Disorders of the shoulder Flashcards
What is the common type of shoulder dislocation and why?
Anterior
- The glenoid fossa is shallow
- Although the joint is strengthened on its
superior, anterior and posterior aspects, it is weak at its inferior aspect
What is a subcoracoid location shoulder dislocation?
The head of the humerus dislocates anteroinferiorly, but then displaces in an anterior direction (subcoracoid location = 60% of cases) due to the pull of the muscles
and disruption of the anterior capsule and ligaments.
What is a subglenoid location shoulder dislocation?
The head of the humerus comes to lie antero-inferior to the glenoid (subglenoid location = 30% of cases)
- Hand behind head, force of arm posteriorly
How does the arm present in an anterior shoulder dislocation?
The arm is held in a position of external rotation and slight abduction
- Direct blow to posterior shoulder
What is a Bankart lesion or labral tear?
The force of the humeral head popping out of the socket often causes part of
the glenoid labrum to be torn off. Sometimes a small piece of bone can be torn off with 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 the anterior lip of the glenoid fossa. This can cause a dent (indentation fracture) in the posterolateral
humeral head.
What is significant about a Hill-Sachs lesion?
It increases the risk of secondary osteoarthritis in the shoulder joint
How can posterior shoulder dislocations occur?
They tend to occur when there are violent muscle contractions due to an epileptic
seizure, electrocution or a lightning strike; when there is a blow to the anterior
shoulder; or when the arm is flexed across the body and pushed posteriorly.
How does the arm present in a posterior dislocation?
Internally rotates and adducted. Flattening/squaring of the shoulder with a prominent coracoid process. The arm cannot be externally rotated into the anatomical position.
How can a posterior shoulder dislocation be spotted on an X-ray?
A posterior dislocation of the shoulder can easily be missed on an X-ray as it looks ‘in joint’. However, because the arm is internally-rotated, the projection of the humeral head onto the X-ray film changes to a more rounded shape – the ‘light bulb’ sign. The glenohumeral distance is also increased.
What injuries are commonly associated with posterior dislocations?
Fractures, rotator cuff tears and Hill-Sachs lesions
How might an inferior shoulder dislocation occur?
After inferior dislocation, the head of the humerus sits inferior to the glenoid. The mechanism is forceful traction on the arm when it is fully extended over the head, as may occur when grasping an object above the head to break a fall i.e. a hyperabduction injury.
What injuries are associated with posterior shoulder dislocations?
Damage to nerves, rotator cuff tears and injury to blood vessels.
What is the most common complication of shoulder dislocation in any direction?
Recurrent dislocation due to damage to the stabilising tissues surrounding the shoulder (glenoid labrum, capsule, ligaments etc.). The chance of further dislocation can be estimated at 60% but depends on age and activity level. As we age, our tissues lose elasticity, so the
risk of recurrent dislocation is approximately 90% in 20-year-olds, falling to only 10% in
40-year-olds. Each dislocation results in further damage to the humeral head and glenoid, therefore it is unsurprising that the risk of osteoarthritis increases with the number of dislocations.
Which artery can be damaged in a shoulder dislocation?
Damage to the axillary artery occurs in 1–2% of shoulder dislocations, more commonly in the older age group as their blood vessels are less elastic. The patient may have a haematoma, absent pulses and/or a cool limb.
Which nerve can be damaged in a shoulder dislocation?
The axillary nerve wraps around the neck of the humerus, and supplies the deltoid muscle and the skin overlying the insertion of deltoid. This is known as the regimental badge area as it corresponds with where a shoulder badge
would be worn on the sleeve of a jacket. Most people with axillary nerve damage recover fully, as the symptoms resolve when the shoulder is reduced (i.e. put back in position). Less commonly, dislocation of the shoulder may damage the cords of the brachial plexus or musculocutaneous nerve.
Why might a fracture occur in a shoulder dislocation?
When there is a traumatic mechanism of injury, first-time dislocation, or the person is aged over 40
What are the commonly affected bones if a shoulder dislocation results in a fracture?
Commonly affected bones include the head or greater tubercle of the humerus, the clavicle and the acromion.
Where do most clavicle fractures occur?
In the middle third of the clavicle
How do most clavicle fractures occur?
Falls onto the affected shoulder or onto the outstretched hand
How are clavicle fractures treated?
Most clavicle fractures are treated conservatively (i.e. without surgery), using a sling
When might a fractures clavicle need surgical fixation?
- Complete displacement (so the bone ends are not in apposition and cannot unite)
- Severe displacement causing tenting of the skin, with the risk of puncture
- Open fractures (fracture associated with a break in the integrity of skin)
- Neurovascular compromise
- Fractures with interposed muscle
- Floating shoulder: clavicle fracture with ipsilateral fracture of glenoid neck
Which nerves can get damaged in a clavicle fracture?
The suprascapular nerve may be damaged by the elevation of the medial part of the fracture. The supraclavicular nerves (C3,4) may also be damaged resulting in paraesthesia over the 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)
Which functions are compromised with a rotator cuff tear?
The rotator cuff is responsible for stabilising the glenohumeral joint, abducting, externally rotating and internally rotating the humerus.
When the rotator cuff tendons become torn, these functions are compromised.
Which tendon is most often torn in a rotator cuff tear?
he tendons of the rotator cuff are torn much
more frequently than the muscles and, of these, the supraspinatus tendon is the most frequently affected where it passes beneath the coracoacromial arch, tearing at the site of its insertion into the greater tubercle of the humerus.
How do most rotator cuff tears occur?
Most rotator cuff tears are chronic, resulting from extended use in combination with
other factors such as poor biomechanics or muscular imbalance. The most common
cause is age-related degeneration. With age, the blood supply to the rotator cuff tendons decreases, impairing the body’s ability to repair minor injuries. The principal theory is a 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 type of activity is a risk factor for rotator cuff tears?
Recurrent lifting and repetitive overhead activity are also risk factors (e.g. carpenters, painters), as are sports that involve repeated overhead motion (e.g. swimming, volleyball, tennis, weightlifting). As you would expect, rotator cuff tears are more common in the shoulder of the dominant arm, but a tear in one shoulder signals an increased risk of a tear in the opposite shoulder.
What is the most common presentation clinically of rotator cuff tears?
Anterolateral shoulder pain, often radiating down the arm
What is impingement syndrome?
Impingement syndrome occurs when the supraspinatus tendon impinges (rubs or
catches) on the coraco-acromial arch, leading to irritation and inflammation.
How is impingement of the supraspinatus caused?
The space between the head of the humerus and the coracoacromial arch is
relatively small (1 - 1.5cm). Impingement may be caused by anything that narrows
this space further e.g. thickening of the coracoacromial ligament, inflammation of
the supraspinatus tendon, subacromial osteophytes (in osteoarthritis).
What causes the pain in impingement syndrome, and what worsens it?
When the shoulder is abducted or flexed, the space becomes narrowed further, resulting in symptoms of pain, weakness and reduced range of motion. The pain is often worsened by shoulder overhead movement and may also occur at night, especially if the patient is lying on the affected shoulder.
What is the pain onset it impingement syndrome?
The onset of the pain may be acute if it is due to an injury, or may be insidious
(gradually increasing) if it is due to a gradual process such as osteophyte formation. The pain is described as dull rather than sharp, and lingers for long periods of a time, making it hard to fall asleep at night. Other symptoms can include a grinding or popping sensation during movement of the shoulder.
What is the most common form of impingement syndrome?
The most common form is impingement of supraspinatus tendon under the acromion during abduction of the shoulder. This creates a ‘painful arc’ between 60 and 120 degrees of abduction (below 60°and above 120°, patients experience significantly less, or no, pain). Patients often report pain on reaching upwards to brush their hair or to lift a food can from an overhead shelf.
How does calcific supraspinatus tendinopathy present?
It can present with acute or chronic pain, often aggravated by abducting or flexing
the arm above the level of the shoulder, or by lying on the shoulder. Mechanical symptoms may also occur due to the physical presence of a large deposit, leading to stiffness, a snapping sensation, catching, or reduced range of movement of the
shoulder.
How does calcific tendinopathy occur?
Calcific tendinopathy is believed to be multifactorial. One theory is that regional
hypoxia leads to tenocytes being transformed into chondrocytes and laying down cartilage in the tendon. Calcium deposits are then formed through a process resembling endochondral ossification. Another theory involves ectopic bone formation from metaplasia of mesenchymal stem cells normally present in tendons into osteogenic cells.
When does calcific tendinopathy cause the most pain?
They are crystalline in their ‘resting phase’.
However, they are eventually reabsorbed by
phagocytes, and it is during this reabsorption stage that they tend to cause the most pain.
What is adhesive capsulitis?
Adhesive capsulitis, typically referred to as ‘frozen shoulder’ is a painful and disabling
disorder in which the capsule of the glenohumeral joint becomes inflamed and stiff, greatly restricting movement and causing chronic pain. The pain is usually constant, worse at night and exacerbated by movement and cold weather.
What are the risk factors for adhesive capsulitis?
- Female gender
- Epilepsy with tonic seizures (i.e. sudden muscle contractions)
- Diabetes mellitus (the theory is that glucose molecules bond to the capsular
collagen) - Trauma to the shoulder
- Connective tissue disease
- Thyroid disease (hypo and hyperthyroidism)
- Cardiovascular disease
- Chronic lung disease
- Breast cancer
- Polymyalgia rheumatica (an inflammatory condition causing muscle pain and
weakness) - Parkinson’s disease
- Long periods of inactivity (from injury, stroke or illness) can precipitate
frozen shoulder, and it can also occur alongside other shoulder problems e.g.
calcific tendinopathy or rotator cuff tear.
How is adhesive capsulitis treated?
Treatment usually involves physiotherapy, analgesia and anti- inflammatory medication. Patients sometimes undergo manipulation under anaesthesia, which breaks up the adhesions and scar tissue in the joint to help restore range of motion. Intense post-operative physiotherapy then helps to maintain the movement that has been gained.
What joint of the shoulder does OA mainly affect?
