Rotator Cuff Injury
The rotator cuff is a group of 4 muscles and their tendons that form a cuff which stabilises the humerus within the glenoid cavity. They provide dynamic stability and strength to the shoulder joint. Rotator cuff injuries are a common source of shoulder pain. They are caused by forceful, repeated overhead or pulling movements (such as in competitive swimmers). They can also accompany acute dislocation in older patients. The supraspinatus muscle-tendon unit is the most commonly affected.
The rotator cuff muscles have relatively poor blood supply, and this predisposes them to degeneration and tearing. Rotator cuff tears occur more commonly in older patients. 4–20% of 40- to 50-year-olds have an asymptomatic tear while > 50% of > 70-year-olds have an asymptomatic tear.
Rotator cuff muscles
| Muscle | Innervation | Action |
|---|---|---|
| Supraspinatus | Suprascapular nerve | Initiates abduction (0- 15 degrees) |
| Infraspinatus | Suprascapular nerve | External rotation and abduction |
| Teres minor | Axillary nerve | External rotation and adduction |
| Subscapularis | Upper and lower subscapular nerve | Internal rotation |
- Tests for isolated supraspinatus muscle injury
- Supraspinatus muscle can be assessed in isolation using the full can or empty can tests.
- Empty can test
- The patient holds arms out (90 degrees abducted, 30 degrees in front)
- The patient then points the thumbs down
- The examiner pushes the arms down against resistance
- Test is positive if there is pain
- Full can test
- Similar to the empty can test but the patient points their thumbs up
- Empty can test
- Supraspinatus muscle can be assessed in isolation using the full can or empty can tests.
Classification
| Type | Length of tear | Symptoms | Treatment |
|---|---|---|---|
| Small tears | < 1 cm | Usually asymptomatic | If symptomatic: conservative cuff rehabilitation, regular review |
| Intermediate tears | 2-4 cm | Symptoms of impingement (pain) and weakness of the shoulder | Decompression and tendon/ muscle repair |
| Large tears | > 5 cm | Pain and weakness with abduction limited to below 60 degrees, characteristic hunching of the shoulder, may result in secondary osteoarthritis ‘cuff tear arthropathy’ | Decompression and tendon/ muscle repair |
- Aetiology of rotator cuff injuries
- Degenerative (most common): due to repetitive or forceful overhead movements
- Acute: trauma-related, often in patients older than 40. May be accompanied with a shoulder dislocation.
- Signs and symptoms
- Shoulder pain
- At night when laying on the affected shoulder
- With specific movement e.g. lifting and lowering the arm, pulling movement
- Shoulder weakness (experienced with the same movement that causes pain)
- Shoulder pain
- Investigations
- X-ray
- Ultrasound
- MRI of the joint
- Non-operative treatment
- Rest or activity modification
- NSAIDs
- Physiotherapy
- Corticosteroid injections
- Operative treatment
- Open or arthroscopic repair: sutures and anchors to reattach the tendon to its insertion on the head of the humerus
- Recovery
- Immobilization for 4 – 6 weeks with progressive range of motion
- Followed by strengthening for 8 – 12 weeks
Acute rotator cuff tears
Most tears of the supraspinatus occur from degeneration and will therefore be associated with impingement symptoms. However, they may also occur secondary to trauma. These patients present soon after the event and have profound weakness and loss of function with minimal pain. On examination, there is marked restriction of abduction (less than 90°), with a characteristic hunching of the shoulder (due to elevation and rotation of the scapula to attempt to aid abduction). Diagnosis is confirmed by ultrasound or MRI. Early repair is indicated, and often no decompression is necessary.