«By David G. Drucker B.S. University of California, Davis, 2009 THESIS Submitted as partial fulfillment of the requirements for the degree of Master ...»
Investigation of the Mechanical Response of the Anterior and Posterior Cervical and
Lumbar Disc Bulge
David G. Drucker
B.S. University of California, Davis, 2009
Submitted as partial fulfillment of the requirements
for the degree of Master of Science in Bioengineering
in the Graduate College of the
University of Illinois at Chicago, 2012
Farid Amirouche, Mechanical and Industrial Engineering, Chair and Advisor David Eddington Jun Cheng
ACKNOWLEDGEMENTSI would like to thank research advisor Dr. Farid Amirouche for all of the support and advise he has given me for this project. Thank you for furthering my educational curiosity in biomechanics. I would also like to acknowledge Dr. Giovanni F. Solitro for all of his hard work and support. Special thanks Dr. David Eddington and Dr. Jun Cheng for taking time out of their schedules and lending their expertise in this project. Special thanks to Dr. Ashish Upadhyay for his clinical expertise and disc analysis. Lastly thank you to the students in the lab for offering encouragement.
TABLE OF CONTENTSSUMMARY
1. ANATOMY OF THE HUMAN LUMBAR AND CERVICAL SPINE
1.1 Anatomy of the Vertebra
1.2 Anatomy of the Cervical Spine
1.3 Anatomy of the Lumbar Spine
1.4 Soft Tissue Anatomy
1.5 Intervertebral Disc
1.6 Annulus Fibrosis
1.7 Nucleus Pulposus
1.8 Articular Facet Joints
2. MECHANICS OF THE SPINE
2.1 BIOMECHANICS OF THE SPINE SEGMENT
3. REVIEW OF EXISTING IVD EXPERIMENTAL MECHANICAL TESTING STUDIES 14
3.1 Current Literature of lumbar specimen testing
3.2 Current literature of cervical specimen testing
4. SPECIFIC AIMS TO MEASURE AND ANALYZE THE IVD BULGE
5. METHODS OF EXPERIMENTAL TESTING
5.1 Specimen Preparation
5.2 Mechanical Testing Protocol
5.3 Positioning of Linear Variable Differential Transformer on the Specimens.......... 26
5.4 Experimental Data Processing and Analysis
5.5 Phase 2. Specimen Preparation and Testing: Laminectomy
5.6 Phase 2. Specimen Preparation and Testing: Facetectomy
5.7 Specimen Dissection and Inspection
6. RESULTS OF EXPERIMENTAL TESTING
6.1 Phase 1 Results Intact Cervical Spine
6.2 Phase 2 Results Laminectomy Cervical Spine
6.3 Phase 2 Results Facetectomy Cervical Spine
6.4 Phase 1 Results Intact Lumbar Specimens
6.5 Phase 2 Results Laminectomy Lumbar Specimens
6.6 Phase 2 Results Facetectomy Lumbar Specimens
6.7 Anterior and Posterior Bulge analysis at each Spine Level: Cervical Spine......... 64
6.8 Anterior and Posterior Bulge analysis at each Spine Level: Lumbar Spine.......... 69
6.9 Analysis of the Average Deformation Response
6.10 Analysis of the Removal of the Articular Facets in the Lumbar Region.............. 76
6.11 Analysis of the Removal of the Articular Facets in the Cervical Region............. 78
6.12 Dissection of Cervical Specimens
6.13 Dissection of the Lumbar Specimens
6.14 Comparison of each Configuration: Lumbar Spine
6.15 Comparison of each Configuration: Cervical Spine
LIST OF TABLESTable I. Comparison of the results of the studies and deformation Values
Table II. Table of rigidity values
Table III. Comparison on the amount of bulge with and without facets in the lumbar spine
Table IV. Comparison on the amount of bulge with and without facets in the Cervical Spine
LIST OF FIGURESFigure 1 Cervical Spine
Figure 2. Lumbar vertebra
Figure 3 Specimen preparation. As shown here from Lin 1978. The vertebrae are constrained in a polyester resin (Lin et al, 1978)
Figure 4. Specimen Image after testing as shown here from the Wenger 1997 study.
The IVD is clearly bulging.
Figure 5. Specimen preparation and testing set up for the 2010 Cuchanski study (Cuchanski 2010)
Figure 6. Diagram of Anterior Deformation and Load Directions.
Figure 7. Experimental Setup Lumbar Specimen
Figure 8. Sensor Placement Intact Cervical specimen
Figure 9. Cervical Laminectomy Cut
Figure 10. Lumbar Laminectomy
Figure 11. Cervical laminectomy mechanical test
Figure 12. Lumbar laminectomy Mechanical setup
Figure 13. Cervical facetectomy posterior view
Figure 14. Cervical Spine C5-C6 facetectomy mechanical testing Upper posterior view.
Figure 15. Lumbar facetectomy
Figure 16. Lumbar facetectomy mechanical testing.
Figure 17. Example of Sagittal Cut Specimen L2-L3
Figure 18. Average Anterior Bulge Intact Specimens
Figure 19. Average Vertical Deformation for Cervical Intact Specimens
Figure 20. Comparison of the Gap height change in Cervical Spine studies.
................ 45 Figure 21. Vertical deformation perpendicular to the axial plane.
Figure 22. Anterior Bulge in the cervical Spine
Figure 23. Posterior Bulge Cervical spine under laminectomy
Figure 24a,b. Anterior and posterior IVD bulge slope comparison
Figure 25. Vertical Cervical deformation facetectomy
Figure 26. Anterior bulge cervical spine facetectomy
Figure 27. Posterior cervical bulge: facetectomy
Figure 28. Vertical deformation Lumbar intact
Figure 29. Anterior lumbar bulge intact
Figure 30. Lateral Bulge Lumbar, Intact
Figure 31.Comparison of the Existing literature to the current study with respect to the gap deformation.
Figure 32 Comparison of the Existing literature to the current study with respect to the anterior bulge.
vi Figure 33. Comparison of the Existing literature to the current study with respect to the lateral bulge
Figure 34. Vertical deformation Lumbar laminectomy
Figure 35. Anterior Bulge lumbar laminectomy
Figure 36. Lateral bulge Lumbar Laminectomy
Figure 37. Posterior Bulge Lumbar Laminectomy
Figure 38. Vertical Deformation Lumbar Facetectomy
Figure 39. Anterior Bulge Lumbar Facetectomy
Figure 40. Lateral Bulge Lumbar Facetectomy
Figure 41. Posterior Bulge Lumbar Facetectomy
Figure 42. Comparison of C3-C4 Anterior and Posterior Bulge Laminectomy.
............. 65 Figure 43. C5-C6 Comparison of Anterior and Poster Bulge Laminectomy.................. 66 Figure 44. Comparison of C7-T1 Anterior and Posterior Bulge Laminectomy............... 66 Figure 45. C3-C4 Comparison of Anterior and Posterior bulge Facetectomy................ 67 Figure 46. Comparison of C5-C6 Anterior and Posterior Bulge Facetectomy............... 68 Figure 47. Comparison of C7-T1 Anterior and Posterior Bulge Facetectomy................ 68 Figure 48. Comparison of T12-L1 Anterior and Posterior Bulge Laminectomy............. 69 Figure 49. Comparison of L2-L3 Anterior and Posterior Bulge Laminectomy................ 70 Figure 50. Comparison of L4-L5 Anterior and Posterior Bulge Laminectomy................ 70 Figure 51. Comparison of T12-L1 Anterior and Posterior Bulge Facetectomy.............. 71 Figure 52. Comparison of L2-L3 Anterior and Posterior Bulge Facetectomy................ 72 Figure 53. Comparison of L4-L5 Anterior and Posterior Bulge Facetectomy................ 72 Figure 54. Average Deformations Laminectomy Lumbar
Figure 55. Average Deformations Lumbar Facetectomy
Figure 56. Average Deformation Cervical laminectomy
Figure 57. Average Deformations Cervical Facetectomy
Figure 58. Axial cut C3-C4
Figure 59. Axial cut specimen 1 C7-T1
Figure 60. Sagittal cut.
Figure 61. Sagittal Cut.
Figure 62. Sagittal Cut.
Figure 63. Axial Cut Specimen T12-L1
Figure 64. Sagittal Cut and Axial Cut, Specimen T12-L1
Figure 65. Sagittal Cut.
Figure 66. Sagittal and Axial Cut.
Figure 67. Sagittal Cut.
Figure 68. Average Vertical Deformation after each modification
Figure 69. Average Vertical Deformation after each modification
Figure 70. Average Posterior Bulge of the lumbar Specimens after each modification.
89 Figure 71. Average Posterior Bulge of the Lumbar Specimens after each modification 90 vii Figure 72. Average Vertical Deformation of the Cervical Specimens after each modification.
Figure 73. Average Anterior Bulge of the Cervical Specimens after each modification.
91 Figure 74. Average Posterior Bulge of the Cervical Specimens after each modification92
The spine is an important structure that provides support, flexibility, range of motion and protection. Neck and lower back pain are significant problems in the aging population. In this dissertation the cervical and lumbar intervertebral disc bulge response to compressive forces will be analyzed. Eleven cervical specimens and seven lumbar specimens are compressed in a series of three cycles with increasing loads to 550 N. The vertical deformation and anterior bulge is measured in multiple configurations including intact, laminectomy, and facetectomy the posterior bulge is also measured in the latter two configurations. The changes in the bulging patterns are compared and analyzed.
It is shown that as the cervical specimens were compressed stiffening affect in the anterior bulge occurs that did not appear in the vertical deformation response. Upon further investigation, using the laminectomy configuration to gain access to the posterior Intervertebral Disc (IVD) region, it was found that the posterior bulge did not experience a stiffening effect. Additionally, when the articular facets were removed to assess the changes that the articular facets impose on the anterior and posterior disc bulge, it was shown that a translation of the vertebral bodies occurs in the cervical and lumbar regions but in opposite directions suggesting that the orientation of the articular facets may play a role in the deformation response of the IVD. The results from this study can be used as a basis for further studies to develop diagnostic techniques for spinal injuries and ailments like herniation, spondylolisthesis, among others.
The spine is an anatomical structure that begins just below the skull and extends down just past the pelvis; it provides support, stability and flexibility for the upper body (Middleditch et al, 2005). It also protects the spinal cord which is vital to the central nervous system (Middleditch et al, 2005). The spine supports the body to maintain an upright direction, improves flexibility, provides a large range of motion, serves as attachment points for muscles and protects the spinal cord. The spine is composed of a total of 29 vertebrae separated into four regions: cervical, thoracic, lumbar and sacral, each with functional, anatomical, physiological differences (Middleditch et al, 2005).
The spinal column is composed of vertebrae, cartilage and ligaments. The vertebral column alternates between vertebral bodies and intervertebral discs in the anterior region and the posterior elements and two articular facet joints in the posterior region (Middleditch et al, 2005). The vertebral bodies are composed of a hard cortical shell about one millimeter thick and softer trabecular bone on the interior (Silva et al, 1994). The trabecular bone is structured into vertical and horizontal struts providing a light, strong support structure to assist in resisting the buckling of the cortical shell in compression or bending (Thomsen et al. 2002). The trabeculae are orientated along the axis of greatest stress and strain (Middleditch et al, 2005) this is in accordance to wolf’s law that states that the orientation of bone aligns itself in the direction of the greatest stress (Chamay et al,1972). The pores between the struts are filled with marrow and other cells to provide nutrition and life support (Keaveny et al, 2001). In the posterior region, the posterior elements or posterior arch is composed of the spinous process, transverse processes, lamina, articular facets, and pedicles (Middleditch et al, 2005).
The spinous process can limit the amount of extension that the bending of the joints is allowed as well as providing attachment points for ligaments, tendons and muscles (Middleditch et al, 2005). Transverse process on each of the lateral sides limits the amount of lateral bending as well as providing attachment points for ligaments, tendons and muscles (Middleditch et al, 2005). Pedicles connect the transverse processes to the vertebral bodies. Laminae connect the spinous process to each of the transverse processes. Articular facet joints act in conjunction with the intervertebral disc to connect vertebrae to the adjacent level (Middleditch et al, 2005). The intervertebral disc and articular facets provide flexibility and due to relatively small young’s modulus provides a reliable point for bending, rotation and deformation.
The purpose of the vertebra is to transmit load through the spine, provide for attachment points for ligaments tendons and muscles, and create space between the pelvis, thorax and head (Drake et al, 2010). The vertebrae must resist compressive and shear forces and bending and rotational moments. The vertebral body contains an outer shell of hard cortical bone less than 1 mm of thickness (Silva et al, 1994), young’s modulus of 18.6 GPa, encasing soft cancellous trabecular bone young’s modulus of