Background and Etiology
The shoulder complex is built for mobility, however this ability to move comes with the designation of being the most unstable joint in the body. The shoulder is composed of three osseous joints and one articulation, with stability provided by muscles, ligaments, the glenoid labrum and joint capsule.
There are different degrees of instability including instability and laxity in one direction, multidirectional instability, shoulder subluxation and shoulder dislocation. When referring to shoulder instability, we are referring primarily to the glenohumeral joint.
The glenohumeral joint is a ball and socket joint between the head of the humerus bone (ball) and the glenoid fossa of the scapula (socket) or shoulder blade. The head of the humerus is large and the glenoid fossa is small, resulting in an unstable but mobile joint.
Unidirectional Instability
The shoulder depends on ligaments, muscles and the labrum for stability. Therefore, if a person has loose ligaments or weak muscles the shoulder can become unstable. The shoulder does not actually dislocate, but can slide around in the glenoid fossa. Repetitive overhead activities can also produce instability. Anterior instability is the most common.
Multidirectional Instability
This is a less common situation where there is instability in many directions. This may occur in people who have loose ligaments throughout their body. It is common in athletes who rely on overhead motions like those used in volleyball, swimming and overhead throwing. Individuals who have a history of dislocation may be prone to instability.
Subluxation
A subluxation is a partial dislocation of the shoulder, because the humerus does not completely come out of the glenoid fossa. This is most common after trauma to the shoulder or from a fall (often on an outstretched hand.) People with loose or lax ligaments are most susceptible to this type of instability. It can even get to the point where these incidents occur while performing simple activities like putting on a shirt.
Dislocation
A shoulder dislocation is when the head of the humerus actually comes out of the glenoid fossa. Ninety percent of shoulder dislocations occur anterior (toward the front of the shoulder). Less than 10% of the shoulder dislocations occur posteriorly. The initial injury is usually acute, caused by direct or indirect trauma. In anterior dislocations the shoulder is usually in an abducted external rotation position (hand behind head). Posterior dislocations may be caused by spasm from seizure, electrocution or falling on an outstretched arm. Dislocations are most common in the younger population. Glenoid Labrum tears may be secondary injuries in the younger individual, while rotator cuff tears may occur in the older population. When the shoulder dislocates it stretches the ligaments that stabilize and support the joint. Repeated dislocations can result in permanent ligament laxity, which causes chronic reoccurring dislocations.
- Weakness of the rotator cuff and laxity of the glenohumeral ligaments are the most common cause of shoulder instability.
- General ligamentous laxity may predispose an individual to instability or dislocation.
- Repetitive strain injuries (RSI) at work, or overuse activities are common in people who participate in sport activities and individuals who have jobs that require performing activities of a repetitive nature, like working on an assembly line.
- Those participating in activities like swimming or activities characterized by overhead motion like tennis, softball, baseball, volleyball, overhead throwing and other repetitive sport activities may aggravate the shoulder, resulting in shoulder instability.
- Sudden trauma or accident like a fall on the shoulder or a fall when the arm is placed in an abducted externally rotated position (hand behind head) can also cause a shoulder dislocation.
Instability or Subluxation:
- General tenderness of the shoulder area
- Discomfort with movement, especially with overhead activities
- Pain with overhead activities or sleeping on the effected side
- Feeling that the arm is “dead” after repeated activity
- A feeling that the shoulder will “go out” when reaching up and behind the head. This is called the Apprehension Sign.
Dislocation
- Significant pain of the shoulder
- Prefers to keep the arm held at the side, and inability or unwillingness to move the arm.
- Loss of normal rounded contour of the shoulder
- Swelling, weakness, numbness and occasional bruising of the shoulder area
Treatment of Shoulder Instability
Conservative treatment of shoulder instability is the first line of action. This includes physical therapy to reduce inflammation and associated pain. In addition, a regiment of exercises to improve rotator cuff strength and shoulder stability should be initiated. In more severe cases of instability involving the glenoid labrum, surgical intervention may be necessary.
Treatment of Shoulder Dislocations
Physicians reduce acute dislocations using several techniques, which may or may not require radiographic examination.
- Age and activity level are factors that guide treatment
- In young athletes (15 to 25 years old,) surgical intervention is considered based on the high risk of recurrence, apprehension, impact on sports participation and quality of life
- Generally arthroscopic repair is used for the younger population
- There is a lower rate of occurrence among 25 to 40 year olds therefore members of this population respond better to conservative interventions
- People 40 years old and over have an even lower rate of recurrence, but do have increased risk of residual disability from rotator cuff tear and nerve or vascular injury
- Conservative treatment whether post surgical or non-surgical is typically recommended
- Typically a period of immobilization with the arm held in internal rotation supported by a sling for up to six weeks is recommended
Physical Therapists are professionals, educated and trained to administer interventions. As stated in The Guide to Physical Therapist Practice interventions are the skilled and purposeful use of physical therapy methods and techniques to produce changes consistent with the diagnosis, prognosis, and the goals of the patient or client. Common interventions in the treatment of Shoulder Instability include:
- Manual Therapeutic Technique (MTT): hands on care, including soft tissue massage, and joint mobilization by a physical therapist to modulate pain and reduce any soft tissue or tendon irritation.
- Therapeutic Exercises (TE) including strengthening exercises to improve strength of the rotator cuff muscles in the shoulder and increase stability.
- Neuromuscular Reeducation (NMR) to restore stability, begin retraining the upper extremity, improve proximal joint stability and improve movement technique and mechanics (for example, throwing or reaching over head) in daily use of the involved upper extremity.
- Modalities that can include the use of ultrasound, electrical stimulation, ice, cold laser and others to decrease pain and inflammation at the shoulder and tendons.
- Home program that includes strengthening, stretching and stabilization exercises as well as instructions to help the person perform daily tasks and advance to the next functional level.
Procedures that your physician may recommend and perform in addition to physical therapy.
- Relocation and initial immobilization of the dislocated shoulder
- REST and ICE
- The use of NSAIDS (Non Steroidal Anti-Inflammatory Drugs)
- Steroidal Injections to reduce inflammation
- Pain medication to reduce the discomfort and allow the patient to perform the recommended exercises
- Surgery to correct underlying pathology and avoid instability and repeated dislocations. This may include labral repairs or procedures to tighten the shoulder capsule or ligaments.
Prognosis
Most people recover full function following a course of conservative care of physical therapy to strengthen and stabilize the shoulder. Those with more involved situations such as labral tears, chronic dislocations and/or rotator cuff tears will require surgery and intensive physical therapy afterward to restore full function.
