Orthopaedic Surgery - Shoulder Instability

Basics

Shoulder instability describes:

Abnormal symptomatic translation of the humeral head relative to the glenoid

beyond the limits of normal physiologic motion.

It is common in:

Young

Active

and

Athletic patients.

Instability Versus Laxity

It is important to distinguish:

Instability

from

Laxity.

Instability is the patient’s subjective experience of:

Painful slipping

Subluxation

Apprehension

or

Dislocation.

Laxity is an objective finding of:

Excessive joint translation on examination.

A patient may have physiologic laxity without:

Symptoms or true instability.

Classification

Shoulder instability may be classified according to:

Direction

Cause

and

Severity.

Classification by Direction

Instability may be:

Anterior

Posterior

or

Multidirectional.

Classification by Etiology

It may be:

Traumatic

or

Atraumatic.

Classification by Degree

Instability events may consist of:

Subluxation

or complete:

Dislocation.

Multidirectional Instability

Multidirectional instability is defined as symptomatic abnormal translation in:

More than one direction.

It commonly has an element of:

Generalized ligamentous laxity

and may involve:

Both shoulders.

Anterior Instability

Traumatic anterior instability is the:

Most common pattern

and often follows a true:

Anterior shoulder dislocation.

Posterior Instability

Posterior instability may result from:

Trauma

such as seizures or electrical injury

or from repetitive loading in athletes such as:

Football linemen.

It may also occur without a single major traumatic event.

Epidemiology

Shoulder instability is common in:

Young athletic populations.

It is among the most frequent shoulder problems encountered in:

Sports medicine.

Posterior Instability

Posterior instability accounts for approximately:

10% of shoulder instability cases.

It is substantially less common than:

Anterior instability.

Incidence

Anterior shoulder dislocation requiring closed reduction has historically been reported at approximately:

24 per 100,000 persons per year.

Posterior instability has been estimated at approximately:

1.1 per 100,000 persons per year.

Age Distribution

Posterior instability peaks in:

Men aged approximately 20–49 years

and in:

Women older than approximately 70 years.

Multidirectional Instability

The exact incidence is unknown.

It is particularly common in athletes involved in:

Gymnastics

Swimming

Volleyball

and other activities requiring repeated:

Overhead motion.

It often becomes symptomatic during the:

Second or third decade of life.

Risk Factors

Important risk factors include:

Young age

Male sex

Contact or collision sports

Connective-tissue disorders

Generalized hyperlaxity

Previous contralateral instability

Seizure disorder

and selected:

Glenoid morphologies.

Glenoid Morphology

Posterior instability is associated particularly with:

Glenoid retroversion

and

Glenoid hypoplasia.

These abnormalities may reduce posterior containment of the:

Humeral head.

Athletic Risk

Certain sports place the shoulder repeatedly in positions that stress specific stabilizers.

Examples include:

Football

Gymnastics

Swimming

Volleyball

and other overhead activities.

Age

Patients younger than approximately:

20 years

have an increased risk of:

Recurrent instability.

Genetics

Historically, traumatic shoulder instability was not considered a primarily:

Genetic disorder

in patients without connective-tissue disease.

However, altered collagen biology may contribute in selected patients.

Reduced expression of:

COL5A1

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

Etiology

The shoulder has exceptional mobility but relatively limited inherent:

Bony stability.

Normal stability depends on both:

Static

and

Dynamic stabilizers.

Static Stabilizers

These include:

Glenoid morphology

Labrum

Capsule

Glenohumeral ligaments

and

Negative intra-articular pressure.

Dynamic Stabilizers

These include:

Rotator cuff muscles

Long head of the biceps

and

Periscapular musculature.

Anterior Instability Mechanism

The classic mechanism for traumatic anterior instability involves:

Abduction

External rotation

and often:

Extension

with a force that drives the humeral head:

Anteriorly.

Posterior Instability Mechanism

Posterior instability may result from:

Posteriorly directed force

or an axial load with the arm in:

Internal rotation

and

Adduction.

Multidirectional Instability Mechanism

Multidirectional instability is often produced by a combination of:

Biologic factors

such as ligamentous laxity

and

Environmental or activity-related factors

such as repetitive overhead sports.

Associated Conditions and Lesions

Shoulder instability may be associated with:

Bankart lesions

Bony Bankart lesions

HAGL lesions

ALPSA lesions

GLAD lesions

Labral tears

Hill-Sachs lesions

Reverse Hill-Sachs lesions

Rotator cuff tears

Tuberosity fractures

and

Generalized hyperlaxity.

ALPSA Lesion

An:

Anterior labroligamentous periosteal sleeve avulsion

occurs when the anteroinferior labrum and attached ligamentous structures are stripped medially from the:

Glenoid neck

while remaining attached to the:

Periosteum.

Bankart Lesion

A Bankart lesion involves injury to the:

Anteroinferior labrum and capsuloligamentous complex.

It may be:

Soft tissue

or

Bony.

HAGL Lesion

A:

Humeral avulsion of the glenohumeral ligament

occurs when the inferior glenohumeral ligament is avulsed from its:

Humeral attachment.

GLAD Lesion

A:

Glenolabral articular disruption

involves injury to the:

Labrum

and adjacent:

Glenoid cartilage.

Hill-Sachs Lesion

Anterior instability may produce a:

Posterolateral or posterosuperior humeral head compression defect.

This is known as a:

Hill-Sachs lesion.

Reverse Hill-Sachs Lesion

Posterior instability may produce an:

Anteromedial humeral head impaction defect

known as a:

Reverse Hill-Sachs lesion.

Posterior Instability Pathology

Posterior instability may be associated with:

Posterior labral tearing

Posterior cuff fraying

Posterior capsular injury

and

Glenoid retroversion or hypoplasia.

Diagnosis

Diagnosis depends on:

History

Physical examination

and

Imaging.

The clinician must determine whether observed laxity is:

Physiologic

or

Pathologic and symptomatic.

Signs and Symptoms

Patients may report:

Pain

Apprehension

Sensation of slipping

Recurrent subluxation

or

Frank dislocation.

Tenderness

Tenderness may be present around the:

Shoulder girdle

particularly after an acute instability event.

Range of Motion

Attempted motion may produce:

Pain

or a sense of:

Instability.

Abnormal Arm Position

During an acute dislocation, the arm may be held in a characteristic:

Abnormal posture

depending on the direction of displacement.

Physical Examination

A complete examination should include:

Inspection

Palpation

Range of motion

Rotator cuff strength

Instability testing

Hypermobility assessment

and

Neurovascular examination.

Sulcus Sign

The sulcus sign is produced by applying:

Downward traction

to the relaxed arm.

A visible depression below the acromion indicates:

Inferior humeral translation.

It is particularly useful in assessing:

Inferior laxity

and

Multidirectional instability.

Apprehension Test

The shoulder is placed in:

Abduction

and

External rotation.

A sensation of impending dislocation rather than pain alone suggests:

Anterior instability.

Relocation Test

Posteriorly directed pressure on the humeral head during the apprehension position that reduces:

Apprehension

supports the diagnosis of:

Anterior instability.

Acute Setting

Apprehension and relocation testing should not be performed aggressively during an:

Acute unreduced dislocation.

Beighton Score

The:

Beighton hypermobility score

can be used to assess:

Generalized ligamentous laxity.

This is especially relevant in patients suspected of having:

Multidirectional instability.

Load-and-Shift Test

The examiner stabilizes the scapula and translates the humeral head:

Anteriorly

and

Posteriorly.

Excessive translation or reproduction of symptoms suggests:

Instability.

Posterior Stress Testing

Posterior instability may be evaluated using:

Posterior load-and-shift

Posterior stress test

Jerk test

and

Kim test.

Jerk Test

The arm is elevated to approximately:

90°

with internal rotation and axial loading.

A painful:

Clunk

or sudden posterior translation suggests:

Posterior instability or posterior labral pathology.

Kim Test

The Kim test applies a:

Posteroinferiorly directed force

while elevating the arm.

Pain or a posterior clunk may indicate:

Posteroinferior labral injury.

Rotator Cuff Examination

Assess:

Supraspinatus

Infraspinatus

Teres minor

and

Subscapularis strength.

Cuff injury may coexist with:

Instability, especially in older patients.

Neurovascular Examination

Neurovascular status should be assessed:

Before and after reduction

when a dislocation is present.

Particular attention should be paid to the:

Axillary nerve.

Imaging

Plain Radiographs

A full conventional shoulder series is usually the initial study.

At minimum, obtain:

Anteroposterior

and

Axillary views.

Axillary View

The axillary view is essential for identifying:

Posterior dislocation

and determining the relationship between the:

Humeral head

and

Glenoid.

Posterior dislocations are commonly missed when this view is omitted.

Postreduction Imaging

Postreduction radiographs are necessary to:

Confirm concentric reduction

and identify associated:

Fractures

or

Bony defects.

CT

CT is useful for assessing:

Glenoid bone loss

Hill-Sachs defects

Reverse Hill-Sachs lesions

Fracture morphology

and abnormal:

Glenoid version.

MRI

MRI is useful for evaluating:

Labral tears

Capsular injury

Rotator cuff tears

HAGL lesions

and other:

Soft-tissue abnormalities.

MR Arthrography

MR arthrography can improve detection of:

Subtle labral

and

Capsuloligamentous lesions

in patients with chronic or recurrent instability.

Pathological Findings

Histopathological testing is:

Not routinely required.

The relevant pathology is usually defined by:

Clinical examination

and

Imaging.

Differential Diagnosis

Important alternative diagnoses include:

Acromioclavicular injury

Clavicle fracture

Proximal humerus fracture

Rotator cuff tear

and other causes of shoulder pain or apparent instability.

Treatment

General Principles

Treatment depends on:

Direction

Cause

Frequency

Structural damage

and whether instability is:

Traumatic or atraumatic.

Acute Dislocation

If a true dislocation is present, treatment begins with:

Urgent closed reduction.

The technique depends on the:

Direction of displacement.

Reduction

Reduction should be performed using:

Gentle controlled maneuvers

with appropriate:

Analgesia

and

Muscle relaxation.

Posterior dislocations require techniques different from:

Anterior dislocations.

Immobilization

After uncomplicated anterior dislocation, a sling or immobilizer may be used for approximately:

7–10 days

primarily for:

Pain control.

Posterior Dislocation Immobilization

After posterior dislocation, some patients are placed in an:

External rotation brace

to reduce recurrent posterior translation during healing.

Range of Motion

Gentle shoulder motion may begin after:

Acute pain improves.

The sling can be discontinued gradually as:

Comfort allows.

Return to Sport

Athletes may return when they have:

Full range of motion

Symmetric strength

Minimal pain

and sufficient:

Dynamic stability.

In-Season Return

Athletes returning during the same season may use an adjustable brace that limits:

Abduction

and

External rotation.

However, recurrent instability during in-season return is:

Common.

Historical data suggest that only a minority may complete the remainder of the season without another instability event.

Activity Modification

For:

Multidirectional instability

and

Subtle posterior instability

initial treatment centers on:

Activity modification

and

Rehabilitation.

Sport Cessation

Temporary cessation of the provocative sport may be necessary for:

Posterior

or

Multidirectional instability

when symptoms are driven by repetitive athletic loading.

Physical Therapy

Physical therapy is central to treatment, particularly for:

Atraumatic

Posterior

and

Multidirectional instability.

Anterior Instability Rehabilitation

After uncomplicated anterior dislocation, therapy can begin once:

Acute pain subsides.

If fractures or other injuries are present, rehabilitation may need to be:

Delayed.

Posterior Instability Rehabilitation

After posterior dislocation, strengthening may be delayed for several weeks, often approximately:

4–6 weeks

depending on associated injury and stability.

Multidirectional Instability Rehabilitation

Patients with multidirectional instability usually require a prolonged course of:

Dynamic stabilization exercises

often lasting approximately:

4–6 months.

Rehabilitation Goals

Therapy emphasizes:

Rotator cuff strengthening

Scapular stabilization

Proprioception

Neuromuscular control

and

Closed kinetic-chain exercises.

Medication

Symptomatic treatment may include:

NSAIDs

Acetaminophen

and

Ice.

A short course of opioid medication may occasionally be used after an acute dislocation, but prolonged use is generally avoided.

Surgery

Surgical treatment is selected according to the:

Underlying structural lesion.

First-Time Dislocation

Surgery after a first-time anterior dislocation remains:

Individualized.

Young athletes at high risk of recurrence may be considered for:

Early stabilization.

Bankart Repair

Soft-tissue Bankart lesions are commonly treated with:

Arthroscopic labral and capsular repair.

Bony Bankart Repair

Significant glenoid rim fractures may require:

Arthroscopic

or

Open fixation or reconstruction.

Hill-Sachs Lesions

Surgical treatment depends on:

Size

Location

Engagement

and the amount of associated:

Glenoid bone loss.

Bone Loss

Recurrent instability can progressively enlarge:

Glenoid

and

Humeral head bone defects.

Substantial glenoid bone loss may require a:

Bone-augmentation procedure

rather than isolated soft-tissue repair.

Tuberosity Fractures

Associated greater or lesser tuberosity fractures are treated according to:

Displacement

Patient function

and

Rotator cuff integrity.

Rotator Cuff Tears

Rotator cuff tears associated with dislocation, especially in patients older than approximately:

50 years

may require:

Surgical repair

when clinically significant.

Irreducible Dislocation

If the shoulder cannot be reduced by closed methods, urgent:

Open reduction

is indicated.

Posterior Instability Surgery

Procedures may include:

Posterior labral repair

Posterior capsular plication

or correction of substantial:

Bone deficiency or abnormal glenoid morphology.

Multidirectional Instability Surgery

Patients with persistent symptomatic multidirectional instability despite prolonged rehabilitation may undergo:

Capsular plication

or another capsular volume-reduction procedure.

Follow-Up

After a simple dislocation, patients are generally reviewed within approximately:

7–10 days.

Early Follow-Up

The clinician should reassess:

Pain

Neurovascular status

Rotator cuff function

Range of motion

and associated:

Fracture or soft-tissue injury.

Sling Weaning

Patients with uncomplicated dislocations should gradually:

Wean from the sling

as pain improves.

Multidirectional Instability Follow-Up

Patients undergoing nonoperative treatment for multidirectional instability should be seen periodically to evaluate:

Compliance

Strength

Scapular control

and

Response to therapy.

Posterior Instability Follow-Up

After posterior instability or dislocation, immobilization strategy and timing of:

Physical therapy

should be individualized according to:

Structural injury

and

Clinical stability.

Prognosis

Prognosis depends on:

Age

Direction of instability

Athletic demands

Degree of laxity

and associated:

Structural damage.

Recurrence in Young Patients

Recurrent instability is very common in:

Teenagers

and

Young adults.

Historical recurrence rates in teenagers have approached:

80%.

Age Effect

The younger the patient at the first instability event, the greater the likelihood of:

Recurrent episodes.

Structural Risk Factors

Recurrence is more likely when associated with:

Labral tears

Capsular injury

Bone loss

Rotator cuff tearing

or

Fracture.

Posterior Instability Outcomes

Football players treated with arthroscopic posterior labral repair often demonstrate a:

High rate of return to play.

Throwing athletes may have more difficulty returning to their:

Previous performance level.

Multidirectional Instability Outcomes

Many patients improve with:

Structured rehabilitation.

Younger athletes may have less predictable success with therapy alone.

Surgical capsular stabilization can produce:

Good functional outcomes

Low recurrence

and

High return-to-sport rates

in appropriately selected patients.

Complications

Recurrent Instability

The most common long-term complication is:

Recurrent subluxation or dislocation.

Glenohumeral Arthritis

Repeated instability episodes may contribute to:

Progressive cartilage damage

and eventually:

Glenohumeral osteoarthritis.

Nerve Injury

Transient:

Neurapraxia

occurs in a minority of patients.

The:

Axillary nerve

is most commonly involved.

Stiffness

Excessive immobilization or surgery may result in:

Loss of shoulder motion.

Vascular Injury

Vascular injury is:

Rare

but has been reported, particularly after traumatic dislocation.

Abnormal pulses or limb perfusion require:

Urgent assessment.

Patient Monitoring

Long-term follow-up should assess:

Recurrent episodes

Pain

Range of motion

Strength

Scapular control

Apprehension

and the effectiveness of:

Rehabilitation.

Key Principle

Shoulder instability is symptomatic abnormal motion of the humeral head relative to the glenoid and must be distinguished from asymptomatic physiologic laxity.

It may be:

Anterior, posterior, or multidirectional, and may arise from traumatic or atraumatic mechanisms.

Young patients, athletes, patients with:

Hyperlaxity

and those with:

Labral or bony defects

have the greatest risk of recurrence.

Treatment ranges from:

Urgent reduction and short-term immobilization after dislocation

to prolonged:

Rotator cuff and scapular stabilization therapy

for atraumatic or multidirectional disease.

Surgery is reserved for:

Recurrent instability, significant labral or capsular injury, substantial bone loss, persistent posterior instability, multidirectional instability that fails rehabilitation, or irreducible dislocation.