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Shoulder Dislocation and Instability

What is a shoulder dislocation versus subluxation?

The shoulder joint is a ball-and-socket joint formed by the head of the upper arm bone called the humerus and the glenoid (i.e. socket component) of the scapula.  In a shoulder dislocation, the head of the humerus fully pops out from the glenoid.  A shoulder subluxation is when the joint partially comes out of place.  Both are different from a Shoulder Separation, which is a where the Clavicle bone separates from the Acromion bone. 

Why do shoulder dislocations occur and what causes them?

The shoulder joint is the most mobile joint in the body due to the fact that the head of the humerus is so much larger than the glenoid, and thus has been likened to a golf ball sitting on a tee.  With increased mobility, however comes less stability. To keep the ball from falling off the tee, the humerus bone is held to the glenoid by ligaments (Labrum), which are like leather bands that connect the two bones. 

 

In general, trauma such as with a fall onto an outstretched arm, direct blow to the shoulder, surfing, or motor vehicle accidents can lead to a shoulder dislocation.  It’s important to keep in mind that certain patients are what we call “ligamentously lax”.  The soft tissue structures that support the shoulder are inherently looser in these patients, which can result in shoulder subluxations and even dislocations with minimal trauma (i.e. during sleep and normal everyday activities).

 

What types of injuries happen with a shoulder dislocation?

Multiple injuries can happen when the shoulder dislocates.  First, for a shoulder to dislocate, usually the ligaments are torn or at least stretched out.  Other damage such as rotator cuff tears, and joint cartilage damage often occurs, and can lead to early-onset arthritis (refer to the section on shoulder glenohumeral joint arthritis for more information).

Fractures and bone defects can also occur, the two most common being a Bony Bankart lesion and a Hill-Sachs deformity.  In a Bony Bankart lesion, not only are the labrum and common ligament of the shoulder torn, but a portion of the glenoid fossa (i.e. shoulder socket) is fractured.  In a Hill-Sachs deformity, the head of the humerus sustains a bony defect (i.e. indentation) as it forcefully impacts the shoulder socket during dislocation.  Nerve injuries, although rare, can also occur.

 

Symptoms

Patients who fully dislocate usually will feel the joint pop out, followed by pain, limited range of motion, weakness, and deformity of the shoulder.  

Numbness and tingling may also occur, especially in those joints that are not reduced back to their normal position in a expeditious manner.  

Patients who suffer subluxations may also feel like their joint pops momentarily out of the joint, or may just feel clicking, pain, and occasional numbness and tingling.

 

Diagnostic Imaging

An x-ray is usually ordered first to ensure the shoulder has been reduced to its normal location and to evaluate for a fracture.  An MRI is also usually ordered to further evaluate for injuries to the labrum and other soft tissue structures of the shoulder.

 

Treatment

Any shoulder that is dislocated needs to be reduced back into position as soon as possible.  The longer it remains dislocated the harder it is to put it back in place, and the more likely other complications such as neurovascular compromise can occur.  Patients will then normally be immobilized in a sling for up to 4-6 weeks depending on the patient’s age and other factors.  Following immobilization, the patient will begin physical therapy to focus on strengthening the supporting muscles of the shoulder for 6 weeks or longer.

 

Young patients with a 1st time traumatic shoulder dislocation, high-demand athletes, recurrent dislocators, and patients who continue to experience instability despite nonoperative means would benefit from operative intervention.  The reason for the surgical recommendation for 1st time dislocators in young patients is that it has been shown that in patients who are 25 yrs or younger who dislocate for the first time, the chance of redislocating is extremely high (greater than 90%). 

 

In these patients, Dr. Steven Lee will repair the ligaments/labrum

arthroscopically using suture anchors.  Arthroscopy involves making a very small incision over the shoulder and introducing a small video camera into the shoulder joint.  The image is then projected onto a monitor in real time so that the labrum and surrounding structures can be examined.  Additional small incisions are then made in order to introduce other small arthroscopic instruments to repair the labrum. Shoulder arthroscopy is minimally invasive and can result in less soft tissue disruption, less pain, and minimal scar formation.  Advancements in technology married with Dr. Lee's extensive experience has transformed this previously complicated procedure into one that can be performed in about 20 minutes in an outpatient ambulatory setting.  Learn more about scheduling surgery. 

 

Patients with significant glenoid (shoulder socket) bone loss following dislocation may require surgery to restore lost bone.  Think of glenoid bone loss as chipping off a portion of the golf tee.  If a large enough portion of the tee is missing, then the golf ball will not be able to securely sit on the tee.  There are a variety of techniques for performing this surgery.  Choosing the best technique is individualized to each patient and dependent on a variety of factors. 

 

Patients with large Hill-Sachs lesions (bone defect or indentation of the humeral head) may experience catching and locking of the shoulder with certain movements and may therefore benefit from something called a Remplissage Procedure.  In this procedure, a portion of one of the rotator cuff muscles called the infraspinatus is tied down into the defect to limit rotation of the humeral head and prevent catching and locking.  Many additional factors other than the size of the Hill-Sachs lesion go into to determining who is a good candidate for this procedure.   

 

Post-Operative:

Patient's undergoing surgery to the repair the labrum +/- shoulder capsule will have their incision sites sutured and dressed and they will be placed into a shoulder sling after surgery. Patients are instructed to stay in the sling until their first post-op appointment 7-10 days after surgery.  Sutures are usually removed at the first post-op appointment and patients are usually instructed to remain in the sling for an additional 4 weeks.  Formal Physical Therapy is usually started around 4 weeks after surgery, although basic home exercises will be instructed to the patient prior to this.  Patients will initially remain in the sling when not doing Physical Therapy and can expect to slowly wean use of the sling as Physical Therapy progresses.  Return to normal activity/sports usually takes 4-6 months depending on the activity or sport.

 

Learn more about post-operative care.

 

Post-Operative Instructions

Download here.

 

 

 

 

 

 

 

 

*It is important to note that all of the information above is not specific to anyone and is subject to change based on many different factors including but not limited to individual patient, diagnosis, and treatment specific variables.  It is provided as an educational service and is not intended to serve as medical advice.  Anyone seeking specific orthopedic advice or assistance should consult Dr. Steven Lee or an orthopedic specialist of your choice.

*Dr. Steven Lee is a board certified orthopedic surgeon and is double fellowship trained in the areas of Hand and Upper Extremity Surgery, and Sports Medicine. He has offices in New York City, Scarsdale, and Westbury Long Island.