Shoulder Dislocation

United States statistics

The shoulder is the most commonly dislocated joint in the body.[1, 4, 6]

Although most shoulder dislocations occur anteriorly, they may also occur posteriorly, inferiorly, or anterior-superiorly.

Patients with a previous shoulder dislocation are more prone to redislocation. This occurs because the tissue does not heal properly and/or because the tissue stretches out and becomes more lax.

Other factors that show a clear correlation to redislocation are the age of the patient and concomitant rotator cuff tears and fractures of the glenoid.

Younger patients (teenagers and those aged 20 years) have a much higher frequency of redislocation than patients in their 50s and 60s.[7] Many physicians believe that age is less of a predisposing risk factor for redislocation than activity level.

Patients who tear their rotator cuffs or fracture the glenoid during their shoulder dislocation have a higher incidence of redislocation than patients without these problems.

In a retrospective cohort study, Kardouni et al found the 10-year incidence rate of shoulder dislocations in US Army soldiers to be 3.13 per 1000 person-years, or a total of 15,426 incident shoulder dislocations. The recurrence rate was 28.7%. Injury risk was greater in males and soldiers aged 40 years or younger, with recurrence risk increased by concurrent axillary nerve injury and age of 35 years or less.[8]

Shoulder stability is maintained by the glenohumeral ligaments, the joint capsule, the rotator cuff muscles, the negative intra-articular pressure, and the bony/cartilaginous anatomy.

The main stabilizers of the shoulder joint are the ligaments and the capsule complex. Multiple ligaments are present, but the inferior glenohumeral ligament is the most important and the one most commonly injured during an anterior shoulder dislocation. The injury may be a tear of the ligament/capsule off one of its bony attachments, and/or it may cause a stretch injury to these structures.

Tears in the rotator cuff muscles may also lead to shoulder instability. Four rotator cuff muscles (supraspinatus, infraspinatus, subscapularis, and teres minor) are present in the shoulder. They are found on top of the glenohumeral ligaments and the bones. Large rotator cuff tears may lead to shoulder instability, even with intact glenohumeral ligaments. Instability of the shoulder can also occur from injury to the nerves that control the shoulder muscles, specifically the axillary nerve.

The shoulder is a very mobile joint; therefore, it is often placed in awkward positions during sports (specifically abduction and external rotation). Thus, the force from a fall or a blow may be sufficient to cause damage to the ligaments. If the force is strong enough, the athlete may tear the ligaments/tendons, fracture the glenoid or humerus and from this, dislocate the shoulder.

Approximately 95% of shoulder dislocations result from a major traumatic event, and 5% result from atraumatic causes. Distinguishing the type and severity of the event is important to determine the true etiology of the dislocation. This distinction is necessary to determine the treatment.[1, 4, 9, 2, 5]

With a traumatic dislocation, the cause is obvious; however, atraumatic dislocations can result for different reasons. Ligamentous lax shoulders may dislocate with little or no trauma. Patients with lax ligaments may have 2 loose shoulders, but only 1 may be symptomatic. Congenital causes, such as excessive retroversion of the humeral head or malformation of the glenoid, can lead to instability. Neuromuscular causes, such as injury to the axillary nerve or cerebral palsy, have also been associated with shoulder instability.

Age at dislocation is the most important prognostic indicator for recurrence of shoulder dislocations. Younger age at initial injury increases the likelihood for future dislocation. The recurrence rate is thought to be 90% if the initial episode occurs in the teen years. In patients aged 40 years or older, the recurrence rate is 10-15%. Most redislocations occur within 2 years of the primary injury. Persons with axillary nerve injuries can be expected to recover completely within 3-6 months.

Complications

The most common complication of an acute shoulder dislocation is recurrence. This complication occurs because the capsule and surrounding ligaments are stretched and deformed during the dislocation. Age is the most important indicator for prognosis; dislocations recur in approximately 90% of teenagers.

Another common complication following dislocation is fracture. The most common type is a Hill-Sachs lesion or compression fracture of the posterior humeral head. Fractures of the proximal humerus, greater tuberosity, coracoid, and acromion have also been described.

Rotator cuff tears also commonly occur as a result of shoulder dislocations, and the frequency of this complication increases with age. This complication can be expected in 30-35% of patients aged 40 years or older. Slow progression in return to active function following shoulder dislocation in a middle-aged patient should warrant a workup for a rotator cuff tear.

Vascular injuries are rare, but they do occur, especially in older patients. Vascular injuries are more common with inferior dislocations and usually involve a branch of the axillary artery.

Nerve injuries are much more common than vascular injuries, especially with anterior or inferior dislocations. The axillary nerve is the nerve injured most often and may be crushed between the humeral head and the axillary border of the scapula or injured by traction from the humeral head. Axillary nerve injury has been reported in as many as 33% of acute anterior dislocations.

Educate the patient on the importance of strength training following shoulder dislocation. The patient must understand that recurrence is possible and therapy should be used to prevent recurrence.

For more patient education information, see Shoulder Dislocation Diagnosis and Treatment.

Patients with a dislocated shoulder report a myriad of symptoms to their physician.

Because most dislocations happen from trauma, patients report feeling the shoulder pop out or roll out during the incident. Different shoulder positions during the dislocation tear different ligaments. Thus, trying to determine the shoulder position at the time of the injury is important. The most common dislocation is anterior. In an anterior dislocation, the patients report having their arm abducted and externally rotated.

It is important to ask the patient if he or she had to go to the emergency department to have the shoulder reduced. If so, he or she should have a radiograph of the dislocated shoulder. If not, ask the patient if he or she popped the shoulder back in or if it just went back in by itself. This can clue the treating physician as to how loose the shoulder has become.

Patients with very loose joints (hyperlaxity) report feeling like their joint rolls out of the socket. These patients can usually "roll" the shoulder back in.

Remember that patients with previous shoulder dislocations are more apt to redislocate, so ask about any previous dislocations.

When the shoulder dislocates, the nerves in the shoulder area can get stretched out. Some patients report stingers or numbness running down their arm at the time of the dislocation.

The physical examination in a patient suspected of having a dislocated shoulder should confirm what the clinician picked up from the history of the injury.

If the patient has a dislocated shoulder, range of motion (ROM) is poor and the patient is in a lot of pain. If the shoulder is anteriorly dislocated, the arm is in slight abduction and external rotation. In patients who are thin, the prominent humeral head can be felt anteriorly and the void can be seen posteriorly in the shoulder.

Posterior shoulder dislocations can be easy to miss, because the patient usually keeps his or her arm in internal rotation and adduction (ie, the patient holds the arm up against his or her abdomen). In patients who are thin, the prominent head can be seen and palpated posteriorly. Poster shoulder dislocations can be missed, because the patient appears to only be guarding the extremity. If the proper radiographs are not obtained, the diagnosis will be missed (see Imaging Studies).

Performing a detailed neurovascular examination before and after the shoulder has been reduced is imperative. Injury to the axillary nerve during shoulder dislocation has been reported to be as high as 40%. The healthcare provider should document the status of the neuromuscular examination before and after any dislocated shoulder reduction.

Laboratory studies are not necessary to diagnose shoulder dislocation injuries.

Radiographs

When dealing with shoulder instability, obtaining 2 orthogonal views of the shoulder is imperative.

The author suggests routinely ordering an anteroposterior (AP) view of the shoulder and an axillary lateral view. If an axillary lateral radiography cannot be obtained, then a scapular Y view may be taken in its place. If good radiographs cannot be obtained, order a computed tomography (CT) scan. This study can be performed quickly and is not expensive.

Posterior shoulder dislocations can look like a normal shoulder on the AP view. If an orthogonal view radiograph is not obtained, the diagnosis may be missed.

Magnetic resonance imaging (MRI)

MRI can show damage to ligaments that may be torn with shoulder dislocation. They are better seen with the injection of contrast into the joint before the MRI evaluation. The bony architecture on these studies can also be appreciated.

Patients older than 45 years may also tear the rotator cuff tendons when the shoulder is dislocated. The tendons are less elastic and do not stretch out during the incident and thus tear. Proper diagnosis is necessary to get these patients back to their preinjury status. If the patient is older than 45 years and has marked weakness in the strength testing of the rotator cuff muscles, an MRI is a great tool to assess for tears.

The most important treatment of an acute shoulder dislocation is prompt reduction of the glenohumeral joint.[1, 2, 3] Numerous reduction techniques have been described that can be performed after administering an intra-articular injection or after putting the patient under conscious sedation. After determining the direction of the dislocation, the physician must remember that the most important aspect of reduction is relaxation of the shoulder musculature. Once reduction has been accomplished, postreduction radiographs are necessary to verify reduction.

Shoulder reduction techniques are as follows:

• For the more common anterior dislocations, one of the oldest methods of reduction is the Hippocratic method, in which the physician's foot is placed in the patient's axilla while gentle longitudinal traction is applied. Internal or external rotation of the shoulder may facilitate reduction.

• The Stimson technique involves having the patient lie prone on an examining table, allowing the affected arm to hang off the bed. Again, longitudinal traction and internal or external rotation are applied to the arm. Weights can also be added to the patient's wrist to facilitate reduction.

• The Milch maneuver is one in which abduction and external rotation are applied to the affected extremity while the physician's thumb disengages the humeral head. This technique can also be attempted with the patient in the prone position.

• Finally, one of the simplest maneuvers is passive forward elevation of the arm while the physician maneuvers the humeral head with the opposite hand.

Differentiating a posterior from an anterior dislocation is important, because the reduction maneuvers differ. If reduction cannot be achieved with the patient under conscious sedation, general anesthesia may be needed for adequate relaxation. The patient should be in the supine position. The affected arm should be adducted with the application of gentle traction. The humeral head should be maneuvered anteriorly by the examiner's hand. The arm should not be rotated externally because the presence of a humeral fracture is possible.

Related Medscape Reference topics include Joint Reduction, Shoulder Dislocation, Anterior.

Rehabilitation program

Physical therapy

In the acute phase of a dislocated shoulder, therapy should be limited. The arm should be immobilized in a sling and swathed for 1-3 weeks. The actual position of the arm in the sling has been debated and thought to be more beneficial to the torn soft tissues with the arm in external rotation.[10, 11, 12, 13] Recent literature has shown that having the arm in internal rotation while in the sling has no impact on the rate of recurrent dislocation when compared with patients immobilized in external rotation.[14] While the patient is in the sling, elbow, wrist, and hand range of motion should be encouraged. Working with the parascapular muscles is also important during this acute phase of rehabilitation since this can be initiated while the patient is still in the sling. These exercises should be continued when the patient comes out of the sling.

Active and passive flexion, extension, abduction, and internal/external rotation begin at about the third week, when the patient comes out of the sling. The authors encourage patients to get about 10 degrees of improvement in their motion per week. One will find that patients usually progress faster than 10 degrees per week. It is important to educate the patient and inform him or her that getting all of the motion back "right away" can be detrimental to the stability of their shoulder. Rehabilitation should be geared to gently restoring the range of motion over 6-8 weeks.

A good adage during the first 3 weeks after a shoulder dislocation is to "keep the hand in view." While looking forward, the patient should never let his or her hand be placed in a position outside the line of vision. This instruction assures a midrange position that does not compromise apposition of the torn or stretched anterior capsular structures to the glenoid.

Surgical intervention

The recurrence rate for shoulder instability is highly dependent on the age of the patient. Nonoperative care should be performed first before entertaining the thought of surgery. Most patients are able to rehabilitate their shoulder with rest and physical therapy.[1, 9]

A meta-analysis of 10 studies with 1324 patients analyzed the risk factors which predispose first-time traumatic anterior shoulder dislocations to events of recurrence. The study concluded that men, patients younger than 40 years at initial dislocation, shorter time from initial dislocation, hyperlaxity and lack of greater tuberosity fracture were key risk factors that increase the risk of recurrent instability after first-time traumatic anterior shoulder dislocations in adults.[15, 16]

In patients who have recurrent shoulder instability, operative care should be highly considered.[4, 2, 5] Numerous studies have shown the increased likelihood of traumatic glenohumeral arthritis in patients with multiple shoulder dislocations. Operative care may consist of both open or arthroscopic treatment of the cause of instability.

The goal of an operative repair is to reattach the torn tissue back to the place where it tore off of the bone. The most likely spot where the ligament tears is the glenoid. Recurrent shoulder dislocations also stretch out the ligaments. It is imperative to also address the tissue laxity during the operative procedure. The surgery can be done through small incisions (arthroscopy) or with an open incision. 

A meta-analysis of 22 studies (n = 1633) comparing open versus arthroscopic surgical treatment of anterior shoulder dislocation found that either can produce reliable and reproducible results with satisfactory outcomes and recurrence rates between 10% and 15%.[17]

In a systematic review of 56 studies, Williams et al reported the following complication rates for different types of surgery for anterior glenohumeral joint dislocation[18] :

• Arthroscopic soft-tissue repair: 1.6%
• Arthroscopic repair combined with arthroscopic remplissage: 0.5%
• Open soft-tissue repair: 6.2%
• Open labral repair with remplissage: 2.3%
• Open bone-block procedure: 7.2%
• Arthroscopic bone-block procedure: 13.6%

Rehabilitation program

Physical therapy

After the initial period of immobilization, passive ROM exercises should begin. Older individuals should begin performing ROM of the shoulder after 1 week of immobilization, because these patients are prone to shoulder stiffness. Passive ROM exercises should include shoulder pendulum exercises and an overhead pulley system for the shoulder. Goals for passive ROM should be 30° of external rotation and 90° of flexion for the first 3 weeks, followed by 40° of external rotation and 140° of flexion for the second 3 weeks.

The rotator cuff may also have been injured during the dislocation, so the therapist should be cognizant of the status of the rotator cuff during the early phase of rehabilitation.

Surgical intervention

Athletes who demonstrate symptomatic instability during guarded physical therapy should be considered for an MRI evaluation and probable arthroscopic or open anterior shoulder tissue repair.

Rehabilitation program

Physical therapy

More vigorous therapy can be initiated after full passive ROM has been regained, usually after 6 weeks. Rotator cuff strengthening exercises can be initiated with the use of rubber tubing or weights. Because the rate of shoulder redislocation is so much higher in young adults, vigorous training and strengthening should be delayed until approximately 3 months after the injury. Swimming is an ideal exercise to regain shoulder strength and should be encouraged once strengthening exercises have begun.

A literature review by McIntyre et al indicated that in patients with posterior glenohumeral instability, strengthening the rotator cuff and posterior deltoid may decrease pain, increase function, and reduce instability recurrence, particularly in those with nontraumatic instability who have not had surgery.[19]

Shoulder dislocations are extremely painful events. If relocation is not accomplished within an hour, anesthesia via conscious sedation is necessary in the emergency department setting. Medications for this technique are not discussed in this article.

Oral narcotic analgesics are reasonable for a period of days, but prolonged use is categorically inappropriate.

Class Summary

Pain control is essential to quality patient care. Analgesics ensure patient comfort, promote pulmonary toilet, and have sedating properties, which are beneficial for patients who have sustained trauma. A 3- or 4-day supply of hydrocodone or similar opioid analgesic should be provided following shoulder relocation.

Hydrocodone and acetaminophen (Lortab, Norco, Vicodin)

Drug combination for moderate to severe pain.

Hydrocodone and ibuprofen (Vicoprofen, Ibudone, Xylon)

Drug combination for short-term (< 10 d) relief of moderate to severe acute pain.

Oxycodone and acetaminophen (Endocet, Percocet, Primlev)

The combination of oxycodone and acetaminophen is used for the relief of moderate to severe pain.

Oxycodone (Oxaydo, OxyContin, Roxicodone)

Oxycodone is indicated for the relief of moderate to severe pain.

Tramadol (ConZip, Ultram, Ultram ER)

Tramadol inhibits ascending pain pathways, altering the patient’s perception of and response to pain. It inhibits the reuptake of norepinephrine and serotonin.

Codeine and acetaminophen (Tylenol #3, Tylenol #4)

Acetaminophen and codeine combintation is used for the treatment of mild to moderate pain.

Class Summary

NSAIDs have analgesic, anti-inflammatory, and antipyretic activities. Their mechanism of action is not known, but they may inhibit cyclooxygenase activity and prostaglandin synthesis. Other mechanisms may also exist, such as leukotriene synthesis inhibition, lysosomal enzyme release, lipoxygenase activity, neutrophil aggregation, and various cell membrane functions. During rehabilitation, shoulder discomfort may interfere with sleep or basic ADLs. Oral NSAIDs should decrease the discomfort. NSAIDs do not speed recovery and should not be used to accelerate physical therapy goals.

Ibuprofen (Motrin, Caldolor, Advil, Provil)

Drug of choice for mild to moderate pain. Inhibits inflammatory reactions and pain by decreasing prostaglandin synthesis.

Naproxen (Naprosyn, Anaprox DS, Naprelan, Aleve)

For mild to moderate pain. Inhibits inflammatory reactions and pain by decreasing the activity of cyclooxygenase, which results in a decrease of prostaglandin synthesis.

Ketoprofen

For mild to moderate pain and inflammation. Small initial doses are indicated in small and elderly patients and in those with renal or liver disease.

Doses >75 mg do not increase the therapeutic effects. Administer high doses with caution and closely observe the patient for response.

Return to play in patients following a shoulder dislocation is determined when full range of motion (ROM) and strength have been regained. Return to play is usually sooner for older adults than for younger athletes, because the fear of redislocation is much lower in older adults. Usually, older adults can return to play within 3 months. With younger adults, conditioning can continue through shoulder rehabilitation; however, decisions about returning to play should be more conservative than those in older adults. Again, absolute criteria are full ROM and full strength.

When determining a patient's return to competitive sports, the author uses the following criteria:

• Scapular stability through full ROM

• Normal scapulohumeral rhythm

• Full active and passive ROM

• Rotator cuff strength at 80% of opposite side

• Pain-free activities of daily living (ADLs)