Shoulder Dislocation Flashcards
Practice Essentials
Shoulder dislocations may occur from a traumatic injury or from loose capsular ligaments. Different conditions may affect the stabilizing structures of the shoulder and, thus, negatively affect patients with shoulder dislocations
This article focuses on glenohumeral joint dislocation. Although acromioclavicular (AC) joint separations are sometimes called shoulder dislocations by nonmedical persons, these are not true shoulder dislocations. Shoulder dislocations occur when the head of the humerus comes out of its socket, the glenoid.
Workup imaging of shoulder dislocation
When dealing with shoulder instability, obtaining 2 orthogonal views of the shoulder is imperative. Magnetic resonance imaging (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.
Treatment of Shoulder Dislocation
The most important treatment of an acute shoulder dislocation is prompt reduction of the glenohumeral joint. 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.
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. While the patient is in the sling, elbow, wrist, and hand range of motion (ROM) 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. After the initial period of immobilization, passive ROM exercises should begin. More vigorous therapy can be initiated after full passive ROM has been regained, usually after 6 weeks.
In patients who have recurrent shoulder instability, operative care should be highly considered. The goal of an operative repair is to reattach the torn tissue back to the place where it tore off of the bone. Recurrent shoulder dislocations also stretch out the ligaments. It is imperative to also address the tissue laxity during the operative procedure.
Epidemiology of Shoulder Dislocation
The shoulder is the most commonly dislocated joint in the body.
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.
Functional Anatomy of Shoulder Dislocation
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.
Sport-Specific Biomechanics
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.
Physical Exam
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
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.
Causes
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. [
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.
