Lumbar Spine Structure, Function and Common Disorders

Question 1

What is the vertebral column made up of?

Answer 1

33 vertebrae - 7 cervical, 12 thoracic, 5 lumbar, 5 sacral and 4 coccygeal - 24 separable/discrete single vertebrae capable of individual movement and 9 vertebrae fused to five 2 innominate structures (sacrum and coccyx).

Question 2

What are the functions of the vertebral column?

Answer 2

It’s the central bony pillar of the body, which supports the skull, pelvis, limbs and thoracic cage, protects the spinal cord and cauda equina and moves - high flexible structure of bone, intervertebral discs and ligaments and haemopoiesis (red marrow). It acts as a conduit through which the spinal cord passes and allows the spinal nerves to leave or join the cord at specific points.

Question 3

The weight of the body is projected into the lower limbs about a line passing centrally through the natural curvatures of the spinal column, how does this account for a change in size/shape as the column descends?

Answer 3

Vertebral bodies increase in size as the compression forces increase (inferiorly); the sacral vertebrae are fused, widened and concave anteriorly to transmit the weight of the body through the pelvis to the legs.

Question 4

What are the movements of the lumbar spine?

Answer 4

Flexion/extension, lateral flexion and rotation.

Question 5

Structure of a typical lumbar vertebra - general characteristics: _______ shaped vertebral body, vertebral _____ posteriorly and vertebral foramen for spinal cord and ___________. The vertebral arch gives rise to 7 processes, what are they?

Answer 5

Kidney
Arch
Meninges
1 spinous, 2 transverse, 2 superior and 2 inferior articular processes (for facet joints).

Question 6

The vertebral body is usually the largest part of the vertebra, made up of 10% _____________and 90% _____________ bone and is usually the main _______ bearing component - the main site of contact between __________ vertebrae. The end plates are articular surfaces covered with __________ cartilage (linked by IV discs, sizes increases inferiorly).

Answer 6

Cortical
Cancellous
Weight
Adjacent
Hyaline

Question 7

Apart from at vertebral bodies, where do lumbar vertebrae articulate and how?

Answer 7

2 superior articular processes (facets) face posteriorly and interlock with the vertebrae above them (opposite for inferior articular processes). These processes are lined with cartilage - synovial joints formed between vertebral arches of adjacent vertebrae. Strengthened by ligamentum flavum.

Question 8

What makes up the vertebral arch?

Answer 8

The lamina and the pedicel make up the vertebral arch. The lamina is between the spinous and transverse process, while the pedicle is between the vertebral body and the transverse/articular processes.

Question 9

What is the lumbar facet joint orientation and explain its purpose?

Answer 9

The interlocking design of the facet joint prevents anterior displacement and the orientation determines the flexion/extension permitted. The lumbar facet joint orientation is 45 degrees, so better for flexion/extension and worse for rotation.

Question 10

Intervertebral discs make up ___% of the length of the vertebral column (you lose height with ____) -70% _______, 20% collagen and 10% proteoglycans. They are slightly ________ shaped, to work with the curvature of the spine. The 2 regions are the _________ _________ (central) and ________ _________ (peripheral).

Answer 10

25
Age
Water
Wedge
Nucleus pulposus 
Annulus fibrosis

Question 11

Where do the spinal nerves emerge, out of the spinal column?

Answer 11

The intervertebral foramina.

Question 12

The annulus fibrosus has a complex structure, explain it along with its function.

Answer 12

Lamellae of annular bands (thin sheets of ring shaped bands) in varying orientations - outer layer is type 1 collagen and the inner bands are fibrocartilaginous. It surrounds the nucleus pulposus, acts as a shock absorber and is highly resistant under compression (stronger than a vertebral body).

Question 13

The nucleus pulposus is the remnant of the __________ and made up of gelatinous type ___ collagen. It has a high ____________ pressure, so changes in size throughout the day and with ____. It is surrounded entirely by the annulus fibrosus and is centrally located in an infant and then more __________ in an adult.

Answer 13

Notochord
II
Osmotic pressure
Age
Posteriorly

Question 14

Why is it suggested in manual handling to bend knees and not the back, when lifting something heavy?

Answer 14

Intervertebral discs are very strong in axial compression.

Question 15

Ligaments of the vertebral column provide stability, list 5 of the major ones.

Answer 15

Anterior longitudinal ligament, posterior longitudinal ligament, ligamentum flavum, interspinous ligament and supraspinous ligament.

Question 16

Describe (position and function) and compare the anterior and posterior longitudinal ligaments.

Answer 16

The anterior is stronger than the posterior. The anterior longitudinal ligament runs from the anterior tubercule of the atlas down to the sacrum, united with the periosteum of the vertebral bodies and mobile over the intervertebral discs. It prevents hyperextension. In contrast, the posterior longitudinal ligament runs from the body of the axis to the sacral canal. It continues superior to the axis as the ‘tectorial membrane’, is relatively weak (narrower), prevents hyperflexion and its position determines the site of disc prolapse.

Question 17

Describe the ligamentum flavum.

Answer 17

It’s yellow, because of its elastic fibres and is present between the laminae of adjacent vertebrae. It gets stretched during spine flexion.

Question 18

What are the interspinous ligaments for and how do they change along the spine?

Answer 18

The interspinous ligaments are relatively weak sheets of fibrous tissue uniting spinous processes along adjacent borders. They are well developed only in the lumbar region, provide stability in flexion and fuse with the supraspinous ligament.

Question 19

What makes up the supraspinous ligament, where and what happens to it when the spine moves?

Answer 19

Strong bands on white fibrous tissue connects the tips of adjacent spinous processes. It is lax in extension and tight in flexion (providing mechanical support for the vertebral column).

Question 20

In general, what type of forces do the anterior and posterior ligaments of the spinal column help to deal with?

Answer 20

The posterior help with tension forces and the anterior with compression forces.

Question 21

What does the sacrum articulate with?

Answer 21

The sacrum articulates with L5 superiorly, the ilium laterally and the coccyx inferiorly. (A posterior view shows the superior articular facets, medium sacral crests, posterior sacral foramina and sacral hiatus.

Question 22

The coccyx, is the remnant of the tail and we easily fractured in falls. Human tails are rare and easily removed (surgically), what does the coccyx articulate with?

Answer 22

The coccygeal cornua, superiorly.

Question 23

In utero, the spinal column is all kyphotic (concave anteriorly, as in flexion), what are the curvatures in an adult?

Answer 23

Cervical lordosis, thoracic kyphosis, lumbar lordosis and sacral/coccygeal kyphosis.

Question 24

What is the advantage of the 4 distinct curvatures of the sinusoidal profile in a young adult?

Answer 24

It confers great flexibility and resistance.

Question 25

The 2 kyphoses (________) of the spine are continuations of the __________ curvature of the foetus and the lordoses (C and L) are _________. The spinal column is _____________ first when a young child lifts its head and then with crawling and walking.

Answer 25

T and S-C
Primary
Secondary
Remodelled

Question 26

Where the centre of gravity passes through the vertebral column, you might find weak points, where?

Answer 26

C1-2, C7-T1, T12-L1 and L5-S1.

Question 27

What is the term for when secondary curvatures start to disappear in old age and a continuous primary curvature is reestablished?

Answer 27

Senile kyphosis.

Question 28

In what situation is the physiological curvature slightly modified?

Answer 28

Exaggeration of lumbar lordosis in pregnancy.

Question 29

In a lumbar puncture, where are you trying to puncture (why) and how do you get there?

Answer 29

You are aiming for between L4 and L5 (after conus medullaris so only mobile spinal nerve roots, not the cord - least chance of neurological damage), so palpate to the iliac crest then head to the midline.

Question 30

When performing a lumbar puncture, what does the needle travel through to get to the cerebral spinal fluid?

Answer 30

Skin, subcutaneous tissue, supraspinous ligament, interspinous ligament, ligamentum flavum (which is thick, so provides a bigger give), epidural fat and veins, dura mater (final give) then arachnoid mater (middle of 3 layers that makes up meninges)to get to the subarachnoid space.

Question 31

Lower back pain is common, how common?

Answer 31

50% of the U.K. population report episodes of back pain for at least 24hrs in a year - half of these last over 4 weeks. It is abnormal not to have it.

Question 32

Mechanical back pain occurs when the spine is loaded (sitting/standing), what relieves and aggregates it and what predisposes you?

Answer 32

It is relieved by set and gets worse with exercise, it is intermittent and often triggered by innocuous activity. Predisposed if: overweight, unhealthy lifestyle, deconditioned core muscles. Behavioural modifiers may affect recovery time (think similarly to mental health - job, beliefs/fears, relationships, accidents, benefits).

Question 33

What happens in disc degeneration and ‘marginal osteophytosis’?

Answer 33

The nucleus pulposus can dehydrate with age, so height of the intervertebral discs decrease. The load stress on the intervertebral discs alter, leading to reactive marginal osteophytosis adjacent to the affected end plates. As disc space decreases in height, increased stress on facet joints lead to osteoarthritis (innervated by meningeal branch of spinal nerve -> pain). Decreased size of intervertebral foramen and compression of the spinal nerve.

Question 34

If given sick leave, how likely is it for patients with back pain to return to work?

Answer 34

After a sick leave of 6 months, 50% return to work and if it’s 1 year, only 5%, which is why it’s important to get patients back to day to day life quickly.

Question 35

What are the 4 mechanisms of a ‘slipped disc’?

Answer 35

Disc degeneration - chemical changes with ageing lead to dehydration and bulge, Prolapse - protrusion of np with slight impingement into spinal canal,
Extrusion - np breaks through ap, but remains in the disc space and
Sequestration - np breaks through at and separates from main body of disc in the spinal canal.

Question 36

What happens in the long term with a ‘slipped disc’ caused by sequestration?

Answer 36

The disc material won’t return to the main body and is inflammatory, so is lost and there’s irreversible change - symptoms resolve when there is no longer fragment in the canal.

Question 37

Where are slipped discs most likely to occur?

Answer 37

They most commonly occur at L4/5 or L5/S1. It will usually herniate posters-laterally, causing comoresseion to move the posterior spinal nerve root. Type of disc prolapse: paracentral (96%), far lateral (2%) and canal filling (CES/cauda equnia syndrome-2%).

Question 38

What is sciatica?

Answer 38

Compression of the nerve roots which contribute to the Sciatic nerve (L4-S3) - mostly from a slipped disc.

Question 39

Where is the pain/parasthesia in sciatica?

Answer 39

It is based on dermatomes, so L4-medial leg, L5-lateral anterior leg and medial/central dorsum of foot, S1- back of heel, sole of foot and some lateral dorsum, S2- posterior thigh and posterior, superior leg, S3-inner buttock.

Question 40

With a prolapsed disc, which nerve root is compressed and what happens in the long term?

Answer 40

Paracentral is the most common direction of a prolapse, so it won’t hit the exiting nerve root, as it’s already left the spinal canal, so it irritates the one below (far lateral prolapse does hit exiting nerve root). In prolapsed discs for 30-50 year olds, 90% resolve in 3 months (wait ages for consultation).

Question 41

What happens in Cauda Equina Syndrome (CES)?

Answer 41

There’s a canal-filling disc, compressing the lumbar and sacral nerve roots in 30-50 y/o - no CSF behind the disc prolapse, as the canal is full of the disc material - bilateral sciatica, perianal numbness, painless retention of urine, urinary/faecal incontinence - need to treat in 48hrs of sphincter symptoms to be in a good prognostic group, or intermittent self catheterisation, sexual dysfunction etc.

Question 42

Lumbar canal stenosis:
Occurs in the _________ - disc _______, Arthritis in _____ joints - expand as as ligamentum flavum ages, it expands - restricts space for _______. Could lead to _____________: pain in legs when walking - here neurogenic, but could be vascular.

Answer 42

Elderly
Bulge
Facet
Nerve
Claudication

Question 43

Explain a vascular cause for claudication.

Answer 43

Venous engorgement - more blood flow, but less scope for venous drainage, leading to blood pooling and sciatica.

Question 44

Why is spondylolisthesis and the different types?

Answer 44

A slip forwards of the vertebra above on the vertebra below. Types:
Dysplastic - abnormality in shape of facet joint,
Isthmic - defect in pars articularis (in between superior and inferior articular processes),
Degenerative (arthritic),
Iatrogenic or
Pathological.

Question 45

How do Isthmic and and Degenerative spondylolisthesis present?

Answer 45

Isthmic spondylolisthesis presents with back pain and L5 sciatica, as the arch is not intact, no central canal stenosis - present in adolescence/adulthood once disc starts to age.
Degenerative spondylolisthesis presents with claudication as the posterior arch is intact, so stenosis develops (same progression as lumbar canal stenosis).

Question 46

How does lumbar canal stenosis progress?

Answer 46

70% stay the same, 15% get progressively worse and 15% get better - treat when restricted walking distance (claudication) affects quality of life.