Orthopaedic Surgery - Shoulder Dislocation

Basics

The shoulder is the:

Most commonly dislocated major joint.

Its predisposition to dislocation reflects the combination of:

Extensive range of motion

and relatively limited inherent:

Bony stability.

The glenohumeral joint therefore relies heavily on:

Capsular

Labral

Ligamentous

and

Muscular restraints

to maintain stability.

Classification

Shoulder dislocations are primarily classified according to the:

Direction of displacement of the humeral head.

The major types are:

Anterior

Posterior

and

Inferior dislocation.

Anterior Dislocation

Anterior dislocations account for approximately:

95% of shoulder dislocations.

The humeral head typically moves:

Anterior and inferior to the glenoid.

Posterior Dislocation

Posterior shoulder dislocation is substantially less common but clinically important because it is:

Frequently missed.

Failure to obtain an adequate:

Axillary or equivalent lateral view

is a major reason the diagnosis is overlooked.

Arm Position

The position in which the patient holds the arm often reflects the:

Direction of dislocation.

Anterior and posterior dislocations typically produce different characteristic postures.

Spontaneous Reduction

Some shoulder dislocations:

Reduce spontaneously

at the time of injury or before medical evaluation.

In these patients, residual:

Pain

Instability

Labral injury

or

Fracture

may provide evidence that a dislocation occurred.

Age-Related Injury Pattern

Associated injuries vary considerably with:

Patient age.

Younger Patients

Patients approximately:

30 years or younger

are more likely to sustain injury to the:

Labrum

Capsule

or

Glenoid rim.

Older Patients

Patients older than approximately:

40–50 years

have a higher likelihood of associated:

Rotator cuff tear

Greater tuberosity fracture

and

Neurovascular injury.

Prevention

There is no completely effective method of preventing traumatic shoulder dislocation.

Avoidance of:

Contact and collision sports

may reduce exposure to a common mechanism in younger patients.

Epidemiology

Shoulder dislocation occurs most frequently in:

Young males

with another incidence peak occurring in:

Older adults.

Sex

Historical series report that males account for approximately:

74% of shoulder dislocations.

Age Distribution

The highest incidence occurs in:

Males younger than 20 years.

A second peak occurs in individuals older than approximately:

70 years.

This produces a:

Bimodal age distribution.

Incidence

The overall incidence in the United States has historically been estimated at approximately:

24 per 100,000 persons per year.

Geriatric Considerations

Approximately:

20% of shoulder dislocations

occur in patients older than:

60 years.

Older-Adult Associated Injuries

Compared with younger patients, older individuals have an increased incidence of:

Rotator cuff tears

Greater tuberosity fractures

and

Peripheral nerve injury.

Rotator Cuff Evaluation in Older Patients

Persistent weakness following reduction in an older patient should raise concern for:

Acute rotator cuff tear.

MRI or ultrasound may be appropriate when there is:

Significant weakness

or an abnormal examination after reduction.

Pediatric and Adolescent Considerations

The incidence is particularly high among:

Adolescent boys, especially around 14–16 years of age.

Recurrence following nonoperative treatment may be very high in this group and can resemble that seen in:

High-risk young adults.

Risk Factors

Important risk factors include:

Male sex

Contact sports

Collision sports

Generalized ligamentous laxity

Connective-tissue disorders

Previous shoulder dislocation

Risk Factors for Recurrent Instability

Recurrent dislocation is associated with:

Young age at first dislocation

Male sex

Hyperlaxity

Glenoid bone loss

Humeral head bone loss

Repeated instability episodes

and the amount of time and activity exposure after the:

Initial dislocation.

Early Age at First Dislocation

An initial dislocation before approximately:

20 years of age

is strongly associated with a higher likelihood of:

Recurrent instability.

Genetics

Traumatic shoulder instability has traditionally not been regarded as primarily:

Genetic.

However, alterations in collagen biology may contribute to susceptibility in some individuals with:

Recurrent instability

or underlying connective-tissue laxity.

Reduced expression of:

COL5A1

has been reported in capsular tissue from some patients with recurrent instability.

Etiology

The classic mechanism of an anterior shoulder dislocation is:

Abduction

External rotation

and

Extension

with a force directed so that the humeral head is driven:

Anteriorly.

Predisposing History

Important historical factors include:

Previous shoulder trauma

and

Prior dislocation or instability episodes.

Posterior Dislocation Mechanisms

Posterior dislocations may occur after:

Seizure

Electrical injury

or trauma that produces forceful:

Internal rotation and adduction.

Because the deformity may be subtle, these injuries require a:

High index of suspicion.

Associated Conditions and Injuries

The patient’s age helps predict the pattern of associated damage.

Patients Younger Than 40 Years

Younger patients commonly sustain injuries involving the:

Capsule

Glenoid

and

Labrum.

Bankart Lesion

A Bankart lesion involves injury to the:

Anteroinferior glenoid labrum and capsuloligamentous structures

after anterior dislocation.

Bony Bankart Lesion

When the anterior-inferior glenoid rim is fractured, the injury is termed a:

Bony Bankart lesion.

The lesion may therefore be:

Soft-tissue

Bony

or a combination of both.

Patients Older Than 40 Years

Older patients are more likely to sustain:

Rotator cuff tears

Greater tuberosity fractures

Lesser tuberosity fractures

Articular cartilage injuries

Coracoid fractures

and

Neurovascular injury.

Hill-Sachs Lesion

Anterior shoulder dislocation may create a:

Compression defect of the posterolateral or posterosuperior humeral head

when it impacts the:

Anterior glenoid rim.

This is known as a:

Hill-Sachs lesion.

Reverse Hill-Sachs Lesion

Posterior shoulder dislocation may produce an:

Anteromedial humeral head impaction defect

known as a:

Reverse Hill-Sachs lesion.

Diagnosis

Diagnosis is based on:

History

Physical examination

and

Radiographs.

Signs and Symptoms

Typical findings include:

Severe shoulder pain

Tenderness

Inability or unwillingness to move the shoulder

and visible alteration in:

Shoulder contour.

Arm Support

Patients frequently support the injured arm using the:

Opposite hand

to minimize painful motion.

Neurovascular Symptoms

Patients may develop:

Numbness

Weakness

or other evidence of:

Nerve injury.

The:

Axillary nerve

is the most commonly affected.

Axillary Nerve Findings

Axillary nerve dysfunction may cause:

Reduced sensation over the lateral shoulder

and

Deltoid weakness.

Physical Examination

A careful examination should be performed:

Before and after reduction.

Inspection

Inspect the shoulder girdle for:

Asymmetry

Loss of normal contour

Swelling

Ecchymosis

and deformity.

Anterior Dislocation Appearance

With anterior dislocation, the shoulder may appear:

Squared off

with a prominent:

Acromion

and loss of the normal rounded deltoid contour.

Palpation

The displaced humeral head may occasionally be palpable:

Anteriorly

or

Posteriorly

depending on the direction of dislocation.

Sulcus Sign

The sulcus sign demonstrates:

Inferior laxity

but is more relevant to chronic instability evaluation than to the immediate management of an acute dislocation.

Apprehension and Relocation Tests

These tests are useful after the acute injury has resolved to evaluate:

Anterior instability.

They should not be aggressively performed during the:

Acute dislocation episode.

Neurovascular Examination

Document before and after reduction:

Axillary nerve sensation

Deltoid function

Distal motor function

Peripheral pulses

Capillary refill

and overall:

Limb perfusion.

Range of Motion and Strength

Formal testing of:

Active motion

Passive motion

and

Shoulder girdle strength

should usually be deferred until after:

Reduction

and reduction of acute pain.

Imaging

Plain Radiographs

Conventional radiographs are generally sufficient to confirm the diagnosis.

At minimum, imaging should include:

Anteroposterior view

and

Axillary or equivalent orthogonal view.

Axillary View

The axillary view is particularly important for detecting:

Posterior shoulder dislocation.

If AP and scapular-Y views appear normal but clinical suspicion remains, an:

Axillary view

should be obtained whenever feasible.

Posterior Dislocation Pitfall

Posterior dislocation may be missed when only:

AP radiographs

are obtained.

This is one of the classic diagnostic pitfalls in shoulder trauma.

Scapular Y View

The scapular-Y view can help demonstrate the relationship between the:

Humeral head

and

Glenoid.

However, it does not completely replace the:

Axillary view.

Postreduction Radiographs

Radiographs should be obtained after reduction to:

Confirm concentric reduction

and evaluate for associated:

Fractures

Hill-Sachs lesions

or other bone injury.

CT

CT is useful for assessing:

Glenoid bone loss

Humeral head defects

Fracture configuration

and complex:

Bony instability lesions.

MRI

MRI is useful for evaluating:

Labral tears

Capsular injury

Rotator cuff tears

Biceps pathology

and other:

Soft-tissue injuries.

Pathological Findings

Histopathological testing is:

Not routinely required

for traumatic shoulder dislocation.

Differential Diagnosis

Important alternative or associated diagnoses include:

Acromioclavicular injury

Cervical spine injury

Clavicle fracture

Labral injury

Proximal humerus fracture

Rotator cuff tear

Treatment

General Principles

Acute shoulder dislocation requires:

Prompt closed reduction

after appropriate assessment and imaging.

The direction of the dislocation must be understood because it influences the:

Reduction technique.

Urgency

Reduction should be performed:

Urgently

to relieve pain, reduce neurovascular stretch, and minimize ongoing:

Cartilage and soft-tissue injury.

Analgesia and Sedation

Options include:

Intra-articular local anesthetic

Procedural sedation

Intravenous analgesia

or other appropriate pain-control strategies.

Muscle Spasm

Muscle spasm can prevent easy reduction.

Adequate:

Analgesia

Relaxation

and gentle technique reduce the risk of:

Iatrogenic fracture or soft-tissue injury.

Reduction Principles

Reduction should be:

Slow

Controlled

and

Gentle.

Forceful manipulation should be avoided.

Stimson Technique

The patient lies:

Prone

with the affected arm hanging over the side of the table.

Gentle downward traction, historically sometimes assisted by:

Weights

allows gradual muscle relaxation and reduction.

Traction-Countertraction

With the patient supine, gentle longitudinal traction is applied to the:

Affected arm

while countertraction is applied across the torso using:

A sheet or assistant.

Milch Technique

The arm is gradually:

Abducted

while the examiner controls the humeral head.

Once adequate abduction is achieved, gentle:

External rotation

may assist reduction.

FARES Technique

The:

FARES technique

uses gentle longitudinal traction while the arm is progressively abducted with small:

Vertical oscillations.

It is designed to provide:

Fast, atraumatic reduction

without abrupt force.

Posterior Dislocation Reduction

Posterior dislocations require special caution.

Forceful:

External rotation

should be avoided because it can cause:

Proximal humerus fracture

particularly when a reverse Hill-Sachs lesion is present.

Posterior Reduction Principle

Reduction generally involves:

Gentle traction

Controlled internal rotation

and carefully directed force on the:

Proximal humerus

to disengage the humeral head from the posterior glenoid.

Irreducible Dislocation

If closed reduction fails, the patient requires:

Urgent open reduction.

Failure may result from:

Interposed soft tissue

Fracture fragments

or an entrapped:

Humeral head defect.

Immobilization

After uncomplicated reduction, patients are typically placed in a:

Sling

or

Shoulder immobilizer.

Duration of Sling Use

A short period of approximately:

7–10 days

is often sufficient for pain control in simple dislocations.

The exact duration depends on:

Age

Associated injury

and

Comfort.

Early Motion

After acute pain subsides, patients should gradually begin:

Gentle range-of-motion exercises.

Prolonged immobilization should be avoided, especially in:

Older patients

because of the risk of:

Shoulder stiffness.

Return to Sport

Athletes may return when they have:

Full or near-full range of motion

Symmetric strength

Minimal or no pain

and sufficient:

Stability for sport-specific activity.

Bracing for Contact Sports

Some contact athletes use braces that limit:

External rotation

and

Abduction

during return to play.

However, recurrent instability after return to competition remains:

Common.

Physical Therapy

Physical therapy may begin after the:

Acute pain subsides.

Rehabilitation Goals

The goals are to restore:

Range of motion

Rotator cuff strength

Scapular control

and

Symmetric shoulder function.

Associated Injuries

If a patient has an associated:

Fracture

Rotator cuff tear

or other significant injury, rehabilitation may need to be:

Delayed or modified.

Need for Therapy

Not every uncomplicated dislocation requires formal:

Physical therapy.

A structured home program may be sufficient for some patients.

Medication

First-Line Analgesia

Pain may be treated with:

NSAIDs

and

Acetaminophen.

Opioids

A short course of opioid analgesia may occasionally be needed for:

Severe acute pain.

Routine prolonged opioid treatment should be avoided.

Surgery

Surgical treatment after a first-time shoulder dislocation is:

Individualized.

First-Time Dislocation

Many first-time dislocations are initially managed:

Nonoperatively.

However, early surgery may be considered in selected:

Young high-risk athletes

or patients with significant structural injury.

Surgical Target

Surgery should address the specific abnormality responsible for instability, as identified clinically and with:

MRI

CT

or other advanced imaging.

Bankart Repair

Young patients commonly have a:

Bankart lesion.

Soft-tissue Bankart lesions are typically repaired:

Arthroscopically

with restoration of the:

Labrum and capsule.

Bony Bankart Repair

A significant glenoid rim fracture may require:

Arthroscopic

or

Open fixation or reconstruction

depending on the size and configuration of the:

Bone defect.

Hill-Sachs Lesion

Large humeral head defects that engage the glenoid may contribute to:

Recurrent instability.

Remplissage

A:

Remplissage procedure

fills the Hill-Sachs defect using posterior capsulotenodesis, typically involving the:

Infraspinatus tendon and posterior capsule.

This reduces the tendency of the defect to:

Engage the anterior glenoid.

Bone Reconstruction

Very large humeral head defects may occasionally require:

Bone grafting

or other reconstructive procedures.

Greater Tuberosity Fracture

Associated greater tuberosity fractures are treated according to:

Displacement

Rotator cuff function

and

Patient activity level.

Rotator Cuff Repair

Complete rotator cuff tears associated with dislocation in older patients may require:

Arthroscopic

or

Open repair

when medically and functionally appropriate.

Glenoid Bone Loss

Substantial anterior glenoid bone loss is an important cause of:

Recurrent instability.

Latarjet Procedure

The:

Latarjet procedure

transfers the:

Coracoid process

to the anterior glenoid to augment deficient:

Glenoid bone stock

and provide additional dynamic stability.

Other Bone-Block Procedures

Alternative bone-augmentation techniques may be used depending on:

Defect size

Prior surgery

and surgeon preference.

Follow-Up

Patients are generally reassessed within approximately:

7–10 days

after injury.

Early Follow-Up Goals

The clinician should reassess:

Pain

Neurovascular function

Rotator cuff strength

Range of motion

and possible associated:

Fractures or soft-tissue injuries.

Sling Weaning

Patients with uncomplicated dislocations are usually encouraged to:

Gradually discontinue sling use

as pain improves.

Advanced Imaging

Further MRI or CT may be obtained when there is concern for:

Rotator cuff tear

Labral injury

Bone loss

Persistent weakness

or

Recurrent instability.

Prognosis

Prognosis depends heavily on:

Age at first dislocation

Sex

Activity level

and the amount of:

Structural damage.

Recurrence in Young Patients

Recurrent instability is particularly common in patients younger than approximately:

21 years.

Historical studies have reported recurrence rates approaching:

80% in teenagers

after nonoperative treatment.

Effect of Age

The younger the patient at the time of the initial dislocation, the greater the likelihood of:

Recurrence.

Male Sex

Male sex has also been associated with a higher risk of:

Recurrent instability

in several studies.

Associated Pathology

Recurrence risk increases when dislocation is accompanied by:

Labral injury

Capsular injury

Glenoid bone loss

Hill-Sachs lesion

or other structural abnormalities.

Complications

Recurrent Instability

The most common long-term complication in young patients is:

Recurrent dislocation or subluxation.

Glenohumeral Arthritis

Repeated instability episodes may contribute to progressive:

Glenohumeral osteoarthritis.

Even a single traumatic dislocation can occasionally produce:

Long-term chondral damage.

Chondral Injury

Dislocation may damage:

Articular cartilage

of the glenoid or humeral head.

Labral Tears

Labral injury is common, particularly after:

Anterior dislocation in younger patients.

Nerve Injury

Transient nerve injury or:

Neurapraxia

occurs in a minority of patients.

Historical estimates are approximately:

5%.

Axillary Nerve

The:

Axillary nerve

is the most commonly injured nerve.

Patients should be examined for:

Lateral shoulder numbness

and

Deltoid weakness.

Rotator Cuff and Nerve Injury Association

Rotator cuff tears and peripheral nerve injuries may coexist, particularly in:

Older patients.

The presence of one should prompt consideration of the:

Other.

Proximal Humerus Fracture

A shoulder dislocation may occur with:

Greater tuberosity fracture

or other proximal humerus fractures.

Vascular Injury

Vascular injury is:

Rare

but can occur, particularly in:

Older patients

or high-energy trauma.

Loss of pulses, expanding hematoma, or limb ischemia requires:

Urgent vascular assessment.

Patient Monitoring

Follow-up should evaluate:

Pain

Range of motion

Strength

Neurovascular status

Rotator cuff function

and evidence of:

Recurrent instability.

Key Principle

Shoulder dislocation is most commonly anterior and occurs because the glenohumeral joint sacrifices stability in order to achieve exceptional mobility.

Young patients most often sustain:

Labral and capsular injuries, while older patients are more likely to have:

Rotator cuff tears, tuberosity fractures, and nerve injuries.

Diagnosis requires appropriate radiographs, especially an:

Axillary view to avoid missing posterior dislocation.

Treatment begins with:

Urgent gentle reduction, postreduction imaging, short-term sling use, and progressive rehabilitation.

Surgery is considered for:

Recurrent instability, significant Bankart or Hill-Sachs lesions, substantial glenoid bone loss, associated rotator cuff tears, fractures, or irreducible dislocation.