Simple Approach to the Shoulder Complex
Shoulder diagnosis and assessment can be confusing and difficult, with the shoulder being a complex of 30 muscles, 5 joints and many ligaments. However, there are many typical patterns to common shoulder disorders and in this presentation we aim to present a simplified (although not fully comprehensive) approach to common shoulder conditions.
A SIMPLE APPROACH TO THE SHOULDER COMPLEX
Lennard Funk, 2008
With its 5 joints, 8 ligaments and 30 muscles, the shoulder complex presents a compromise between stability and mobility, and the result is that it is inherently unstable.
Regarding the muscles, those attached to the scapula, such as trapezius and serratus transfer energy to the arm, along with pectoralis and latissimus dorsi; while the rotator cuff muscles maintain the centre of rotation of the humeral head, and its position in the glenoid.
The primary sources of pain are:
1. AC joint, including the articular meniscus
2. Subacromial area, with the rotator cuff, the bursa and the acromion
3. Glenohumeral joint, including the articular labrum, the biceps and the capsule
1. Subacromial Area
Pain from the subacromial area is often worst over the upper arm. Patients show the affected area as a broad area over the lateral upper arm - the 'grasping sign'. Pain may radiate down the arm, but proximal radiation is unusual.
The tests for subacromial pain ( impingement pain ) that are most useful are the Hawkin's and Neer's signs:
- Hawkin's Test : The patient is examined in sitting or standing, with their arm at 90 deg and their elbow flexed to 90 deg, supported by the examiner to ensure maximal relaxation. The examiner then stabilises proximal to the elbow with their outside hand and with the other holds just proximal to the patient's wrist. They then quickly move the arm into internal rotation.
- Neer's Sign : Pain at the mid-range of passive abduction with the arm internally rotated.
The common causes of subacromial pain are impingement, rotator cuff tears and calcific tendonitis.
Rotator cuff tears may be acute (traumatic), chronic (degenerative) or acute on chronic. It is the acute and acute on chronic tears which generally require surgical intervention. These would typically have a history of some trauma (albeit minor). The pain is present when bringing the arm down from an abducted position, as well as on elevation. Impingement pain is only felt when elevating the arm in abduction (known as mid-arc pain or painful arc)
Calcific tendonitis is a more extreme version of impingement and the acute calcific deposit may be disabling.
Ultrasound scan is the easiest, quickest and cheapest modality to differentiate between the above pathologies and diagnose any associated pathologies (commonly biceps).
When to refer for surgical opinion: For impingement, I recommend referral if the pain is severe, persists at night and reduces quality of life, and also if physiotherapy and injection therapy fail to settle the symptoms adequately. For rotator cuff tear, we recommend referral for all young active cases. For elderly or sedentary people, injection and physiotherapy are usually satisfactory.
2. Acromioclavicular Joint
Acromioclavicular joint pain is typically located specifically over the joint - the 'pointing sign'. Pain may radiate to the neck. Cervical spondylsosis and AC Joint arthritis commonly present together. The AC joint is loaded maximally when adducting the arm in flexion, therefore the most widely used test is the scarf (or forced adduction) test - the 90 degrees flexed arm on the affected side is forcibly adducted across the chest. It is essential that the patient reports the pain as being specifically over the AC joint with this test for a positive test. It is common to feel posterior capsule stretch pain with the test (false positive).
Paxinos test is loading the joint in the horizontal direction (shear) - The examiner's hand is placed superior to the ipsilateral mid-clavicle. Pressure is applied by the thumb in an anterosuperior direction and inferiorly with the index-middle finger to the
midshaft of the clavicle.
An injury to the AC joint is typically sustained from a direct fall on the point of the shoulder. The injury may range from a torn meniscus of the joint to a complete dislocation .
AC joint pain in the absence of an injury is usually arthritis in patients over 30 years of age. Osteolysis is a stress fracture of the lateral end of the clavicle and is typically seen in weight-lifting males under the age of 30. Ultrasound and/or x-rays are useful in confirming an AC joint pathology, but the diagnosis is generally clinical. Recommendations for referral are the same as those for impingement pain.
3. Glenohumeral joint
Glenohumeral joint pain can easily be diagnosed by pain reproduced on rotating the joint (GHJ) with the arm by the side (similar to hip joint pain). The pain is mainly felt deep in the joint, but may radiate down the arm also. If the GHJ is stiff (limitation in passive external rotation) then frozen shoulder (primary or secondary should be considered. This is also generally a younger age group than GHJ arthritis . The main investigation is AP and axillary view x-rays of the shoulder.
NSAIDs, injections and physiotherapy is indicated for pain that is not disabling. However if the pain is disabling with night and rest pain, referral to a shoulder surgeon is recommended.
Red Flag conditions giving severe, unremitting shoulder pain are:
- frozen shoulder
- acute calcific tendonitis
- discogenic pain (C5-7)