The cervical spine

anatomy of atlanto-occipital joint atlanto-axial joint and lower cervical spine. kinematics (includes osteokinematics and arthrokinnematics) and kinetics

1. THE CERVICAL SPINE VIBHUTI NAUTIYAL MPT (MUSCULOSKELETAL)

2. STRUCTURE Consists of 7 vertebrae in total Divided into 2 distinct parts: The upper cervical spine or cranio-vertebral region The lower cervical spine Cranio-vertebral region includes the occipital condyles and C1-C2 Lower cervical spine includes the vertebrae of C3-C7

3. CRANIO- VERTEBRAL REGION ATLAS: Function of the atlas is to cradle the occiput and to transmit forces from the occiput to the lower cervical spine. It has no V.B or spinous process Shaped like a ring There are 2 large lateral masses that have a vertical alignment under each occipital condyle that transmit forces The lateral masses are connected by an anterior and posterior arch that form the ring structure and also creates large transverse process for muscle attachments

4. The lateral masses include 4 articulating facets: 2 superior facets 2 inferior facets Atlas also possesses a facet on the internal surface of the anterior arch for articulation with the dens of axis Superior zygapophseal facets: Large Kidney shaped Deeply concave to accommodate the large convex articular surfaces of the occipital condyles

5. Inferior zygapophyseal facets: Slightly convex Directed inferiorly Articulates with the superior zygapophyseal facets of the axis

6. AXIS: Primary function of the axis are: Transmit the combined load of the head and the atlas Provide motion into axial rotation of the head and atlas Anterior portion of the body extends inferiorly and a vertical projection called the dens arises from the superior surface of the body Dens has an anterior facet for articulation with the anterior arch of the atlas and a posterior groove for articulation with the transverse ligament

7. The arch of the axis has inferior and superior zygapophyseal facets for articulation The spinous process is large and elongated with a bifid tip Superior facets face upward and laterally Inferior facets face anteriorly

8. ARTICULATIONS ATLANTO-OCCIPITAL JOINT: Composed of the right and left deep concave superior facets of the atlas that articulates with the right and left convex occipital condyles True synovial joint Lie nearly in the horizontal plane

9. ATLANTO-AXIAL JOINT: 3 synovial joint 1 median (pivot joint) and 2 lateral joint Median joint consists of odontoid process of C2 that articulated with a facet on the internal surface of the atlas (C1) 2 lateral joints are composed of right and left superior facets of the axis that articulates with the right and left slightly convex inferior facet on the atlas

10. CRANIO VERTEBRAL LIGAMENTS 4 of the ligaments are continuation of the longitudinal tract system: Posterior atlanto-occipital and atlanto-axial membranes: Continuation of the ligamentum flavum Less elastic Therefore permit greater ROM, especially into rotation Anterior atlanto-occipital and atlanto-axial membranes: Continuation of ALL

11. Tectorial membrane: Continuation of the PLL in the upper 2 segments Broad and strong Originates from the posterior V.B of axis Covers the dens and its cruciate ligament Inserts at the anterior rim of the foramen magnum

12. Ligamentum nuchae: Thick Extends from the spinous process of C7 to the external occipital protuberance Evolution of the supraspinous ligament Resist the flexion moment of head

13. Transverse ligament: Stretches across the ring of the atlas Divides the ring into a large posterior section for the spinal cord Has a thin layer of articular cartilage on its anterior surface for articulation with the dens Longitudinal fibres extend superiorly to attach to the occipital bone Inferior fibres descend to the posterior portion of the axis Transverse portion holds the dens in close approximation against the anterior ring of the atlas

14. Prevent anterior displacement of C1 and C2 Transverse atlantal ligament is very strong and the dens will fracture before the ligament will tear Alar ligament: 2 alar ligament Arise from the axis or either side of the dens Extend laterally and superiorly to attach to roughened areas on the medial sides of the occipital condyles and to the lateral masses of the atlas

15. Relaxed with the head in mid-position or neutral Taut in flexion and rotation of the head and neck Right upper and left lower portion limit left lateral flexion Prevent distraction of C1 and C2 Weaker than the transverse atlantal ligament Runs in a fan shaped arrangement from the apex of the dens to the anterior margin of the foramen magnum of the skull

16. LOWER CERVICAL REGION BODY: Small Transverse diameter is more than AP diameter and height Transverse and AP diameter increases from C2 to C7 with a significant increase in both diameters in the upper end plate of C7. Posterolateral margins of the upper surfaces of the V.B from C3 to C7 support uncinated processes that give the upper surfaces of these vertebrae a concave shape in the frontal plane. Anteroinferior border of the V.B forms a lip that hangs down toward the V.B below, which produces a concave shape of the inferior surface of the superior vertebra.

17. ARCHES: PEDICLES: Project posterolaterally Located halfway between the superior and inferior surfaces of the V.B Laminae : Thin and slightly curved Project posteromedially

18. Zygapophyseal articular processes: Support paired superior facets that are flat and oval, face superoposteriorly Width and height of these facets gradually increase from C3-C7 Inferior facets face anterolaterally and lie closer to the frontal plane Transverse processes: Foramen is located in the transverse process bilaterally Groove for the spinal nerves

19. Spinous processes: Short, slender and extend horizontally Tip is bifid Length of the spinous process decreases slightly from C2-C3, remains constant from C3-C5 and increase at C7 Vertebral foramen: Large triangular

20. KINEMATICS OSTEOKINEMATICS/ ARTHROKINEMATICS: ATLANTO- OCCIPITAL JOINT: Condylar synovial joint Permits active F-E as a nodding motion Deep walls of the atlantal sockets prevent translation, but the concave shapes does allow rotation to occur F/E: sagittal plane around mediolateral axis F: occipital condyles roll forward and slide backward E: occipital condyles roll backward and slide forward

21. Flexion is limited by: Osseous contact of the anterior ring of the foramen magnum with the dens Tension in the posterior neck muscles and tectorial membrane Impaction of submandibular tissues against the throat E is limited by occiput compressing the sub occipital muscles

22. Atlanto - axial joint: Plane synovial joiont Allow F/E, lateral flexion and rotation Median atlantoaxial joint permits rotation Rotation is limited by 2 alar ligaments, capsule of lateral atlanto - axial joint Rotation coupled with ipsilateral lateral flexion Lateral flexion coupled with ipsilateral rotation F: anterior tilt with anterior translation E: posterior tilt with posterior translation

23. KINETICS No disks are present at either the atlanto - occipital or atlanto - axial joint Compressive loads→ transferred directly through the atlanto - occipital joint→ articular facets at the axis→ transferred through pedicles and laminae of the axis to the inferior surface of the body→ 2 inferior zygapophyseal articular processes→ adjacent inferior disk From C3-C7 compressive forces are transmitted by 3 parallel columns: Single anterocentral column: V.B and disks 2 rodlike posterolateral column: left and right zygapophyseal joints Compressive loads in end range F/E > erect stance and standing postures

24. CAPSULAR PATTERNS Equal restriction of E and lateral flexion Flexion and rotation are not affected