The Shoulder Flashcards
What makes up the shoulder?
The pectoral, scapula and lateral supraclavicular regions
What makes up the pectoral girdle?
Sternum, clavicle and scapula
What is the role of the pectoral girdle?
Very mobile, bony ring to keep arm away from body so it has a great range of movement
What is the pectoral girdle like posteriorly?
It is incomplete as the scapula doesn’t articulate with the vertebral column via bone but does so by muscle
What is the pectoral girdle like anteriorly?
The clavicle articulates with the axial skeleton
Where do the axial and appendicular skeleton articulate?
At the sternoclavicular joint between the manubrium of the sternum and the clavicle
What is the shape of the clavicle and why?
S shaped as it gives it compressibility and resilience
Where is the clavicle? (where does it end)
Anterior bone, overlies 1st rib and ends at the acromioclavicular joint
Where/what is the acromion?
Lateral bone of the scapula at the end of the spine, runs posteriorly for muscles to attach to, top of glenohumeral joint
What are some features of the scapula?
Posterior, triangle shaped, glenoid cavity with glenohumeral joint, muscle attachment bone, overlies the rib cage posteriorly
What is a clavicle fracture caused by?
Direct or indirect force, force of falling onto the hand travels up the bones in forearm and arm to reach the final clavicle bone.
What movements occur in a clavicle fracture?
Weight of the arm drags the lateral fragment of the clavicle inferiorly and the sternocleidomastoid pulls the medial fragment superiorly
What positional change can be seen from a clavicle fracture?
Lateral side is lower whilst medial side is higher pushing skin up as bone is very superficial anyway, also arm may be a little bit lower
What is the sternocleidomastoid muscle?
Anterior muscle in the neck, at the sternum-clavicle-mastoid process joint.
Who most commonly has clavicle fractures? and why
Makes up 2-5% of adult fractures but more so in children as clavicle is the last bone to ossify.
What does the clavicle protect? What does this mean?
The apex of the lung, the brachial plexus and the major underlying vessels SO all at risk if clavicle is damaged in a fracture for example fragments of bone can damage lungs causing pneumothorax
What ribs does the scapula over lie?
2nd-7th ribs
What does the spine of the scapula separate?
The supraspinous fossa and the infraspinous fossa
What is at the lateral end of the scapula?
The acromion which forms the subcutaneous point of the shoulder
What is the shape of the scapula?
triangular and flat
What features are seen on the anterior view of the scapula?
Glenoid cavity, acromion, coracoid process, subscapular fossa
What features are seen on the posterior view of the scapula?
Supaspinous fossa, coracoid process, acromion, supraspinous fossa, neck of scapula, infraspinous fossa
What is the largest bone in the upper limb?
Humerus
Where does the humerus articulate with the scapula?
Glenohumeral joint
What is a tuberosity and what bone has it?
Protuberance for muscle tendons to attach to
Humerus - greater tuberosity is larger and anterior, lesser tuberosity,
What separates the tuberosities
Bicipital groove/inter-tubicular groove which tendon form coracoid process runs through
What are the 3 main joints in the shoulder?
Sternoclavicular Joint
Acromioclavicular Joint
Glenohumeral Joint
What structures meet at the sternoclavicular joint?
Manubrium of the sternum, clavicle, 1st costal cartilage
What is the strongest joint and the weakest joint?
Strongest - sternoclavicular
Weakest - Glenohumeral joint
What ligaments are in the sternoclavicular joint?
Costoclavicular ligament
Anterior sternoclavicular ligament
Interclavicular ligament
What does the costoclavicular ligament attach?
The sternoclavicular joint to the 1st rib limiting its movement
Why does the sternoclavicular joint have limited movement?
Costoclavicular ligament joins sternoclavicular joint to 1st rib
What is the role of the interarticular disc?
Holds the manubrium and the clavicle together and closely packs them, made up of fibrous tissue
What structures make up the acromioclavicular joint?
Acromion and clavicle
Where is the acromioclavicular joint found?
2-3cm from the point of the shoulder
What is special about the acromioclavicular joint?
No muscles cross it and instead it is moved by the muscles of the scapula
How strong is the acromioclavicular joint?
stronger than glenohumeral joint but weaker than sternoclaviular joint
What movement can occur in the acromioclavicular joint? What muscles cause them?
Related to scapula movements:
depression (gravity)
elevation (trapezium)
Protraction (serratous anterior and pectoralis minor)
Retraction (trapezium)
Upward rotation (trapezium and serratous anterior)
Downward rotation (latissimus dorsi)
What is special about the latissimus dorsi?
It is the only muscle which moves both the upper and lower limb
What structures make up the glenohumeral joint?
Glenoid cavity and the humerus head
What is the glenoid labrum? What is its role? How does it work?
Shallow glenoid cavity which is deepened by the fibrocartilage ring. Forms a suction cup to hold the humerus head inside the cavity, thin film of synovial fluid between the humerus and the glenoid cavity creates surface tension
What is the weakest joint in the body?
Glenohumeral joint
How is there such a large freedom of movement at the glenohumeral joint?
Loose fibrous joint capsule, baggy with lots of space around the humerus head
What movements can occur at the glenohumeral joint and by which muscles?
Flexion - deltoid (anterior part), pectoralis major, coracobrachialis stabilises the joint
Extension - latissimus dorsi, deltoid (posterior part), teres major, triceps brachi stabilise joint
Abduction - deltoid (all of it), supraspinatus for the last 10 degree
Adduction - latissimus dorsi, pectoralis major, mainly gravity
Medial and lateral rotation - subscapularis, suprasniatus, infraspinatus, teres minor
Why Is the supraspinatus at risk of damage?
As goes under the acromion
Where are the rotator cuff muscles and what do they do?
Form musculotendinous cuff around the glenohumeral joint which blends with articular capsule
Attach to the greater and lesser tuberosity
Contract and hold large humerous head in shallow glenoid cavity
What happens at the scapulothoracic joint?
Head of the humerus uses articular surface for 90 degree turn and the remainder is from scapula rotation using th serratus anterior and trapezium
For every 15 degree shoulder abduction how much does the glenohumeral and scapulothoracic joints contribute?
Glenhomueral - 15 degrees and scapulothoracic 5 degrees
In a 180 degree turn how much of the turn occurs where?
glenohumeral - 120 degrees, scapulothoracic - 60 degrees
What movements does scratching your back form the top use?
External rotation and abduction
What movements does scratching your back form the side/bottom use?
Internal rotation and adduction
What is a bursa?
Extension of a joint cavity
What is the role of bursa?
Act as cushions to reduce friction
What is the risk of bursa?
Bursa can become inflamed and damaged which would damage the tendon underneath
What is an example of bursitis?
Subacromial bursa - pain and inflammation on abduction of the arm
Which joint is most likely dislocated?
Glenohumeral
What are the movements in a glenohumeral dislocation?
joint fully abducted tilting head of humerus inferiorly onto weaker part of joint
Stronger flexor and adductor muscles pull humeral head anteriorly
Gravity pulls humerus inferiorly so rounded profile of the shoulder is lost
What happens to the glenoid labrum in a glenohumeral dislocation?
Stripped from anterior aspect of glenoid cavity making the joint weaker
How might an axillary nerve injury occur? What does this result in?
From glenohumeral dislocation as axillary nerve has close relationship with inferior part of glenohumeral joint
Innervates the deltoid so abduction is impaired
Loss of sensation over regimental badge
