Shoulder Subluxation


Original Editor ­ Bart Moreels

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Definition

Shoulder subluxation, a subset of shoulder instability, occurs when the shoulder joint partially dislocates. In this condition the humeral head slips out of the glenoid cavity as a result of weakness of rotator cuff or laxity of the glenohumeral ligaments. Watch this 4 minute video for an introduction..

Epidemiology

Studies are limited that investigate the epidemiology of shoulder subluxation, with most studies focus more on shoulder dislocations.

• In a study on shoulder subluxations, 45.5% experienced the first subluxation event, while the remaining 54.5% had recurrent shoulder subluxation.
• Shoulder subluxations frequently occur in people with hemiplegic stroke or with a paralysed upper limb (see Hemiplegic Shoulder Subluxation). The reported incidence varies greatly from 17% to 81%  . 

Etiology

Causes can be classified as traumatic, non-traumatic or neuromuscular:

1. Traumatic cause: more frequent in active young individuals. Prevalent in for example: boxers,; non-contact sport with repetitive shoulder movements; a hand in the outstretched position.
2. Non-traumatic cause: multifactorial. For example: patients may have suboptimal shoulder muscle control or tendon/ligament injury in the rotator cuff interval
3. Neuromuscular causes: for example stroke, cerebral palsy, and brachial plexus injury.

Characteristics/clinical presentation

The main problem with shoulder subluxation is the instability of the glenohumeral joint. Common symptoms of chronic shoulder instability include:

• Recurrent shoulder dislocations
• Periodic instances of the shoulder giving out
• A persistent feeling of the shoulder being loose or slipping in and out of the joint.
• Pain

Research by Basmajian determined that the supraspinatus and in minor ways also the posterior fibres of the deltoid muscle play a key role in maintaining glenohumeral alignment. Chaco and Wolf did confirm this in their study, which said that the supraspinatus is very important in preventing the downward subluxation of the humerus.

Subluxation occurs with the shoulder in abduction and external rotation.

Other research shows that the most important ligamentous structure to maintain correct shoulder position and also to prevent shoulder subluxation is the inferior glenohumeral ligament.This ligament is most important during external rotation and abduction during the cocking face of the throwing motion.

Shoulder subluxation can lead to soft tissue damage as traction damage can occur due to gravitational pull forces and poor protection is offered by a weak shoulder. It is usually quite painful, and there might be a partial numbness of the shoulder, arm, and hand.

Differential Diagnosis

• Acromioclaviculair joint injuries: common and often seen after bicycle wrecks, contact sports, and car accidents. The acromioclavicular joint is located at the top of the shoulder where the acromion process and the clavicle meet to form a joint. Several ligaments surround this joint, and depending on the severity of the injury, a person may tear one or all of the ligaments. Torn ligaments lead to acromioclavicular joint sprains and separations.
• Bicep tendinopathy, is an inflammatory process of the long head of the biceps tendon and is a common cause of shoulder pain due to its position and function.
• Clavicular injuries: Although clavicle fractures are common and usually heal regardless of the selected treatment, complications are possible, warranting careful attention to these injuries.
• Rotator cuff injuries are a common cause of shoulder pain in people of all age groups. They represent a spectrum of disease, ranging from acute reversible tendinitis to massive tears involving the supraspinatus, infraspinatus, and subscapularis. Diagnosis is usually made through detailed history, physical examination, and often, imaging studies.
• Shoulder dislocations may occur from a traumatic injury or from loose capsular ligaments. Different conditions may affect the stabilising structures of the shoulder and, thus, negatively affect patients with shoulder dislocations.
• Swimmer's shoulder is the term used to describe the problem of shoulder pain in the competitive swimmer. Swimming is an unusual sport in that the shoulders and upper extremities are used for locomotion, while at the same time requiring above average shoulder flexibility and range of motion (ROM) for maximal efficiency. This is often associated with an undesirable increase in joint laxity.

Diagnostic Procedures

Symptoms
Patients with shoulder subluxations commonly present with:

• Pain in the shoulder region
• Loss of range of movement 
• The palpable gap between acromion and humeral head (this can be informally measured in finger-widths)

Functional testing

• The subluxation test is positive = resistance is given when the patient brings arm in throwing stance, in internal rotation direction.
• Pain in the ventral capsule indicates a frontal capsule lesion.
• Pressure during resistance test on the dorsal part of the humerus can provoke ventral gliding. The result is sudden pain in the
• shoulder and in a number of cases there is a subluxation to the front. This test can be conducted in different degrees of abduction and with or without the support of the upper arm.

Radiographic measurements are considered to be the most accurate way of evaluating the degree of subluxation

Outcome Measures

• Oxford Instability Shoulder Score (OISS): a 12-item questionnaire with five possible Likert style responses for each question and has a range from 0 to 48 (with a score of 48 indicating better shoulder function). The OISS has been developed and validated for shoulder instability and has also undergone testing to assess responsiveness in shoulder instability patients.
• Western Ontario Shoulder Instability Index (WOSI): a 21-item questionnaire with a 100-mm horizontal visual analogue scale under each question for patient responses and ranges from 0 to 2100 and is converted to a percentage, with 100% representing the highest possible shoulder-related quality of life. The WOSI is a rigorously designed and evaluated measurement tool for patients with shoulder instability and has been shown to have excel- lent responsiveness in posterior instability.

Examination

First, the examiner should ask the patient about the history of the reason he subluxated his arm. Then he can perform an inspection, when he does he should make sure that he can have a visual on both shoulders at the same time to see the difference.
After this you could use different tests to test whether the patient had a subluxation of the shoulder:

• Load and shift test

In this test, the examiner stabilises the scapula and moves the humeral head to the posterior and anterior. With this test, the examiner can feel if the humeral head is going to subluxate.

• Push-Pull test

The patient's arm is placed in 90 degrees of adduction and 30 degrees of forward flexion. With his other hand, the examiner grasps the mid humerus and provides posteriorly directed force. This test is used to measure the posterior laxity of the shoulder.

• Protzman test

This test is similar to the Load and shift test but the second hand is placed in the axilla to feel for translation of the humeral head or to feel if the humeral head subluxates over the rim.

Physical Therapy Management

For Traumatic and Non-Traumatic Patient, see also detailed information here Shoulder Instability

Prevention of reccurance
Strengthening exercises to re-establish the strength of the rotator cuff muscles is recommended. 
Initial physical therapy interventions may include:

• Mobility exercises including PROM, AAROM, AROM
• Motor control training
• Scapular stabilization
• Isometric and low-grade strengthening exercises
• Manual therapy directed at the Glenohumeral,recurrencelavicular and Sterno-Clavicular joint

• Manual therapy of cervicothoracic spine and upper ribs
• Activity modification

Late stages of rehabilitation of rotator cuff injury include progressive resistive strengthening, proprioception and sport-specific exercises.