The rotator cuff consists of a group of four shoulder muscles (supraspinatus, infraspinatus, teres minor, subscapularis) and their tendons originating from the scapula attaching to the humeral head, which provides the glenohumeral joint additional stability. Injury can include tendinopathy and tears, presenting typically as subacromial pain. This is the most common cause of shoulder pain presenting to primary care, commonly affecting those between 35 and 75 years old. A typical history includes acute trauma, repetitive overhead activity, or chronic degeneration.

Rotator cuff injury is a continuum ranging from impingement to partial and full thickness tears. The exact pathophysiology of these are unclear, but current consensus is a combination of intrinsic tendon degeneration and impingement contribute.

Intrinsic tendon degeneration

• Tendon hypo-perfusion of a watershed area
• Repetitive micro-trauma

Impingement syndrome can be classified as external, internal or secondary.

• External
  • Compression of rotator cuff tendons as they pass underneath the coracoacromial arch
  • Narrowing of this space can occur due to osteophyte formation, bony spurs or malunion after fractures
• Internal
  • Associated with overhead and throwing sports activities
  • Under surface fraying of infraspinatus tendon on the posterior glenoid
  • Increased association with labral disorders
• Secondary
  • Glenohumeral instability leads to slight humeral head subluxation
  • This narrows the acromiohumeral interval

The pre-existing degenerative changes that occur above can progress to partial and full thickness tears.

Individuals with rotator cuff injuries can be broadly divided into 2 groups according to their presenting clinical features:

1. Those with subacromial impingement symptoms (SAIS):

• Occurs commonly in patients under 25 years old
• Typically active individuals or those involved in manual labour
• Insidious onset over weeks to months
• Pain (79%) typically localised to the anterior superior shoulder
• Worse at night and at rest, typically exacerbated by lying on the affected side
• Painful arc of motion
  • During arm abduction, shoulder pain occurs between 60 to 120º
  • Pain eases beyond 120º but can return when returning the arm back to its original position
  • Reports of difficulty during daily activities such as combing hair or reaching up to open a cupboard

2. Those with symptoms of a torn rotator cuff tendon:

• More common in those between 40-70 (0.25 per 100,000 patients)
• Can present as an acute tear:
  • Usually due to trauma (fall, lifting or catching something heavy)
  • Commonly with pre-existing degeneration, however, in younger patients, significant force can cause tears along with concomitant injuries
• Chronic degenerative tears:
  • Most commonly due to excessive repetitive motions and normal age-related muscular deterioration
  • Greater incidence with increasing age
• Pain is the most commonly reported symptom (83%)
  • Lateral aspect of shoulder, particularly greater tuberosity and subacromial bursa regions
  • 8-40% may be asymptomatic
• Muscular weakness and atrophy (50-63%)
  • Inability to abduct the arm above 90º
  • Supraspinatus and infraspinatus atrophy in massive tears

In addition to these clinical features, there are a number of specific tests that can be performed.

In those with suspected SAIS, two common examination signs can be elicited using:

Neer's impingement test

• Anterolateral shoulder pain reported during forward flexion with arm internally rotated

Hawkin's test

• Forced internal rotation of an arm held at shoulder height and elbow bent at 90º causes anterolateral shoulder pain

In patients with suspected rotator cuff tendon tears, the following special tests can elucidate the tendon(s) affected:

'Empty can test'

• Evaluates supraspinatus
• Patient's raise their arm to 90º in the scapular plane
• The arm is internally rotated (thumbs down)
• Downward pressure is applied to their arm
• Presence of weakness or pain indicates a tear

Posterior cuff test

• Evaluates infraspinatus
• Weakness or pain on resisted external rotation suggests a tear

Gerber's lift-off test

• Evaluates subscapularis
• Patient attempts to lift a hand from small of the back, while resistance is applied
  • Weakness or pain suggests a subscapularis tear

The British Elbow and Shoulder Society (BESS) and British Orthopaedic Association (BOA) guidelines on investigating rotator cuff disorders do not routinely recommend investigations on initial presentation to primary care.

However, if the patient has: a history of trauma, is not improving with conservative treatment, symptoms persisting for more than 4 weeks, restriction of movement or severe pain, then plain film radiographs (true AP and lateral or scapular Y views) can be considered in a primary care setting

• If patients present acutely on a background of trauma, findings may include:
  • Glenoid fracture
  • Greater tuberosity humerus fracture
  • Glenohumeral dislocation
• In patient's with a chronic presentation there may be evidence of:
  • Reduced acromiohumeral distance
  • Osteophyte, sclerosis and cyst formation (signs of osteoarthritis)
  • Calcium deposits from calcific tendonitis

Further investigation by injection with local anaesthetic into the subacromial space can be performed in primary care (if the clinician possesses the necessary skills):

• Can help differentiate between tears and SAIS
• If strength on retesting does not improve following injection, a rotator cuff tear is likely

If patients continue to have symptoms after 6 weeks of non-surgical care they can be referred to secondary care for further investigation:

MRI is often the 1st line investigation in hospital, with sensitivities close to 100% for full-thickness rotator cuff tears. Signs of rotator cuff abnormalities include:

• Hyperintense signal on T2 imaging extending to articular or bursal surfaces
• Discontinuity within tendons
• Use of gadolinium arthrography alongside MRI was shown in a meta-analysis to be the most sensitive and specific technique for both full and partial-thickness rotator cuff tears
• Impingement/tendonitis can be more difficult to elucidate but may show evidence of inflammation on MRI:
  • Increased fluid in subacromial space and subdeltoid bursa
  • Thickening and increased signal of tendons

Ultrasound has been shown to have comparable sensitivity to MRI for detecting full-thickness tears and can be performed alongside/instead of MRI:

• Performs better in the presence of metallic prostheses
• Allows dynamic evaluation of the shoulder
• A major limitation is the operator-dependent nature of the modality

The main conditions to consider when suspecting rotator cuff injury, depend upon the nature of the presentation (acute or chronic and activities prior to symptoms):

The BESS/BOA commissioning guidelines in 2014 advised the following management of suspected rotator cuff injury of those presenting to primary care:

• Rest in the acute phase
• Offer paracetamol as 1st line analgesia. If no benefit consider oral NSAID
• Referral for a course (usually 6 weeks) of physiotherapy
• Consider subacromial corticosteroid injection
  • Only one should be administered due to risk of tendon damage
  • A second injection can be administered if a good response to the 1st course and to facilitate physio exercises

The following are indications for referral to secondary care for consideration of surgery:

• Pain and loss of function despite appropriate non-operative treatment
• Sudden loss of ability to actively raise the arm (with or without trauma) on an urgent 2-week pathway
  • Suggestive of acute cuff tear

Depending upon the underlying pathology the following procedures are indicated:

Acromioplasty

• Mainly indicated in SAIS
  • Impingement pain and absence of rotator cuff tear
  • Impingement pain and irreparable rotator cuff tear
  • Impingement pain and patient declines repair
• Surgical intervention involves sub-acromial decompression through:
  • Removal of the subacromial bursa
  • Removal of bony spurs
  • Removal of a section of the acromion
• Aims to increase the volume of the subacromial space, preventing mechanical irritation of the rotator cuff tendons
• A recent randomised controlled trial published in 2018, showed surgical decompression had better outcomes for shoulder pain and function versus no treatment, but this difference was not clinically significant

Rotator cuff repair

• Indicated in rotator cuff tears
  • Acute (traumatic or chronic degenerative) tear
  • Persistent subacromial pain and weakness with radiologically proven full-thickness tear despite appropriate conservative treatment
• Aims to reattach the cuff tendons to the bone
• Open or arthroscopic tendon repair
• A recent Cochrane review from 2019, found rotator cuff repair had little or no impact on overall pain, function or quality of life compared to non-operative treatment