Shoulder dislocation and reduction

INTRODUCTION — Shoulder dislocations are the most common of all major joint dislocations and frequently present to clinics and emergency departments. This topic review will discuss the mechanism of injury, evaluation, reduction, and subsequent management of shoulder dislocations. Evaluation of the patient with shoulder pain and other shoulder injuries are discussed separately. (See "Evaluation of the adult with shoulder complaints" and "Acromioclavicular joint injuries ("separated" shoulder)" and "Frozen shoulder (adhesive capsulitis)" and "Multidirectional instability of the shoulder" and "Presentation and diagnosis of rotator cuff tears" and "Subacromial (shoulder) impingement syndrome" and "Clinical manifestations and diagnosis of osteoarthritis", section on 'Shoulder'.)

EPIDEMIOLOGY — Shoulder dislocations account for 50 percent of all major joint dislocations [1-5]. Anterior dislocation is most common, accounting for 95 to 97 percent of cases. Posterior dislocation accounts for 2 to 4 percent, and inferior dislocation (ie, luxatio erecta, which means "to place upward") accounts for 0.5 percent [6].

According to a review of a large United States injury database including nearly 9000 cases of shoulder dislocation, the incidence is 23.9 per 100,000 person-years [5]. Almost 72 percent occur in males, and nearly one-half occur in patients between the ages of 15 and 29 years. The most frequently cited mechanism was a fall, found in nearly 60 percent of cases. Almost one-half occurred in the home, while approximately one-third occurred at sites for sport or recreation. Overall, almost one-half of shoulder dislocations occurred while the patient was engaged in a sport or recreational activity.

In a Norwegian registry study, two-thirds of shoulder dislocations were reduced in the emergency department, while approximately one-fourth were reduced prior to arrival at the emergency department [7]. The rate of spontaneous reduction was small (0.6 percent).

CLINICAL ANATOMY — The shoulder joint is inherently unstable (figure 1A-C and figure 2 and figure 3 and figure 4). The glenoid is shallow, allowing for a wide range of motion, with only a small portion of the humeral head articulating with the glenoid in any position (figure 5). The glenoid labrum is a fibrocartilaginous structure that surrounds the glenoid and inserts into the edge of the joint capsule. The distal portion of the joint capsule attaches to the humeral neck. The inferior glenohumeral ligament represents the anterior-inferior portion of the capsule (figure 2). This ligament is thicker than the rest of the joint capsule and provides the strongest impediment to anterior dislocation.

The rotator cuff muscles (figure 6) provide additional support of the glenohumeral joint. The subscapularis muscle lies anterior to the joint capsule and acts as a secondary support resisting dislocation. Posteriorly, the supraspinatus, infraspinatus, and teres minor pull the humeral head into the glenoid and help to prevent it from anterior subluxation [8].

The axillary nerve, the nerve most often injured with shoulder dislocations, runs inferiorly to the humeral head and wraps around the surgical neck of the humerus (figure 7). It innervates the deltoid and teres minor muscles and the skin overlying the lateral shoulder ("shoulder badge" distribution). Shoulder anatomy is discussed in greater detail separately. (See "Evaluation of the adult with shoulder complaints", section on 'Anatomy and biomechanics'.)

PREHOSPITAL MANAGEMENT — Shoulder dislocations sometimes occur at sporting events, where clinicians capable of performing a reduction are often present, or in remote wilderness settings. In such situations, there may be no easy way to get the patient to a hospital in a timely manner, and delays can complicate subsequent reduction attempts. Early reduction avoids the development of muscle spasms that may increase the difficulty of performing the procedure. The results of one retrospective study suggest that delays as short as 10 minutes increase the likelihood of failed reduction [9]. Several articles have addressed the topic of prehospital reduction of anterior shoulder dislocation and have concluded that it is safe and effective [10-14].

When contemplating a reduction in the prehospital setting, the clinician should consider the following:

●Age of the patient (fractures are less common in patients younger than 30)

●History of prior shoulder dislocations

Reduction is not contraindicated in the setting of common fracture types (ie, Hill-Sachs, Bankart, greater tuberosity). Patients with prior shoulder dislocations may know whether they required sedation for prior reductions, suggesting that reduction would need to be performed at a hospital with appropriate medications.

The same reduction techniques used in the hospital can generally be used successfully in the prehospital setting. These include the Stimson, external rotation, scapular manipulation, Spaso, and traction-countertraction techniques as well as self-reduction techniques. Reported success rates range from 55 to 95 percent [11]. (See 'Reduction procedure' below.)

Following successful prehospital reduction, immobilization and prompt referral should be performed in the same manner as in the hospital. At the discretion of the treating clinician, an athlete whose shoulder is successfully reduced and has no other concerning injuries may be permitted to remain on the sideline with their team until the match is completed.

EVALUATION — Patients suspected of a shoulder dislocation need a thorough examination and frequently need diagnostic imaging to diagnose dislocation and associated injuries. (See 'Imaging studies' below.)

Anterior shoulder dislocation

Mechanism of injury — An anterior shoulder dislocation is usually caused by a blow to the abducted, externally rotated, and extended arm (eg, player blocking a basketball shot). Alternatively, a blow to the posterior humerus or a fall on an outstretched arm may cause an anterior dislocation.

Examination — An anteriorly dislocated shoulder causes the arm to be slightly abducted and externally rotated. The patient resists all movement. The acromion appears prominent in thin individuals, and there is loss of the normal rounded appearance of the shoulder (picture 1).

Clinicians should perform a neurovascular examination, paying particular attention to distal pulses and the function of the axillary nerve, the nerve most commonly injured with anterior shoulder dislocations. Axillary nerve dysfunction manifests as loss of sensation in a "shoulder badge" distribution (lateral aspect of shoulder over deltoid), although this finding is not reliably present [15,16]. Deltoid muscle weakness may also be present but is impractical to assess during the acute injury [17]. Some degree of axillary nerve dysfunction is present in over 40 percent of patients with an anterior dislocation, but most patients recover completely without intervention [16,18]. In many cases, dysfunction resolves with reduction [19].

Imaging studies

Plain radiographs

When to obtain radiographs and what to look for — Many clinicians obtain radiographs before and after reduction of an anterior shoulder dislocation, but imaging is not always necessary. Initial radiographs confirm the diagnosis and exclude fractures; post-reduction radiographs confirm successful reduction and exclude any fracture caused by the procedure [20].

Clinically important fractures occur in approximately 25 percent of adults with anterior shoulder dislocations [19,21]. In a retrospective case-control study, three factors were associated with fracture [21]:

●Age over 40

●First-time dislocation

●Traumatic mechanism (eg, fight or fall)

When all three factors were absent, the negative predictive value for the presence of a fracture was 96.6 percent (95% CI 88.3-99.6). Based upon this study and other observational data, we believe that prereduction radiographs are unnecessary if none of the listed criteria are met and the clinician feels confident of the diagnosis of anterior shoulder dislocation [22-25].

In the pediatric population, clinically significant fractures sustained from shoulder dislocations caused by a low-energy mechanism (eg, tackle made in junior high school American football game, simple fall not from a height) are less common than in adults, and prereduction radiographs likely have limited utility [26].

If prereduction shoulder radiographs are obtained, look carefully for a surgical neck fracture of the humeral head. While an associated surgical neck fracture is rare, attempts at reduction are contraindicated in this setting due to the increased likelihood of displacing the fracture and causing avascular necrosis of the humeral head.

What views to obtain — When glenohumeral dislocation is suspected and imaging is to be performed, we obtain an anteroposterior (AP) (image 1 and image 2) and a scapular "Y" view (image 3) at a minimum. An axillary view (image 4) may be useful and should be obtained whenever there is uncertainty regarding the diagnosis on initial radiographs. The diagnosis of an anterior shoulder dislocation is often straightforward and the injury easily visualized on the AP view (image 5). The dislocated humeral head usually lies in a subcoracoid position (figure 8). If the humeral head is subclavicular or subglenoid, there has been a greater degree of displacement, and a concomitant greater tuberosity fracture or rotator cuff tear is usually present (figure 8).

A false dislocation of the humeral head may be seen on the AP radiograph in the setting of a proximal humerus fracture if a hemarthrosis pushes the humeral head inferiorly, giving the appearance of an anterior shoulder dislocation. In most cases, a false dislocation can be distinguished from a true dislocation using the axillary view (described below).

The scapular "Y" view is taken with the beam directed parallel to the scapular body. The "Y" is formed by the body, spine, and coracoid process. The glenoid falls in the center of the "Y" and is normally obscured by the humeral head. When an anterior dislocation is present, the humeral head appears medial to the "Y" (image 6). There may be false negatives with the scapular view, so an axillary view should also be obtained whenever there is uncertainty.

The axillary view is taken with the patient's arm abducted. The radiograph plate is placed on the patient's shoulder and the x-ray beam projects through the axilla to the plate (picture 2 and image 7). The patient's arm need not be abducted 90 degrees, as this position causes pain. About 10 to 15 degrees of abduction, or just enough to get the x-ray tube between the patient's arm and hip, is usually sufficient to obtain the appropriate view. When an axillary view cannot be obtained due to patient discomfort, a Velpeau axillary view can be helpful. For this view, the patient leans back 15 degrees over the edge of a table, and the beam is directed from above the shoulder to the plate placed on the edge of the table.

Another view that may be helpful for identifying a dislocation is the true AP (Grashey) view in which the beam is directed at a 45-degree angle in a medial-to-lateral direction with the x-ray plate just posterior and parallel to the scapular body (figure 9). This view helps clinicians identify subtle joint incongruities (image 2).

Computed tomography — Computed tomography (CT) is not routinely indicated for the evaluation of an acute shoulder dislocation. Exceptions might include instances where the exact location of the humeral head cannot be determined using plain films (eg, possible false dislocation), when a surgical neck fracture is suspected but not clearly present on plain radiographs, or when a CT angiogram is to be performed because there are signs of axillary artery injury. Should surgery be necessary, CT may be obtained for operative planning.

Ultrasound — Although ultrasound may be less accurate at detecting potential fractures associated with anterior shoulder dislocations, systematic reviews of prospective observational studies and randomized trials report that it is accurate for confirming both the diagnosis and successful reduction (image 8) [27-30]. Ultrasound may be most useful for assessing the success of a reduction attempt in real time while the patient remains sedated and further reduction attempts can be made if needed before sedation wears off. The technique to assess a shoulder dislocation using ultrasound is as follows:

●The clinician stands behind the patient with the ultrasound display screen in front of the patient (image 9).

●The ultrasound transducer (curvilinear or linear) is placed horizontally on the posterior shoulder at approximately the level of the scapular spine. A curvilinear transducer is better for larger patients.

●The clinician locates the humeral head in relation to the glenoid fossa. This may require sliding the transducer right, left, up, or down to achieve the best view.

Associated injuries (Hill-Sachs and Bankart) — Associated fractures identified on plain radiographs include Hill-Sachs deformities, Bankart lesions, and greater tuberosity fractures. A Hill-Sachs deformity is a cortical depression in the humeral head created by the glenoid rim during dislocation (image 10) [31]. They occur in 35 to 40 percent of anterior dislocations and are seen on the AP radiograph with the arm in internal rotation [8]. Bankart lesions occur when the glenoid labrum is disrupted during dislocation (image 11). Bony Bankart lesions, in which a bone fragment is avulsed, are present in 5 percent of patients, while soft tissue Bankart lesions (no bone is avulsed) occur in approximately 90 percent of patients younger than 30 years old with an anterior shoulder dislocation [18,32]. Hill-Sachs and Bankart injuries appear to be more common with recurrent dislocation [33]. Greater tuberosity fractures are present in 10 percent of patients (image 12) [34]. Indications for orthopedic referral, including selected Bankart and Hill-Sachs lesions, are discussed separately. (See 'Indications for surgical consultation' below.)

Posterior shoulder dislocation

●Mechanism of injury – A blow to the anterior shoulder, axial loading of an adducted and internally rotated arm, and violent muscle contractions following a seizure or electrocution represent the most common causes of posterior shoulder dislocation [35-37].

●Examination – Examination reveals prominence of the posterior shoulder with flattening anteriorly. The coracoid process appears prominent. The patient holds the arm in adduction and internal rotation and is unable to externally rotate (picture 3 and movie 1) [38].

●Imaging studies – Radiographic evidence of a posterior shoulder dislocation on a standard AP view is subtle and may go undetected in up to 50 percent of cases [39]. Clues to the diagnosis include the lightbulb sign, rim sign, and trough line sign (image 7 and image 13).

The lightbulb sign manifests because the humeral head is internally rotated and the tuberosities no longer project laterally, resulting in a circular appearance of the humeral head (image 13) [40].

The rim sign refers to the distance from the medial aspect of the humeral head to the anterior glenoid rim. Although this distance may be normal with a posterior dislocation, if there is superimposition of these two structures or conversely, a widened joint space (>6 mm), posterior dislocation should be suspected (image 7 and image 13).

The trough line sign is present when two parallel lines of cortical bone are seen on the medial cortex of the humeral head. One line represents the medial cortex of the humeral head, while the other line represents the "trough" of an impaction fracture (referred to as the "reverse Hill-Sachs lesion") on the anterior articular surface of the humeral head [41].

Additional imaging modalities that may be useful include CT and ultrasound. With posterior dislocations, CT can be helpful when the presence of a dislocation cannot be determined using plain radiographs [42]. CT is also useful for determining the size of a reverse Hill-Sachs impaction fracture (image 14). (See 'Posterior shoulder dislocation reduction' below.)

Preliminary case reports suggest that ultrasound is a useful tool for identifying posterior shoulder dislocations and confirming their successful reduction [43-45].

●Associated injuries – Posterior shoulder dislocations are commonly associated with tuberosity and surgical neck fractures of the humerus, reverse Hill-Sachs lesions, and injuries to the labrum and rotator cuff [38,46]. In cases where plain radiographs are indeterminate for dislocation, CT is diagnostic and reveals the size of the articular surface impaction fracture, enabling the orthopedic surgeon to determine the most appropriate treatment [47].

Inferior shoulder dislocation (luxatio erecta)

●Mechanism of injury – Inferior dislocations are most commonly caused by axial loading with the arm fully abducted or forceful hyperabduction of the arm [48]. Such dislocations frequently occur when patients fall and suddenly grasp an object above their heads, causing hyperabduction.

●Examination – Patients with this injury hold the involved arm above their head and are unable to adduct the arm (picture 4) [49]. The forearm is pronated and in most cases rests on the top of the head. Approximately 60 percent of patients will have some degree of neurologic dysfunction, with the axillary nerve most commonly involved [50]. Axillary nerve injury typically manifests as sensory loss over the lateral shoulder. In most cases, neurologic dysfunction resolves spontaneously following reduction. Rotator cuff tears or greater tuberosity fractures are present in 80 percent of cases. Arterial injury occurs in up to 10 percent of patients and can manifest as an absent or discrepant radial pulse [51,52].

●Imaging studies – Radiographs reveal the humeral head beneath the coracoid or the glenoid (image 15). Associated fractures include the greater tuberosity (most common), acromion, scapula, humeral head, coracoid, and glenoid.

●Associated injuries – In addition to the fractures noted above, inferior shoulder dislocations have the highest incidence of axillary nerve and artery injuries among all types of shoulder dislocations [49,52].

REDUCTION PROCEDURE

Informed consent — Inform the patient of the risks specific to the agents to be used if procedural sedation is planned. The risks of the procedure itself are minimal and include the rare incidence of fractures of the humerus, glenoid, or coracoid process. Rotator cuff injuries may also occur but are usually present prior to reduction. Axillary artery or nerve injury may occur during reduction, especially with techniques that require a significant amount of traction, but such complications are rare.

Materials — Depending on the reduction technique, no materials may be required. Approximately 10 to 15 pounds (4.5 to 7 kgs) of weight is needed for the Stimson technique; bed sheets are used with the traction-countertraction technique. An assistant is required for many of the reduction techniques. If procedural sedation is deemed necessary, a nurse is required to prepare medications, administer oxygen, place the patient on appropriate monitors, and place an intravenous (IV) line. Airway management equipment is moved to the bedside if procedural sedation is to be provided. A 20-mL syringe, a 20-gauge needle, and 1% lidocaine are needed when intra-articular lidocaine injection is given for analgesia.

Contraindications and precautions — Delays in reducing dislocated shoulders may be necessary due to the need to treat life- or limb-threatening conditions. (See "Initial management of trauma in adults".)

Obtain orthopedic surgery consultation for older adult patients with dislocations that present subacutely (after 7 to 10 days) because of the relatively high incidence of vascular injury and fractures that occur with reduction attempts [8,15]. Consultation with an orthopedic surgeon should also be obtained when a surgical neck fracture is identified concomitantly with any type of shoulder dislocation (image 16). An attempt at closed reduction in such cases is likely to displace the fracture or worsen existing displacement and may increase the likelihood of avascular necrosis of the humeral head.

Analgesia and sedation

Suggested approach — Any of the techniques described below (procedural sedation and analgesia [PSA], intra-articular injection, peripheral nerve block) may be used to provide analgesia for patients undergoing reduction of a shoulder dislocation. For anterior shoulder dislocations (particularly those presenting within 24 hours), recurrent dislocations, and those not associated with severe trauma, we prefer to avoid the use of sedating medications whenever possible. For patients requiring analgesia who are at increased risk of complications from the IV medications used for PSA, we prefer to use either an intra-articular injection or peripheral nerve block, each performed under ultrasound guidance.

Systematic reviews of 12 randomized trials involving 630 patients presenting to the emergency department with acute anterior shoulder dislocation found no significant difference in reduction success between patients managed with intra-articular lidocaine (IAL) injection and IV sedation (RR 0.93, 95% CI 0.86-1.01), nor was there a difference in post-reduction pain scores [53,54]. IAL was associated with significantly fewer adverse events, 1.3 versus 20.8 percent (RR 0.16, 95% CI 0.07-0.33), and a shorter length of stay. The reviewers noted wide variation among trials (eg, medications used for PSA, reduction techniques, effectiveness of study blinding methods), making the conclusions less certain.

Reduction without analgesia — Reduction can frequently be obtained without analgesia in patients with anterior dislocations that are recent (ie, less than 24 hours), recurrent, or relatively nontraumatic [17]. This approach is attractive because it is rapid, avoids complications from medications, and requires fewer personnel. Reduction without analgesia works best with techniques that do not require significant traction (ie, external rotation, scapular manipulation, or Milch technique) [55].

Procedural sedation and analgesia — Procedural sedation and analgesia (PSA) is administered to relieve pain and to reduce spasm in the muscles of the rotator cuff. Commonly used medications include propofol, ketamine, etomidate, and fentanyl and midazolam. [56,57]. Propofol and etomidate are particularly useful because of their rapid onset, short duration of action, and infrequent side effects. (See "Procedural sedation in adults in the emergency department: General considerations, preparation, monitoring, and mitigating complications" and "Procedural sedation in children: Approach".)

If PSA is used, continuous monitoring with capnography and pulse oximetry is required, as well as frequent blood pressure measurements. Monitoring begins before any medications are given and continues until the patient is fully awake and able to protect their airway. (See "Carbon dioxide monitoring (capnography)".)

Intra-articular injection — Intra-articular lidocaine is inexpensive, provides pain relief, avoids potential complications from IV sedatives, and results in a rapid recovery time [58-61]. We suggest it be used in patients with comorbidities that put them at risk of complications from procedural sedation [62]. Injection is not made through skin or soft tissue that shows signs of infection. Coagulation disorders are a relative contraindication. Intra-articular injection fails more often in patients presenting more than six hours after injury [63].

A lateral injection approach is best when the humoral head is dislocated anteriorly. To perform the injection, identify the acromion process over the lateral aspect of the shoulder. The injection is made laterally, approximately 1 cm inferior to the acromion process. After cleaning the skin and providing local skin anesthesia, inject 20 mL of 1% lidocaine using an 18- or 20-gauge needle into the glenohumeral joint. Direct the needle medially and inferiorly and advance to a depth of 2.5 to 3 cm. Use of ultrasound guidance helps to ensure injection in the proper location [64-66].

A systematic review of five randomized trials (211 patients) comparing intra-articular lidocaine and PSA reported no significant difference in the rate of successful shoulder reduction but found more adverse effects (relative risk [RR] 0.16, 95% CI 0.06-0.43) and a longer mean time spent in the emergency department among patients given PSA [67]. However, the rate of adverse effects from PSA differs substantially according to the medications used.

Nerve blocks — Several brachial plexus nerve blocks for shoulder reduction have been described [68,69]. The performance of these nerve blocks is discussed separately. (See "Interscalene block procedure guide" and "Upper extremity nerve blocks: Techniques", section on 'Suprascapular nerve block' and "Ultrasound for peripheral nerve blocks".)

Ultrasound-guided interscalene and suprascapular nerve blocks are two methods for controlling pain and facilitating shoulder reduction [69-73]. In a systematic review and meta-analysis of five randomized trials involving a total of just over 200 patients with shoulder dislocation, nerve blocks were less effective for achieving reduction but led to shorter lengths of stay and lower rates of adverse effects, including respiratory events, compared with procedural sedation [73]. Most included studies involved small numbers, were performed at a single center, and varied substantially in approach, including nerve block selection (interscalene in three studies, suprascapular in two), medications, and dosing and were at significant risk of bias due to issues with blinding and reporting, making it difficult to draw definitive conclusions.

Anterior shoulder dislocation reduction

Suggested approach — No clear evidence exists supporting the superiority of any one of the many methods used to reduce anterior shoulder dislocations [25,74,75]. The method employed depends on clinician preference and the patient's condition. Generally, a technique that is quick and simple and requires neither significant force nor IV medication is ideal. We suggest starting with scapular manipulation. If unsuccessful, we proceed to the external rotation technique, adding the Milch technique if needed. If reduction is not accomplished using these approaches, then traction-countertraction or the Stimson technique can be used. All techniques are described below. It is best to perform reduction early, as delays are associated with lower success rates. (See 'Reduction techniques' below.)

Successful reduction is heralded by a "clunk" as the humeral head relocates and the return of the normal contour of the shoulder. With more gradual techniques (eg, external rotation), reduction may be more subtle with no appreciable "clunk." The ability of the patient to place the hand of the affected extremity on the opposite shoulder further confirms reduction. (See 'Post-reduction assessment' below.)

Pediatric considerations — Traumatic glenohumeral dislocation in children younger than 10 years of age is rare, accounting for fewer than 2 percent of all cases. Closed reduction is usually possible using the same techniques as those for adults. Nevertheless, because of the possibility of concomitant physis (ie, growth plate) fractures, we recommend orthopedic consultation prior to any attempt at reduction unless vascular compromise necessitates immediate treatment [76].

Reduction techniques — A wide range of techniques are used to reduce anterior shoulder dislocations [75,77,78]. In one comprehensive review, 21 different techniques for reducing anterior shoulder dislocations were described [77]. Most techniques use combinations of traction, external rotation, and scapular manipulation. With proper muscle relaxation, most techniques have high success rates. Below, we present several commonly used methods, including our preferred technique. As a reminder, a neurovascular examination should be performed both prior to and after reduction.

●Scapular manipulation – Scapular manipulation is quick, easy, and well tolerated by the patient and therefore is a good first maneuver. The method employs rotation of the scapula to disengage the humeral head from the glenoid and allow it to reduce into the glenoid. Success rates range from 80 to 100 percent [79-82]. The procedure takes one to five minutes, and premedication is generally unnecessary. It is easiest to perform with the patient upright but can also be performed with the patient prone if necessary.

●Upright scapular manipulation (preferred) – The author's preferred method for the upright technique is as follows:

•Place the head of the bed at 90 degrees. Have the patient dangle their legs over the side of the gurney and rest their unaffected shoulder against the upright portion of the bed. Encourage the patient to relax their shoulder muscles.

•Stand behind the patient and locate the scapula. Next, simultaneously push the tip medially and the acromion inferiorly using your thumbs, thereby rotating the scapula.

•While you are doing this, an assistant provides gentle forward or downward traction on the arm [83,84]. To exert downward traction, the assistant holds the patient's wrist firmly with one hand and the already flexed elbow with the other hand and pushes down on the elbow while holding the wrist in place (picture 5 and movie 2). Downward traction helps to prevent movement of the patient's arm and may increase success rates.

●Prone scapular manipulation – The patient's arm hangs off the side of the stretcher and is allowed to drop towards the ground. About 10 to 15 pounds (5 to 7 kgs) of weight can be hung from the arm using a prefabricated wrist splint as an alternative to an assistant providing traction [82]. The scapula is manipulated in similar fashion to the upright approach.

●External rotation technique – The external rotation technique reduces anterior glenohumeral dislocation by overcoming spasm of the internal rotators of the humerus, unwinding the joint capsule, and enabling the external rotators of the rotator cuff to pull the humerus posteriorly [85,86]. This method is safe, is easy to understand and teach, has no reported complications, and requires only one clinician [87,88]. It is successful in 80 to 90 percent of cases [87,89]. In one small case series, 81 percent of patients who were successfully treated required no sedation, and another observational study reported similar results [87,90].

The technique is performed as described below and depicted in the following photograph and video (picture 6 and movie 3):

•Have the patient lie supine with their elbow flexed to 90 degrees (this relaxes the long head of the biceps and allows movement of the humeral head [34]).

•Grasp the flexed elbow with one hand to maintain the adducted position of the arm and hold the wrist of the patient's arm with your other hand.

•Ask the patient to let their arm fall to the side (ie, externally rotate) slowly (over 5 to 10 minutes) while you gently guide the hand (picture 6). Whenever the patient feels pain or muscle spasm, stop and allow the muscles to relax.

•Reduction generally occurs with the arm externally rotated between 70 to 110 degrees [91]. Reduction is often subtle, and the "clunk" of the humerus rearticulating with the glenoid, typical of more forceful reduction techniques, is not appreciable.

●Milch technique – If reduction is not achieved with the external rotation approach, even after the arm is fully externally rotated, the Milch technique can be added. To perform this technique, abduct the now fully externally rotated arm into an overhead position, maintaining external rotation throughout the abduction. Reduction is achieved by applying gentle traction in line with the humerus and direct pressure over the humeral head with the clinician's thumb in the axilla (picture 7).

Milch surmised that in the overhead position, the muscles about the shoulder were in alignment with one another, and with cross-stresses thereby eliminated, nothing would prevent reduction of the humeral head [92,93]. Success rates of this technique range from 86 to 100 percent [55,94-96].

●Stimson technique – If the above techniques are unsuccessful, one alternative method is the Stimson technique, which involves placing the patient prone and hanging the affected extremity off the edge of the bed with 10 to 15 pounds (4.5 to 7 kgs) of weight (picture 8). Reduction is usually achieved within 30 minutes.

●Traction-countertraction – Traction-countertraction employs a sheet wrapped under the axilla. While one assistant provides gentle, continuous traction at the wrist or elbow, the other provides countertraction with the sheet from the opposite side of the patient (picture 9 and movie 4).

●Spaso technique – The Spaso technique employs gentle vertical traction and external rotation in the supine patient to reduce the dislocation, usually within one to two minutes (picture 10) [97,98].

●Fares technique – In this technique, the patient lies supine on a stretcher with the affected upper extremity at their side. The clinician grasps the patient's wrist and gently pulls the arm to provide traction. No countertraction is used. The arm is gradually abducted while the clinician continuously moves the arm up and down in an arc of approximately 10 cm. The up-and-down motion helps relax the shoulder musculature. If the shoulder has not reduced by 90 degrees of abduction, external rotation is added. A video of the technique is provided (movie 5).

In a randomized trial, the Fares technique performed comparably to the external rotation technique (76 of 80 [95 percent] shoulders reduced versus 73 of 80 [91 percent] shoulders reduced, respectively) [99].

●Cunningham technique – To perform this technique, the clinician sits in front of the patient, who assumes a comfortable sitting position [100]. The patient places the hand on the affected side atop the clinician's shoulder. The clinician rests one arm gently in the patient's elbow crease while the other hand gently massages the patient's biceps, deltoid, and trapezius muscles to help them relax. While encouraging the patient to relax, the clinician instructs the patient to pull their shoulder blades together and straighten their back. This maneuver moves the scapula medially and removes the major obstacle preventing reduction of the humeral head.

●Davos technique – To perform this reduction technique, the patient sits upright on a stretcher and flexes the hip and knee on the ipsilateral side of the shoulder dislocation (picture 11). The patient then clasps the fingers of both hands together around their flexed knee, after which the clinician binds the wrists together with an elastic bandage to allow the patient to relax their fingers. Next, the clinician puts weight on the patient's foot (eg, sits on their foot) to hold it stationary. The patient is then instructed to relax their shoulder and arm muscles and then extend their head back and let the shoulders roll forward with the arms extended.

Originally described in 1993, this technique was studied retrospectively in 100 patients with a reported success rate of 86 percent [101].

●Elbow technique – The patient is placed in a supine position. The clinician stands on the side of the dislocated shoulder, inferior to the patient's arm and looking towards the head of the bed. The clinician holds the patient's wrist with the outside extremity's hand and applies a gentle traction, keeping the elbow straight. The patient's arm is lifted to 45 degrees of forward flexion and 45 degrees of abduction. Next, the clinician grabs the patient's wrist with the inside extremity's hand, leans forward, and places the inside extremity's elbow on the patient's mid-humerus. A force is placed on the mid-humerus by the clinician's elbow that pushes the shoulder posteriorly, superiorly, and laterally back into its reduced position [102].

●Nicola technique – The patient sits upright in a chair and the clinician stands behind the patient. With a closed fist, the clinician places their hand in the patient's axilla. With the other hand, the clinician grasps the elbow and applies gentle downward traction. Gradually, the clinician pulls the elbow medially using the hand in the axilla as a fulcrum to facilitate reduction [103]. This maneuver can also be performed with the clinician in front of the patient.

●Other, non-preferred approaches – Other methods include the wrestling technique [104], chair technique [105], Eskimo technique [106], Hippocratic technique [107], and Kocher method [108]. These techniques are either more complex or associated with undesirable complications. Both the Hippocratic and Kocher techniques are associated with a high rate of fractures, brachial plexus injury, and vascular injury compared with other techniques and should be avoided.

Self-reduction techniques for patients — When assistance is not available, the patient may need to perform a reduction by themselves. The following techniques have been described:

●GONAIS technique – The patient grasps a stationary, waist-high object and then applies gentle traction by leaning back and then stepping backward [109]. Gradually, the shoulder is forward flexed to approximately 90 degrees. At that point, the patient begins to squat down all while maintaining continuous traction. After completely squatting, the patient moves a few steps backward to increase traction. If reduction does not occur, the opposite arm can be used to apply pressure to the displaced humeral head in a superior direction.

●Modified Davos technique – The patient clasps their hands together around the flexed ipsilateral knee from a seated position [110]. The patient then leans back slowly and extends their hip, pausing whenever the pain is too much, until reduction occurs.

Posterior shoulder dislocation reduction — The size of the articular surface defect ("reverse Hill-Sachs deformity") and the duration of the dislocation factor into the decision of whether to perform a closed reduction. Some authors recommend open reduction for defects that involve greater than 25 percent of the humeral head [35,38]. Dislocations older than three weeks are usually irreducible, and attempts at closed reduction in the emergency department or clinic are often futile. Closed reduction may be performed in the operating room under general anesthesia or in the emergency department with procedural sedation [111]. (See "Procedural sedation in adults in the emergency department: General considerations, preparation, monitoring, and mitigating complications".)

Closed reduction is performed using axial traction on the adducted arm with the elbow flexed (picture 12 and movie 6). While traction is applied, the arm is internally rotated and adducted. Sheets may be used in a similar manner to the traction-countertraction method to reduce an anterior dislocation [3]. Direct pressure on the posterior aspect of the dislocated humeral head, directing it anteriorly, or gentle lateral traction using a sheet looped under the axilla to unlock the glenoid rim may assist reduction. If successful, the arm is immobilized in a neutral position [38].

Inferior shoulder dislocation reduction — Reduction of luxatio erecta (inferior shoulder dislocation) is performed using traction-countertraction in line with the abducted humerus. Gentle, gradual adduction of the arm reduces the dislocation (picture 13 and movie 7) [6,112,113]. Closed reduction is successful in most cases unless a "buttonhole" deformity (humeral head is trapped in a tear of the inferior capsule) exists, in which case open surgical reduction is required [49].

An alternative method to closed reduction involves converting the inferior dislocation to an anterior one and then reducing the anterior dislocation [114]. To accomplish this, the clinician holds the humeral shaft with one hand while the other hand supports the arm at the elbow and provides inline traction on the arm. The hand on the humeral shaft is used to reposition the humeral head anterior to the shoulder. At this point, the patient's humerus can be adducted against their torso. Techniques for reducing anterior shoulder dislocations can then be used. (See 'Anterior shoulder dislocation reduction' above.)

Post-reduction assessment — Several clues suggest that reduction of an anterior shoulder dislocation has been successful. These include:

●An audible, visible, or palpable "clunk" as the humeral head relocates

●Return of the rounded appearance of the shoulder

●Fullness of the humeral head in its normal position during palpation

●Decreased pain

●Increased range of motion (if the patient can touch the opposite shoulder with the palm of the affected extremity, reduction has occurred)

Where available, bedside ultrasound reveals whether reduction has occurred (see 'Ultrasound' above). As with all reductions, a post-reduction neurovascular examination should be performed.

Post-reduction radiographs are necessary only if the clinician is uncertain whether the reduction has been successful. Post-reduction radiographs are unlikely to identify a clinically significant fracture if none was identified on prereduction radiographs [23,24,115-118].

INDICATIONS FOR SURGICAL CONSULTATION — The indications and timing for surgical referral can be summarized as follows:

●Anterior, posterior, and inferior shoulder dislocations that are successfully reduced, and are without signs of vascular injury, should be referred as an outpatient to an orthopedic surgeon for evaluation within about one week.

●Immediate, emergency consultation with orthopedic and vascular surgery should be obtained for any shoulder dislocation associated with signs suggestive of a vascular injury (most common with inferior dislocations).

●Prior to any attempt at reduction, orthopedic consultation should be obtained for any shoulder dislocation with a concomitant surgical neck or humeral shaft fracture.

●Orthopedic consultation should be obtained for older adults with subacute dislocations (after 7 to 10 days) because of the relatively high incidence of vascular injury and fractures that may occur with reduction attempts.

●Orthopedic surgery consultation is necessary for any shoulder dislocation that is not successfully reduced.

●Reduction of a posterior shoulder dislocation with a reverse Hill-Sachs deformity involving more than 25 percent of the articular surface may need to be performed in the operating room, and orthopedic consultation should be obtained.

Primary arthroscopic repair of a soft tissue Bankart lesion (glenoid labrum injury without avulsion fracture) is widely recommended for young (less than 35 years of age), first-time dislocators who engage in demanding physical activities. Surgery reduces the high rate of subsequent redislocation in this group compared with physiotherapy alone [119-125]. Generally, repair is performed within about 10 days. Suitable patients should be referred to an orthopedic surgeon to discuss treatment options.

In a systematic review of five randomized trials involving predominately young, active males (mean age approximately 23 years), the risk of recurrent shoulder instability following a first anterior dislocation was significantly lower among patients treated with surgical repair (n = 126) compared with those managed nonoperatively (n = 133, 6.3 versus 46.6 percent) [126].

In a systematic review of 60 studies of first-time (primary), traumatic, anterior shoulder dislocation, most involving predominately young males, surgical repair followed by physical therapy was found to be substantially more effective at reducing the risk of recurrence [127]. A meta-analysis of seven of the included studies involving 345 patients found that those managed with physical therapy alone were just over twice as likely to experience recurrent instability (RR 2.03, 95% CI 1.03-3.97), while those treated with surgery and physical therapy were almost twice as likely to return to their prior sports and activities, although this latter finding did not reach statistical significance (RR 1.81, 95% CI 0.96-3.43).

Other indications for surgery include displaced greater tuberosity fractures, Bankart fractures that create glenohumeral instability, and significant Hill-Sachs lesions [18]. Bankart and Hill-Sachs lesions are described above. (See 'Associated injuries (Hill-Sachs and Bankart)' above.)

A Bankart fracture involving a bone fragment greater than 20 percent of the area of the inferior glenoid is generally considered "critical" and requires urgent orthopedic referral [128,129]. If the clinician has any doubt about the size or area of involvement of a Bankart lesion, it is best to obtain orthopedic consultation.

Orthopedic referral should be obtained for significant Hill-Sachs lesions. Injuries may be managed nonoperatively if the bony defect is small (<20 percent of the articular surface of the humeral head) and the glenohumeral joint remains stable during desired activities [130].

Late surgical indications include recurrent instability or activity limitations [11].

COMPLICATIONS — Reduction of an anterior shoulder dislocation in the emergency department is unsuccessful in 5 to 10 percent of cases [8]. Interposition of the biceps tendon, joint capsule, or fracture fragments within the joint is the most common cause [8,131].

Vascular and persistent nerve injuries are rare complications of reducing dislocated shoulders. Nerve injury, most often of the axillary nerve, occurs more often in older adults and possibly when methods that employ traction on the abducted arm are used [16]. Axillary nerve injury is managed conservatively. After four weeks, an electromyogram (EMG) and nerve conduction study is performed if necessary. If surgery is needed, it is best performed within three to six months [132]. Other less common nerve injuries include damage to the brachial plexus, radial, ulnar, or musculocutaneous nerves. Shoulder dislocation accounts for 7 percent of brachial plexus injuries [133]. Treatment is conservative (ie, physical therapy), and recovery generally occurs within three to four months [133,134].

Axillary artery injury from attempts at shoulder reduction is rare but more common in older patients with chronic dislocations [15]. Approximately 200 cases of axillary artery injury due to anterior shoulder dislocation have been reported [135]. Approximately 90 percent of these injuries occur in patients over the age of 50 due to joint capsule adhesions and atherosclerosis with loss of vessel elasticity [136]. If arterial injury is suspected based on increasing upper extremity pain, a diminished pulse, or a large hematoma, immediate reduction of the dislocation is performed, if it has not been done already, followed by axillary computed tomography (CT) angiography and vascular surgery consultation [136,137]. Venous injury rarely occurs but usually presents as pain and swelling in the extremity from venous thrombosis [138].

Rotator cuff tears after anterior shoulder dislocations are uncommon in younger patients but occur in over one-half of patients over the age of 40 [15]. A complete rotator cuff tendon tear has been reported in 14 percent of patients with shoulder dislocation [138]. Diagnosing a rotator cuff tear is difficult immediately after an injury but is often noted during follow-up by difficulty or pain when the patient abducts the arm. Such tears may be difficult to distinguish from axillary nerve injuries, which also present with abduction difficulty [138].

Glenoid bone loss is a potential long-term complication of shoulder dislocation, not of reduction [139].

FOLLOW-UP CARE — After successful reduction of a shoulder dislocation, the shoulder is immobilized and the patient is referred to an orthopedic surgeon within one week. The most common complication of an anterior shoulder dislocation is recurrent dislocation, which occurs in 50 to 90 percent of patients under the age of 20 and in approximately 5 to 10 percent of patients over age 40 [8,15,140-143]. Efforts to prevent redislocation include altering the position of immobilization, increasing the duration of immobilization, physical therapy, and operative repair.

Immobilization — Following reduction of an anterior dislocation, the best position in which to immobilize the shoulder (internal versus external rotation) remains controversial [119,144]. The traditional position of adduction and internal rotation is easiest and most comfortable for the patient, and this is our preferred approach. A collar and cuff, sling and swathe, or a commercially available shoulder immobilizer are equally effective. Immobilization in external rotation has been studied to determine if it reduces the rate of redislocation by better approximating the torn labrum, thereby allowing for improved healing and greater shoulder stability. Pending further study, we believe that either approach is acceptable.

In patients under 30 years old, the shoulder is immobilized for three weeks [140,145-147]. In patients over 30 years old, the rate of redislocation is lower, and earlier mobilization (after one week) is permitted to reduce joint stiffness [17,18,140,147]. For patients of all ages, gentle pendular motion exercises should be performed during the immobilization period to retain mobility and reduce the risk of frozen shoulder. (See "Frozen shoulder (adhesive capsulitis)".)

Preliminary studies had suggested that recurrent dislocation was less likely if the shoulder was immobilized in 10 degrees of external rotation [145,148-150]. This approach was based on the commonly held belief that detachment of the glenoid labrum (ie, Bankart lesion) is the major reason for high redislocation rates among younger patients. If the shoulder was immobilized in external rotation, the damaged and intact parts of the glenoid labrum would lie closer to one another and be more likely to heal [148,151-153]. While this theory makes intuitive sense, the evidence available from randomized trials does not consistently demonstrate lower redislocation rates among patients immobilized in external rotation [144,154,155].

Rehabilitation — An appropriate rehabilitation program reduces the rate of redislocation and is recommended for first-time dislocators who do not have surgery [119,156]. During the initial period of immobilization (usually three weeks), the patient wears the immobilizer at all times unless bathing, mobilizing the elbow and wrist, or performing Codman exercises (gentle shoulder range-of-motion exercises with the arm suspended). Abduction and external rotation must be avoided because these motions stress the anterior capsule [18].

In subsequent weeks, active-assisted range-of-motion exercises and then isometric strengthening exercises for the muscles of internal rotation and adduction are added to the program. The approach to rehabilitation used for patients with multidirectional shoulder instability is suitable for patients with shoulder dislocation. (See "Multidirectional instability of the shoulder", section on 'Physical therapy'.)

Generally, by week 12, limited return to sporting activities is permitted, followed by full return to sporting activities as tolerated by week 16 [120,121,140]. During vigorous activity, patients recovering from a shoulder dislocation may benefit from added support (picture 14).

SUMMARY AND RECOMMENDATIONS

●Clinical anatomy and mechanism of injury – Shoulder (ie, glenohumeral) dislocations account for 50 percent of all major joint dislocations. Anterior dislocations comprise the large majority of these. Shoulder anatomy and mechanisms of dislocation are discussed above. (See 'Clinical anatomy' above.)

●Anterior dislocation

•Presentation and imaging – An anteriorly dislocated shoulder causes the arm to be slightly abducted and externally rotated. The patient resists all movement, and the acromion appears prominent (picture 1). Proper evaluation includes a neurovascular examination, with particular attention to distal pulses and the function of the axillary nerve, which is most commonly injured. Radiographs routinely obtained include the anteroposterior (AP), scapular "Y," and axillary views (image 5 and image 6 and image 4). Ultrasound is useful but may not reveal fractures (image 8). (See 'Anterior shoulder dislocation' above.)

•Associated fractures – Clinically important fractures occur with approximately 25 percent of anterior shoulder dislocations. Factors associated with fracture include age over 40, first-time dislocation, and traumatic mechanism (eg, fight or fall). When all three factors are absent, a fracture is highly unlikely. (See 'Anterior shoulder dislocation' above.)

•Reduction technique – No one of the many methods used to reduce anterior shoulder dislocations is proven to be superior. We suggest starting with scapular manipulation. If unsuccessful, we proceed to the external rotation technique, adding the Milch technique if needed. If these are unsuccessful, traction-countertraction or an alternative technique may be used. Each technique is described in the text, along with appropriate analgesia and monitoring and potential complications. (See 'Reduction procedure' above.)

•Immobilization – Following reduction, the patient's injured arm is immobilized in a position of adduction and internal rotation. A collar and cuff, sling and swathe, or commercially available shoulder immobilizer are equally effective. (See 'Immobilization' above.)

●Posterior dislocation – A posterior shoulder dislocation causes prominence of the posterior shoulder with flattening anteriorly. The coracoid process appears prominent. The patient holds the arm in adduction and internal rotation and is unable to externally rotate (picture 3). Posterior dislocations are commonly associated with tuberosity and surgical neck fractures. Signs of this dislocation on a standard anteroposterior radiograph are subtle and often missed. Clues to the diagnosis include the lightbulb sign, rim sign, and trough line sign (image 7 and image 13). (See 'Posterior shoulder dislocation' above.)

●Inferior dislocation – Patients with inferior shoulder dislocation hold the involved arm above their head and are unable to adduct the arm (picture 4). Approximately 60 percent of patients have some neurologic dysfunction, with the axillary nerve most commonly involved. Neurologic dysfunction usually resolves spontaneously following reduction. Rotator cuff tears or greater tuberosity fractures are present in 80 percent of cases. Arterial injury occurs in approximately 3 percent of patients. Radiographs reveal the humeral head beneath the coracoid or the glenoid (image 15). (See 'Inferior shoulder dislocation (luxatio erecta)' above.)

●Indications for surgical referral – Anterior, posterior, and inferior shoulder dislocations that are successfully reduced, and are without signs of vascular injury, should be referred as an outpatient to an orthopedic surgeon for evaluation within about one week. Other indications for surgical referral are reviewed in the text and include the following:

•Immediate, emergency consultation with orthopedic and vascular surgery should be obtained for any shoulder dislocation associated with signs suggestive of a vascular injury (most common with inferior dislocations).

•Prior to any attempt at reduction, orthopedic consultation should be obtained for any shoulder dislocation with a concomitant surgical neck or humeral shaft fracture.

•Orthopedic consultation should be obtained for older adults with subacute dislocations (after 7 to 10 days) because of the relatively high incidence of vascular injury and fractures that may occur with reduction attempts.

•Orthopedic surgery consultation is necessary for any shoulder dislocation that is not successfully reduced.