Shoulder dislocation refers to dislocation of glenohumeral joint. Shoulder dislocation is a common injury and occurs more in young adults. Although the shoulder can be dislocated by direct trauma such as a blow directed at the proximal humerus, indirect force is the most common cause of shoulder sprain, subluxation, or dislocation.
The shoulder is the most commonly dislocated joint in the body. Most of the dislocations are anterior though these may also occur posteriorly, inferiorly, or anterior-superiorly.
Patients with history of dislocation are more prone to redislocation.
Teenagers and adults in their twenties have shoulder dislocation more commonly than older patients.
Persons with greater activity level i.e. athletes are at greater risk.
Patients who tear their rotator cuffs or fracture the glenoid during their shoulder dislocation have a higher incidence of redislocation.
The incidence of all traumatic shoulder dislocations has been estimated at 11 cases per 100,000 person-years.
It is more common in males in age group 20-30 years and in females in age group 61-80 years.
Anterior dislocation is most commonly seen in those aged 18-25 years due to sporting injury. The second most common age group to sustain anterior dislocation is in elderly persons due to their susceptibility to falls.
Relevant Anatomy, Pathophysiology and Biomechanics
The shoulder joint is formed by four articulations
- Sternoclavicular joint
- Acromioclavicular Joint
- Glenohumeral joint
- Scapulothoracic joint
All of these joints work together for smooth functioning of the shoulder. Shoulder dislocation occurs at glenohumeral joint.
[Read anatomy of shoulder joint]
Stability of the shoulder joint is maintained mainly by by the glenohumeral ligaments and the joint capsule. Other factors are the rotator cuff muscles, the negative intra-articular pressure, and the bony/cartilaginous anatomy.
Inferior glenohumeral ligament is the most important ligament for shoulder stability [and is most common injured in an anterior shoulder dislocation]
Rotator cuff muscles are also important fro shoulder stability. These muscles are namely supraspinatus, infraspinatus, subscapularis, and teres minor.
Shoulder dislocation occurs commonly during sports, due to a fall or blow.
Other mechanisms include, assaults, seizures, throwing an object, reaching to catch an object, forceful pulling on the arm, reaching for an object, turning over in bed, or even combing hair.
Initial dislocation requires quite a forceful mechanism. But recurrent dislocations may occur with trivial forces such as combing the hair because the limb reaches in a position where it becomes easier to dislocate.
It is most commonly dislocated joint, a price it pays for mobility.
Types of Shoulder Dislocation
Dislocation of shoulder can be of following types
Anterior Shoulder Dislocation
Over 95% of shoulder dislocation cases are anterior. Anteriorly the dislocation could be sub-coracoid, sub-glenoid, subclavicular and, very rarely, intrathoracic. The subtypes denote position of the dislocated head
Anterior shoulder dislocations usually result from abduction, extension, and external rotation of shoulder such as throwing a overhead ball or a volleyball spike. Fall on an outstretched hand is also a cause.
In this, the humeral head is forced out of the glenohumeral joint, rupturing or detaching the anterior capsule from its attachment to the head of the humerus or from its insertion to the edge of the glenoid fossa with or without lateral detachment.
Posterior Shoulder Dislocation
Posterior dislocations are caused by severe internal rotation and adduction and can occur due to electrocution or seizure and may be caused by strength imbalance of the rotator cuff muscles. It is a relatively uncommon injury.
A fall on an outstretched arm or direct blow is also known to cause posterior dislocation. Occasionally, a severe direct blow may cause a posterior dislocation.
Rarely seizures can result in bilateral posterior dislocation.
Inferior Shoulder Dislocation
It is the least common the three 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.
The neck of the humerus is levered against the acromion and the inferior capsule tears as the humeral head is forced out inferiorly. Luxatio erecta almost always has an associated fracture or soft-tissue injury. Inferior dislocations have the highest incidence neurovascular compromise.
Inferior dislocations have a high complication due to vascular, neurological, tendon, and ligament injuries.
Mechanism of Injury
Anterior dislocation is caused by a combination of abduction, extension, and external rotation forces. Due to this, force is indirectly transferred to the anterior capsule and ligament resulting in dislocation.
Trauma is the most common cause of anterior dislocation.
Posterior dislocation is generally caused by convulsive disorders. However, convulsive disorders can result in anterior dislocations as well through indirect forces.
Apart from trauma and convulsion disorders, dislocations may result from violent muscle contraction, by electrical shock and sudden jerky force to shoulder.
A direct force applied to the anterior shoulder an indirect posterior force applied through the arm up to the shoulder may also result in dislocations.
Clinical Presentation
Patients with shoulder dislocation generally complain of severe shoulder pain and decreased range of motion. The attitude of the limb guides to the type of dislocation.
The most common dislocation is anterior where the patient keeps the abducted and externally rotated.
Acute dislocations occurring first time are more painful in comparison to recurrent dislocations but it is not rule of thumb.
Patients with previous dislocations are at greater risk of redislocation and it is important to enquire if any previous history of dislocation is there.
On examination, the patient is found to keep limb in particular attitude depending on the type of dislocation.
If the shoulder is anteriorly dislocated, the arm is in slight abduction and external rotation. The patient bends forward and may support the limb with other hand. Patient is in extreme pain and very apprehensive about movements of shoulder.
On examination the shoulder contour is lost and glenoid is empty. Humeral head can be palpated anteriorly.
Patient resists abduction and internal rotation and is unable to touch the opposite shoulder.
In posterior dislocation, the limb is in internal rotation and adduction. The patient keeps his arm held up against his or her abdomen.
Shoulder squared off due to loss of contour. Coracoid process is prominent. However, shoulders may look identical in bilateral dislocation. A prominent head can palpated posteriorly especially in thin persons.
In inferior dislocation or luxatio erecta, the arm is fully abducted with elbow supported behind or on head.
Head of humerus may be palpated on the lateral chest wall.
A detailed neurovascular examination should be carried.
Patient should be examined for ligamentous laxity, axillary nerve palsy. Any neurological disorder should also be ruled out.
Shoulder dislocation refers to dislocation of glenohumeral joint. Shoulder dislocation is a common injury and occurs more in young adults. Although the shoulder can be dislocated by direct trauma such as a blow directed at the proximal humerus, indirect force is the most common cause of shoulder sprain, subluxation, or dislocation.
The shoulder is the most commonly dislocated joint in the body. Most of the dislocations are anterior though these may also occur posteriorly, inferiorly, or anterior-superiorly.
Patients with history of dislocation are more prone to redislocation.
Teenagegers and adults in their twenties have shoulder dislocation more commonly than older patients.
Persons with greater activity level i.e. athletes are at greater risk.
Patients who tear their rotator cuffs or fracture the glenoid during their shoulder dislocation have a higher incidence of redislocation.
The incidence of all traumatic shoulder dislocations has been estimated at 11 cases per 100,000 person-years.
It is more common in males in age group 20-30 years and in females in age group 61-80 years.
Anterior dislocation is most commonly seen in those aged 18-25 years due to sporting injury. The second most common age group to sustain anterior dislocation is in elderly persons due to their susceptibility to falls
Associated Injuries
Fractures
About 30% of shoulder dislocations have associated fractures.
Hill Sachs Lesion
The most common associated injury is a compression fracture that results in the formation of a groove in the posterolateral aspect of the humeral head. This lesion is seen in 54-76% of dislocations.
Bankart Lesion
It is a fracture of the anterior rim of the glenoid fossa which occurs due to impaction of the humeral head against the anteroinferior glenoid labrum. Rupture of the joint capsule and inferior glenohumeral ligament injury are also associated.
Greater Tuberosity Fracture
10-15% of the patients have greater tuberosity fracture.
Other fractures are rare.
Rotator Cuff Injury
40%-85% of dislocations have associated rotator cuff injury. It is more common in older patients.
Other Injuries
- Glenohumeral ligament is injured in 55%
- Axillary nerve – 3% of anteroinferior dislocations.
- Brachial plexus – rarely
Axillary artery injury is rare but should be suspected if brachial plexus is injured. Maximum number of arterial injuries occur in luxatio erecta [about 3%]
Differential Diagnoses
Imaging
X-rays
Radiography is a very important aid in making and confirming diagnosis of shoulder dislocation. It also helps to find direction of the dislocation and existence of associated fractures .
Following views are used around the shoulder
Anteroposterior View
The anteroposterior view is obtained with the patient’s back flat on the cassette and the x-ray beam at right angles to this plane and centered on the shoulder..
Anteroposterior View In Plane of Scapula
This view is most easily accomplished by placing the scapula flat on the cassette and passing the x-ray beam at right angles to this plane, centering it on the coracoid process.
Lateral View
The view is at right angles to the AP in the plane of the scapula . The x-ray cassette is placed anterolateral to the shoulder, which will be perpendicular to the line on the scapula.
The x-ray is focused in line of spine of scapula onto the cassette.
In this view, in normal shoulder the head is at the center of the arms of the Y, that is, about the glenoid fossa. In posterior dislocations the head is seen posterior to the glenoid. In anterior dislocations it is anterior to the glenoid.
Axillary View
The cassette is placed on the superior aspect of the shoulder of the abducted arm. Beam passes between the chest and the arm in a direction perpendicular to the cassette from the shoulder.
An axillary radiograph is diagnostic of shoulder dislocation and also demonstrate fractures, as well as fractures of the head, the glenoid or of the lesser tuberosity of the humerus
The Apical-Oblique View
The patient sits with the scapula flat against the cassette. The x-ray beam is directed 45 degrees to the coronal plane and 45 degrees caudally and centered on the coracoid. This view also reveals both anterior glenoid lip defects and fractures of the humeral head.
Special Views
A number of special views have been described for identifying humeral head defects. These are AP radiograph in internal rotation, tangential view. Hill-Sachs view and Stryker notch view.
However, for most of the patients anteroposterior and an axillary lateral view or scapular Y views would be sufficient. A computed tomography should be done if x-rays are not conclusive.
[It is important to get two views done. Posterior shoulder dislocation can be missed on the anteroposterior view as the x-ray may appear normal.]
X-ray Findings
Anterior Dislocation
Image Credit: Radiopaedia
Anterior dislocation show by subcoracoid position of the humeral head in the anteroposterior view.
In scapular Y view, the humeral head lies anterior to the glenoid or center of Y formed on x-ray “Y.”
In an axillary view, the, humeral head appears fallen anterior to the glenoid. [often compared to golf ball and tee]
Posterior Dislocation
AP view may pass as normal or show a normal walking stick contour of the humeral head. It may resemble a light bulb or ice cream cone, depending upon the degree of rotation.
In scapular “Y” view, the humeral head lies behind the glenoid (the center of the “Y”).
In an axillary view, the golf ball or humeral head” falls posteriorly off the tee or glenoid.
Luxatio Erecta
Anteroposterior view may show the arm raised over the head with the humeral head inferior to the glenoid.
Computed Tomography
These are helpful in revealing the extent of fractures of the glenoid or humeral head compression fractures.
MRI
MRI can show damage to ligaments that may be torn with shoulder dislocation. Rotator cuff injuries could be documented with MRI.
Treatment of Shoulder Dislocation
Patient should be administered drugs in emergency situation to control pain.
Closed Reduction
A dislocated shoulder warrants reduction as early as possible. Before reduction is attempted it is prudent to get a pre-reduction film so that any associated bony injury could be known beforehand. Prereduction film may be omitted in recurrent dislocation of shoulder though.
Like any other dislocation, acute shoulder dislocation should be reduced as quickly and gently as possible.
The key to a successful reduction adequate analgesia and relaxation.
Reductions are carried under sedation or general anesthesia .
Intra-articular lidocaine can be used where first option cannot be exercised.
There are many reduction maneuvers described for shoulder reduction.
The reduction often is palpable to the physician. A palpable or audible relocation is noted when shoulder reduces.
If the patient is under general anesthesia, the reduction may be checked in C-arm.
A conscious patient may be asked to touch the uninjured shoulder to safely demonstrate a successful reduction.
After the reduction, shoulder is reduced with sling and swathe.
As a rule, neurovascular examination must be performed before and after reduction.
[Know about traction and countertraction]
Techniques of Reduction for Anterior Dislocation of Shoulder
Kocher’s Method
- Bend the supinated arm at the elbow, press it against the body
- Externally rotate until resistance is felt.
- Lift the externally rotated upper part of the arm in the sagittal plane as far as possible forwards.
- Rotate internally.
Stimson’s Method
- The patient lies prone on the bed with the dislocated arm hanging over the side.
- Traction is provided by up to 10 kg of weight attached to the wrist or above the elbow.
- The reduction occurs spontaneously or apply gentle internal/external humeral rotation.
- Reduction may take 20-30 minutes.
External Rotation Method
- The patient lies supine, adduct the arm and flex it to 90° at the elbow.
- Slowly rotate the arm externally, pausing for pain.
- Reduce the shoulder before reaching the coronal plane.
Traction Counter-traction Method
- Patient lies supine
- Apply axial traction to the arm with a sheet wrapped around the forearm and the elbow bent at 90°.
- Assistant applies countertraction using a sheet wrapped under the arm and across the chest
- The shoulder is gently rotated internally and externally to disengage the humeral head from the glenoid.
Scapular Rotation Method
- Patient lies prone
- Apply manual traction or 5-15 lb of hanging weight to the wrist.
- Rotate the inferior tip of the scapula medially and the superior aspect laterally.
Or
- Patient sits
- An assistant provides traction-countertraction by pulling on the wrist with one hand and bracing the upper chest with the other.
- Scapular rotation is then performed.
Milch Technique
In this method, abduction and external rotation are applied to the affected extremity while the physician’s thumb disengages the humeral head with the the patient in the prone position.
Techniques of Reduction for Posterior Dislocation of Shoulder
- Apply gentle, prolonged axial traction on the humerus.
- Add gentle anterior pressure while coaxing the humeral head over the glenoid rim.
- Slow external rotation may be required.
Techniques of Reduction for Inferior Dislocation of Shoulder [Luxatio Erecta]
- Maintain gentle axial traction on the humerus while gentle abduction is maintained and countertraction is applied
- Apply countertraction across the ipsilateral shoulder.
- Following reduction, slowly adduct the arm.
Follow-up and Physical Therapy
Most of the dislocations are amenable to closed reductions. Very rarely, open reduction may be needed.Buttonholing of the humeral head through the capsule usually requires open reduction.
The limb is immobilized for about three weeks before in shoulder immobilizer or sling and swathe. In sling, elbow, wrist, and hand range of motion are encouraged and continued when the patient comes out of the sling.
After sling is removed, active and passive flexion, extension, abduction and internal/external rotation are begun. Full range of motion is gained around 6-8 weeks after sling removal.
More vigorous therapy can be initiated at this point.
These include rotator cuff strengthening exercises and strengthening exercises. Swimming is considered to be an excellent exercise for shoulder strengthening.
For young athletes, strenuous training should be deferred till 3 months.
Surgery
Sometimes associated fractures might need surgical repair after shoulder is reduced.
Rarely, failure of closed reduction may occur due to button holing or soft tissue interposition.
All these are indications of open reduction of shoulder joint.
A shoulder with recurrent dislocation problem should be considered for surgery either open or arthroscopic.
Primary surgical repair of initial acute traumatic shoulder dislocations in young adults can be considered for demanding physical activities like sports.
Return to Play
Return to play in athletes can be considered when full range of motion (ROM) and strength have been achieved.
Complications of Shoulder Dislocation
Recurrent shoulder dislocation
Recurrent dislocation of shoulder is most common complication of acute shoulder dislocation due to deformation and stretching of the surrounding tissues.
Recurrent dislocations are more common in young adults as compared to older people.
Injuries to Surrounding Tissues
Hill-Sachs lesion, Bankart lesion, and rotator cuff injury as discussed in associated injuries.]
Fracture of the greater tuberosity, acromion, coracoid, clavicle, and humeral neck also occur.
Neuro-vascular injury
Nerve injuries are much more common than vascular injuries.
The axillary nerve is reported to be injured in 3- 33% of acute anterior dislocations.
Rarely, radial nerve and brachial plexus may be injured.
Vascular injuries are rare. These are more common with inferior dislocations and usually involve a branch of the axillary artery.
Arterial injury is more probable if there is injury to brachial plexus.
Prognosis of Shoulder Dislocation
90% of the teen dislocations recur. In patients older than 40 years, the rate decreases to 10-15%.
Most redislocations occur within 2 years of the primary injury.
Patients with axillary nerve injuries usually recover completely within 3-6 months. Some patients may require surgical exploration.
Age is a major factor in the likelihood of sustaining a recurrent shoulder dislocation.
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