Shoulder dislocation refers to dislocation of the glenohumeral joint. Shoulder dislocation is a common injury and occurs more in young adults.
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 anterosuperiorly.
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.
Following persons are at increased risk of getting shoulder dislocated-
- Prior history of shoulder dislocation
- Young adults [owing to greater activity]
- Persons with greater activity levels i.e. athletes
The incidence of all traumatic shoulder dislocations has been estimated at 11 cases per 100,000 person-years.
Anterior dislocation is most commonly seen in those aged 18-25 years due to a 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 glenohumeral joint is part of the shoulder joint. The other joints that are part of shoulder joint are
- Sternoclavicular joint
- Acromioclavicular Joint
- Scapulothoracic joint
All of these joints work together for the smooth functioning of the shoulder. The shoulder dislocation is commonly used term for dislocation at the glenohumeral joint.
[Read anatomy of shoulder joint]
The glenohumeral joint is a ball-and-socket synovial joint formed by the articular surfaces of the glenoid cavity of the scapula and the head of the humerus.
The glenoid cavity depth is increased by a rim of fibrocartilage called glenoid labrum which is composed of dense fibrous tissue.
The stability of the shoulder joint is maintained mainly by the glenohumeral ligaments and the joint capsule. Other factors are the rotator cuff muscles [supraspinatus, infraspinatus, subscapularis, and teres minor] the negative intra-articular pressure, and the bony/cartilaginous anatomy.
The inferior glenohumeral ligament is the most important ligament for shoulder stability [and is most commonly injured in an anterior shoulder dislocation]
Common causes of shoulder dislocation are
- Sports injury
- Fall
- Direct blow on the shoulder as in assault
- Throwing or catching an object with overhead abduction
- Seizures
- Forceful pulling on the arm
Initial dislocation requires quite a force. But recurrent dislocations may occur with trivial forces such as combing the hair [overhead abduction]. That causes the limb to reaching a position where it becomes easier to dislocate.
Associated Injuries
- Hill Sachs Lesion
- A compression fracture that results in the formation of a groove in the posterolateral aspect of the humeral head
- Seen in 54-76% of dislocations.
- Bankart Lesion
- Fracture of the anterior rim of the glenoid fossa
- Due to the impaction of the humeral head against the anteroinferior glenoid labrum
- Rupture of the joint capsule and inferior glenohumeral ligament injury may be associated.
- Greater Tuberosity Fracture – 10-15%
- Rotator Cuff Injury
- Glenohumeral ligament injury
- Axillary nerve – 3% of anteroinferior dislocations.
- Brachial plexus/axillary artery injury
- Rare
- Mostly with luxatio erecta
Types of Shoulder Dislocation
Dislocation of the shoulder can be of the following types depending on the position of the head of the humerus relative to glenoid cavity.
Anterior Shoulder Dislocation
Over 95% of shoulder dislocation cases are anterior. That means the head of the humerus lies anteriorly in relation to the glenoid.
The dislocation could be sub-coracoid, sub-glenoid, and subclavicular. Very rarely, the and, very rarely, intrathoracic. The subtypes denote a position of the dislocated head.
Anterior shoulder dislocation usually results from abduction, extension, and external rotation of shoulder such as throwing an overhead ball or a volleyball spike. Fall on an outstretched hand could also be a cause.
The humeral head is forced out of the glenohumeral joint, rupturing or detaching the anterior capsule from the head of the humerus or the edge of the glenoid fossa with or without lateral detachment.
Posterior Shoulder Dislocation
Posterior dislocations are caused by severe internal rotation and adduction. These can occur due to electrocution or seizure. An imbalance 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 [Luxatio Erecta]
It is the least common of all dislocations of the shoulder and accounts for less than 1% of all shoulder dislocation cases.
It is caused by a hyperabduction 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 of neurovascular compromise.
This is also called luxatio erecta because the arm appears to be permanently held upward or behind the head.
Clinical Presentation
There is a history of acute injury especially in shoulders dislocating for first time.
Subsequent recurrent dislocations may occur with lesser force. In fact, the shoulders that have dislocated multiple times can be dislocated with minimal trauma. Sometimes a patient may dislocate the shoulder with raising of the arm as in combing.
Therefore, the ptients with previous dislocations are at greater risk of redislocation and it is important to inquire if any previous history of dislocation is there.
There is severe shoulder pain following shoulder dislocation.
The attitude of the limb guides to the type of dislocation.
- Anterior
- Abducted and externally rotated
- Patient bends forward and may support the limb with other hands.
- Posterior dislocation
- Limb in internal rotation and adduction
- Patient keeps his arm held up against his or her abdomen.
- Luxatio erecta
- Arm fully abducted with elbow supported behind or on the head.
On examination, the shoulder contour is lost and glenoid is empty. The humeral head can be palpated anteriorly.
Patient resists abduction and internal rotation and is unable to touch the opposite shoulder.
Shoulder squared off due to loss of contour. Coracoid process is prominent. However, shoulders may look identical in bilateral dislocation. A prominent head can be palpated posteriorly especially in thin persons.
Head of the humerus may be palpated on the lateral chest wall.
A detailed neurovascular examination should be carried.
The 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 a 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 the age group 20-30 years and in females in the age group 61-80 years.
Anterior dislocation is most commonly seen in those aged 18-25 years due to a sports injury. The second most common age group to sustain anterior dislocation is in elderly persons due to their susceptibility to falls
Differential Diagnoses
Imaging
X-rays
Radiography is a very important aid in making and confirming the diagnosis of shoulder dislocation. It also helps to find a 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 a line of the spine of scapula onto the cassette.
In this view, in the 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. The 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 a shoulder dislocation. Rotator cuff injuries could be documented with MRI.
Treatment of Shoulder Dislocation
The patient should be administered drugs in an 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 is an adequate analgesia and relaxation.
Reductions are carried under sedation or general anesthesia.
Intra-articular lidocaine can be used where the 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 the 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, the shoulder is kept reduced with sling and swathe.
As a rule, a 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 a gentle internal/external humeral rotation.
- The 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 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, the 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 a sling, elbow, wrist, and hand range of motion are encouraged. Exercises are continued after removal of the sling too.
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 until 3 months.
Surgery
Sometimes associated fractures might need surgical repair after shoulder is reduced.
Rarely, failure of closed reduction may occur due to buttonholing or soft tissue interposition.
All these are indications of open reduction of the 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 a full range of motion (ROM) and strength have been achieved.
Complications of Shoulder Dislocation
Recurrent shoulder dislocation
Recurrent dislocation of a shoulder is the 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.
The arterial injury is more probable if there is an 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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