Anterior shoulder instability typically results from a dislocation injury to the shoulder joint when the humeral head (ball) of the humerus (upper arm bone) is displaced from its normal position in the center of the glenoid (socket) and the joint surfaces no longer touch each other.
The most common dislocation is anterior, accounting for more than 90 percent of shoulder dislocations, where the humeral head is displaced in front of and below the glenoid.
What Is Anterior Shoulder Instability?
Because the shoulder has more motion than any other large joint in the body, it is the most often dislocated large joint. The shoulder is like a golf ball on a golf tee, with many structures contributing to its stability.
These structures include the bony contours of the humeral head (ball) and glenoid (socket), the labrum, the capsule and ligaments, and the rotator cuff muscles. The labrum surrounds the rim of the socket and helps keep the head of the humerus in place.
When the shoulder is dislocated, these stabilizing structures may be injured to different degrees, including the humeral and glenoid bone, labrum, capsule and ligaments, and rotator cuff muscles. In younger, active patients, the labrum commonly tears away from the glenoid along with the attached stabilizing capsule and ligaments. This is called a Bankart lesion.
Without repair, the shoulder may remain unstable and continue to dislocate, potentially causing further injury to the stabilizing structures.
Causes and Risk Factors
Causes and risk factors for anterior shoulder dislocation and instability can include:
- A direct blow to the shoulder
- Tackling or falling on an outstretched arm
- Repetitive throwing motion or swimming
- A previous shoulder dislocation injury
- A congenital abnormality, such as a shallow or malformed joint surface
- Violent muscle contractions associated with seizures
- Contact sports, such as football, wrestling, and basketball
- Sports involving repetitive overhead activity, such as baseball, volleyball, and swimming
- Sports requiring forceful lifting, hitting, or twisting
- Previous shoulder dislocations or sprains
- Shoulder fracture
- Repeated shoulder injury
- Poor physical conditioning, including strength and flexibility
Symptoms
Frequent signs and symptoms can include:
- Severe shoulder pain at the time of the dislocation
- Loss of shoulder function and severe pain when attempting to move the shoulder
- Apprehension or the feeling that the shoulder wants to slip out of place with overhead positions
- Tenderness, deformity, and swelling
- Pain with shoulder movement, particularly reaching overhead or heavy lifting
- Pain that awakens you at night
- Loss of strength
- Numbness or paralysis in the upper arm and deltoid muscle from pinching, stretching, or pressure on nerves
- Crepitation (a “crackling” feeling or sound) with shoulder motion or when the injured area is touched
Diagnosis
Following a shoulder dislocation, X-rays, MRI studies, and sometimes CT scans may be needed to determine the full extent of injury to the stabilizing structures of the shoulder joint.
Treatment
Shoulder dislocations should be reduced (put back in place) as soon as possible for the comfort of the patient and to release potentially damaging traction on nerves and blood vessels. It may also help restore blood flow to the humeral head bone that may be obstructed with the dislocation.
Following reduction, slings should be discontinued and early range of motion and gentle strengthening should begin to restore shoulder function.
Younger patients often require arthroscopic surgery to repair the torn labrum, capsule, and ligamentous structures and sometimes fractures of the bone or tears in the rotator cuff. Early surgery is typically recommended in younger, active patients to repair the torn labrum and capsular ligaments and restore shoulder stability.
Patients over age 40 have a lower risk for re-dislocation, and conservative treatment is often an option. However, these patients have a higher risk of tearing the rotator cuff with a dislocation, which may also require surgery.
Recovery and Outcomes
Following reduction of a shoulder dislocation, early functional recovery is excellent, but re-dislocation rates can be high even with proper treatment.
For younger, active patients, re-dislocation rates without surgical repair are extremely high. These patients often require arthroscopic repair of the injured stabilizing structures, including the torn labrum, capsule, and ligaments.
Patients older than age 40 have lower re-dislocation rates but a higher rate of rotator cuff injury. These patients can often be treated successfully without surgery unless a rotator cuff tear or fracture is present that requires surgical treatment.
Each subsequent dislocation may require less force to cause another dislocation, and repeated injuries can contribute to an unstable or arthritic shoulder.
When to See Dr. Chudik
If you experience a shoulder dislocation, recurrent instability, or the feeling that your shoulder wants to slip out of place with certain movements, contact Dr. Chudik’s office for an evaluation.
Call 630-324-0402, email contactus@chudikmd.com, or request an appointment online.