Orthopaedic Surgery - Shoulder Impingement Syndrome

Basics

Shoulder impingement syndrome is a common cause of:

Shoulder pain

particularly during:

Overhead activity.

The most common form is:

External or subacromial impingement.

Spectrum of Disease

Shoulder impingement has traditionally been viewed as a spectrum extending from:

Subacromial bursitis

to

Partial-thickness rotator cuff tearing

and eventually:

Full-thickness rotator cuff tearing.

However, the relationship between actual mechanical contact with the acromion and rotator cuff degeneration is complex.

Both:

Intrinsic tendon degeneration

and

Extrinsic mechanical factors

likely contribute.

Major Types

The two principal categories are:

External impingement

and

Internal impingement.

Less common forms include:

Subcoracoid impingement.

External Impingement

External or subacromial impingement is the:

Most common type.

It involves painful contact or compression of structures within the:

Subacromial space.

Subacromial Space

The subacromial space lies between the:

Acromion superiorly

and

Humeral head inferiorly.

Structures occupying or traversing this space include:

Supraspinatus tendon

Infraspinatus tendon

Long head of the biceps

Joint capsule

Subacromial-subdeltoid bursa

Coracoacromial ligament.

Mechanism of External Impingement

Compression of the rotator cuff against the:

Acromion

and

Coracoacromial arch

has historically been considered an important contributor to:

Rotator cuff disease.

The pathological spectrum may range from:

Inflamed and thickened bursal tissue

to

Bursal-sided partial-thickness cuff tearing.

Acromial Morphology

The acromion is commonly described as:

Flat

Curved

or

Hooked.

Hooked morphology has historically been associated with a higher prevalence of:

Rotator cuff tearing.

However, acromial shape should be interpreted as one factor among several rather than as the sole cause.

Structural Causes of Reduced Subacromial Space

Conditions that may decrease the available space include:

Subacromial osteophytes

Greater tuberosity exostosis

Acromial fracture

Os acromiale

Acromioclavicular osteophytes

Proximal humeral malunion.

Soft-Tissue Causes

The space can also effectively narrow because of enlargement or inflammation of:

Rotator cuff tissue

Subacromial bursa

or deposition of:

Calcium within a tendon.

Internal Impingement

Internal impingement occurs predominantly in:

Overhead throwing athletes.

It involves contact between the:

Articular surface of the posterosuperior rotator cuff

and

Posterosuperior glenoid or labrum.

Throwing Phase

Symptoms typically occur during the:

Late cocking

or

Early acceleration phase

of throwing, when the shoulder is in:

Abduction

and

Maximal external rotation.

Internal Impingement Pathology

Associated abnormalities may include:

Partial articular-sided supraspinatus tears

Posterior rotator cuff fraying

Posterior labral tears

Posterosuperior glenoid cartilage defects

and

Bennett lesions.

Bennett Lesion

A Bennett lesion is a:

Posteroinferior glenoid rim exostosis

or ossific change associated with chronic repetitive throwing.

Peel-Back Phenomenon

Extreme external rotation during throwing can place torsional force on the:

Posterosuperior labrum

through the long head of the biceps.

This may produce the:

Peel-back phenomenon

and contribute to:

Superior or posterosuperior labral tearing.

Contributing Factors in Internal Impingement

Internal impingement is often multifactorial.

Important contributors include:

Posterior capsular contracture

Glenohumeral internal rotation deficit

Scapular dyskinesis

Subtle anterior microinstability

Adaptive remodeling in throwing athletes.

Prevention

External impingement symptoms may be reduced by maintaining:

Rotator cuff strength

Scapular control

and

Shoulder flexibility.

Throwing Athletes

For overhead athletes, prevention emphasizes:

Appropriate throwing mechanics

Posterior shoulder flexibility

Scapular stabilization

and management of:

Training volume.

Epidemiology

Shoulder impingement is among the:

Most common causes of shoulder pain.

Its reported prevalence varies because the term has historically encompassed several overlapping:

Subacromial disorders.

Incidence

The exact incidence is difficult to determine because diagnostic definitions vary.

Nevertheless, subacromial pain and impingement-type symptoms represent a:

Very common source of shoulder dysfunction.

Risk Factors

Important risk factors include:

Increasing age

Repetitive overhead activity

Throwing sports

Swimming

Volleyball

Tennis

Gymnastics

Occupational overhead work.

Genetics

There is no established specific:

Genetic association

for shoulder impingement syndrome.

Etiology

Pain commonly occurs during:

Forward elevation

and

Internal rotation.

Multiple structural and functional abnormalities may contribute.

Proximal Humeral Malunion

Malunion involving the:

Greater tuberosity

or proximal humerus may mechanically narrow the:

Subacromial space.

Coracoacromial Ligament

Thickening of the:

Coracoacromial ligament

may contribute to subacromial contact.

Acromioclavicular Arthritis

Inferiorly projecting osteophytes from the:

AC joint

may reduce the space available for the:

Rotator cuff.

Rotator Cuff Weakness

Weakness or tearing of the rotator cuff may permit:

Superior migration of the humeral head

which can further decrease the:

Subacromial space.

Neurologic Weakness

Rarely, weakness from:

Cervical radiculopathy

or

Suprascapular neuropathy

may impair the supraspinatus and infraspinatus enough to alter shoulder mechanics.

Subacromial Bursitis

Inflammation and thickening of the:

Subacromial bursa

commonly accompany symptomatic external impingement.

Internal Impingement Etiology

Excessive repetitive external rotation in throwers may produce contact between the:

Posterior cuff

and

Posterior-superior glenoid.

Posterior Capsule Contracture

Tightness of the posterior capsule is a common finding and can contribute to:

Glenohumeral internal rotation deficit

and altered humeral translation.

Scapular Dyskinesis

Abnormal scapular motion may reduce:

Effective subacromial clearance

and disturb the normal:

Scapulohumeral rhythm.

Associated Conditions

Common associated abnormalities include:

Glenohumeral internal rotation deficit

Hooked acromion

Os acromiale

Posterior capsular contracture

Partial articular-sided supraspinatus tears

Rotator cuff tears

Scapular dyskinesis

Diagnosis

Diagnosis is primarily based on:

History

Physical examination

and selective:

Imaging.

Signs and Symptoms

Typical symptoms include:

Shoulder pain with overhead activity

Difficulty performing work or sport

and

Night pain or difficulty sleeping.

Activity-Related Pain

Pain commonly occurs during:

Reaching overhead

Throwing

Swimming

Lifting

or repetitive occupational use.

Physical Examination

A complete examination should assess:

Range of motion

Rotator cuff strength

Scapular mechanics

Impingement signs

and associated:

Labral or instability findings.

Neer Impingement Sign

The examiner passively forward elevates the arm.

Reproduction of shoulder pain, often above approximately:

90° of elevation

suggests:

Subacromial pain or impingement.

Neer Impingement Test

Historically, the Neer test refers to repeating the painful maneuver after:

Subacromial local anesthetic injection.

Relief of pain supports the subacromial space as the:

Pain generator.

Hawkins Test

With the shoulder and elbow flexed to:

90°

the examiner forcibly:

Internally rotates the shoulder.

Pain suggests:

Subacromial impingement or rotator cuff pathology.

Jobe Test

The arm is elevated in the:

Scapular plane

and internally rotated or pronated while resistance is applied.

Pain or weakness suggests:

Supraspinatus pathology.

Internal Impingement Examination

Internal impingement may produce posterior shoulder pain with:

Abduction

and

Maximal external rotation.

Range of Motion

Both shoulders should be compared for:

Internal rotation

External rotation

Forward elevation

and

Total rotational arc.

Contracture

Loss of motion may indicate:

Posterior capsular tightness

or another shoulder contracture contributing to symptoms.

Scapular Examination

Observe the scapula during:

Forward elevation

and

Abduction

for:

Winging

Asymmetric motion

or

Dyskinesis.

Imaging

Plain Radiographs

Conventional shoulder radiographs are useful for identifying:

Calcific tendinitis

Arthritis

Acromial abnormalities

Proximal humeral malunion

Os acromiale

and other bony causes of pain.

Acromiohumeral Distance

The distance between the acromion and humeral head can be assessed on radiographs.

A normal interval is generally around:

7–14 mm

depending on technique and patient factors.

Marked narrowing may suggest:

Chronic rotator cuff insufficiency.

Acromial Morphology

Radiographs may also demonstrate:

Flat

Curved

or

Hooked acromial morphology.

MRI

MRI is useful for evaluating:

Rotator cuff tendons

Subacromial bursitis

Labral pathology

Biceps abnormalities

and alternative diagnoses.

Internal Impingement Imaging

MRI or MR arthrography may demonstrate:

Articular-sided cuff tearing

Posterior labral injury

or other changes associated with:

Internal impingement.

Bennett Lesion Imaging

A Bennett lesion may be visible as a:

Posterior glenoid rim exostosis.

Pathological Findings

Possible pathological findings include:

Rotator cuff tendinosis

Interstitial cuff tearing

Partial-thickness tearing

Full-thickness tearing

Thickened inflamed bursa.

Differential Diagnosis

Important alternatives include:

Acromioclavicular arthritis

Biceps tendinopathy

Calcific tendinitis

Cervical radiculopathy

Adhesive capsulitis

Glenohumeral arthritis

Symptomatic os acromiale

Rotator cuff tear

Scapular winging

Scapular dyskinesis

Suprascapular neuropathy

Thoracic outlet syndrome

Treatment

General Principles

Initial treatment is typically:

Nonoperative.

The cornerstone of treatment is:

Physical therapy

combined with:

Activity modification

and symptomatic medication.

Activity Modification

Avoid or temporarily reduce activities that reproduce symptoms, particularly:

Repeated overhead motion

Heavy lifting

or

Throwing.

Throwing Athletes

Athletes with internal impingement should temporarily stop:

Throwing or painful overhead activity

and enter a structured:

Sport-specific rehabilitation program.

Physical Therapy

Rehabilitation should emphasize:

Rotator cuff strengthening

Periscapular strengthening

Scapular stabilization

Range-of-motion restoration

and correction of:

Scapular mechanics.

Rotator Cuff Strengthening

Improving cuff strength helps maintain the humeral head:

Centered within the glenoid

and may reduce abnormal superior translation.

Periscapular Strengthening

Strengthening the:

Trapezius

Serratus anterior

Rhomboids

and other scapular stabilizers can improve:

Scapulothoracic rhythm.

Range of Motion

Any limitation in:

Posterior shoulder flexibility

or

Internal rotation

should be addressed when clinically relevant.

Sleeper Stretch

The:

Sleeper stretch

may be used selectively in throwing athletes with:

Posterior shoulder tightness

or

Glenohumeral internal rotation deficit.

It should be performed carefully to avoid provoking symptoms.

Sport-Specific Rehabilitation

Internal impingement rehabilitation should ultimately address:

Throwing mechanics

Kinetic-chain function

Core strength

Scapular control

and progressive return to:

Overhead activity.

Medication

First Line

Symptomatic treatment may include:

NSAIDs

and

Acetaminophen.

Subacromial Corticosteroid Injection

A subacromial corticosteroid injection may provide:

Temporary pain relief

and can assist participation in:

Physical therapy.

It may also have diagnostic value.

Repeated injections should be used cautiously because of potential adverse effects on:

Tendon tissue.

Surgery

Surgery is reserved for patients with:

Persistent symptoms despite appropriate nonoperative treatment

or those with a specific structural lesion requiring correction.

Acromioplasty

Acromioplasty has historically been used to enlarge the:

Subacromial space

by reshaping the undersurface of the:

Acromion.

Its routine value for isolated subacromial pain without a clear structural indication remains:

Debated.

Distal Clavicle Excision

When symptomatic:

AC joint osteophytes or arthritis

contribute to pain, distal clavicle excision may be considered in selected patients.

Bursectomy

Inflamed:

Subacromial bursal tissue

may be removed arthroscopically when persistent symptoms accompany other surgically treated pathology.

Rotator Cuff Treatment

If a rotator cuff tear is identified, treatment may include:

Débridement

or

Repair

depending on:

Tear depth

Size

Location

and patient factors.

Internal Impingement Surgery

Surgical treatment may include:

Rotator cuff débridement or repair

Labral débridement or repair

and, in selected cases,

Posterior capsular release.

Follow-Up

Patients should be monitored throughout:

Rehabilitation

and after:

Injection or surgery.

Prognosis

Most patients improve with:

Nonoperative treatment.

Historical series suggest successful outcomes in approximately:

70–80%

with a combination of:

Physical therapy

and

Subacromial injection.

Factors Associated With Better Outcome

Historically reported favorable factors include:

Shorter duration of symptoms

Less prolonged work absence

and lack of substantial:

Acromioclavicular degeneration.

These associations should not be interpreted as deterministic for an individual patient.

Surgical Outcome

Patients who undergo surgery after unsuccessful conservative treatment may experience improvements in:

Pain

and

Shoulder function.

Long-Term Decompression Outcomes

Historical long-term follow-up after subacromial decompression has demonstrated acceptable results in many patients, although current practice places more emphasis on:

Rotator cuff pathology

Scapular mechanics

and avoiding unnecessary decompression.

Return to Sport in Internal Impingement

Return-to-play rates are generally favorable, but return to the same performance level depends on:

Extent of cuff injury

Labral involvement

and the athlete’s:

Throwing demands.

Complications

Potential complications of treatment include:

Acromial fracture

Skin discoloration after corticosteroid injection

Infection

Deltoid dysfunction

Neurovascular injury

Seroma

Hematoma

Complex regional pain syndrome

and general:

Medical complications.

Deltoid Dysfunction

Open decompression procedures can rarely injure the:

Deltoid attachment

and lead to impaired:

Shoulder elevation.

Corticosteroid Skin Changes

Subacromial corticosteroid injection may occasionally cause:

Skin depigmentation

or

Subcutaneous fat atrophy

near the injection site.

Patient Monitoring

Follow-up should assess:

Pain

Range of motion

Rotator cuff strength

Scapular control

and ability to resume:

Work or sport.

Internal Impingement Monitoring

In throwing athletes, rehabilitation goals include restoration of:

Full functional range of motion

Strength

Dynamic stability

Scapular mechanics

and

Neuromuscular control.

Return to throwing should occur through a:

Graduated sport-specific progression.

Key Principle

Shoulder impingement syndrome encompasses a group of subacromial and internal contact disorders that produce pain during shoulder elevation or overhead activity.

External impingement most commonly involves the:

Rotator cuff and subacromial bursa beneath the coracoacromial arch, whereas internal impingement primarily affects:

Overhead athletes through contact between the posterosuperior cuff and glenoid.

Treatment begins with:

Activity modification, rotator cuff and scapular rehabilitation, restoration of motion, analgesic therapy, and selective subacromial injection.

Surgery is reserved for:

Persistent symptoms or clearly defined structural pathology, and routine acromioplasty for nonspecific subacromial pain remains:

Controversial.