What is multidirectional shoulder instability?

Multidirectional shoulder instability is a problem of the shoulder joint in which the upper arm (humerus) is displaced from its normal position in the center of the socket (glenoid) and the joint surfaces to no longer touch each other. With this type of instability, the humerus may move in front of (anterior), below (inferior), or behind (posterior) the glenoid. Because the shoulder has more motion than any other large joint in the body, it is the most commonly dislocated large joint.

The shoulder is like a golf ball on a golf tee. A few of the many structures that provide shoulder stability include the cartilage rim (labrum), which helps provide depth to the socket; the capsule, with thickenings that are the ligaments of the shoulder; and the muscles of the rotator cuff, which surround the shoulder.

Dislocated shoulders

To dislocate the shoulder, the rotator cuff muscles need to be stretched or torn, the capsule and ligaments need to be stretched, and often the labrum is pulled off the glenoid. Subluxation of this joint is also common in sports; this is when the ball of the humerus does not stay centered in the socket with shoulder motion and feels like it will slip out of place.

Subluxation of the shoulder leads to overuse of the rotator cuff muscles by trying to keep the humeral head in the center of the socket causing rotator cuff symptoms. Further, fatigue of the rotator cuff muscles as the deltoid muscle contracts may push the humeral head up to the roof of the shoulder, pinching the subacromial bursa and supra-spinatus tendon (part of the rotator cuff). This type of instability tends to occur in loose-jointed (“double-jointed”) people.

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How does multidirectional shoulder instability occur?

• Direct blow to the shoulder or backward force on an extended or outstretched arm or arm overhead (traumatic causes are not as common)
• Usually, microtraumatic or atraumatic onset
• Repetitive throwing motion or swimming
• End result of a severe shoulder sprain
• Congenital abnormality (you are born with it), such as a shallow or malformed joint surface or a ligament disorder
• Powerful muscle twisting or violent muscle contraction

Some people can willfully produce a recurrent dislocation.

What increases the risk?

• Loose joints
• Contact sports (football, wrestling or basketball)
• Sports that involve repetitive overhead activity, such as baseball, volleyball or swimming
• Sports that require forceful lifting, hitting or twisting
• Previous shoulder dislocations or sprains
• Shoulder fracture
• Repeated shoulder injury of any kind
• Poor physical conditioning (strength and flexibility)

What are the symptoms of multidirectional shoulder instability?

• Severe pain in the shoulder at the time of injury, although many people do not have an injury and may not have pain that is severe
• Pain when using the arm overhead or carrying heavy objects with the arm at the side
• Loss of shoulder function and pain when attempting to move the shoulder
• Commonly, both shoulders affected
• Feeling like the shoulder will to slip out of place
• Tenderness, deformity (fullness in the armpit and prominent roof of the shoulder or fullness in the back of the shoulder) and, occasionally, swelling
• Pain with moving the shoulder, especially when reaching overhead; pain with heavy lifting; pain that awakens at night
• Loss of strength
• Numbness or paralysis in the upper arm and deltoid muscle from pinching, stretching or pressure on the blood vessels or nerves
• Feeling and sound of crepitation (“crackling”) when the injured area is touched or with shoulder motion
• Decreased or absent pulse at the wrist because of blood vessel damage (rare)

How is it treated?

Non-operative treatment: After reduction (repositioning of the bones of the joint), treatment consists of ice and medications to relieve pain. Immobilization by sling or immobilizer for three to eight weeks is usually recommended to protect the joint while the ligaments heal. After immobilization, stretching and strengthening of the stiff, injured, and weakened joint and surrounding muscles (due to the immobilization and the injury) are necessary. These may be done with or without the assistance of a physical therapist or athletic trainer.

Operative treatment: Reduction usually can be performed without surgery; surgery may rarely be necessary to restore the joint to its normal position, as well as to repair ligaments.

Surgery for shoulder instability is reserved for people who have recurrent shoulder dislocations or subluxations that affect activities of daily living or sports activities. Usually these patients have tried an appropriate rehabilitation program for at least six months with symptomatic recurrent shoulder dislocation or subluxation. This type of instability is uncommonly due to trauma. More often, there is no history of trauma or repetitive trauma, such as with repetitive throwing or swimming. The likelihood of success of a rehabilitation program is 80 percent.

Surgery may also be performed in a patient who has had a prior failed operation for shoulder instability. The goal of surgery is to stabilize the shoulder to prevent further subluxations or dislocations. One of the reasons the shoulder is the most commonly dislocated major joint is that it has more motion than any other major joint.

Tightening the shoulder joint may reduce some shoulder motion. Stabilizing the shoulder is done by tightening the capsule. The directions of instability are anterior (front), posterior (back), or inferior (below the glenoid). Less often, other structures may be moved or used to replace or give additional support to the capsule of the shoulder. Recurrent dislocations or subluxations without fracture are rarely associated with arthritis. Thus, the timing of surgery in relation to the injury is not critical. The results of shoulder stabilization for multidirectional instability are not as good as for anterior stabilization.

Different techniques are in use at this time. There are arthroscopic techniques and open-incision techniques. The overall goal is to tighten the capsule and ligaments. Although the looseness is in more than one direction, there is usually one direction of instability or looseness that predominates. The surgical approach is dependent on the direction of greatest looseness and on the degree of ligament laxity. The surgical approach may be from the front of the shoulder, the back of the shoulder, or both.

One of the most popular open techniques involves getting to the shoulder capsule by splitting or moving muscles and tightening the stretched capsule and ligaments by folding the excess capsule underneath itself and stitching it together with sutures (threads), with or without surgical anchors, which are inserted into the glenoid rim. This can be done in the front of the shoulder or from the back of the shoulder. Usually some looseness of the back of the shoulder and bottom of the shoulder can be eliminated when tightening from the front of the shoulder.

Arthroscopic techniques involve using small incisions (arthroscopy portals) to tighten the stretched capsule, either by folding the excess capsule underneath itself and sewing it together with sutures (threads), with or without surgical anchors, which are inserted into the glenoid rim, or by using heat to shrink it.

Other techniques do not try to replicate the normal anatomy of the shoulder capsule and ligaments. These include moving muscle to reduce shoulder motion or moving bone from another area and using the bone to block shoulder dislocations.

What are the complications of treatment?

Possible complications of operative treatment include:

• Surgical complications not specifically associated with this injury, such as pain, bleeding (uncommon), infection (<1percent), nerve injury (uncommon), stiffness, problems with anesthesia, and inability to return to previous level of pre-injury activity.

When can you return to your sport/activity?

With appropriate reduction (repositioning of the joint) and immobilization for three to six weeks, healing of ligaments can be expected in 6 weeks. Repeated shoulder dislocations and subluxations are common. If customary treatment does not prevent a recurrence, athletic activities should be modified until surgery can be performed to cure the problem. For those whose symptoms aren’t caused by injury, rehabilitation has a high likelihood of success. Return to sports depends on the type of sport and position, as well as the quality of ligaments at the time of repair. Usually six to 12 months is necessary after surgery before returning to sports. Full shoulder motion and strength are necessary before returning to sports.

How can multidirectional shoulder instability be prevented?

• Appropriately warm up and stretch before practice or competition
• Maintain appropriate conditioning:
  • Shoulder strength
  • Flexibility and endurance
  • Cardiovascular fitness
• For participation in contact sports, wear protective shoulder pads