Download Muscles and movements of back

MD 2016
Back Muscles & Movements
Applied Anatomy
A/Prof Chris Briggs
Anatomy & Neuroscience
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Learning Objectives
• Movements of back & effects on nerve roots.
• Organisation & functions of back muscles
(superficial, intermediate & deep layers).
• Supply systems - blood & nerve supply
• Disc prolapse & pain associated with nerve
root compression
• Disc degeneration & its consequences
Suggested pre-reading
Clinically Orientated Anatomy, Moore 7th ed.
Chapter 4, Back,.
Movements of Back
Flexion
Extension
CIBA Clinical Symposia: Low Back
Pain
Flexion mainly occurs in lumbar spine
– enhanced by lumbar lordosis.
Flexion causes nucleus to project
posteriorly
Hyperflexion stretches sciatic nerve &
may cause nerve root pain
In extension thoracic spine has
minimal movement (retains
kyphosis) but lumbar spine
increases lordosis
Hyperextension loads facet
surfaces – ‘closes joints down’
Lateral flexion
Rotation
Small degree LF in thoracic
spine but limited by ribs. Most
occurs in lumbar spine
Similar pattern in rotation
Movements of Back
(1) Enhanced by:
Thickness of IV-discs - note wedgeshape at L5/S1
(2) Limited by:
Orientation of articular facets –
control movement (in certain
directions)
Thoracic – permit
rotation in coronal
plane
Lumbar – permit
flexion/extension in
sagittal plane
Visible Human Project - National Library of
Medicine
Lumbosacral –
limit movement
in sagittal plane
Netter, F.H. Interactive Atlas of Human Anatomy. 3rd ed. Figs. 143A
Muscles of back – regional & functional
• (1) Superficial (extrinsic)
muscles - all attach to and act on
the upper limb.
• They include:
- trapezius
- latissimus dorsi
- rhomboids
- levator scapulae
• Superficial muscles of the back
(except trapezius) originate from
cervical myotomes & are
innervated by anterior rami.
Nerves remain faithful to
embryological origin
Grant’s Method of Anatomy 11th ed
(1989) Williams & Wilkins ISBN 0-68300374-7 Fig 29-5
Image from Anatomedia ‘General
Anatomy’ module
Superficial muscles of back
Anatomedia: Back Dissection module
Note posterior rami penetrating (but not
supplying) superficial muscles – passing to skin
Intermediate muscles of the back
Intermediate muscles (serratus
posterior superior and inferior)
act on the ribs and are
innervated by anterior rami.
Accessory muscles of respiration
Deep muscles of the back
Deep muscles may be organized
into:
- Erector spinae (tend to run
medial to lateral across 5-7
vertebral segments)
- Spinalis, Longissimus &
Iliocostalis
- Regional subdivisions: capitis,
cervicis, thoracic, lumborum
-** Lateral border of erector
spinae corresponds with angle of
rib – most common site of rib
fracture
-Transversospinalis (short
muscles run from lateral to medial
across fewer vertebral segments)
-multifidus, rotatores.
Grant’s Method of Anatomy 11th ed (1989) Williams & Wilkins ISBN 0683-00374-7 Fig 29-9 & 10
Function of deep back muscles
(1) Erector spinae are prime
movers, responsible for
(concentrically) returning
the flexed trunk to the
upright (extended) posture.
•They also work
eccentrically in controlling
flexion
•They are electrically
‘quiet’ in full flexion –
dangers of ‘lifting’ in
flexed posture
Muscles & Movements MA MacConaill & JV Basmajian, Williams &
Wilkins 1969
(2) Transversospinalis
- segmental stabilisers
- act together with deep
abdominal muscles (esp.
transversus abdominis)
forming ‘corset’ around trunk
via lumbar fascia
- waste rapidly following back
injury
- back strengthened via
contraction of deep abdominal
muscles - ‘core strengthening’
Netter, F.H. Interactive Atlas of
Human Anatomy. 3rd ed. Figs.
143A
• Dorsal type skin
• Superficial veins & lymphatics pass
anteriorly
• - veins to azygos system
• - lymphatics to axillary (inguinal)
nodes
• Arteries pass through muscles with
dorsal rami to skin
Blood vessels & segmental supply
Angiosomes of back
Angiosome = ‘vascular
territory’
Nerve supply of deep back muscles
Posterior rami
innervate:
- facet joints
- deep back muscles
- overlying skin
Thoracic DR
Dermatomes
Lumbar DR
Peripheral nerve
supply (posterior rami)
& dermatomes of back
Back pain
• Compressive or neurogenic (nerve
related) pain occurs when nerve
roots are irritated or pinched.
• Common causes:
- herniated discs
- spinal stenosis
Disc prolapse
Penetration of nucleus into (and
through) annulus.
3 types:
Postures likely to increase
loads on lumbar I-V discs
Posterior longitudinal
ligament
Netter, F.H. Interactive Atlas of
Human Anatomy. 3rd ed. 146B
Reflex muscle
spasm
Contributors to disc prolapse
-15 deg lumbar flexion – forces
nucleus posteriorly
-15 deg rotation – max torsion in
annulus, only 50% fibres resist force
- slight LF forces nucleus posterolaterally
- be overweight
- keep lower limbs fully extended
- pick up heavy object near opposite
foot
- repeatedly do this while using
laryngeal muscles to call for help
Nerve root compression
Direction of lumbar
disc prolapse – note
nerve root in upper
part of foramen
Anatomedia: ‘Back’ module
Nerve root affected by
lumbar disc prolapse –
note narrow lumbosacral
foramen, large
lumbosacral disc & S1
nerve root
FRACTURES
Pars inter
inter-articularis
Spondylolisis &
‘listhesis’ of L4 on L5
and L5 on S1. Fracture
at pars inter-articularis
Spondylosis & spinal stenosis
• With aging, bones tend to lose water, become less dense (degenerative change) spondylosis - may cause an overgrowth
of bone producing bony spurs (osteophytes) that can extend into
the foramina, narrowing them (stenosis) & compressing exiting
nerve roots.
CIBA Clinical Symposia: Low Back
Pain
Degenerative & systemic conditions
www.arthritisvic.org.au/Arth
ritis/ankyspond.htm
Images courtesy Prof Kim Bennell
Compression fracture – often
associated with osteoporosis.
Pain & limitation of function
Other causes of back pain:
Cardiovascular (eg. aortic aneurism)
Neoplasia (particularly in older person)
- Tumour metastasis (from lung, breast,
thyroid, kidney, prostate)
Infection
Ankylosing spondylitis. Affects
spine, joints of pelvis ultimately
leading to fusion (ankylosis)