MSK 5 - The Lumbar Spine (anatomy + disorders) Flashcards
Describe the gross structure of the vertebral column
- 33 vertebrae (7 cervical, 12 thoracic, 5 lumbar, 5 sacral + 4 coccygeal)
- Sacral + coccygeal vertebrae fused to give 2 innominate structures (sacrum + coccyx)
What are the 4 main functions of the lumbar spine?
1) Support - of the thoracic spine + pelvis
2) Protection - of the spinal cord + cauda equina
3) Movement - highly flexible structure
4) Haemopoiesis - in red marrow
Describe the structure of an individual lumbar vertebra and the functions of the individual parts.
Split into: (see slide 5)
1) Anterior region - consisting of vertebral body (largest part), kidney shaped. End plates superiorly + inferiorly lined with hyaline cartilage. Linked to adjacent vertebral bodies by intervertebral discs. Main weight bearing part of vertebra (80% of weight) - made from 90% cancellous and 10% cortical bone.
2) Posterior region - consists of vertebral arch and vertebral foramen. Arch linked to adjacent vertebrae by articular processes. Foramen contains conus medullaris, cauda equina + meninges. Posterior region has 2 pedicles, 2 lamina + 7 processes (slide 9)
Why does the size of the vertebral body increase from superior to inferior? (i.e.: down the column)
- To resist the greater compressive forces distally (i.e.: there are more structure above it going further down the column so greater compressive force).
How are facet joints on the posterior region of lumbar vertebrae formed?
Which movements does their orientation allow?
What are the 4 primary movement of the lumbar spine?
- Facet joints are paired to form zygapophyseal joints from articulation of the inferior and superior articular processes.
- They are orientated at a 45* angle in the coronal plane, allowing flexion, lateral flexion + rotation//also preventing anterior displacement of vertebrae
- Flexion/Extension, Lateral flexion + Rotation
How many fused vertebrae are the sacrum and coccyx formed from?
Where do the spinal nerve exit the sacrum?
Sacrum = 5
Coccyx = 4
- Spinal nerve exit spinal canal via sacral foramina and sacral hiatus
- Coccyx is the remnant of the tail, which humans are very rarely born with (removed surgically)
What are the 3 types of joint in the lumbar spine - give an example of each.
1) Fibrous - non-mobile - e.g.: sacroiliac joint
2) Secondary cartilaginous - partially mobile - e.g.: intervertebral discs
3) Synovial joints - highly mobile - e.g.: facet joints
Describe the composition, structure and role of intervertebral discs
Composition = 70% water, 20% collagen, 10% proteoglycans.
Structure = 1) Nucleus pulposus (central region), is the remnant of the notochord, made from gelatinous, type 2 collagen. 2) Annulus fibrosus - surrounds pulposus, made from type 1 collagen and layers of annular bands. it is avascular + aneural.
Role = Accounts for 25% length of the vertebral column Changes heigh throughout day and with age. Acts as shock absorbers, highly resilient under compression (force applied from the nucleus onto the annulus) and keeps vertebrae separate.
What are the 5 ligaments of the vertebral column? What are their common functions?
Which ligaments are stronger - the anterior or posterior ones?
- Supraspinous, interspinous, ligament flavum, posterior longitudinal, anterior longitudinal (3 x posterior, 2 x anterior)
- Provide stability and limits to ROM
- Anterior ligaments are stronger.
What are the 2 anterior region ligaments of the lumbar vertebra, their positioning and their roles?
1) Anterior longitudinal ligament - anterior to vertebral body, mobile over intervertebral discs + prevents hyperextension
2) Posterior longitudinal ligament - runs throughout lumbar spine, weaker than the ALL, prevents hyperflexion.
What are the 3 posterior region ligaments of the lumbar vertebra, their positioning and their roles?
1) Supraspinous ligament - on the tips of the adjacent spinous/articulating processes. They are strong bands of white fibrous tissue, lax in extension and prevent hyperflexion.
2) Interspinous ligament - weak sheet of fibrous tissue that unite spinous processes.
3) Ligamentum flavum - contain elastin, found between laminae of adjacent vertebrae. Stretched during flexion.
What type of forces are applied through the spine during flexion?
How does force transmission change with age?
- Compression through anterior side, tension through posterior side.
Young = 80% of body weight through vertebral bodies, 20% through facet joints.
Elderly = disc dehydration, leading to loss of disc height 65% through vertebral bodies, 35% through facet joints.
What are the natural curvatures of the vertebral column segments?
- Cervical = lordosis (anterior curve)
- Thoracic = kyphosis (posterior curve)
- Lumbar = lordosis
- Sacral = kyphosis
- Coccyx = kyphosis
3 x kyphosis, 2 x lordosis.
Describe the structure of the vertebral column in the foetus and the evolution that occurs in the first 18 months.
- C-shaped (flexed in single curvature) - in a kyphosis - known as the primary curvature. This is retained throughout life in thoracic, sacral and coccygeal regions.
- Primary curvature is remodelled to add 2 x secondary curvatures
- 1) Cervical lordosis - when young child begins to lift its head
- 2) Lumbar lordosis - when the child begins to stand up and walk (this allows up to stand upright/separates us from other animal)
What happens to the shape to the vertebral column in old age?
What curvature exaggeration occurs in pregnancy + why?
- Secondary curvatures start to disappear + loss of disc height
- Continous primary curvature re-established.
- Exaggeration of lumber lordosis, allows pregnant women to keep head centred over pelvis as foetus growth causes shift in centre of gravity.
