Tears of the rotator cuff

Definition

A rotator cuff tear (RCT) is an injury, where tendons of muscles of the rotator cuff are torn.

Aetiology

The aetiology of RCTs is multifactorial and - if no appropriate trauma was present - most presumably due to degenerative processes [1]. Trauma can lead to a RCT too but is clinically much less relevant. It is not fully understood, where the degenerative processes originate. it is theorised however that mechanical factors such as imbalance of muscles, nutritional factors with hypovascularisation and even calcium phosphate crystals are the root cause in developing RCTs [2]. Additionally, several factors first and foremost an increased lateral extension of the acromion (wider critical shoulder angle), but also smoking, increasing age, history of trauma, hypercholesterolemia and a familial predisposition were found to increase the risk of developing a rotator cuff tear [1].

Studies have shown that in over 90% of cases, the supraspinatus tendon is affected and that most often glenohumeral kinetics are affected, resulting in a superior migration of the humeral head [3]. This explains the concomitant impingement symptoms patients can experience after suffering a tear of the supraspinatus muscle

The RCTs are generally divided into two different groups as they are treated differently:

• Full-thickness tears

  • Involve the entire thickness of a tendon

• Partial-thickness tears

  • Only parts of the tendon are torn (e.g. bursal sided, intratendineous, articular sided)

Epidemiology

Chances of developing a RCT increase with older age [1, 2]. Therefore, approximately 25% of patients in their 60s suffer from full-thickness tears, in contrast to 50% of individuals in their 80s [1]. In addition to that, a study has found that from a population of 683 patients, 36% of individuals with shoulder pain had a RC tear in comparison to only 16.9% of asymptomatic patients [1].

History

As older patients often do not realise they tore parts of the rotator cuff, the examiner should pay close attention to signs of shoulder weakness such as having trouble brushing ones teeth or combing ones hair [4]. Younger patients with RCTs on the other not rarely pinpoint a certain traumatic event.

Disease specific diagnosis

When inspecting the patient, the examiner should look for signs of atrophy of the supraspinatus and other muscles of the rotator cuff.

Active and passive range of motion are to be assessed, where only the active component should be affected [4]. In addition to that, strength testing is a vital part of the diagnosis as well as being able to visualise trends [4].

There are numerous specific tests for each muscle of the rotator cuff. In the following, examples are given for each muscle or functional muscle group:

• Lift-off test (Subscapularis muscle)

  • The hand of the affected shoulder is placed behind the back with the elbow in 90° flexion. The patient is then asked to lift the hand off the back, which is not possible if the subscapularis tendon is torn and the test is positive.

• Internal lag sign (Subscapularis muscle)

  • The hand of the affected shoulder is placed behind the back with the elbow in 90° flexion. The examiner lifts off the hand and the patient is asked to maintain the position. If the patient is unable to do so, the test is positive.

• Drop arm (Supraspinatus muscle)

  • The arm is placed in 90° abduction and the patient is asked to slowly descend the arm into neutral position. The test is positive if the patient immediately drops the arm.

• External lag sign (Infrapinatus & supraspinatus muscle)

  • The elbow is placed in 90° flexion as the examiner fully externally rotates the arm. Positive findings are when the patient is unable to maintain the starting position

• Hornblowers sign (Infraspinatus & teres minor muscle)

  • The shoulder is placed in 90° abduction as well as the elbow in 90° flexion. The patient is then asked to externally rotate against the resistance of the examiner. Pain or inability to execute external rotation is seen as a positive finding.

• Drop Sign (Infraspinatus muscle)

  • The shoulder is placed in 90° abduction, the elbow in 90° flexion as the examiner rotates the arm externally. A positive test is when the patient is unable to maintain the starting position.

Although these tests are important to distinct between different pathologies, imaging diagnostics reign supreme when it comes to diagnosing RCTs. MRI is important as it allows the examiner to visualise the extent of the tear as well as atrophy and fatty degeneration of the affected muscles [2]. Ultrasound has been reported to diagnose partial- and full-thickness tears with 91% and 100% accuracy and is therefore an important diagnostic tool with the added advantage of the possibility of specific dynamic examination and ten times higher resolution compared to a conventional 3 Tesla MRI device. [2]. For images of cases please visit Radiopaedia.org.

There are several different classification systems for bone changes in RCTs. However, they do not have the same treatment implications as the other two modalities mentioned before.

Differential Diagnosis

• Acromioclavicular Osteoarthritis

• Glenohumeral Osteoarthritis

• Calcific tendinitis

• Lesion of the long biceps tendon

• Subacromial pain syndrome

Note: These diagnoses can be found concomitant as they may be the result of or may result in each other.

It is known that full-thickness tears do not heal on their own, but rather progress in size if not repaired surgically [1]. Progression in size also correlates with muscle atrophy and symptoms [1, 5]. Symptomatic as well as asymptomatic chronic, atraumatic full-thickness tears progress at a similiar rate [5]. In addition, fatty infiltration and muscle atrophy were shown not to improve after surgical repair and that the presence is associated with a poorer outcome [2].

However, the overall prognosis with both operative and conservative management is very favourable. With 90% satisfactory results after surgical treatment in a follow up of 10 years, data shows that treatment of rotator cuff tears has advanced swiftly [1].