Which overall group does posterior axio-appendicular muscles belong to?
- Intrinsic
What are the two different overall types of muscles in the back?
- Intrinsic
- Extrinsic
What are the three types of posterior axio-appendicular muscles?
- Superficial group: Trapezius and latissimus dorsi
- Deep muscles: Levator scapulae and rhomboids
- Scapulo-humeral: deltoid, teres major and 4 rotator cuff muscles
Where is the trapezius attached and on which joint does it act?
- Direct attachment of pectoral girdle to trunk
- Acts on scapulo-thoracic joint
What three parts are there to the trapezius and what body movements do they allow?
- Superior: elevates scapula (e.g. Shrugging)
- Middle: retracts scapula (e.g. Squaring of shoulders)
- Inferior: depresses scapula
How does the scapula rotate?
- Superior and inferior parts of trapezius act together to rotate the scapula upwards and outwards on chest wall (elevating glenoid cavity)
- Serratus anterior muscle also aids upwards rotation of scapula
What does scapula rotation allow?
- Abduction of arm above horizontal (90 degrees)
Describe the latissimus dorsi.
- Wide origin
- Narrow insertion
- Large
- Fan shaped
What are the attachments for the latissimus dorsi?
- Last 6 thoracic vertebrae
- Thoracolumbar fascia
- Iliac crest to floor of intertubercular groove
What body movements is the latissimus dorsi responsible for?
- Powerful adductor of arm at shoulder joint
- Extends arm at shoulder joint
- Medial rotator
What nerve supplies the latissimus dorsi?
- Thoraco-dorsal nerve
What is the role of rhomboids major and minor?
- Retracts scapula
- Rotates scapula depressing glenoid cavity
What is the role of levator scapulae muscle?
- Elevates scapula
- Rotates scapula depressing glenoid cavity
Which nerves supply the levator scapulae muscle?
- Dorsal scapula nerve
- Cervical nerve
Which are the scapulo humeral muscles?
- Deltoid
- Teres major
- Rotator cuff muscles
What are the three main fibres of the deltoid muscle and what movement do they allow?
- Anterior fibres (clavicular): flexion of arm at SJ
- Middle fibres (acromial): abducts arm from 15-90 degrees
- Posterior fibres (spinal): extends arm at SJ
What is the main role of the deltoid?
- Powerful abductor of arm at SJ
What nerve supplies the deltoid?
- Axillary nerve
What is the origin and insertion of the deltoid?
- Anterior, upper surface of the clavicle
- Acromion
- Spine of scapula
What is the origin and insertion of the teres major?
- Origin: Inferior angle of scapula
- Insertion: Upper humerus
What is the main actions that the teres major plays a role in?
- Adducts arm
- Medial rotation
Which nerve supplies the teres major?
- Lower subscapular nerve
Outline the steps to describe a joint.
- Articular surfaces
- Capsule
- Ligaments
- Movements
- Blood supply
- Nerve supply
What is the shoulder joint also known as?
- Gleno-humeral joint.
Describe the Gleno-humeral joint.
- Synovial ball and socket joint
- Wide range of movements in multiple planes
- Lined by hyaline cartilage
- Glenoid cavity is deepened by glenoid labrum (ligament)
What is a bursae?
- Small sac with synovial fluid to aid movement.
Why is the SJ unstable?
- Glenoid cavity is shallow
- Disproportionate articular surfaces for joint
- Loose capsule (lax)
What stabilises the SJ?
- Rotator cuff muscles
- Ligaments
- Capsule
Why is the SJ so unstable?
- Needs to be able to cover multiplanar movement.
Where is the glenoid capsule attached to?
- Glenoid labrum and margins of glenoid cavity of scapula
- Anatomical neck of humerus
What is the ‘path’ of the capsule?
- Bridges intertubercular groove
- Dips down medially to surgical neck (to provide laxity for full abduction)
Why is there a small opening anteriorly in the glenoid cavity?
- So synovial membrane of SJ can communicate with subscapular bursa
Describe the synovial membrane’s role in the gleno-humeral joint.
- Synovial membrane lines capsule and bone up to edge of articulating surfaces.
- Tendon of long head of biceps lies within joint cavity
- Tubular sleeve of synovium reflects back around bicep’s tendon
- Synovium and joint cavity is continuous with subscapular bursa via gap in capsule.
What components is the extra capsular ligament comprised of?
- Coracoacromial ligament (CAL): between acromion and coracoid process
- Coracohumeral ligament (CHL): coracoid process to anterior part of greater tubercle
- Transverse humeral ligament: holds tendon of long head of biceps in place during movement.
What is the position and role of the Coracoacromial arch?
- Stong osteoligamentous structure
- Overlies humeral head
- Prevents upper displacement of humerus
What are the rotator cuff muscles?
- Collective name for 4 short muscles:
- Supraspinatus
- Infraspinatus
- Teres minor
- Subscapularis
What are the actions of the individual muscles of the rotator cuff?
- Supraspinatus: initiation and 1st 15 degrees of abduction
- Infraspinatus: Lateral rotation of the arm
- Teres minor: Lateral rotation of arm (weak adductor)
- Subscapularis: medial rotation of arm
How do the muscles act as a cuff on the glenoid-humeral joint?
- Tendons blend together to form a cuff
- Tendinous cuff fuses with capsule
- Inserted to greater and lesser tubercles close to articular region
- Tone of the muscles hold them close to the glenoid cavity
- Supraspinatus tendon’s separated from CAA by subacromial bursa
There’s a space between acromion and head of humerus what’s in this space and how large is the space?
- ~1-1.5cm
- Subacromial bursa
- Rotator cuff tendons
- Capsule
- Tendon of long head of biceps
What are the muscles stabilising SJ?
- Deltoid
- Long heads of biceps and triceps
What is the role of the subscapular bursa?
- Facilitates movement of tendon of Subscapularis muscle of scapula
- Communicates with joint cavity
What is the role of the subacromial bursa?
- Facilitates movement of supraspinatus tendon under CAA, deltoid muscle over SJ capsule and greater tubercle of humerus
What damage to the subacromial bursa may lead to restriction of movement?
- Inflammation of bursa-subacromial bursitis
- Pain on abduction of arm from 15-130 degrees
What provides overall stability of the SJ?
- Tendons of rotator cuff
- Coracoacromial arch (CAA)
- Gleno-humeral ligaments
- Coracohumeral ligament
- Deepening of GC by glenoid labrum
- Splinting effect of long heads of biceps/triceps
Which type of dislocation of the gleno humeral joint is most common and why?
- Anterior
- As humeral head locates anteriorly due to pull of powerful adductors
- Humeral head comes to lie below coracoid process
Why may an initial dislocation lead to recurrent dislocation?
- Capsule and rotator cuff may tear
- Poor healing
- Recurrent dislocation.
What nerve may be injured during a dislocation of the shoulder?
- Axillary nerve
What signs are there of axillary nerve injury?
- Paralysis of deltoid muscle - loss of abduction
- Loss of sensation in regimental badge area - supplied by lateral cutaneous nerve
What problems may tendons of the rotator cuff rubbing under CAA lead to?
- Irritation and inflammation of rotator cuff tendons/SA bursa
- Subacromial bursitis
- Supraspinatus tendinitis
- Rotator cuff injury
- Degeneration and rupture of tendons
What are the risk factors associated with rotator cuff injuries?
- Repetitive overuse - e.g. sporting activities/working involving overhead arms (painter)
- Old age - degeneration
- Avascularity of supraspinatus tendon.