1. Anatomy and Mobility of the Spine

2. All joints are trade-off between mobility and stability
Figure 9.1

3. Factors that influence mobility and stability of a joint
Articulating surface and surrounding bones
Determines types of movements possible
Bone-hitting-bone can limit movements
Joint capsule and ligaments
Can restrict or permit movements
Muscle that crosses joint or is near joint
Can stabilize joints
Can limit movement
E.g., hip and knee flex more passively than actively

4. Spine:
A series of 24 individual vertebrae + sacrum (5 fused vertebrae) + coccyx (~4 fused vertebrae).
Functionally:
bears and transmits upper body weight onto the pelvis while permitting movement.
Accomplished by being made of many individual bones stacked on one another
Small movement between each vert  considerable mobility with decent stability
protects the spinal cord

5. Regions
Cervical — secondary curve—created and maintained by muscle use associated with upright posture
Thoracic—primary curve—present at birth and maintained by associated bones
Lumbar — secondary curve—created and maintained by muscle use associated with upright posture
Sacrococcygeal—primary curve—present at birth and maintained by associated bones
Presence of Curves places body weight in the correct place for upright posture.
Primary curvatures are less mobile, but more stable and less prone to injury.

6. Vertebral Anatomy Body is the weight bearing portion
Processes are sites of muscle and ligament attachment
the pedicle and lamina help create the vertebral foramen through which passes the spinal cord (also protects the cord)
Articulating processes help define movements that are possible between adjacent vertebrae

7. Intervertebral Joints
nucleus pulposus
annulus fibrosus
There are two joints between individual vertebrae
Joints between bodies: symphysis—intervertebral discs
disc both absorbs shock and acts as a flexible spacer that allows intervertebral movement.
Joint between superior and inferior articulating processes (facets): synovial joint
direction/orientation and shape of the articulating processes defines/determines what kind of movements are possible between vertebra—especially the degree of rotation possible

8. Joints of the spine
intervertebral disk--symphisis
synovial joint –plane-- between articulating processes

9. Spinal nerves pass through this opening

10. Refer to lecture notes for details on the structure and function of intervertebral discs

11. Herniation of disc (rupturing and protrusion of nucleus pulposus) can pinch nerves between the expanded disc and nearby bone structures which creates pressure on the nerve and thus pain and dysfunction.

12. Joint Mobility
Mobility (types and range of motion) at a joint can be influenced by:
shape of articulating bone surfaces and boney structures interfering with joint movement (bone-bone interference)
ligaments becoming tight and braking/stopping further movement in a particular direction
the compression of soft tissue (e.g., muscle, adipose) preventing further joint movement.

13. Ligaments of the spine

14. Ligaments of the Spine: Simplified Scheme
anterior ligaments
Posterior ligaments
lateral ligaments

15. Bones are held in place and supported in much the same way that a pole is supported/held in place by guy-lines/ropes anchoring them into the ground. Bone—which structurally bears/transmits compressive force is supported (i.e., held in place) by fibrous tissue and muscle—tensile structures (the tensegrity model)

16. In extension/hyperextension:
SPINAL EXTENSION
In extension/hyperextension:
spinous processes move toward one another and can limit movement on the side being moved to
Anterior ligaments become tight and limit/brake movement
Note: nucleus pulposus is being pushed anteriorly

17. There are no boney structures of the vertebrae to limit flexion
SPINAL FLEXION
In Flexion:
There are no boney structures of the vertebrae to limit flexion
Posterior ligaments become tight and act as a brake to flexion
Note: the disc is stressed toward the posterior.

18. LATERAL FLEXION (I.E., SIDE BENDING)
The transverse processes on the side being flexed toward (ipsilateral) move toward one another and will limit movement
the lateral ligament on the opposite side (contralateral) will become tight to limit movement
Note: disc being stressed toward the side being bent away from (contralateral).

19. ROTATION
Largely influenced by orientation of articulating processes and presence/absence of ribs