Biomechanics of spine

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Biomechanics of spine

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Biomechanics of spine

  1. 1. Biomechanics of spine Cervical & Thoracic 1
  2. 2. 12 Thoracic 5 Lumbar 5 Sacral 7 Cervical 4 Coccygeal 2
  3. 3. The Curves • Primary and • Secondary curves. 3
  4. 4. Typical vetebrae A. The anterior portion of a vertebra is called the vertebral body. B. The posterior portion of a vertebra is called the vertebral or neural arch. The neural arch is further divided into the pedicles and the posterior elements. 4
  5. 5. Typical vetebrae • The posterior elements are the laminae, the articular processes, the spinous process, and the transverse processes. 5
  6. 6. Vertical Trabeculae • The various trabeculae are arranged along the lines of force transmission. 6
  7. 7. The Inter vertebral Disk 7
  8. 8. The Inter vertebral Disk A. Under compressive loading, the NP attempts to expand. Tension in the AF rises. B. A force equal in magnitude but opposite in direction is exerted by the AF on the NP, which restrains radial expansion of the NP and establishes equilibrium. The nuclear pressure is transmitted by the AF to the end plates. A B 8
  9. 9. IVD Problems 9
  10. 10. Ligaments 10
  11. 11. Joints • Interbody Joints • Zygapophyseal Articulations 11
  12. 12. Kinematics • Flexion • Extension • Lateral flexion • Rotation. 12
  13. 13. Kinematics A. The addition of an intervertebral disk allows the vertebra to tilt, which dramatically increases ROM at the interbody joint. B. Without an intervertebral disk, only translatory motions could occur. 13
  14. 14. Kinematics Coupled Motion • Lateral flexion is coupled with axial rotation 14
  15. 15. Kinetics • Axial Compression • Bending • Torsion • Shear 15
  16. 16. Kinetics A. Side-to-side translation (gliding) occurs in the frontal plane. B. Superior and inferior translation (axial distraction and compression) occur vertically. C. Anteroposterior translation occurs in the sagittal plane. D. Side-to-side rotation (tilting) in a frontal plane occurs around an anteroposterior axis. E. Rotation occurs in the transverse plane around a vertical axis. F. Anteroposterior rotation (tilting) occurs in the sagittal plane around a frontal axis. 16
  17. 17. Biomechanics of spine Cervical Region 17
  18. 18. Structure Two distinct regions: • The upper cervical , or craniovertebral region and • The lower cervical region 18
  19. 19. Craniovertebral Region ATLAS 19 The atlas is a markedly atypical vertebra. It lacks a body and a spinous process.
  20. 20. Craniovertebral Region AXIS • The dens (odontoid process) arises from the anterior portion of the body of the axis. • The superior zygapophyseal facets are located on either side of the dens. 20
  21. 21. Craniovertebral Articulations • The median atlantoaxial articulation is seen, with the posterior portion (transverse ligament) removed to show the dens and the anterior arch of the atlas. • The two lateral atlantoaxial joints between the superior zygapophyseal facets of the axis and the inferior facets of the atlas can be seen on either side of the median atlantoaxial joint. 21
  22. 22. Craniovertebral Ligaments • Atlantal cruciform ligament • Alar ligaments 22
  23. 23. Craniovertebral Ligaments A. Posterior atlanto-occipital and atlantoaxial membranes. B. Anterior atlanto- occipital and atlantoaxial membranes. 23
  24. 24. Craniovertebral Ligaments • The tectorial membrane is a continuation of the posterior longitudinal ligament. 24
  25. 25. The Lower Cervical Region The body of a typical cervical vertebra is small and supports uncinate processes on the Postero lateral superior and inferior surfaces. 25
  26. 26. Intervertebral Disk A. Superior view shows crescent- shaped anulus fibrosus. B. B. Lateral view shows uncovertebral cleft. 26
  27. 27. Interbody Joints • The cervical vertebra exhibit raised superolateral lips known as uncinate processes. • These articulate with the margins of the vertebral body above, forming the uncovertebral joint or "joint of Luschka." 27 A. Lateral view of an inter body saddle joint of the lower cervical spine. B. Anterior view showing how the convex inferior surface of the superior vertebra fits into the concave superior surface of the inferior vertebra.
  28. 28. Zygapophyseal Joints 28
  29. 29. Kinematics Nodding motions of the atlanto-occipital joints. A. Flexion. B. B. Extension. 29
  30. 30. Kinematics • Superior view of rotation at the atlantoaxial joints: The occiput and atlas pivot as one unit around the dens of axis. 30
  31. 31. Kinematics A. Flexion of the lower cervical spine combines anterior translation and sagittal plane rotation of the superior vertebra. B. Extension combines posterior translation with sagittal plane rotation. • The range for flexion and extension increases from the C2/C3 segment to the C5/C6 segment, and decreases again at the C6/C7 segment 31
  32. 32. Kinetics • cervical region bears less weight and is generally more mobile. • No disks are present at either the atlanto- occipital or atlantoaxial articulations; • The trabeculae show that the laminae of both the axis and C7 are heavily loaded 32
  33. 33. Biomechanics of spine Thoracic Region 33
  34. 34. Structure • The 1st and 12th are transitional vertebrae • 1st, 9th, 10th, 11th, 12th are atypical vertebrae 34
  35. 35. Typical Thoracic Vertebrae A. Lateral view of the thoracic vertebra shows the superior and inferior facets of the zygapophyseal joints and the demifacets for articulation with the ribs. B. Overlapping of spinous processes in thoracic region. C. Superior view of a thoracic vertebra, showing the small, circular vertebral foramen, the costotubercular facets for articulation with the tubercles of the ribs, and the superior costocapitular facets for articulation with the heads of the ribs. 35
  36. 36. Intervertebral Disks 36
  37. 37. Articulations • Interbody Joints • Zygapophyseal Joints 37
  38. 38. Kinematics • the range of flexion and extension is extremely limited • Rotation of a thoracic vertebral body to the left produces a distortion of the associated rib pair that is convex posteriorly on the left and convex anteriorly on the right. 38
  39. 39. Kinetics • The thoracic region is subjected to increased compression forces in comparison with the cervical region, because of the greater amount of body weight that needs to be supported and the region’s kyphotic shape. 39
  40. 40. 40 http://www.pt.ntu.edu.tw/hmchai/kines04/KINoutline.htm

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