Trauma and orthopaedics (4): The shoulder Flashcards
the scapula
Also known as the shoulder blades. It articulates with the humerus at the glenohumeral joint, and with the clavical at the acromioclavicular joint.
- Connects the upper limb to the trunk
- Triangular, flat bone
the clavicle
The collarbone extends between the manubrium of the sternum and the acromion of the scapula.
- Long bone
- Can be palpated along its length
- In thin individuals it is visible under the skin.
- Main functions
- Attaches the upper limb to the trunk as part of the shoulder girls
- Protects the underlying neurovascular structures supplying the upper limb
- Transmits force from the upper limb to the axial skeleton
joints between the clavicle and scapula
Acromioclavicular
- Plane type synovial joint
- Located at the lateral end of the clavicle
Sternoclavicular joint
- Synovial joint between the clavicle and the manubrium of the sternum
- Only attachment of the upper limb to the axial skeleton
- Very mobile joint
- Can function more like a ball-and-socket type joint
the shoulder joint
articulating surfaces of the glenohumeral joint
- Head of the humerus with the glenoid cavity of the scapula
- Head of humerus= much larger than the glenoid fossa
- Gives wide range of movement at the cost of inherent instability
- To reduce disproportion in surfaces, the glenoid fossa is deepened by the glenoid labrum
- Fibrocartilage rim
- Head of humerus= much larger than the glenoid fossa
- Synovial joint
- Articulating surfaces covered with hyaline cartilage
stability of the glenohumeral joint
Rotator cuff muscles – surround the shoulder joint, attaching to the tuberosities of the humerus, whilst also fusing with the joint capsule. The resting tone of these muscles act to compress the humeral head into the glenoid cavity.
Glenoid labrum – a fibrocartilaginous ridge surrounding the glenoid cavity. It deepens the cavity and creates a seal with the head of humerus, reducing the risk of dislocation.
Ligaments – act to reinforce the joint capsule, and form the coraco-acromial arch.
Biceps tendon – it acts as a minor humeral head depressor, thereby contributing to stability.
synovial membrane of the shoulder joint
- Lines the inner surface of the joint capsule and produces synovial fluid to reduce friction between the articular surfaces
synovial bursa of the shoulder
Bursa
To reduce friction several synovial bursae are present- cushion between tendons and other joint structures
Subacromial -located deep to the deltoid and acromion, and superficial to the supraspinatus tendon and joint capsule. Reduces friction beneath the deltoid, promoting free motion of the rotator cuff tendons
Subscapular – located between the subscapularis tendon and the scapula. It reduces wear and tear on the tendon during movement at the shoulder joint.
Factors that contribute towards mobility of glenohumeral joint
- Type of joint- ball and socket
-
Bony surfaces- shallow glenoid cavity and large humeral head
- 1:4 disproportion in surfaces
- Commonly used analogy is gold ball and tee
- Inherent laxity of joint capsule
Factors that contribute towards stability
- Rotator cuff muscles
-
Glenoid labrum- fibrocartilaginous ridge surrounding the glenoid cavity
- Deepens the cavity and creates a seal with the head of the humerus-n reducing risk of dislocation
- Ligaments- act to reinforce the joint capsule- forms the coracoacromial arch
- Biceps tendon- acts as a minor humeral head depression
rotator cuff muscles
subscapularis
supraspinatus
infraspinatus
teres minor
arterial supply of the glenohumeral joint
anterior and posterior circumflex humeral arteries (branches of the axillary artery (branches of the suprascapular artery also contribute)
nervous supply of the glenohumeral joint
axillary, suprascapular and lateral pectoral nerve
muscle compartments of the upper limb can be divided into
intirnsic and extrinsic muscles
extrinsic muscle
Originates from the torso (trunk) and attach to the bones of the shoulder (clavicle, scapula and humerus). Located in the back- also known as the superficial back muscles.
Muscles are organised into two layers: Superficial layer and a deep layer
superficial extrinsic muscles
trapezius
latissimus dorsi
deep extrinsic muscles
levator scapulae
rhomboids
- minor
- major
intrinsic muscles
Originate from the scapula and/or clavicle and attach to the humerus. Six muscles- the deltoid, teres major, and 4 rotator cuff muscles (supraspinatus, infraspinatus, subscapularis and teres minor)
important areas found within the shoulder region
brachial plexus
axilla region
brachial plexus
The brachial plexus is a network of nerve fibres that supplies the skin and musculature of the upper limb. It begins in the root of the neck, passes through the axilla, and runs through the entire upper extremity.
The plexus is formed by the anterior rami (divisions) of cervical spinal nerves C5, C6, C7 and C8, and the first thoracic spinal nerve, T1.
Acronyms
Real Teenagers Drink Cold Beer- roots, trunks, divisions, cords, branches
Men Are Mean Really Usually- musculocutaneous, axially, median, radial, ulnar
3 Musketeers (C5, C6, C7)
2 Assassinations (C5, C6)
4 Mice (C6, C7, C8, T1)
5 Rats (C5, C6, C7, T1)
2 Unicorns (C8, T1)
axilla region
frozen should is also called
adhesive capsulitis
RF for frozen shouklder
It most commonly affects people in middle age. Diabetes is a key risk factor.
Adhesive capsulitis can be:
- Primary – occurring spontaneously without any trigger
- Secondary – occurring in response to trauma, surgery or immobilisation
pathophysiology of frozen should
inflammation and fibrosis in the joint capsule lead to adhesions (scar tissue). The adhesions bind the capsule and cause it to tighten around the joint, restrict movement in the joint