a Six Degree of Freedom Robotic Testing Machine for Spine Testing

11. Testing of cervical spine Experimental procedure Specimen was fixed in the cups. Whole setup was fixed in the machine with zero load on the specimen.

12. Results Joint capsule

13. Testing of cervical spine Experimental procedure • Insertion sites position data was recorded once the bodies were separated. Insertion sites position

14. Testing of cervical spine Ligament force calculation

15. Testing of cervical spine Ligament length calculation

16. Results Anterior Longitudinal ligament

17. Results Anterior Longitudinal ligament

18. Results Anterior Longitudinal ligament

19. Results Intervertebral disc

20. Results Intervertebral disc

21. Results Intervertebral disc

22. Results Joint capsule

23. Results Joint capsule

24. Significance • This investigation will establish newer testing methodology, which will enable faster and more resource efficient biomechanical testing of the spine.

25. Data generated from a test on one specimen: • Multi directional load-displacement data for the motion segment. • Contribution of soft tissue sub structures to motion segment stiffness in multiple loadings. • The load in a soft tissue structure for an applied external motion segment load. • Force-displacement information for individual soft tissue structures. • Attachment site geometry. • Soft tissue simple strain under a variety of loads. • Stress-strain behavior for some structures • Non-linear bending stiffness of the disk in simple and combined loadings.

26. Limitations • Slow loading rate • Load distribution result applicable to impact loading is dependent on similar reduced relaxation function among soft tissue structures. • Difficulty in isolating and removing some soft tissue structures. • Wrapping of soft tissue around bone that is not accounted for in length calculations. • A more sophisticated geometric model would be helpful for some tissues • Limited upper range of applied loads to reduce chance of fixation and specimen failure. • A concern with older tissue donors

27. Thanks SCIB

28. Future • Test more specimens • Look for more collaborators