Practice Essentials
Shoulder dislocations account for almost 50% of all joint dislocations. Most commonly, these dislocations are anterior (90-98%) and occur because of athletics and trauma. Most anterior dislocations are subcoracoid in location. Subglenoid, subclavicular, and, very rarely, intrathoracic or retroperitoneal dislocations may occur.
Nonoperative treatment of shoulder dislocations remains a controversial topic. The risk of recurrence with nonoperative treatment depends on age and activity level. Recurrence rates tend to decrease with age and to increase with higher activity levels.
Surgery may be indicated if patients are unable or unwilling to change their occupation or avoid participating in high-risk sports and if they have recurrent dislocations or subluxations. Surgery in patients with voluntary shoulder dislocations associated with psychiatric illnesses may have less reliable outcomes.
For patient education resources, see the Breaks, Fractures, and Dislocations Center, as well as Shoulder Dislocation.
Etiology
The usual mechanism of injury is extreme abduction, external rotation, extension, and a posterior directed force against the humerus. Forceful abduction or external rotation alone can also lead to dislocation (~30% of cases), as can a direct blow to the posterior humerus (29%), forced elevation and external rotation (24%), and a fall onto an outstretched hand (17%). [1, 2]
Posterior dislocations are less common (2-10%) and result from the application of an axial load to the adducted and internally rotated arm. Classic posterior dislocations also occur as a result of electrocution or seizures because of the strength imbalance between the internal rotators (subscapularis, latissimus dorsi, and pectoralis major muscles), which overpower the external rotators (teres minor and infraspinatus muscles).
Inferior dislocations are rare and result from a hyperabduction force that causes the humeral neck to lever against the acromion. Diagnosing inferior dislocations is critical because of the high incidence of complications. Neurologic injuries (particularly axillary nerve lesions) are associated with inferior dislocations in as many as 60% of cases, vascular injuries occur in about 3.3% of cases, rotator cuff tears occur in 80-100% of cases, [3] and greater tuberosity fractures and pectoralis major avulsions are also associated with inferior dislocations.
Superior dislocations are extremely rare and result from an extreme force in a cephalic direction to the adducted arm. Acromioclavicular injuries and fractures of the acromion, clavicle, and tuberosities may occur with superior dislocations.
Atraumatic instability is usually multidirectional and commonly occurs in individuals with generalized hyperlaxity due to connective tissue disorders, such as Ehlers-Danlos syndrome and Marfan syndrome. A small or flat glenoid fossa, excessive anteversion or retroversion of the glenoid, weak rotator cuff muscles, neuromuscular disorders, or a redundant capsule may also jeopardize the concavity-compression, adhesion-cohesion, or the glenoid suction-cup phenomena that aid in stability of the shoulder.
Multidirectional instability most commonly occurs in younger populations (usually < 30 years) and is often familial and bilateral. The first dislocation often occurs after a minor injury or after a period of disuse. Patients may experience subluxations that progress over time to actual dislocations, which spontaneously reduce. These dislocations may be voluntary or involuntary. Voluntary dislocations have been associated with psychiatric illnesses and may be used in attention-seeking behavior. Surgery may be avoided in this population because the instability is likely to recur.
Prognosis
Studies examining immobilization of the shoulder in external rotation have not shown this to yield any consistent decrease in shoulder instability recurrence as compared with sling immobilization in internal rotation. [4, 5]
In a study by Owens et al, acute arthroscopic Bankart repair in young, active patients with first-time traumatic anterior glenohumeral dislocations resulted in excellent subjective function and return to athletics, with an acceptable rate of recurrence and reoperation. [6] Of 39 patients followed (40 shoulders), six patients sustained recurrent dislocations, nine had subluxation events, and six underwent revision stabilization surgery.
Maier et al compared the clinical benefit of operative stabilization in younger patients (49 patients < 40 years) and older patients (23 patients >40 years) after anterior shoulder dislocation and found that there was significant reduction in recurrence in both groups. [7] However, the clinical functional results measured by the Constant score, Rowe score, and disabilities of the arm, shoulder, and hand (DASH) score revealed significantly better outcomes in the younger group.
In a study by Cordischi et al involving skeletally immature patients (14 patients aged 10.9-13.1 years) who sustained a primary traumatic unidirectional anterior shoulder dislocation, patients who were treated nonoperatively fared better than those treated by surgery (average Western Ontario Shoulder Instability index [WOSI] score of 9.1 vs 151.7, respectively). [8] According to the authors, in the pediatric skeletally immature patient, nonoperative treatment results in low shoulder instability recurrence risk and sound functional outcome.
Abdelhady et al conducted a prospective study to assess the efficacy of the Latarjet procedure in patients with recurrent anterior shoulder dislocation and generalized hyperlaxity. [9] Mean Rowe score was 47.5 points preoperatively and increased to 91.07 postoperatively; the increase was statistically highly significant. Mean range of postoperative external rotation was 69.29°. The investigators concluded that in these patients, the Latarjet procedure has a higher success rate than capsulolabral repair procedures.
Longo et al conducted a systematic review of the literature to evaluate clinical outcome, rate of recurrence, complications, and rate of postoperative osteoarthritis in patients with anterior shoulder instability managed with Latarjet, Bristow, or Eden-Hybinette procedures. [10] The review included 46 studies, in which 3211 shoulders were evaluated. The mean value of the Coleman Methodology Score (CMS) was 65 points. Preoperatively, the most commonly detected injuries were glenoid bone loss and Bankart lesions.
The investigators concluded that the open Bristow-Latarjet procedure was a valid surgical option for treating anterior shoulder instability. [10] Clinical outcomes associated with the Eden-Hybinette procedure were very similar to those of the Bristow-Latarjet technique, but the former was associated with a higher rate of postoperative osteoarthritis and recurrence. An arthroscopic Bristow-Latarjet procedure appeared to be better in terms of prevention of recurrence and rehabilitation, but further studies are needed to confirm this difference.
Blonna et al studied 60 patients with posttraumatic recurrent anterior shoulder instability that was treated either with the arthroscopic Bankart repair (n = 30) or the open Bristow-Latarjet procedure (n = 30). [11] The primary outcomes were return to sport (Subjective Patient Outcome for Return to Sports [SPORTS] score), rate of recurrent instability, Oxford Shoulder Instability Score (OSIS), Subjective Shoulder Value (SSV), WOSI, and range of motion (ROM). After a mean follow-up of 5.3 years (range, 2-9), arthroscopic stabilization provided better return to sport and subjective perception of the shoulder than the open Bristow-Latarjet procedure.
Virk et al assessed the time to recurrence (TTR) of instability and disease-specific outcome measures in 80 patients (82 shoulders) with recurrent traumatic anterior shoulder instability and a Bankart lesion on diagnostic arthroscopy who underwent open (n = 24) or arthroscopic (n = 58) Bankart repair. [12] The mean time to recurrence of postoperative instability was significantly shorter in the arthroscopic group than in the open group (12.6 ± 2.7 months vs 34.2 ± 12 months). The authors suggested that in view of the longer time to recurrence after open Bankart repair, this approach might be better suited to individuals in heavy-duty professions (contact athletes and workers who perform heavy manual labor).
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The rotator cuff interval is closed with a nonabsorbable suture. The T-capsulotomy incision is planned with dotted lines.
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Superomedial (SM) and inferomedial (IM) flaps created by T-capsulotomy incision. First, the IM flap will be advanced superiorly and laterally, and then the SM flap will be advanced inferiorly over the top of the IM flap.
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The finished repair with the superomedial (SM) flap advanced inferiorly, overlapping the previous inferomedial (IM) flap advancement. Note how the axillary pouch has been eliminated.
