3: Shoulder & Arm Flashcards
what does the biceps tendon reflex test
spinal cord segment C6 as this myotome is predominantly responsible for elbow flexion and supination
rupture of the biceps tendon
- long head may rupture near to its scapular origin most commonly in pt >50 following fairly minimal trauma
- typically accompanied by ‘snap’ sound in shoulder whilst lifting
- flexion of arm at elbow produces firm lump in lower arm = unopposed contracted muscle belly of biceps called Popeye sign
in a ruptured biceps tendon, why will the patient not notice much upper limb weakness
because the action of brachialis (flexion) and supinator muscles are intact so management usually conservative
what is a bursa
fluid filled sac that provides a cushion between tendon and bone/ligament to allow smooth gliding action of tendon
what are the two main bursa of the shoulder
subscapular and subacromial bursae
subacromial bursa
- lies under the acromion
- separates supraspinatus tendon from overlying coraco-acromial ligament, acromion, coracoid process and from deep surface of deltoid muscle
- reduces friction as the supraspinatus tendon passes under these structures
subscapular bursa
- located between tendon of subscapularis and neck of scapula
- protects tendon of subscapularis muscle as it passes inferior to root of coracoid process and over neck of scapula
what is the subacromial space
space between the coraco-acromial arch (formed by the coracoid process, coraco-acromial ligament and acromion) and the head of the humerus, normally measures 1-1.5cm
what structures are found in the subacromial space (4)
- subacromial bursa
- supraspinatus tendon
- joint capsule
- long head of biceps
what is there risk of during abduction
impingement of the soft tissues in the subacromial space –> irritation and inflammation
what muscles carry out shoulder abduction
first 90°
- 0-15° = supraspinatus
- 15-90° = deltoid
above 90°
- rotation of the scapula by: upper fibres of trapezius and serratus anterior
what muscles carry out shoulder adduction
sternal head of pectoralis major
latissimus dorsi
teres major
what muscles carry out shoulder flexion
- anterior fibres of deltoid
- clavicular head of pectoralis major
- corachobrachialis
- biceps brachii
what muscles carry out extension of the shoulder
posterior fibres of deltoid
latissimus dorsi
teres major
what muscles carry out medial rotation of the shoulder
subscapularis
teres major
sternal head of pectoralis major
latissimus dorsi
what muscles cause lateral rotation of the shoulder
- infraspinatus
- teres minor
how is dynamic stability provided to shoulder
by surrounding muscles
- rotator cuff = most important dynamic stabiliser which all originate from scapular and insert into either greater or lesser tubercle of humerus
what are the four muscles of the rotator cuff
give innervation and actions
- suprasinatus: suprascapular, first 15° of abduction
- infraspinatus: suprascapular, lateral rotation
- subscapularis: upper and lower subscap nerves, medial roation
- teres minor : axillary, lateral rotation and adduction
what can the stabilisers of the shoulder joint be divided functionally into
static: provide stability at rest
dynamic: provide stability during motion
what are the static stabilisers of the shoulder joint
- Congruency of the humeral head and glenoid cavity
- Glenoid labrum, provides circumferential stability
- Joint capsule
- Glenohumeral ligaments, provide stability anteriorly
- Extra-capsular ligaments e.g. coracoacromial arch provides stability superiorly; coracohumeral ligament provides stability superiorly
- Negative intra-articular pressure (holds the humeral head in place by suction)
what are the dynamic stabilisers of the shoulder joint
- Rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis) – provide stability anteriorly, posteriorly and superiorly
-
Extrinsic muscles that cross the shoulder joint:
o biceps brachii (long head) – superiorly
o triceps brachii (long head) – inferiorly
o deltoid – superiorly, anteriorly and posteriorly
o pectoralis major – anteriorly
o coracobrachialis – anteriorly
which part of the shoulder joint is least well supported
inferior aspect
describe the arterial supply to the shoulder joint
- axillary artery passes behind pectoralis minor and at level of surgical neck of humerus, gives off anterior and posterior circumflex humeral arteries
- these encircle neck of humerus to supply shoulder region
- also an arterial anastomosis around margin of scapula which is formed from subscapular artery anastomosing w branches of suprascapular and transverse cervical artery
what does the axillary artery become at the inferior border of the teres major muscle
brachial artery
what does the brachial artery supply
main blood supply to arm and forearm
what does the brachial artery give rise to immediately distal to teres major
profunda brachii (deep brachial artery)
what does the profunda brachii supply
travels w the radial nerve in the radial groove of the humerus and supplies the structures in the posterior compartment of arm (triceps brachii)
how does profunda brachii terminate
by contributing to anastomotic network around elbow joint
describe how the brachial artery terminates
- descends into anterior compartment of arm
- as it passes through cubital fossa, underneath brachialis, it terminated by bifurcating into radial and ulnar arteries
where is the brachial pulse palpated
in the cubital fossa
- medial to tendon of biceps brachii
where is the brachial pulse palpated
in the cubital fossa
- medial to tendon of biceps brachii
what is the nerve supply to the shoulder joint derived from
axillary, suprascapular and lateral pectoral nerve
- all branches of brachial plexus w nerve roots C5/C6
what is the most common type of shoulder dislocation
anterior
why does the shoulder most commonly dislocate anteroinferiorly
- glenoid fossa is shallow
- joint strengthened on superior, anterior and posterior aspects but weak at its inferior aspect
- displaces in an anterior direction due to the pull of muscles and disruption of the anterior capsule and ligaments
- alternatively, humerus may come to lie antero-inferior to the glenoid (subglenoid location)
how is the arm held in an anterior shoulder dislocation
external rotation and slight abduction
when does the first episode of anterior dislocation occur
- when an individual has their arm positioned in abduction and external rotation
- unexpected small further injury forces arm a little further posteriorly, pushing shoulder into an extreme position such that humeral head dislocates antero-inferiorly from glenoid
- alternatively a direct blow to posterior shoulder
what is a Bankart lesion/labral tear
- force of humeral head popping out of socket often causes part of the glenoid labrum to be torn off
- sometimes a small piece of bone can be torn off w the labrum
what is a Hill-Sachs lesion
- when the humeral head is dislocated anteriorly, the tone of the infraspinatus and teres minor muscles means that the posterior aspect of the humeral head becomes jammed against anterior lip of the glenoid fossa
- causes dent (indentation fracture) in the posterolateral humeral head
- inc risk of secondary OA
what causes posterior dislocations
much rarer
- violent muscle contractions due to epileptic seizure
- electrocution or a lightning strike
- blow to anterior shoulder
- when arm is flexed across body and pushed posteriorly
how does a patient w a posterior shoulder dislocation present
- internally rotated and adducted arm
- flattening/squaring of the shoulder w a prominent coracoid process; arm cannot be externally rotated into anatomical position
how do you spot posterior dislocation on X-ray
- can easily be missed as it looks ‘in joint’
- but since arm is internally rotated, projection of the humeral head onto x-ray film changes to a more rounded shape = light bulb sign
- glenohumeral distance is also increased
what injuries are commonly associated w posterior dislocation
fractures
rotator cuff tears
Hill-Sachs lesions
inferior dislocation of the shoulder
mechanism
even rarer (0.5%)
- after this, head of humerus sits inferior to glenoid
- hyperabduction of arm
- forceful traction on arm when it is fully extended over head
what are injuries associated w inferior shoulder dislocations
damage to nerves
rotator cuff tears
injury to blood vessels
what is the most common complication of shoulder dislocation in any direction
recurrent dislocation due to damage to stabilising tissues surrounding the shoulder (glenoid labrum, capsule, ligaments, etc)
- also results in further damage to the humeral head and glenoid = increased risk of OA
which artery can sometimes be damaged in shoulder dislocations
axillary
- more commonly in older age group as their blood vessels are less elastic
- pt may have haematoma, absent pulses and/or cool limb
which nerve is mostly likely to be injured in a shoulder dislocation
axillary 10-40%
- axillary nerve wraps around the neck of the humerus and supplies the deltoid muscle and the skin overlying the insertion of the deltoid (regimental badge areas)
- most ppl will fully recover as symptoms resolve when shoulder is reduced
- less commonly, dislocation of the shoulder may damage the cords of the brachial plexus or musculocutaneous nerve
what bones are commonly affected in fractures associated w shoulder dislocation
head/ greater tubercle of humerus
clavicle
acromion
what else can occur in association w shoulder dislocation
rotator cuff muscle tears - most commonly in older people
- integrity of these muscles should always be assessed as part of follow up of pt after reduction of dislocated shoulder
function of the clavicle
- acts as a strut to brace the shoulder from the trunk so arm has freedom of motion
- transmits forces from the upper limb to the axial skeleton
- provides protection to the brachial plexus, subclavian vessels and the apex of the lung
what is the most common site of a clavicular fracture
middle third of the clavicle
common causes of clavicular fractures
falls onto affected shoulder or outstretched hand
how are clavicular fractures treated
conservatively using sling mostly
what are indications for surgical fixation of clavicular fracture
- complete displacement (bones not in apposition so cannot unite
- severe displacement causing tenting of skin, w risk of puncture
- open fractures (associated w break in skin)
- neurovascular compromise
- fractures w interposed muscle
- floating shoulder: clavicle fracture w ipsilateral fracture of glenoid neck
what will happen to the position of the arm and clavicular fragments in a displaced mid-clavicular fracture
- The sternocleiodomastoid muscle elevates the medial segment
- Because the trapezius muscle is unable to hold the lateral segment up against the weight of the upper limb, the shoulder drops
- The arm is pulled medially by pectoralis major (adduction)
what are potential local complications of mid-clavicular fractures
pneumothorax or injury to surrounding neurovasculature structures
which nerves may be damaged in mid-clavicular break
- suprascapular nerve may be damaged by elevation of the medial part of the fracture
- supraclavicular (C3/4) can also be damaged = paraesthesia over upper chest anteriorly
what is a rotator cuff tear
- a tear of one or more of the tendons of the four rotator cuff muscles of the shoulder (supraspinatus, infraspinatus, subscapularis and teres minor)
- among the most common conditions affecting the shoulder and is frequently seen in both primary care and orthopaedic outpatients
what part of the rotator cuff is most commonly injured
- tendons of the rotator cuff torn much more frequently than muscles
- supraspinatus tendon most frequently affected where it passes beneath the coracromial arch, tearing at site of insertion into greater tubercle of humerus
are most rotator cuff tears chronic or acute
chronic, resulting from extended use in combination w other factors e.g. poor biomechanics or muscular imbalance
what is the most common cause of rotator cuff tears
age related degeneration
- w age, blood supply to the rotator cuff tendons decreases, impairing body’s ability to repair minor injuries
- degenerative-microtrauma model, which supposes that age-related tendon degeneration, compounded by chronic microtrauma, results in partial tendon tears that then develop into full rotator cuff tears
- inflammatory cells are recruited and oxidative stress leads to tenocyte (tendon cell) apoptosis, leading to further degeneration, thus a ‘vicious circle’ is created
what are risk factors for rotator cuff tears
- recurrent lifting and repetitive overhead activity (swimming, volleyball, tennis, weightlifting)
- more common in shoulder of the dominant arm, but a tear in one shoulder signals an increased risk of tear in opposite shoulder
how do patients w rotator cuff tears present
- many are asymptomatic
- but most common presentation: anterolateral shoulder pain, often radiating down the arm
- can occur w activity but shoulder activity above the horizontal position/rest
- pain shoulder when they lean on their elbow and push downwards which will push the head of the humerus superiorly and decrease space between humeral head and coracromial arch
- also pain on flexing shoulder (when reaching forward)
- weakness of shoulder abduction
what else is involved in diagnosis of rotator cuff tear
- history and examination
- MRI and ultrasound
when does impingement syndrome occur
when the supraspinatus tendon impinges on the coracoacromial arch –> irritation and inflammation
what can impingement be caused by
anything that narrows the arch e.g.
- thickening of the coracocramial ligament
- inflammation of the supraspinatus tendon
- subacromial osteophytes (in OA)
symptoms of impingement syndrome
pain, weakness and reduced range of motion when shoulder is abducted or flexed
- pain often worsened by shoulder overhead movement and can occur at night
- pain onset may be acute if due to injury or may be insidious if due to gradual process e.g. osteophyte formation
- dull, sharp, lingering pain
- grinding or popping sensation
most common form of impingement syndrome
- impingement of the supraspinatus tendon under the acromion during abduction of the shoulder
- creates painful arc between 60-120°
- treatment directed at underlying cause
what is calcific supraspinatus tendinopathy
characterised by presence of macroscopic deposits of hydroxyapatite in tendon of supraspinatus
- can occur in any tendon but most commonly ^^
how can calcific supraspinatus tendinopathy present
acute or chronic pain, often aggravated by abducting or flexing the arm above the level of the shoulder or by lying on shoulder
- mechanical symptoms can alo occur due to the physical presence of large deposit = stiffness, snapping sensation, catching or reduced range of movement of shoulder
what is the pathophysiology behind calcific supraspinatus tendinopathy
multifactorial
- regional hypoxia –> tenocytes being transformed into chondrocytes and laying down cartilage in the tendon
- calcium deposits are then formed through a process resembling endochondral ossification
- ectopic bone formation from metaplasia of mesenchymal stem cells normally present int tendons into osteogenic cells
describe appearance of calcific deposits on x-rays
these deposits are visible on x-rays
- crystalline in resting phase
- eventually reabsorbed by phagocytes and during this stage, they tend to cause the most pain
- during this stage, they macroscopically look like ‘toothpaste’ and often appear ‘cloudy’ (less well defined)
treatment of calcific supraspinatus tendinopathy
intially conservative w rest and analgesia
- surgical treatment is sometimes required for persistent symptoms
what is adhesive capulitis (frozen shoulder)
painful and disabling disorder in which the capsule of the glenohumeral joint becomes inflamed and stiff = greatly restricting movement and causing chronic pain
- pain is usually constant, worse at night and exacerbated by movement and cold weather
what are risk factors for adhesive capulitis
- female
- epilepsy w tonic seizures
- diabetes (glucose molecules bond to capsular collagen)
- trauma
- polymyalgia rheumatica
treatment of adhesive capulitis
- physio
- analgesia
- anti-inflamm meds
- sometimes can undergo maniplation under anaesthesia which breaks up adhesions and scar tissue in joint = restore range of motion
- typically resolves w time and can regain 90% of shoulder motion
- opposite shoulder becomes affected in 6% to 17% of patients within 5 years, lending further weight to the autoimmune hypothesis
osteoarthritis of shoulder
similar radiological features to OA in other joints
- more commonly affects the acromioclavicular joint than the glenohuumeral joint
treatment of OA
- initially involves activity modification, NSAIDs
- steroid injections to reduce swelling and thereby alleviate shoulder stiffness and pain
- hyaluronic acid injections into joint (viscosupplementation) to increase lubrication
- Arthroscopy (keyhole surgery) can be performed to remove loose pieces of damaged cartilage from the glenohumeral joint, but some patients will progress to hemiarthroplasty (replacement of the humeral head) or total shoulder replacement (replacement of the humeral head and the glenoid)
muscles of anterior arm
- biceps brachii (long/short head)
- brachialis
- coracobrachialis
muscles of posterior arm
three heads of triceps brachii
origin and insertion of biceps brachii
long head
O: supraglenoid tubercle of scapula
I: into radial tuberosity via biceps tendon (bicipital aponeurosis)
short head
O: coracoid process
I: radial tuberosity
innervation of biceps brachii
musculocutaneous
C5-7 (lateral cord)
action of biceps brachii
- strong supinator @ radioulnar joints
- flex arm @ elbow and shoulder
origin and insertion of brachialis
O: anterior surface of distal 1/2 of humeral shaft
I: coronoid process of ulna and ulnar tuberosity
innervation of brachialis
musculocutaneous
C5-7 (lateral cord)
action of brachialis
flex forearm at elbow
origin and insertion of coracobrachialis
O: coracoid process
I: medial side of humeral shaft
action of coracobrachialis
flex arm at shoulder and weak adductor
origin of long head of triceps brachii
infraglenoid tubercle of scapula
origin of medial head of triceps brachii
shaft of humerus, inferior to radial groove
origin of lateral head of triceps brachii
shaft of humerus, superior to radial groove
when does the first episode of anterior dislocation occur
- when an individual has their arm positioned in abduction and external rotation
- unexpected small further injury forces arm a little further posteriorly, pushing shoulder into an extreme position such that humeral head dislocates antero-inferiorly from glenoid
- alternatively a direct blow to posterior shoulder
