LUMBAR SPINE - ARTHROLOGY Flashcards
The vertebral column
Median and dorsal 33 vertebrae
🔸Cervical- 7
🔸Thoracic- 12. 🔸(24 free vertebrae)
🔸Lumbar-5
Sacral- 5 (fused together to form sacrum)
Coccygeal- 4
(Fused together to form rudimentary tail)
Spinal curvatures
Spine curves when all parts are put together
Primary and secondary curvature is which gives us our normal posture
Cervical curvature – secondary curvature
thoracic curvature – primary curvature
Lumber curvature – secondary temperature
Sacral/coccygeal curvature – primary curvature
Primary Curvature
Thoracic and sacral region primarily for protection there is little or no movement
Thoracic region help to form part of the rib cage- protects lungs
Sacral region help to form part of the pelvic ring – protects pelvic viscera
Secondary curvature
Cervical and lumbar region created by increased anterior thickness in intervertebral discs
- more movements are more likely to be affected by degenerative changes
2 joints at a segment level L2–3
2 joints
Anteriorly :
(Invertebral body +disc)
2nd cartilagineous or Symphyseal joint (mid line of body)
Posteriorly:
Synovial plane or Zygoapophyseal or Facet joint
Superior and inferior facets
Synovial joint
Majority of joints in body
Articular surface = hyaline cartilage
Joint cavity, fibrous capsule, synovial membrane, synovial fluid
Greater reliance on strong ligament to stabilise joint
Range of movement variable
Symphyseal joint
Found in midline of the body
Articular surfaces =
hyaline cartilage
No joint cavity
Bones how together by a fibrocartilaginous plate
Some ligaments hold the bones together
Range of movement = limited degree
Typical lumbar vertebra
L1-4
There are five vertebrae in the lumbar region but L5 is a-typical
(See photo)
Intervertebral disc
24 intervertebral discs and they contribute to a 1/4 of the length of the vertebrae column reason for curvature and spine
Symphyseal joint between intervertebral body and disc
Lumbar discs
Biggest within vertebrae column
10 mm thick
Make up a 1/3 of the height of the vertebral column
Nucleus pulposus
Semi fluid or a ball bearing
Irregularly arranged collagen fibres type 2 3D lattice and a few cartilage cells dispersed in a gel of semi fluid ground substance (hold water within its makeup)
Deformable tissue- can change its shape
Annulus fibrosis
Concentric lamella ( 10–20 layers) of collagen fibres highly organised structure
Within each lamella collagen fibers line parallel to each other at 65–70° angle
Successive layers or a different inclination is to each other i.e. Axa fact provide strength + resilience copes with shearing
Elastic fibres:
1) type l collagen fibres- are in the outermost layer of annulus gives tensile strength
2) type II collagen fibers- inner most layer gives it compressive component
Structure of annulus Is important to maintain the integrity of the intervertebral disc as a whole
Arrangement of annulus fibrosis
Thickenings
Collagen lamella are thicker anteriorly and latterly
finer posteriorly
Disc most likely to fail posteriorly
- If disc prolapse is posteriorly there is chance of spinal-cord entrapment
- If disc prolapse is posterolatterly there is chance of nerve root entrapment
Vertebral End Plates
Structure
Layer of cartilage (0.6-1 mm thick)= hyaline and fibrocartilage
Covers the nucleus but not the entire extent of the annulus fibrosis
Plate is a mixture of hyaline and fibrocartilage:
- Hyaline- closer to vertebral body weaker link when binding disc to body
- Outer most fibres of the annulus fibrosis anchor the intervertebral disc to the adjacent vertebral bodies
- inner surface of end plate is composed of fibrous tissue= inner layers of annulus fibrosis which sweep over and under nucleus fibrosis help to form inner part of vertebral end plate
End-plates are strongly bond to the disks but only weakly attached the vertebral bodies
Vertebral End Plates
Functions
Protect vertebral body from pressure atrophy because the disc has to cope with pressure
Confinees the nucleus fibrosis and annulus fibrosis within their anatomical range
Acts as a semi-permeable membrane for fluid exchange via osmosis
End Plate+Annulus fibrosis
End plate+annulus fibrosis=
Ensures the nucleus fibrosis is completely contained within the intervertebral disc
Nutrition of the disc
Discs have a relatively low metabolic rate
Peripheral part of annulus is supplied by adjacent blood vessels
Majority of disk relies on DUFFUSION from blood vessels within the adjoining cancellous vertebral bodies
Diffuses through end plate and into disc
Intervertebral disc
Functions
Weight-bearing
Shock absorber
Movement
Intervertebral disc- weight bearing
- DISC LOADING– annulus+nucleus are involved in weight-bearing
- TELEPHONE BOOK ANOLOGY– (annulus) healthy lamella will resist buckling due to the bulk of collagen fibres for a limited period of time
- Anulus on its own is not sufficient for load bearing has to be combined effort
Intervertebral discs – weight-bearing
Disc Looding
Compression increases pressure in the nucleus pulposus but due to its deformable nature it changes shape and the force is exerted radially on the annulus and tension in the annulus increases as fibres are stretches
As disc loading increases the tension in the annulus reaches maximum capacity where it can’t stretch any further
As a consequence the nucleus starts to exert pressure on vertebral end plates above and below
As the anulus can no longer stretch and the End plates are a rigid structure which prevent nucleus deforming inferiorly or superiorly = annulus therefore applies an equal and opposite force to that of the nucleus
therefore you end up with a rigid structure through which load can be transmitted
Intervertebral disc
Shock absorber
- Rapid application of forced to the disc is diverted momentarily to annulus
- Annulus have elastic collagen fibres which stretch to absorb the shock and reduce force being passed on to adjacent vertebral bodies
Intervertebral disc
Movement
Nucleus pulposus acts like a semi fluid ball bearing between adjacent vertebrae
It is able to move with in the confines of the intact annulus
Zygoapophyseal joints
Synovial plane joints
Articular processes of vertebral column
LX region
•Superior concave facets face medially and posteriorly
•Inferior facets face laterally and anteriorly
Lax fibrous capsule surround to the joint with synovial membrane
Joints are stabilised by additional ligaments
Zygoapophyseal joints
Articulations
inferior facets of the vertebra above articulating with the superior facets of vertebrae below = joint
Range of movement depends on the shape and orientation of facets
Lots of small movements = quite a bit of movement but still very stable
Superior articular facets
concave transversely flat vertically face medially and posteriorly in direction
Inferior particular facet
Reciprocally curved they are convex transversely flat vertically closer together than superior facet and face laterally and anteriorly
Ligaments supporting vertebral column
1) ALL
2) PLL
3) Supraspinous ligament
4) interspinous ligament
5) ligamentum Flava
6) intertransverse ligament
Spinal longitudinal ligament
Anterior longitudinal ligament (ALL)
Attaches to anterior part of bodies and discs from C1 to pelvic surface of sacrum widening inferiorly (24mm wide)
1 to 2 mm thick consisting of 3 dense layers
Superior fibres= long 7 segmental levels
Deepest= 1 segmental level
Spinal support for anterior part is vertebrae column
Posterior longitudinal ligament (PLL)
Attaches to intervertebral discs and adjacent margins of vertebral column bodies with the vertebral canal
Extending from C2 to sacrum
1- 1.4 mm thick consisting of 2 dense layers
Superior fibres extensive
Deep fibres short
Difference between ALL and PLL
Not as strong as ALL
PLL attaches to the intervertebral disc and the adjacent margins of the vertebral bodies but it doesn’t attach to the backs of the whole of the vertebral body because it needs to allow space for vertebral vein to pass through to supply nutrition for intervertebral disc
Supraspinous ligament
Most posterior
Band of longitudinal fibres extending over and connecting the tips of spinous processes from C7 to sacrum
Superficial fibres are extensive
Deep fibres are shorter
Continuous with the posterior edge of the interspinous ligament anterior to supraspinous ligament
Interspinous ligament
Thin and membranous
Relatively weak best developed in lumbar region
Fibres passed between and unite adjacent vertebral ptocesses
Particularly well-developed in the Lx region
Ligamentum Flava
Passing between both laminae of adjacent vertebrae from C1 to L5
Attaches is to lower border of lamina above the upper border of vertebra below
Medial borders of each ligament me at the root of the spine
Yellowish a parent due to lots of elastin fibres permits separation of lamina during flexion to allow for a good range of movement but during extension it prevents it + stability
Intertansverse ligament
Generally insignificant bands of fibres
connecting adjacent transverse processes lower broader of T.p above and superior boarder of T.p below
Best developed in the Lx region
Absent in the CX region
Flexion of vertebral column
ROM: freely moving
Effect on intervertebral discs:
•Compression of the anterior part of disc
•stretching of the posterior part of disc
•nucleus moves backwards
Effect of facet joints:
•inferior articular facet glide upwards on adjacent superior facets
Effect on soft tissue :
•laminae move apart
Limiting factors: increase tension in •Supraspinous Lig •Interspinous ligament •Ligament Flava •PLL •extensor muscles
Extension of vertebral column
ROM: limited fairly free
Effect on intervertebral discs:
Compression of posterior part of disc
Nucleus moves forwards
stretching of anterior part of disc
Effect of facet joints:
Inferior articular facets glide downwards on the adjacent superior facets = CLOSE PACK POSITION (maximum congruency of articulating surfaces)
Effect on soft tissue
Spinous processes and laminae move closer together
Limiting factors: Increased tension in
•ALL
•Flexor muscles
Lateral flexion of vertebral colum
ROM: free in lumbar region but less than CX region
Effect on 6 discs:
Six disc compression with some degree of torsion
Effect of facet joints:
Inferior articular facet glides downwards on adjacent superior articular facet
Effect on soft tissue:
Laminae move closer together
Limiting factors: tension in
•Ligaments on the opposite side to the movement
•i.e. intertransverse ligament and ligament flava
•Opposite muscles
Rotation
ROM: very limited = shape and orientation of facets
Effect on intervertebral discs:
Torsional affect on desk (windeing up)
50% fibrous will be taught in each direction due to the arrangement of them
Same side laminae move closer together
Opposite side laminae move further apart
Limiting factors: increased tension in
•Ligaments on both sides
•Muscles on opposite side of movement
Intervertebral Foreman
Boundaries
Superior and inferiorly by pedicles of adjacent vertebrae
Anteriorly by vertebral bodies and intervening discs
Posteriorly by articular processes and facet joints
Intervertebral compression
Any reduction in the transverse dimension of the foramen will result in nerve compression
Boundaries of intervertebral foreman
Slightly elongated in the vertical plane
Anterior wall: posterior boarder VB
Posterior wall: anterior part facet joints
Roof: inferior notch of the vertebrae above
Floor: superior notch of the vertebrae below
What passes through the intervertebral foreman
Spinal nerve root
Dorsal root ganglion
Segmental spinal artery
Spinal communicating veins
protection of Vertebral canal
Protected by PLL anteriorly and Lig flava poseriorly
