MSK Session 3 (Lecture 3.2) Flashcards
What are the two groups of muscles of the back?
Intrinsic and extrinsic
What can extrinsic back muscles be divided into?
Superficial and intermediate groups
What do the posterior axio-appendicular muscles do?
Attach the upper limb to the trunk
What are the three groups of AAMs? Give examples of each.
1) Superficial - trapezius & Latissimus dorsi
2) Deep - levator scapulae & rhomboids
3) Scapulo-humeral : deltoid, teres major & 4 rotator cuff
What nerve innvervates the trapezius muscle?
Accessory
Describe the anatomy & function of the trapezius muscle. (3 points)
1) Direct attachemnt of pectoral girdle to trunk
2) Act on scapulothoracic joint
3) Divided into 3 parts :
Superior (elevates scapula)
Middle (retracts scapula)
Inferior (depresses scapula)
What nerve innervates the Latissimus dorsi and where does it originate from?
Thoraco-dorsal nerve
From posterior cord of brachial plexus
Describe the anatomy & function of the latissimus dorsi muscle. (3 points)
1) Large, fan shaped with a wide origin and narrow insertion
2) Extends from: lower thoracic vertebrae, thoracolumbar fascia & iliac crest to floor of intertubecular groove.
3) Powerful adductor of arm, extends arm at shoulder and medial rotator
Which nerves innervate the levator scapulae muscle?
Dorsal scapular & Cervical
Describe the anatomy & function of the levator scapulae muscle (2 points)
1) Elevates scapula
2) Rotates scapula depression GC
Which nerve innervates the rhomboids major and minor and where does it come from?
Dorsal scapular (C5 root of BP)
Describe the anatomy & function of the rhomboids muscle. (3 points)
1) Attaches at the medial border of scapula.
2) Retracts scapula
3) Rotates scapula depressing GC (medial rotation?)
Describe the anatomy & function of the deltoid muscle. (2 points). What nerve supplies this muscle?
1) Axillary nerve
2) Inserts in the deltoid tuberosity
3) Anterior fibres (clavicular) = flexion of arm Middle fibres (acromial) = abducts arm from 15-90 degrees
Describe the anatomy & function of the teres major muscle. (2 points) What nerve supplies this muscle?
1) Lower subscapular
2) From inferior angle of scapula to upper humerus
3) Medial rotator and adductor of arm
What is a bursa(e)?
Small sacs filled with synovial fluid. Lined by synovium reducing friction upon movement.
Where does the shoulder joint move?
1) Glenohumeral and 2) Scapulothoracic (2:1)
Describe the articulating surfaces at the GH joint.
1) Head of humerus
2) Glenoid cavity of scapula
3) Lined by HC
4) 4:1 area disproportion
5) Glenoid cavity deepened by glenoid labrum
Why is the SJ unstable?
1) GC shallow
2) Disporportion of articular surfaces
3) Multiplanar movements
4) Lax capsule
How is stability achieved at the SJ?
1) Rotator cuff (most important)
2) Other muscles
3) Ligaments
4) Capusle
Describe the anatomy of the capsule.
1) Attached to : Glenoid labrum + margins of GC of scapula, anatomical neck of humerus
2) Bridges ITG, dips down medially to surgical neck (provides lax for full abduction)
3) Small opening anteriorly (where synovium communicates with subscapular bursa)
Describe the anatomy of the synovium at the SJ (4 points)
1) Synovium lines capsule + bone upto edge of articulating surfaces
2) Tendon of long head of biceps brachii lies within joint cavity (attached to supra glenoid tubercule of scapula)
3) Tubular sleeve of synovium refelcted back around biceps tendon like a tube
4) Synovium + joint cavity is continuous with subscapular bursa through a gap in the capsule.
What are the three inctracapsular ligaments?
1) Superior, middle and inferior
Describe the intracapsular ligaments.
1) 3 fibrous bands extending between glenoid labrum & humerus
2) Part of the fibrous capsule & reinforces capsule anteriorly
What are the three extracapsular ligaments?
1) Coracoacromial, coracohumeral, transverse humeral
Describe the extracapsular ligaments.
1) CAL : most important
2) CHL : Base of coracoid process to anterior part of greater tubercule
3) THL : holds tendon of long head of biceps in place during shoulder movement.
What is the CAA? Describe it.
Coracoacromial arch = CAL + Acromion + coracoid process
Strong osseoligamentous structure
Overlies humeral head
Prevents its upper displacement of humerus
Clinically important in the ‘painful arc’ syndrome
What are the muscles of the rotator cuff and where they are inserted?
1) Supraspinatus - greater tubercle
2) Infraspinatus - “
3) Teres minor - “
4) Subscapularis - lesser tubercule
What are the actions of the RC muscles?
1) Supraspinatus - initiation and first 15 degrees of abduction
2) Infraspinatus - lateral rotation of the arm
3) Teres minor - lateral rotation of the arm, weak adductor
4) Subscapularis - medial rotation of the arm
Which nerves innervate the RC muscles?
1) and 2) - Suprascapular , C5+6
3) Axiallry
4) Upper and lower subscapular
What is the tendinous cuff?
Tendons of muscles blend to form a cuff which fuses with a capsule therefore strengthening it.
What lies within the space between the acromion and head of humerus? When are these at risk of impingement?
1) Subacromial bursa
2) RC tendons
3) Capsule
4) Tendon of long head of biceps
During abduction
Where is the long head of triceps attached to?
Infra glenoid tubercule
What are the two bursa around the GHJ?
1) Subscapular - facilitates movement of tendon of SSC muscle over scapula
2) Subacromial - facilitates movement of SSP tendon under CAA + deltoid muscle over SJ capsule + greater tubercule of humerus
What is painful arc syndrome?
SSP tendon rubbing under CAA
Inflammation of bursa causing subacromial bursitis - causes pain on abduction of the arm between 50-130 degrees
OR
Impingement of inflamed RC tendons
Causes subacromial bursitis
Supraspinatus tendonitis
Degen + rupture of tendons
Which people are predisposed to acquiring PAS?
1) Repetitive overuse e.g. sporting activities, painter
2) Older people
Avascularity of SSP tendon
In which direction is the GHJ dislocated?
Inferiorly
How is a GHJ dislocated?
Trauma on a fully abducted arm
How is a GHJ defined clinically?
Anterior dislocation because the humeral head located anteriorly, due to pull of adductors.
How can the axillary nerve injured?
Injured during dislocation»_space; close relation to inferior part of joint capsule
How is an axillary nerve injury indicated?
1) Paralysis of deltoid muscle with loss of abduction
2) Loss of sensation in a small area of the skin “regimental badge area” over central part of deltoid supplied by the superior lateral cutaneous nerve
