The shoulder

Question 1

What are the 4 functions of the shoulder?

Answer 1

1. Manipulation of environment
2. Attaches the upper limb to the axial skeleton
3. Clavicle acts as a strut to transmit force to the axial skeleton
4. High mobility and low stability

Question 2

Describe the range of movement of the shoulder

Answer 2

• Flexion: 180 degrees
• Extension: 45-60 degrees
• Abduction: 90 degrees
• Internal rotation: 70-90 degrees
• External rotation: 90 degrees

Question 3

What is the Stanmore triangle?

Answer 3

The Stanmore triangle uses three classifications of shoulder instability based around if a shoulder has some structural traumatic or non-traumatic defects that are contributing to instability, with a third classification for the non-structural but adverse muscle patterning shoulders.

Question 4

What are the 3 points of the Stanmore triangle

Answer 4

Type 1 Traumatic structural – significant trauma, usually unilateral, no abnormal muscle patterning

Type 2 Atraumatic structural – no trauma, structural damage to the articular surfaces, capsular dysfunction, no abnormal muscle patterning

Type 3 Habitual non-structural – no trauma, abnormal muscle patterning, no structural damage to articular surfaces

Question 5

What is a Hill Sachs Lesion?

Answer 5

A Hill–Sachs lesion, or Hill–Sachs fracture, is a cortical depression in the posterolateral head of the humerus. It results from forceful impaction of the humeral head against the anteroinferior glenoid rim when the shoulder is dislocated anteriorly

Question 6

What is a Bankart lesion?

Answer 6

A Bankart lesion is an injury of the anterior (inferior) glenoid labrum of the shoulder. When this happens, a pocket at the front of the glenoid forms that allows the humeral head to dislocate into it. It is an indication for surgery and often accompanied by a Hill-Sachs lesion, damage to the posterior humeral head

Question 7

What is the mechanism that leads to a bankart lesion?

Answer 7

• The lesion is associated with anterior shoulder dislocation. When the humerus is driven from the glenoid cavity, its relatively soft head impacts against the anterior edge of the glenoid. The result is a divot or flattening in the posterolateral aspect of the humeral head, usually opposite the coracoid process. The mechanism which leads to shoulder dislocation is usually traumatic but can vary, especially if there is history of previous dislocations. Sports, falls, seizures, assaults, throwing, reaching, pulling on the arm, or turning over in bed can all be causes of anterior dislocation.

Question 8

What is Type 2 of the Stanmore triangle?

What is the medical and surgical treatment?

Answer 8

This is acquired instability (atraumatic) - either through repetitive microtrauma, which has placed undue stress upon the soft tissues; or rapid, forceful movements that contribute to the overall laxity of the joint. There is structural damage to the articular surfaces.

This is a recognised problem in athletes, particularly throwers and swimmers, where they develop symptoms of instability due to overload and fatigue in the stabilising muscles of the shoulder.

Rehabilitation is focused on restoring muscle imbalance, soft tissue flexibility, proprioception and muscular control.

Surgery is occasionally required in the form of a:

Capsular Shrinkage or Capsular Plication

Question 9

What is type 3 of the Stanmore triangle?

Answer 9

The stability of the shoulder joint throughout its large range of motion comes partly from precise synchronised muscle contractions and relaxations during movement. Each of the 30 muscles moving and stabilising the shoulder need to be activated at specific times. If this pattern is altered instability can occur.

Muscle patterning instability usually occurs in younger patients who can voluntarily slip the shoulder out of joint as a trick movement, but may then go on to dislocate repeatedly uncontrolled (involuntary). It is an instability that is caused by an abnormality of shoulder muscle patterning.

Without treatment, they may progress to the stage where the patient may be aware their shoulder is moving in an abnormal manner but will perceive it to be normal to them. Stress, cough, sneeze may all initiate the shoulder to spontaneously sublux/dislocate out of the patient’s control. Pain is not often an issue but can be when the shoulder remains subluxed for a period of time due to the surrounding shoulder muscles being in continuous action. The patient may not be taken seriously or blamed for causing their shoulder to sublux/dislocate.

The prime aim of treatment is to regain normal neuromuscular control and patterning. This can be difficult, may take time and requires a full team approach to treatment. The team comprises a specialist shoulder physiotherapist, shoulder surgeon and sometimes an occupational therapist and psychologist.

The aim of the rehabilitation should allow full return to work and try not to encourage an avoidance culture.

Question 10

What is subacromial impingement?

Answer 10

Subacromial impingement syndrome (SAIS) refers to the inflammation and irritation of the rotator cuff tendons as they pass through the subacromial space, resulting in pain, weakness, and reduced range of motion within the shoulder.

Question 11

Who does subacromial impingement occur in?

Answer 11

It occurs most commonly in patients under 25 years, typically in active individuals or in manual professions, and accounts for around 60% of all shoulder pain presentations, making it the most common pathology of the shoulder.

Question 12

What are the intrinsic causes of subacromial impingement?

Answer 12

Intrinsic mechanisms involve pathologies of the rotator cuff tendons due to tension, including:

Muscular weakness: Weakness in the rotator cuff muscles can lead to muscular imbalances resulting in the humerus shifting proximally towards the body

Overuse of the shoulder: Repetitive microtrauma can result in soft tissue inflammation of the rotator cuff tendons and the subacromial bursa, leading to friction between the tendons and the coracoacromial arch

Degenerative tendinopathy: Degenerative changes of the acromion can lead to tearing of the rotator cuff, which allows for proximal migration of the humeral head

Question 13

What are the extrinsic causes of subacromial impingement?

Answer 13

Extrinsic mechanisms involve pathologies of the rotator cuff tendons due to external compression, such as:

Anatomical factors: Congenital or acquired anatomical variations in the shape and gradient of the acromion

Scapular musculature: A reduction in function of the scapular muscles, particularly the serratus anterior and trapezius, that normally allow the humerus to move past the acromion on overhead extension, may result in a reduction in the size of the subacromial space

Glenohumeral instability: Any abnormality of the glenohumeral joint or weakness in the rotator cuff muscles can lead to superior subluxation of the humerus, causing an increased contact between the acromion and subacromial tissues

Question 14

What is the clinical features of SAIS?

Answer 14

The most common symptom of SAIS is progressive pain in the anterior superior shoulder. The pain is classically exacerbated by abduction in the affected shoulder and relieved by rest, and may be associated with weakness and stiffness secondary to the pain.

Question 15

How can SAIS be investigated?

Answer 15

Two common examination signs can be elicited in cases of SAIS (specifically for subacromial impingement):

Neers Impingement test – The arm is placed by the patient’s side, fully internally rotated and then passively flexed, and is positive if there is pain in the anterolateral aspect of the shoulder.

Hawkins test – The shoulder and elbow are flexed to 90 degrees, with the examiner then stablising the humerus and passively internally rotates the arm, and the test is positive if pain is in the anterolateral aspect of the shoulder.

MRI imaging of the affected shoulder is often the mainstay of imaging for SAIS. Features that can be seen in affected individuals include formation of subacromial osteophytes and sclerosis, subacromial bursitis, humeral cystic changes, and narrowing of the subacromial space.

Question 16

How can SAIS be managed?

Answer 16

Management
Conservative management is the mainstay of treatment in most cases. Patients should have sufficient analgesia, typically non-steroidal inflammatory drugs, and regular physiotherapy, including postural, stability, mobility, stretching and strength exercises.

For those who require further intervention, corticosteroid injections in the subacromial space can be trialled. Patients should be educated appropriately with adequate warm-up techniques and monitoring for early signs of worsening impingement.

Surgical Intervention
If SAIS persists beyond 6 months without response to conservative management, surgical intervention is recommended.

Surgical intervention is particularly useful in patients with a reduced range of movement and is most commonly arthroscopic. Current surgical techniques include:

Surgical repair of muscular tears, most commonly the supraspinatus and long head of biceps tendon, resulting in an improvement in range of motion
Surgical removal of the subacromial bursa, a bursectomy, increasing the subacromial space and reducing pain
Surgical removal of a section of the acromion, an acriomioplasty, increasing the subacromial space and reducing pain

However, recent evidence from a randomised surgical trial showed that surgical decompression appeared to offer no extra benefit over arthroscopy alone, and indeed that the benefits seen from the surgical intervention might only be the result of a placebo effect or the increased post-operative physiotherapy.

Question 17

What is the rotator cuff and how common is a cuff tear?

Answer 17

The rotator cuff is a group of 4 muscles that support and rotate the glenohumeral joint. Alongside their role in movement of the shoulder, the rotator cuff muscles act to stabilise the humeral head in the glenoid fossa.

Rotator cuff tears are common; acute full thickness tears have an incidence around 2.5 per 10,000 patients for those aged 40-70, whilst the prevalence of a rotator cuff tear in the general population is around 20%.

Question 18

How is a rotator cuff tear classified?

Answer 18

Rotator cuff tears are classified as either acute (lasting <3 months) or chronic (lasting >3 months) tears. They can be either partial thickness or full thickness tears.

Full thickness tears can be further classified into small (<1cm), medium (1-3cm), large (3-5cm), or massive (>5cm or involves multiple tendons) tears.

Question 19

What is the pathophysiology of rotator cuff tears?

Answer 19

Acute tears commonly occur within tendons with pre-existing degeneration, typically occurring alone following minimal force. However, acute tears can occur in young individuals subjected to a larger force; these will therefore often occur alongside other injuries in the young.

Chronic tears occur in individuals with degenerative microtears to the tendon, most commonly from overuse and seen in greater incidence with increasing age.

Question 20

What are the risk factors of a rotator cuff tear?

Answer 20

The main risk factors for rotator cuff tears are age, trauma, overuse, and repetitive overhead shoulder motions (e.g. athletes, certain occupations). Other risk factors include obesity, smoking and diabetes mellitus.

Question 21

What are the clinical tests for a rotator cuff tear?

Answer 21

Patients will present with pain over the lateral aspect of shoulder and an inability to abduct the arm above 90 degrees. Tears are more common in the dominant arm.

On examination, there is often tenderness over the greater tuberosity and subacromial bursa regions. Supraspinatus and infraspinatus atrophy can be seen in massive rotator cuff tears.

Question 22

What specific tests can be used for rotator cuff?

Answer 22

Jobe’s test (the “empty can test”, tests supraspinatus) – place the shoulder in 90° abduction and 30° of forward flexion and internally rotate fully (as if you’re ‘emptying a can’), gently push downwards on the arm.
A positive test is present if there is weakness on resistance

Gerber’s lift-off test (tests subscapularis) – internally rotate the arm so the dorsal surface of hand rests on lower back, then ask the patient to lift hand away from back against examiner resistance
A positive test is weakness in actively lifting the hand away from back (compare to the contralateral side)

Posterior cuff test (tests infraspinatus and teres minor) – the arm positioned at patient’s side, with the elbow flexed to 90°, then the patient is instructed to externally rotate their arm against resistance
A positive test is present if there is weakness on resistance

Patients presenting with clinical features of a rotator cuff tear should have an urgent plain film radiograph to exclude a fracture*.

Once fracture has been excluded, rotator cuff tears can be assessed through further imaging. Ultrasonograhy can establish the presence and size of tear (Fig. 2), whilst MRI imaging can also be used to detect the size, characteristics, and location of the tear.

Question 23

How can a rotator cuff be healed?

Answer 23

Management
Management is dependent on the type of tear and functional status of the patient.

Conservative management is preferred in patients who are not limited by pain or loss of function, or those who have significant co-morbidities and unsuitable for surgery.

Conservative Management
Those who are presenting within 2 weeks since injury can be managed conservatively, including analgesia and physiotherapy with activity modification.

Surgical Management
For those presenting 2 weeks since the injury or remaining symptomatic despite conservative management may be referred for surgical intervention. Large and massive tears should also be considered for surgical repair.

Repairs can be done arthroscopically (allowing for earlier recovery) or via open approach (preferred in large or complex tears)

Prognosis following surgical repair overall tends to be very good, however those with large or massive tears, age >65yrs, poor compliance with rehabilitation programs, or current smokers often have worse outcomes.