The Back

Question 1

What are the landmarks of the back?

Answer 1

The back has several key landmarks that are bony in nature. It runs from the first thoracic vertebrae (T1) to the coccyx, and from the medial border of the scapula along the posterior surface of the ribs down to the iliac crest.

Question 2

How much of the body surface does the back make up?

Answer 2

It makes up around 18% of the body surface.

Question 3

What are the compartments of the back?

Answer 3

The back is arranged into the vertebral column and 2 muscular compartments (superficial/extrinsic & deep/intrinsic)

Question 4

Explain the development of the vertebral column.

Answer 4

During development, the foetal spine is C-shaped in curvature (kyphotic) and secondary curves (lordotic) develop in the cervical region (when the baby begins to lift its head) and the lumbar region (when walking begins).

Question 5

What are the kyphotic and lordotic curves of the spine?

Answer 5

KYPHOITIC CURVES: Thoracic & sacro-coccygeal

LORDOTIC CURVES: Cervical & Lumbar

Question 6

What are some abnormalities of the spine?

Answer 6

Abnormalities can occur in the curvatures of the vertebral column such as Lordosis (over curvature of the lumbar region such as during pregnancy), Kyphosis (over curvature of the thoracic region - hunching) or Scoliosis (spine curves laterally)

Question 7

Give the general features of a typical lumbar vertebrae.

Answer 7

Body: size increases from L1 - L5; they are weight bearing
Epiphyseal ring: situated internally in the vertebral body
Vertebral foramen: posterior to vertebral body, creates the vertebral canal
Processes: extensions for ligament attachments
Vertebral arch: encloses space for the vertebral canal. (has lamina (dorsal) & pedicles)
Articular Processes: in lumbar vertebrae, the articular processes are joined in facet joints/zygapophysial joints, therefore they are lines with hyaline cartilage. These facet joints limit movement and protect the segment from excessive rotation and flexion. There is a facet capsule around the joint for protection.

Question 8

What are some key features of the thoracic vertebrae?

Answer 8

Demifacets: for articulation of the head of two ribs (above and below)
Intervertebral foramen: between two adjacent vertebrae
Foraminae: openings for basivertebral veins. These veins have no valves; allow for flow in both directions (easy communication). This can make it easy for cancerous cells to spread into the vertebral column due to no valves.

Question 9

What are some key features of the sacrum and coccyx?

Answer 9

Sacrum: five fused vertebrae, the S1 facet surfaces are in the coronal plane; has anterior and posterior sacral(IV) foraminae - for nerve roots and vessels (including sacral veins)

Coccyx: There an be a variable number of coccygeal vertebrae.

Question 10

What are the centres of ossification?

Answer 10

There are three primary centres in the body and each natural arch of the vertebrae. At puberty there are 5 secondary centres at the tips of spinous & transverse processes and upper/lower margins of the body (annular epiphysis)

The secondary centres normally close during late adolescence when the vertebral growth is complete.

Question 11

What are some key joints of the back?

Answer 11

IV discs
Lumbosacral
Facet joints

Question 12

Explain the two elements of an intervertebral disc

Answer 12

Nucleus Pulposis: acts as a shock absorber and keeps the vertebrae separated. Weight bearing forces cause the nucleus to bulge.
Annulus Fibrosis: distributes the pressure evenly across the discs and keeps the vertebrae together.

As an individual ages, the water content of the nucleus diminishes. The annulus is in layers of fibrocartilage which are perpendicular to each other meaning that the leads are easier to take at various angles (twisting whilst lifting is dangerous as only 50% of fibres are positions to resist the load)
The recurrent meningeal nerve (sensory & sympathetic fibres) innervates the disc, but only the outer third receives vessels and nerves.

Question 13

What are some features of Facet Joints/ Zygapophysial Joints?

Answer 13

In lumbar vertebrae, articular facets are joined for stability and limiting movement.
The synovial joint is surrounded by a fibrous capsule and is innervated by branches of the posterior ramus of two successive nerve roots (which also supply intrinsic muscles and skin of the posterior trunk)
The orientation of the facet surfaces dictate the direction of movements.

Question 14

What is significant about a fracture of the lumbosacral joint?

Answer 14

A fracture to the pars interarticularis can cause spondylolisis and listhesis of L4 on L5 and L5 on S1 which can be a source of lower back pain and may result in one vertebrae slipping forward in relation to an adjacent vertebrae.

Question 15

What are the contents of the vertebral canal?

Answer 15

Contains the spinal chord, which extends from the brain stem and terminates at L1/L2. There are also 33 vertebrae but only 31 spinal nerves (8C, 12T, 5L, 5S, 1Cox)

Spinal nerve roots leave the spinal chord (ant-motor; post-sensory) and combine to create a spinal nerve which leaves the vertebrae through the intervertebral foramen. The dorsal root ganglion is usually seen at the intervertebral foramen.

The spinal chord is surrounded by meninges (dura, arachnoid, pia mater). The dura and the arachnoid terminate at S1 but the pia extends to the coccyx forming the filum terminale. Since the spinal nerves extend beyond the termination of the spinal chord, these nerves for a structure called the cauda equina that is a bundle of nerves all originating from conus medullaris.

Question 16

What are the ligaments of the vertebral column?

Answer 16

Longitudinal: lie along the ANT and POST sides of the vertebral body (expanding over the IV discs.
Ligamentum Flavum: lines the POST wall of vertebral canal between the vertebrae, connecting the lamina of adjacent vertebrae. This consists of yellow elastic tissue which are almost perpendicular in direction. This elasticity serves to preserve the upright posture and assist the vertebral column in resuming it after flexion. It prevents buckling of the ligament into the spinal canal during extension.
Supraspinous: across the POST surface of spinous processes
Interspinous: between spinous processes of adjacent vertebrae
Intertransverse: Between transverse processes

Question 17

Give an explanation of blood supply and drainage of the back.

Answer 17

Blood supply comes from the posterior intercostals, lumbar arteries and lateral sacral arteries. Blood then drains to the external vertebral venous plexus.

Question 18

What is a lumbar puncture used for?

Answer 18

Epidural Anaesthesia is used to block spinal nerves for abdominal, pelvic and LL surgery. Especially common for pain relief during childbirth.

Question 19

What is Spina Bifida?

Answer 19

Occurs when the sacral region of vertebrae do not fuse appropriately and can lead to LL sensory & motor loss, incontinence and even a herniated spinal chord/nerves.

Question 20

Where in the back does the movement flexion occur?

Answer 20

mainly occurs in the lumbar spine and is enhanced by lumbar lordosis. Flexion causes the nucleus to project posteriorly. Hyperflexion stretches the sciatic nerve and may cause nerve root pain.

Question 21

Where in the back does the movement extension occur?

Answer 21

In extension, the thoracic spine has minimal movement (retains kyphosis) but the lumbar spine increases lordosis. Hyperextension increases stress on facet joints.

Question 22

Where in the back does the movement lateral flexion occur?

Answer 22

There is a small degree of lateral flexion in the thoracic spine but its limited by the ribs. Mostly occurs in the lumbar spine. A similar pattern is seen in Rotation.

Question 23

What influences movements in the back>

Answer 23

Movements of the back are influenced by:

- Thickness of IV discs - enhance movement (may be wedge shaped)
- Orientation of the articular facets - designed to limit movement to certain directions (thoracic allow coronal rotation; lumbar allow flexion/extension in 	sagittal plane; Lumbosacral limit movement in sagittal plane.)

Question 24

What are the superficial muscles of the back?

How are they innervated?

Answer 24

All attach and act on the upper limb. They include trapezius, latissimus dorsi, rhomboids & levator scapulae. The superficial muscles of the back all originate from cervical myotomes and are all innervated by the anterior rami, except for trapezius which is innervated by a cranial nerve.

The posterior rami penetrates but does not supply the superficial muscles, instead passing through to the skin.

Question 25

What are the intermediate muscles of the back? How are the innervated?

Answer 25

Intermediate muscles include serratus posterior, superior & inferior. These act on the ribs and are innervated by anterior rami. They are accessory muscles of respiration.

Question 26

What are the deep muscles of the back? What is their function?

Answer 26

Erector spinae made up of longissimus, spinalis & iliocostalis. These also have regional subdivisions (capitus, cervicis, thoracic, lumborum). These muscles tend to run medial to lateral across 5-7 vertebral segments and the lateral border of erector spinae corresponds with the angle of the rib, making it the most common site of rib fracture.
Transversospinalis are short muscles that run from lateral to medial across few vertebral segments (multifidus, rotatores etc.)

Erector Spinae are prime movers responsible for concentrically returning the flexed trunk to the upright posture. They also work eccentrically in controlling flexion. They are electrically ‘quiet’ in full flexion which is why it is dangerous to lift in a flexed posture.

Transversospinalis are segmental stabilizers that together with deep abdominal muscles form a corset around the trunk via the lumbar fascia. During back injury, these muscles waste rapidly, however core strengthening/contraction of deep abdominal muscles strengthen them.

Question 27

Explain the arterial, venous and neural supply systems of the back muscles.

Answer 27

Dorsal skin has superficial veins and lymphatics that pass anteriorly, along with arteries that pass through the muscles with the dorsal rami to the skin.

There are angiosomes on the back where segments of skin are divided into vascular territories.

The deep back muscles are innervated by the posterior rami which also supply facet joints and the overlying skin.

Question 28

What are some sources of back pain?

Answer 28

Disc Prolapse:
Penetration of the nucleus into (and through) annulus. Poor posture is likely to increase the load on the lumbar IV discs. It can lead to severe root compression
Some contributors to disc prolapse is as follows:
- 15 deg lumbar flexion - forcing nucleus posteriorly
- 15 deg rotation - max torsion in annulus, only 50% fibres resisting force
- slight LF forces nucleus postero-laterally
- overweight/fat
- keeping lower limbs fully extended
- picking up heavy object near opposite foot
- repeatedly doing this while using laryngeal muscles to call for help.

Disc Regeneration:
Often requires surgical intervention as regeneration can lead to fibrotic tissue and bone formation.

Spondylosis:
With aging, bones tend to lose water and become less dense (degenerative change) - spondylosis. This may cause an overgrowth of bone producing bony spurs (osteophytes) that can extend into the foramina, narrowing them (stenosis) and compressing exiting nerve roots.

Other causes of Back Pain:
Compressive Fractures- often associated with osteoporosis and can cause pain and limitation of function

Cardiovascular: aortic aneurism

Neoplasia: particularly in the elderly; and can be associated iwth tumour metastasis from the lungs, breasts, thyroid, kidney, prostate etc.

Infection

Ankylosis

Question 29

What are the two main divisions of lower back pain?

Answer 29

Lower back pain can be divided into two main types:
- Mechanical Type Pain: due to abnormal posture

• Compressive type pain: Also called neurogenic/nerve related pain; occurs when nerve roots are irritated or pinched. Commonly caused by herniated discs or spinal stenosis.