Biomechanics of spine.pptx.dr.shweta soni.

This presentation includes an in-depth exploration of the biomechanics of the spine, starting with an overview of spinal anatomy and its functions. It covers the structural components, such as vertebrae, intervertebral discs, ligaments, and muscles, and their roles in providing support and mobility. The slides delve into the functional biomechanics, explaining various spinal movements like flexion, extension, rotation, and lateral bending, along with the mechanical forces—compression, tension, shear, and torsion—that influence the spine. Additionally, the presentation addresses the concepts of spinal stability and balance, highlighting the importance of core stability. It also discusses common spinal pathologies, their mechanical implications, and the relevance of understanding these aspects in clinical practice and injury prevention.

1. Biomechanics of spine/ vertebral column - Dr. Shweta Soni (PT)

2. 01 02 03 04 Contents: Introduction Structure, functions and properties of regional vertebrae and its parts About surrounding connective tissues Force system, kinetic and kinematic of vertebral column (spine)

3. Introduction: Vertebral column is an amazingly complex structure consist of 33 vertebras It provides stability as well as mobility to the trunk and extremities Protects spinal cord

4. It resembles a curved rod, composed of total 33 vertebrae and 23 intervertebral discs Whole vertebral column divided into 5 regions: Cervical (C1-C7) Thoracic (T1-T12) Lumbar (L1-L5) Sacral (S1-S5) Coccygeal ( 4 vertebras) NOTE: Sacral and coccygeal vertebras are usually fused in the adult, forming individual sacral and coccygeal bones Structure of vertebral column:

5. Provide resilience and flexibility Allow mobility and provide support to body Help to absorb and distribute stresses that occur from everyday activities such as walking or from more intense activities such as running and jumping. Curves : Convexity and concavity Why curves are important ?

6. Primary and secondary curves:

7. Abnormal curves: Abnormal lateral curve of more than 10 degree (twisted disease) Scoliosis Exaggerated thoracic curve (humped disease) Kyphosis Accentuated lumbar curve (bent-backward disease/ sway back deformity) Lordosis 01 02 03

8. Vertebral axial view:

9. Parts of vertebrae:

10. Closer view of structure between 2 vertebras: T he spine won’t be flexible enough to do movements C ausing the vertebral bodies to come into contact with one another and limit movements of vertebral column Intervertebral disk (IVD): What if IVD is not available between 2 vertebras?

11. -It transmit load from one vertebral body to the next -Contribution to stability Function 1 01 03 04 02 They act as a shock absorbers in the spine it r esists to axial, rotational, and bending load Function 2 They act as supporting structures that hold the vertebrae of the spine together and help protect the nerves that run down the spine and between the vertebrae. Function 3 It provides cushioning for the vertebrae and reduce the stress caused by impact Function 4 Functions of (IVD):

12. Size of IVD depends on amount of motion as well as magnitude of the loads that must be transmitted Increases size from cervical (3 mm thickness) to lumbar (9 mm thickness) region IVD absent between C1-C2 and sacrum-coccyx

13. Joints and ligaments:

14. Two important ligaments: Two ligaments strengthen the vertebral body joints: the  anterior and posterior longitudinal ligaments , which run the full length of the vertebral column. The anterior longitudinal ligament is thick and prevents hyperextension of the vertebral column. The posterior longitudinal ligament is weaker and prevents hyperflexion .

15. S everal ligaments: Ligamentum flavum  – extends between lamina of adjacent vertebrae. Interspinous and supraspinous  – join the spinous processes of adjacent vertebrae. The interspinous ligaments attach between processes, and the supraspinous ligaments attach to the tips. Intertransverse ligaments  – extends between transverse processes.

16. Structure of regional vertebra:

17. Cervical : Thoracic : Lumbar :

18. In cervical region two unique vertebras are included C1 and C2 (called the atlas and axis respectively) are specialized to allow for the movement of the head. C1 vertebrae (atlas) C2 vertebrae (axis)

19. Rotational movement of atlas and axis vertebrae while head rotation:

20. Lateral view of regional vertebrae: Cervical : Thoracic : Lumbar :

21. Sacrum and Coccyx:

22. Segmental facet joint position and functions

23. Summery of different shapes of regional vertebrae

24.   Encloses and protects the spinal cord within the spinal canal Protection Carries the weight of the body above the pelvis Support   Has roles in both posture and movement Movement   Forms the central axis of the body Axis Functions of vertebral column :

25. An illustration showing the line of gravity passing through the body of a person standing with ideal posture It establishes and maintains the longitudinal axis of the body: Providing vertical stability throughout trunk and neck The vertebrae are arranged in such a way as to form anterior-posterior (concave-convex) curves in the vertebral column, which can be seen from the side

26. Sagittal plan (side view) alignment and LOG position in relation to plum line:

27. LOG Gravitational moment Anterior to transverse axis for flexion and extension Flexion Passive opposing force Active opposing forces Ligamentum nuchae, Tectorial membrane Posterior neck muscles ATLANTO-OCCIPITAL JOINT

28. LOG Gravitational moment Posterior Extension Passive opposing force Active opposing forces Anterior longitudinal ligament ------- VERTEBRAL COLUMN CERVICAL

29. LOG Gravitational moment Anterior Flexion Passive opposing force Active opposing forces P osterior longitudinal, ligamentum flavum, Supraspinous ligament Extensors VERTEBRAL COLUMN THORACIC

30. Flexion moment at thoracic spine:

31. Extension moment at thoracic spine:

32. LOG Gravitational moment P osterior Extension Passive opposing force Active opposing forces Anterior longitudinal ligament ------ VERTEBRAL COLUMN LUMBAR

33. LOG Gravitational moment Anterior to joint axis Flexion Passive opposing force Active opposing forces Sacrotuberous,sacrospinous,sacroiliac ligaments ------ SACROILIAC JOINT

34. Summary of curves VS plum line:

35. Sagittal imbalance and the different compensatory mechanisms in the spine, pelvis and lower limb areas

36. Available motion of vertebrae in relation to other: Gliding (can occur anterior-posterior, medial-lateral, torsional) Rotation/tilting /rocking of spine (can occur in anterior-posterior and lateral) Distraction and compression Note: These all motions, together with distraction and compression, constitute six degree of freedom

37. 01 02 03 Three-dimensional axes attached to lower vertebra. When a totally unconstrained upper vertebra moves relative to the lower vertebra, it can do so with six degrees of freedom (DOF): One each of translation along each of the x, y and z axes and one each of rotation around each of the x, y and z axes.

38. Kinetics: Axial compression Tension Bending Torsion Shear stress

39. 1 2 3 4 Vertebral column’s ability to resist theses loads depends on: V ertebral type, R ate of loading P ersons age and posture Condition affects vertebral bodies, joints or disk Problems with muscles, capsule and ligaments

40. Axial compression: Force acting through the long axis of the spine at right angles to the disk Compression occurs as results of the: Force of gravity, GRF, forces produce by ligaments and muscular contractions The disks and vertebral bodies resist most of the compressive force Compressive load transfer from superior to inferior end plate Zygapophyseal joints carry 0-30% of compression load .

41. Trabeculae system of bone:

42. Bending:

43. In extension:

44. Lateral bending: Ipsilateral side of disk is compressed Other side stretched in right and left Annulus fibrosus and intertransverse ligament provide stability during and resist extreme motion

45. How much force is applied to the intervertebral disk and its parts during various movements:

46. Reference link: https://www.youtube.com/user/nabilebraheim Updated on: 24 th March, 2024

47. Reference link: https://backcareclinic.co.uk/

48. Torsion:

49. Shear:

50. Summary of all available movements of spine : Article link: updated on 2011 https://www.jscimedcentral.com/public/assets/articles/orthopedics-2-1036.pdf

51. Vector: it is a quantity that possesses both magnitude and direction 01 02 03 Force vectors in vertebral column: Force or loading vector: force applied in a particular direction Extension, vertical compression, axial loading, vertical distraction, lateral flexion or bending, rotation, shear or combination of these

52. Vectors displayed on multiple vertebra 01 The downward red vector displays the force of weight and gravity , which are split into the shear and normal components 02 The vertebral slope, or pitch angle , is used when splitting the weight vector into the shear and normal components. 03

53. Whiteside's construction crane analog the spine: Anterior column resisted compressive forces and the posterior column resisted distraction 01 The equilibrium is maintained by anterior compression vectors against the posterior tension vectors 02 The dorsal ligamentous complex and paraspinal muscles act as a dorsal tension band 03 The gravitational forces exert an axial load leading to a ventral angular vector 04

54. Kinematics :

55. Article link: https://doi.org/10.1007/s10237-019-01215-4 The motions of flexion and extension occur as a result of the tilting and gliding of a superior vertebrae over the inferior vertebra As superior vertebra moves through a rang of motion it follows a series of different arcs, each of which has a different instantaneous axis of rotation

56. Instantaneous axis of rotation (IAR):

57. IAR during flexion and extension: These soft tissues constrain the movement that is possible to the commonly observed path in the sagittal plane of flexion and extension . The motion of rotation in a plane must, by definition, consist of rotation about an axis that is orthogonal (at right angles to both axes) to that plane. If a vertebra is observed to rotate, then it must rotate about a unique axis that, along with the angular displacement , fully describes the change in position. This axis is the “ axis of rotation” (AOR) or the “instantaneous axis of rotation” (IAR) if the rotation is considered at a point in time. The movement occurs as the “center of rotation” (COR). In practice, the terms COR and IAR are used interchangeably.

58. Each segment has unique IAR for every movement and is influenced by spine alignment, anatomy, muscle and loads exerted The IAR is located dorsal (posterior) to the annulus fibrosis in the intact spine

59. According to white and Punjabi, 173 the IAR is located in the ventral portion of the vertebral body The human body’s COG is located approximately 4 cm ventral to the sacrum The cervical IAR is located ventral to the vertebral bodies

60. The most predominant motions that exhibit coupled behaviors are lateral flexion and rotation Coupling is defined as the consistent association of one motion about an axis with another motion around a different axis Coupled motion:

61. Coupling motion:

62. What if coupled movement does not happen? Article link: https://doi.org/10.20385/1860-2037/5.2008.11

63. Anterior longitudinal ligament: The superior vertebra tilts and glides anteriorly over the adjacent tilting and gliding cause compression and bulging of the anterior anulus fibrosus and stretching of the posterior anulus fibrosus Gliding motion

64. The superior vertebra tilts and glides posteriorly over the vertebra below. The anterior anulus fibers are stretched, and posterior portion of the disk bilges posteriorly

65. Posterior longitudinal ligament:

66. Lateral flexion:

67. Evans flag pole concept:

68. Question Other various techniques (devices, goniometer etc ;) Question Radiological Examination? Question Special tests ? . Question Subjective Evaluations? How you can check the stability of spine?

69. Recent evidence (2020) suggested that: The three column concept/theory is often used to determining the stability of thoraco-lumbar spine fractures. NOTE: needed X-ray or MRI of spine then you can easily understand is concept Reference article : https://doi.org/10.1186/s12891-020-03550-5 Su Q, Li C, Li Y, Zhou Z, Zhang S, Guo S, Feng X, Yan M, Zhang Y, Zhang J, Pan J, Cheng B, Tan J. Analysis and improvement of the three-column spinal theory. BMC Musculoskelet Disord . 2020 Aug 12;21(1):537. doi : 10.1186/s12891-020-03550-5. PMID: 32787828; PMCID: PMC7425572.

70. Denis and Ferguson et al. Su’s three-column theory

71. There were three main column of vertebral column as per theory

72. Biomechanical load deflection response:

73. Recent study (2020) shows stress distribution in parts of vertebras during flexion, extension as well as lateral bending and 3D maps of display the fracture line distribution of the vertebral body Reference article: Su Q, Li C, Li Y, Zhou Z, Zhang S, Guo S, Feng X, Yan M, Zhang Y, Zhang J, Pan J, Cheng B, Tan J. Analysis and improvement of the three-column spinal theory. BMC Musculoskelet Disord . 2020 Aug 12;21(1):537. doi : 10.1186/s12891-020-03550-5. PMID: 32787828; PMCID: PMC7425572.

74. Regarding flexion and extension of the spine, there were two main stress centers in the vertebral body, namely the first third and the last third of the vertebral body in front of the spinal canal. In contrast, the middle of the vertebral body and the vertebral body in front of the pedicles were under less stress

75. In terms of lateral bending , the stress on the vertebral body was greater in front of the pedicles on both sides

76. The 3D maps of T11-L5 display the fracture line distribution of the vertebral body