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Shoulder Impingement Syndrome - S2.1

Definition of condition:  Shoulder impingement syndrome is defined as a painful entrapment of the supraspinatus tendon, subacromial-subdeltoid bursa, and/or the biceps tendon between the humeral head and the coracoacromial arch.

Issue statement: Diagnosing a shoulder problem may be difficult because of the number of potential shoulder injuries and the similarity between them.  When determining the cause of shoulder impingement syndrome the interaction of a wide range of risk factors must be considered. It is known that a large percentage of rotator cuff lesions are the end result of impingement which can be caused by a combination of hypovascularity, anatomical variations, degeneration as well as mechanical factors and macrotrauma. The trauma reported by the worker often serves to accelerate the disease process or simply results in symptomatic presentation of the ongoing degenerative process.

WCB-Alberta position

Work relationship criteria

A potential work relationship may exist if one or more of the following causes of impingement are experienced by the worker as a result of work duties:

• prolonged work at or above shoulder level
• repetitive and/or heavy forceful motions involving combined abduction, forward flexion, and internal rotation (impingement position)
• static tensions or positions involving prolonged abduction
• prolonged vibration exposure from heavy handheld vibrating tools (e.g. jackhammer)
• a history of refractory impingement syndrome makes the shoulder susceptible to rotator cuff tears.  In this situation, tears are associated with lifting in supination, heavy lifting, and prolonged work at or above shoulder level.

Non-work related factors that are associated with impingement include:

• aging; it is now known that rotator cuff pathophysiology and degeneration has an absolute association with the aging process
• anatomical variations such as hooked or curved acromion, acromioclavicular joint and coracoid process anomalies
• post-operative or post-traumatic scarring
• glenohumeral instability.

Note: Refer to Table I for a summary of Shoulder Impingement Syndrome including its stages, etiology, diagnosis, management, clinical course and differential diagnosis.

Differential Diagnosis:  Other conditions that can exhibit some of the findings of impingement syndrome include:

cervical radiculopathy	acromioclavicular joint degeneration
glenohumeral arthritis	brachial plexus neuropathy
calcific deposits	neoplasm
adhesive capsulitis	glenohumeral instability (refer to Glenohumeral Instability Guideline)

Clinical criteria

Impingement remains a clinical diagnosis despite advanced imaging capabilities.  A thorough history, physical examination and specific plain radiographs distinguish between the various causes of shoulder pain and guide appropriate treatment.

Changes that occur with rotator cuff impingement are typically categorized into three progressive stages:

• Stage I is characterized by edema and hemorrhage of the bursae and tendons
• Stage II, by thickening and fibrosis of the bursae and tendons
• Stage III, by tendon failure and bony changes.

Stage I - Edema and hemorrhage:

The worker may report pain that:

• is gradual in onset
• is characterized by a dull ache at the anterolateral aspect of the shoulder often with radiation to the deltoid insertion
• follows strenuous activity and may progress to discomfort during sport or regular activity, eventually affecting performance and interfering with sleep
• is worsened by resisted abduction, resisted external rotation, overhead positioning of the arm or direct pressure against the shoulder such as lying on it.  Activities of daily living may trigger the pain.

Physical findings include:

• positive impingement tests
• pain along the bicipital groove with resisted forward flexion and extended elbow with forearm supination
• a painful arc of abduction between 60o and 120o increased with resistance at 90o
• tenderness over the greater tuberosity at the supraspinatus insertion and along the anterior edge of the acromion
• range of motion may be restricted by pain.

Stage II - Fibrosis and tendinitis:

The worker may report:

• aching discomfort often interfering with sleep and work which may progress and interfere with activities of daily living.

Physical findings may include all those mentioned in Stage I plus:

• soft-tissue crepitus
• a catching sensation with reversal of elevation at approximately 100o
• mild limitation to both passive and active range of motion due to pain
• anterior tenderness, which may be exquisite, over either the biceps or the supraspinatus tendon
• subacromial tenderness
• calcification and/or early osteophyte formation.

Stage III - Rotator cuff tears, biceps ruptures and bone changes:

The worker may report:

• prolonged periods of pain particularly at night
• stiffness and weakness.

Physical findings may include all those in Stage II plus:

• weakness especially in abduction and external rotation.  Weakness is greater in workers with large tears.
• wasting with a rotator cuff tear
• crepitus when arm is internally rotated, abducted and flexed
• passive shoulder elevation may be nearly full despite limited active elevation
• biceps tendon involvement with rupture in a high percentage of workers with rotator cuff tears
• acromioclavicular joint tenderness, especially if degenerative changes are present.

Pain-related weakness can be present at any stage but injection of local anesthetic within the subacromial space in Stage III will not eliminate weakness and limitation of active motion. 

Diagnostic criteria

Lab tests 

None

Local Anaesthetic Test - Subacromial injection of short acting anaesthetic (xylocaine/marcaine) may be helpful in determining if impingement syndrome is present by temporarily alleviating pain when the impingement positions are retested post injection.

Imaging

Routine radiography

X-rays are not diagnostic of impingement but possible causes of impingement may be seen i.e., bony changes such as Type II or III acromion.  With Stage I impingement, x-rays are often normal.  However, evidence of instability such as Hill-Sachs or Bankhart lesions should be sought, as should Stage II or III changes such as:

• cystic changes about the greater tuberosity
• sclerotic changes beneath the anterior third of the acromion
• osteophytes along the undersurface of the acromion
• late changes involving narrowing of the subacromial space
• acromioclavicular joint changes.

Plain radiographs are indicated when there is persistent shoulder pain for 6 weeks.  Relevant views for impingement syndrome include:

• true anteroposterior glenohumeral
• supraspinatus outlet
• single anteroposterior of the shoulder girdle
• axillary lateral.

Arthrography

Arthrography can be used to diagnose full-thickness rotator cuff tears.  Indications for arthrography include:

• worker over 40 with impingement syndrome unresponsive to 12 weeks of conservative treatment
• an injury with sudden marked weakness of the shoulder. Electromyography of muscles supplied by C5-6 root may be indicated
• rupture of long head of the biceps associated with shoulder symptoms
• following reduction of a glenohumeral dislocation when the shoulder remains unstable
• an adequately reduced dislocation followed by persistent symptoms in a worker over 40.

Arthroscopy

Arthroscopy permits direct viewing of the rotator cuff, labrum, capsule, and subacromial space.  However, arthroscopy is not considered to be a primary diagnostic tool for determining tears.

MRI

MRI is not used to diagnose early stages of rotator cuff disease.  MRI usually allows detection of:

• full-thickness rotator cuff tears (89-98% accuracy)
• acromioclavicular joint osteoarthritis and capsular hypertrophy
• subacromial bursitis
• tendon damage 
• supraspinatus muscle hypertrophy 
• signs of instability.

MRI may be indicated:

• pre-operatively
• following sudden, profound loss of strength especially after injury or dislocation.

MRI Arthrography

MRI arthrography has been shown to be more accurate than conventional MRI for evaluation of partial-thickness tears.

Ultrasound

Ultrasound has been used to identify rotator cuff tears but is technically difficult to perform and sensitivity is low.

Electrophysiologic tests 

Electrophysiologic tests may be indicated to exclude neurogenic causes of pain, weakness and wasting.

Recommended management

Education

Worker education is an important part of rehabilitation and prevention of re-injury and should include the following:

• anatomy, natural history, and prognosis of shoulder impingement
• diagnosis and expected outcome of treatment
• self care including exercises and application of heat or ice to relieve pain
• proper use of medication
• risk factor modification.

Physical therapy

For all stages of impingement, physical therapy is aimed at a gradual activity progression by:

• decreasing pain and swelling
• restoring normal ROM
• strengthening the rotator cuff muscles
• regaining and improving endurance.

Medical management

Rotator cuff tears can be asymptomatic.  Therefore, when tears are found during investigation for undiagnosed shoulder pain, they may not necessarily be the cause of the shoulder symptomatology.  Imaging results should be carefully correlated with the spectrum of clinical findings to ensure appropriate management.

It is crucial to determine the cause of impingement.  If impingement is caused by glenohumeral instability, classic impingement management i.e., NSAIDs, subacromial injections and potentially an acromioplasty, will result in treatment failure.

Stage I:

Medications

• anti-inflammatories for 1-2 weeks duration
• local corticosteroid injections for refractory cases of rotator cuff syndrome without tear
• non opioid analgesics orally for limited duration.

Long term anti-inflammatory use is not recommended. It is unlikely to have further effect after one month and may cause GI complications.

Stage II:

Conservative management is similar to Stage I.  With workers whose symptoms do not improve or who have repeated flare-ups, subacromial decompression or permanent activity modification may be necessary.

Stage III:

Management is much the same as in Stage II but the need for surgical decompression and possible repair of the rotator cuff is more likely.  Stage III impingement is treated conservatively for a 6-12 month period and then if necessary surgical treatment is considered.

Referrals

Immediate referral to an orthopaedic surgeon is indicated for rotator cuff tears with significant compromise of function.

Discretionary referral to an orthopaedic surgeon is indicated for Stage II impingement following failure of conservative treatments.

Surgical

Indications for Surgery

After an adequate period of conservative management (6-12 months), surgery is indicated for workers with impingement without a tear and with significant functional impairment at the time of presentation.

Earlier surgery may be considered if:

• the local anesthetic test is positive
• the worker is motivated and has attempted an appropriate rehabilitation program without success
• there is a history of pre-treatment symptoms longer than one year duration
• there is significant functional impairment at the time of initial clinical presentation
• there is evidence of full-thickness rotator cuff tear larger than one cm2 on MRI.

Best results are obtained if a large tear is repaired 2 - 3 weeks after it occurs.

Surgical contraindications

Decompression is inappropriate when instability is the primary cause of the impingement syndrome.

Anterior acromioplasty is not performed for simple impingement problems in workers younger than 40 unless overhang and prominence of the undersurface of the anterior acromion are noted.

Fitness to work criteria

Length of disability is influenced by numerous factors such as:

• presence of pre-existing conditions
• severity and duration of symptoms
• severity and duration of rotator cuff tears
• presence of complications (e.g. adhesive capsulitis, arthropathy)
• timing and type of intervention and response to treatment
• dominance of affected limb.

The worker should be relatively free of symptoms in impingement positions before resuming regular work duties.

Work restrictions may be permanent if the job requires sustained, frequent overhead arm positions.

Permanent clinical impairment criteria

Impairment assessment is primarily based on loss of ROM. An extra judgment award may be assessed if this does not address the full extent of impairment.

Table 1

An overview of Shoulder Impingement Syndrome

Impinge ment	Common Age Group (years)	Main Etiologic Factors	Diag- nosis	Manage- ment	Clinical Course	Differ- ential Diag- nosis
Stage I	< 25	*Over- stress *Repe- titive circum- duction activities *Joint laxity	*Clinical *Impinge- ment tests	*Activity modification *Analysis of techniques *Modification of style *Decrease stresses of weight training *Corrective muscle imbalance *Selective stretching *Ultrasound, laser, ice if long-standing, transverse friction, *NSAIDs, steroid injection	reversible	sublux- ation a/c arthritis
Stage II	25 - 40	*Overuse *Sudden increase in activity *Fall or subluxa- tion *Some early degenera- tive changes in cuff *Occasion- ally calcifica- tion	*Clinical *Impinge- ment tests *X-ray films to reveal dystrophic calcification or osteo- phyti clipping *Occasion- ally osteolysis of distal clavicle	*Restrict aggravating activities *Treat as above *Early consideration of steroid injection *Decom- pressive surgery	recurrent pain with activity	adhesive capsulitis   calcium deposits
Stage III	40+	*Occupa- tional *Falls *Sudden increase in activity *Atrophic and degenerative changes in cuff *Occasion- ally acute tear	*Clinical *Impinge- ment tests *External rotation weakness *X-ray plain films *May be superior migration of humeral head *Consider arthrogram (CT) or MRI	*As above *Greater restriction of activity *May need surgical decom- pression or rotator cuff repair	progres- sive disability	cervical radiculitis   neoplasm

[Adapted from Neer, C.S.  (1983).  Impingement Lesions.  Clinical Orthopaedics and Related Research, 173, 70-7 and Reid, D.C. (1992).  Sports Injury Assessment and Rehabilitation, p.936.  New York: Churchill Livingston]

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