2.3 Spinal mechanics & spinal disorders Flashcards
Facet orientations
Thoracic - rotation in coronal plane, limited by ribs
Lumbar - permit F/E in sagittal plane
Lumbosacral - limit movement in sagittal
*sacral facets also prevent sliding forward displacement of L5 (aided by ligaments, muscles, fascial capsules)
Where does flexion in the back usually occur?
- Mainly occurs in lumbar spine - enhanced by lumbar lordosis.
- Hyperflexion stretches sciatic nerve & may cause nerve root pain.
- Flexion causes nucleus to project posteriorly.
Extension of back
- Thoracic spine has minimal movement/retains kyphosis
- Lumbar increases lordosis
- Hyperextension increases stress on facet joints - ‘closes them down’
Lateral flexion & rotation of the back
- Small degree in thoracic spine but is limited by ribs.
- Most occurs in lumbar spine.
When are the back muscles electrically ‘quiet’?
In full flexion.
-dangers of ‘lifting’ in flexed and rotated posture
What is the function of transversospinalis?
- segmental stabiliser of the back
- together with deep abdominal muscles form a ‘corset’ around trunk connecting via lumbar fascia
- strengthened via contraction of deep abdominal muscles (transversus abdominis)
What types of low back pain are there?
- Mechanical type pain - muscle strains, disc prolapse
2. Compressive type pain - typically of nerve root
What happens to deep back muscles following injury?
Pain inhibits muscle contraction, consequently, transversospinalis (TrA) contraction has delayed onset and waste (can be retrained to stabilise lumbar spine).
*diff parts of body are recruited to contract together - integrated movements to facilitate each other’s role, but with injury, there is a significant delay in the contraction of TrA
How do you induce disc prolapse?
- lumbar flexion at 15deg to force nucleus posteriorly
- rotation 15deg produces maximum torsion in annulus where only 50% of the annulus fibres can resist force
- slight LF forces nucleus postero-laterally
- be fat/overweight
- contract trunk muscles
What are the stages of disc prolapse?
Disc prolapse is the penetration of nucleus into (and through) the annulus.
- Bulge
- Herniation
- Extrusion
Prolapse is generally postero-lateral due to PLL.
What do the posterior rami innervate?
- facet joints
- deep back muscles
- overlying skin
What is compressive type pain?
- occurs when nerve roots that leave the spine are irritated/pinched
- common causes: herniated discs, spinal stenosis (anything causing narrowing of bony tube that spinal nerves run in)
Disc prolapse & irritation of nerve roots: what does L5/S1 prolapse result in?
Affects S1 nerve (sciatic n’)
Pain = over hip, postero-lateral thigh, leg & heel. Partial sensory loss in S1 dermatome (back of calf, lateral heel)
Movement = restricted & painful. Weakened plantar flexion (difficulty walking on toes)
Signs = limited straight leg raise, diminished sensation. Wastage of calf muscles lateral foot, diminished or absent ankle reflex.
**L4/L5 also common
Disc & facet joint injury at cervical levels
- Less common than lumbar spine due to structure and loading
- Trauma usually related in F +/- rotation
- May impinge on cord +/- nerve roots in vertebral canal
Whiplash injury = acceleration of head in antero/posterior direction
Facet capsule & articular surfaces, and supporting ligaments are particularly susceptible to injury in hyperextension.
What is spondylosis?
Bones lose water and become less dense with age, hence spondylosis is the resultant overgrowth of bone producing bony spurs (osteophytes) to limit the movement of these bones.
The osteophytes can extend into the foramina, narrowing them (stenosis) and compressing exiting nerve roots.
What happens with degenerative arthritis in the cervical spine?
With the degeneration of IV discs, uncinate processes may come in contact and create osteophytes that can irritate nerve roots and the vertebral artery.
- hypertrophy of intra-canal structures
ie. Ligamentum flavum can begin to ossify in the elderly.
Back fractures on the anterior side
Compression fracture - assoc. w osteoporosis. Results in pain and limitation of function.
Ankylosing spondylitis - affects spine, joints of pelvis, ultimately leading to fusion of spine, commonly affects males in 20s
What are other causes of back pain (non vertebral/spinal cord related)?
- Cardiovascular - aortic aneurism
- Neoplasia - tumour metastasis (lung, breast, thyroid, kidney, prostate) - particularly in older persons
- Infection
Non-mechanical back pain
Back pain may be due to systemic causes - possibly aortic aneurism, metastasis of cancer cells to back.
Possible patient: elderly male with back pain & associated urinary problems
Symptoms: back pain and bilateral radiating pain to thighs
- Patient received forceful manipulation of low back
- Deep aching pain radiating to both thighs
- Aggravated by activity, difficulty walking
- Incontinence of urine, loss of sphincter tone
- Loss of sensation around vulva & anus
Cauda equina compression
- caused by midline IV disc prolapse
- associated w loss of reflexes for pelvic viscera, sensory loss involving sacral nerves (‘saddle anaesthesia’)
What are the compartments (fascia) of the neck?
- Skin, superficial fascia
- Investing fascia (trapezoid, sternomastoid)
- Pretracheal fascia (thyroid gland, larynx)
- Buccopharyngeal fascia (retropharyngeal space)
- Prevertebral fascia (cervical spine, muscle)
- Carotid sheath
What is the Jefferson’s fracture?
Mechanism: Fall onto vertex of skull eg. dive into shallow water. Bilateral fracture anterior arch + pedicle (bony ‘ring’ phenomenon)
Where does the spinal cord at various stages of development?
End 1st trimester = S5
End 2nd trimester = S1
Birth = L3
Adult = L1/L2
What is epidural anesthesia used for?
To block spinal nerves for abdominal, pelvic & LL surgery. Especially for pain relief in childbirth.
Spina bifida
LL sensory & motor loss
Incontinence
What are the alterations of vertebral column in scoliosis?
- spinous processes deviate to concave side
- vertebral body distorted to convex side
- ipsilateral rib pushed laterally & anteriorly
- contralateral rib pushed posteriorly - thoracic cage narrowed
- vertebral canal & IV foramen narrowed on convex side
