|Classification and external resources|
The left shoulder and acromioclavicular joints, and the proper ligaments of the scapula.
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A dislocated shoulder occurs when the humerus separates from the scapula at the glenohumeral joint. The shoulder joint has the greatest range of motion of any joint in the body and as a result is particularly susceptible to dislocation and subluxation. Approximately half of major joint dislocations seen in emergency departments involve the shoulder. Partial dislocation of the shoulder is referred to as subluxation.
|This section requires expansion. (June 2008)|
In over 95% of shoulder dislocations, the humerus is displaced anteriorly. In most of those, the head of the humerus comes to rest under the coracoid process, referred to as sub-coracoid. Sub-glenoid, subclavicular, and, very rarely, intrathoracic or retroperitoneal dislocations may also occur.
Anterior dislocations are usually caused by a direct blow to, or fall on, an outstretched arm. The patient typically holds his/her arm externally rotated and slightly abducted.
It can result in damage to the axillary artery and axillary nerve (C5,C6). The axillary nerve is injured in 37% of shoulder dislocations making it the most commonly injured structure with this type of injury. Other common nerve injuries associated with shoulder dislocation include injury to the the suprascapular nerve (involved in 29% of shoulder dislocations) and the radial nerve (involved in 22% of shoulder dislocations). Axillary nerve damage results in a weakened or paralyzed deltoid muscle. As the deltoid atrophies unilaterally, the normal rounded contour of the shoulder is lost. A patient with injury to the axillary nerve will have difficulty in abducting the arm from approximately 15° away from the body. The supraspinatus muscle initiates abduction from a fully adducted position.
Posterior dislocations are occasionally due to electric shock or seizure and may be caused by strength imbalance of the rotator cuff muscles. Patients typically present holding their arm internally rotated and adducted, and exhibiting flattening of the anterior shoulder and a prominent coracoid process.
Posterior dislocations often go unnoticed, especially in an elderly patient and in the unconscious trauma patient. An average interval of 1 year was discovered between injury and diagnosis of posterior dislocation in a series of 40 patients.
Inferior dislocation is the least likely form, occurring in less than 1% of all shoulder dislocation cases. This condition is also called luxatio erecta because the arm appears to be permanently held upward or behind the head. It is caused by a hyper abduction of the arm that forces the humeral head against the acromion. Inferior dislocations have a high complication rate as many vascular, neurological, tendon, and ligament injuries are likely to occur from this kind of dislocation.
Signs and symptoms
- Significant pain, which can sometimes be felt along the arm past the shoulder.
- Inability to move the arm from its current position, particularly in positions with the arm reaching away from the body and with the top of the arm twisted toward the back.
- Numbness of the arm.
- Visibly displaced shoulder. Some dislocations result in the shoulder appearing unusually square.
- No bone in the side of the shoulder showing shoulder has become dislocated.
Prompt medical treatment should be sought for any suspected dislocation injury. Usually, a dislocated shoulder is kept in its current position by use of a splint or sling (however, see below). A pillow between the arm and torso may provide support and increase comfort. Strong analgesics are needed to allay the pain of a dislocation and the anxiety associated with it, and hence, conservative measures of pain relief should not be attempted.
Emergency department care is focused on returning the shoulder to its normal position via processes known as reduction. Normally, closed reduction, in which several methods are used to manipulate the bone and joint from the outside, is used. A variety of techniques exist, but some are preferred due to fewer complications or easier execution. In cases where closed reduction is not successful, surgical open reduction may be needed. Following reduction, x-ray imaging is often used to ensure that the reduction was successful and there are no fractures. The arm should be kept in a sling or immobilizer for several days, preferably until orthopedic consultation. Hippocrates' and Kocher's method are rarely used anymore. Hippocrates used to place the heel in the axilla and reduce shoulder dislocations. Kocher's method, if performed patiently and slowly, can be performed without anesthesia and if done correctly does not cause pain. Traction is applied on the arm and it is abducted. Then, it is externally rotated, and the arm is adducted following which it is internally rotated and maintained in the position with the help of a sling. A chest x-ray should be taken to confirm whether the head of humerus has reduced back into the glenoid cavity. This methodology is performed with external rotation of shoulder, and adduction of the elbow. Some do not recommend it because of possible neurovascular complications and proximal humerus fractures.
If no medical help is available, for anterior dislocations fairly simple methods can be attempted, such as Milch's method or Stimson's Method.
In Australia, an anterior dislocation reduction method that is commonly used is the Spaso technique. This technique was first used by Spaso Miljesic, a nurse specialising in orthopaedics at Western Health, Melbourne, Australia. The technique is reliable and simple. Holding the patient's wrist, gently flex the arm at the shoulder joint with an extended elbow until 90 degrees is achieved. Then apply gentle traction and external rotation. Listen for a clunk indicating relocation. If the patient experiences pain and muscle spasm, wait until it subsides and gently continue. Procedural sedation may be useful. A recent study found the Spaso technique useful in 87.5% of cases of anterior dislocation with no complications.
The most recent style of shoulder reduction is the Cunningham shoulder reduction, utilizing adduction of a flexed arm with concurrent bicipital massage and postero-superior shrug by the patient. This is a rather new technique but has seen positive outcomes in the ER.
For thousands of years, treatment of anterior shoulder dislocation has included immobilisation of the patient's arm in a sling, with the arm placed in internal rotation (across the body). However, three studies, one in cadavers and two in patients, suggest that the detachment of the structures in the front of the shoulder is made worse when the shoulder is placed in internal rotation to be seen. By contrast, the structures are realigned when the arm is placed in external rotation. New data suggest that if the shoulder is managed non-operatively and immobilised, it should be immobilised in a position of external rotation.
Another study found that conventional shoulder immobilisation in a sling offered no benefit.
Rotator cuff and deltoid strengthening has long been the focus of conservative treatment for the unstable shoulder and in many cases is advocated as a substitute for surgical stabilization. In multidirectional instability patients who have experienced atraumatic subluxation or dislocation events, cohort studies demonstrate good responses to long-term progressive resistance exercises if judged according to function, pain, stability, and motion scores. However, in those experiencing a discrete traumatic dislocation event, responses to non-operative treatment are less than satisfactory, a pattern that inspired the Matsen and Harryman classification of shoulder instability, TUBS (traumatic, unidirectional, Bankart, and usually requiring surgery) and AMBRI (atraumatic, multidirectional, bilateral, rehabilitation, and occasionally requiring an inferior capsular shift). It is thought that traumatic dislocations, as opposed to atraumatic dislocations and instability events, result in a higher incidence of capsuloligamentous injuries that disturb normal anatomy and leave shoulders too structurally compromised to respond to conservative treatment. Pathoanatomic studies of first-time traumatic anterior dislocators reveal a high rate of labral lesions including Bankart lesions.
Some cases require non-emergency surgery to repair damage to the tissues surrounding in the shoulder joint and restore shoulder stability. Some cases in which it is often recommended is in young people who are involved in heavy jobs or sports. Arthroscopic surgery techniques may be used to repair the glenoidal labrum, capsular ligaments, biceps long head anchor or SLAP lesion and/or to tighten the shoulder capsule.
Arthroscopic stabilization surgery is a modern “gold standard” of the Bankart repair, a time-proven surgical treatment for recurrent anterior instability of the shoulder. Surgery to anatomically and securely repair the torn anterior glenoid labrum and capsule can lessen pain and improve function for active individuals. When the front of the shoulder socket has been broken or worn, a bone graft may be required to restore stability. The failure rate following Bankart repair has been shown to dramatically increase from 4% to 67% in patients with significant bone loss. In cases with significant bone loss, improved results have been reported with the Latarjet operation. When the shoulder dislocates posteriorly (out the back), a surgery to reshape the socket may be necessary. Surgery to build up the back of the glenoid socket using an osteotomy and graft can restore shoulder anatomy and lessen pain and improve function. Conversely, there are new procedures that should be investigated as a possible alternative to open surgery.
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