Subacromial Pain Syndrome

Original Editor - David Drinkard, Dorien De Strijcker

Lead Editors Dorien De Strijcker, Naomi O'Reilly, David Drinkard, Els Van Haver, Mariam Hashem, Admin, Kim Jackson, Rachael Lowe, Florence Brachotte, Amanda Ager, Tony Lowe, Kai A. Sigel, Yuli Borremans, Scott Buxton, Tarina van der Stockt, WikiSysop, Wendy Walker, Tyler Shultz, Thaisa Van Bellingen, Wanda van Niekerk, Lauren Lopez, Lucinda hampton, Jess Bell, Robin Tacchetti, Lisa De Donder, Ewa Jaraczewska, Lucas Villalta, 127.0.0.1 and Benjamin Desmedt

Definition/Description

Subacromial Impingement Syndrome (SIS) is one of the most common causes of shoulder pain affecting manual and sedentary workers as well as athletes. SIS can be defined as symptomatic irritation of the rotator cuff and subacromial bursa between the coraco-acromial arch and the humerus during active elevation of the arm above shoulder height.

The subacromial impingement syndrome has both primary and secondary forms. Primary impingement is due to structural changes that mechanically narrow the subacromial space; these include bony narrowing on the cranial side (outlet impingement), bony malposition after a fracture of the greater tubercle, or an increase in the volume of the subacromial soft tissues – due, e.g., to subacromial bursitis or calcific tendinitis – on the caudal side (non-outlet impingement). Secondary impingement results from a functional disturbance of centering of the humeral head, such as muscular imbalance, leading to an abnormal displacement of the center of rotation in elevation and thereby to soft tissue entrapment.

Clinically Relevant Anatomy

Figure 1. Subacromial structures.

The Subacromial joint space is the space beneath the acromion (between the acromion and the top surface of the humeral head). This space is outlined by the acromion and the coracoid process (which are parts of the scapula), and the coraco-acromial ligament which connects the two.

This space contains:
• the coracoacromial arch, composed of the acromion, processus coracoideus and ligamentum coracoacromiale.
• the humerus
• the tendons of the Rotator Cuff: supraspinatus, infraspinatus, teres minor and subscapularis
• the long head of the m. biceps brachii
• the subacromial bursa
• shoulder capsule
• deltoid muscle

Prevalence /Incidence

SIS is the most common disorder of the shoulder, accounting for 44% to 65% of all complaints of shoulder pain.The incidence increases as the population ages.

Peak incidence is during the sixth decade of life. The most common clinical diagnoses are rotator cuff defects (85%) and/or impingement syndromes (74%) . The prevalence of rotator cuff defects rises with age. Up to 30% of persons over age 70 have a total defect, but 75% of such cases are asymptomatic.

Etiology

Primary shoulder impingement occurs when the rotator cuff tendons, long head of the biceps tendon, glenohumeral joint capsule, and/or subacromial bursa become impinged between the humeral head and anterior acromion.

Primary impingement may be due to intrinsic factors:

• Rotator cuff weakness
• Chronic inflammation of the rotator cuff tendons
• Subacromial bursa
• Rotator cuff degenerative tendinopathy
• Posterior capsular tightness leading to abnormal anterior/superior translation of the humeral head.

It may also be due to extrinsic factors:

• Possession of a curved or hooked acromion
• Acromial spurs
• Postural dysfunction
• kinesiophobia or catastrophizing
• Muscle imbalance of the lower and middle trapezius, serratus anterior, infraspinatus and deltoid, coupled with tightness of the upper trapezius, pectorals and levator scapula (upper crossed syndrome). The tightness of the muscles creates a deltoid shear force (crossing of rotator cuff under AC joint), leading to shoulder impingement, tendonitis and bursitis syndromes.

Figure 2. Acromion shapes.

Secondary shoulder impingement is defined as a relative decrease in the subacromial space due to glenohumeral joint instability or abnormal scapulothoracic kinematics. Commonly seen in athletes engaging in overhead throwing activities, secondary impingement occurs when the rotator cuff becomes impinged on the posterior-superior edge of the glenoid rim when the arm is placed in end-range abduction and external rotation. This positioning becomes pathologic during excessive external rotation, anterior capsular instability, scapular muscle imbalances, and/or upon repetitive overload of the rotator cuff musculature.

Clinical Presentation

Figure 3. Painful Arc

The affected patients are generally over age 40 and suffer from persistent pain without any known preceding trauma. Patients report pain on elevating the arm between 70 ° and 120 ° ,the “painful arc” (Figure 3), on forced movement above the head, and when lying on the affected side . The symptoms can be acute or chronic. Most of the time it is a gradual, degenerative condition that causes impingement, rather than due to a strong external force. Therefore, patients often have difficulties with determining the exact time of the complaints.

According to Neer impingement syndrome is divided into three stages:
•Stage I: moderate pain during exercise, no loss of strength and no limitation in movement. Edema and/or hemorrhage may be present. This stage generally occurs in patients less than 25 years of age and is frequently associated with an overuse injury. At this stage the syndrome could be possibly reversible.
• Stage II: pain is usually reported during ADL and especially during the night. loss of mobility is associated with this stage. Stage II is more advanced and tends to occur in patients between 25 to 40 years of age. The pathological changes show fibrosis as well as irreversible tendon changes.
• Stage III: strong restriction in movement due to calcifications and loss of muscle strength.This stage generally occurs in patients over 50 years of age and frequently involves a tendon rupture or tear.

Differential Diagnosis

There are a variety of shoulder conditions that can initially be confused with subacromial impingement . A thorough physical examination should confirm SIS and exclude other conditions such as:

• Rotator cuff tears (partial/full)
• Thoracic outlet syndrome
• Cervical spondylosis
• Rotator cuff tendinitis
• Subluxating shoulder
• Acromioclavicular joint arthritis
• Adhesive capsulitis (“frozen shoulder”) • Glenohumeral arthritis
• Paralysis of the Trapezius
• Calcific tendinitis
• Acute/chronic inflammation of the bursa subacromialis
• Cuff tear arthropathy
• Glenohumeral instability
• Nerve palsy

Diagnostic Procedures

Diagnosis should be based on:

→ History
→ Clinical examination
→ Radiographs
→ MRI

History and clinical examination are necessary. Radiographs may be used to detect anatomical variants, calcific deposits or acromioclavicular joint arthritis. The three recommended views are:
- The antero-posterior view with the arm at 30 degrees external rotation. The anteroposterior view is useful for assessing the glenohumeral joint, subacromial osteophytes and sclerosis of the greater tuberosity. 10
- The outlet Y view is useful because it shows the subacromial space and can differentiate the acromial processes.
- The axillary view is helpful in visualizing the acromion and the processus coracoideus, as well as coracoacromial ligament calcifications.

The size of the subacromial space can also be measured. MRI can show full or partial tears in the tendons of the rotator cuff, cracks in the capsule and inflammation to weak structures.

Ultrasonography and arthrography are being used when rotator cuff tears are suspected or in doubtful (complex) cases. However, arthrography is invasive and expensive, it is the best diagnostic modality. Magnetic resonance imaging is also expensive but it provides the best imaging mode for rotator cuff pathology.

Examination

[1]

Also see Impingement Cluster page
Following tests help to confirm or rule out subacromial impingement:
→ Hawkins-Kennedy
→ Neer impingement test (useful screening test to rule out SAI)
→ Painful Arc (between 60° and 120°) (useful screening and helpful confirming test to rule out SAI)
→ Empty can (Jobe): integrity Supraspinatus[28] (helpful test to confirm SAI)
→ External rotation resistance tests (useful screening and helpful confriming test to rule out SAI)
→ Drop arm sign: to test the integrity of the Infraspinatus.
Patient elevates the arm and returns slowly. The test is positive when the patient has suddenly severe pain or the arm drops all of the suddenly.[28]
→ Lift-off test (or gerber lift test): Integrity Subscapulary muscle. Patient performs an internal rotation by putting his hand on the ipsilateral buttock. Next the patient needs to lift the hand from the buttock against resistance.[28]
→ The horizontal adduction test: arm is in adduction directed to the other shoulder and the elbow is flexed. If pain occurs, then the test is positive.
→ Yergason test: the elbow is flexed at 90 degrees and the forearm pronated. The patient brings actively the forearm in supination against resistance. If there is pain in the bicipital groove area, then there is a disorder of the biceps tendon.
→ Speed test: the elbow is extended and the forearm is supinates. The patient brings his arm in a forward elevation of the humerus ( 60degrees is resisted). When there is pain in the bicipital groove area, then is the test positive.
The most sensitive diagnostic test : Hawkins test, Neer test, horizontal adduction test.
The most specificity test: drop arm test, Yergason test and the speed test.[31]

The combination of the Hawkins-Kennedy test (testing the pain-ful arc) and the infraspinatus muscle test have a considerably higher predictive value (the higher the value, the better):
- 3 tests are positive: the probability that the patient has an impingement is 10,56
- 2 tests are positive: the probability that the patient has an impingement is 5,03
- 1 test is positive: the probability that the patient has an impingement is 0,90
- 0 tests are positive: the probability that the patient has an impingement is 0,17[40]

Outcome Measures

add links to outcome measures here (see Outcome Measures Database)

Medical Management

Surgical intervention is needed when the subacromial impingement lasts 3-6 months without significant improvement, dispite of an appropriate conservative treatment.
Especially when the passive range of motion of the patient is restricted surgery has it benefits. Surgery is also beneficial with a type III acromion in combination with large spurs, a positive response to a lidocaine subacromial injection or changes in the tendon of the rotator cuff (for example inflammation).[14,25]

Several surgical techniques are available, depending on the character and severity of the injury:
Surgical repair of torn tissues, mostly of supraspinatus muscle, long head of biceps tendon or joint capsule. Note: a rotator cuff tear is not an indication for surgery. [13]
Bursectomy or removal of the subacromial bursa.
Subacromial decompression to increase the subacromial space by removing bony spurs or prominences on the underside of the os acromiale[17] or the coracoacromial ligament
Acromioplasty to increase the subacromial space by removing a part of the acromion. Arthroscopic acromioplasty is less invasive and requires lesser rehabilitation than the open (Neer) acromioplasty.

Physical Therapy Management

There is strong evidence that non-operative rehabilitation - when supervised - both decreases pain in the shoulder and increases function. Non-operative treatment should therefore be attempted first, assuming there is no tear that requires surgery. There is no evidence to suggest that treatment is more effective than conservative treatment.
Several conservative treatments are available:[6]
• RICE therapy in the acute phase to reduce pain and swelling
• NSAIDS or nonsteroidal anti-inflammatory drugs
• Corticosteroid injections
• Physical therapy
• Stability and postural correction exercises
• Mobility
• Strengthening
• Stretching exercises
• Manual therapy techniques of the shoulder
• Acupuncture
• Electrical stimulation
• Ultrasound and musculoskeletal ultrasound
• Low-level laser therapy has positive effects on all symptoms except on muscle strength[7]
• Advice and exercise leaflet
Although exercise therapy alone has proved efficient, the addition of manual therapy insures further increase in muscle strength.[8] Exercise therapy is a vital part of treatment for subacromial impingement but results showed no significant difference between home-based exercises and clinical exercise.

Therapeutic exercises should include[9]:
→ Rotator cuff strengthening: External rotation with thera-tubing[35] - Horizontal abduction[35]

→ Lower and middle trapezius strengthening: Eated press up[34] - Unilateral scapular rotation[34]- Bilateral shoulder external rotation[34] - Unilateral shoulder depression[34]

Strengthening of the lower part of the trapezius muscle is an important part of exercise therapy. Individuals with impingement syndrome show greater ratios of upper and lower trapezius activity than asymptomatic individuals.[10] Soft tissue mobilization to normalize muscle spasm and other soft tissue dysfunction has been shown to be effective alongside joint mobilizations to restore motion in treatment of SAI. [10]

→ Anterior and posterior shoulder stretching: Anterior shoulder stretch[36] - Posterior shoulder stretch[36]

Patients with stage 1 impingement often improve with conservative treatment. Conservative training consists of resting and stopping activities. NSAIDS and ice can relieve the pain.
When the acute pain is relieved, a specific strengthening program for the rotator cuff is recommended for prevention of future injuries. The motions of the rotator cuff that are emphasized for strengthening are internal rotation, external rotation and abduction. It is important to remember that the function of the rotator cuff, in addition to generating torque, is to stabilize the glenohumeral joint. Thus, stronger rotator cuff muscles result in better glenohumeral joint stabilization and less impingement. A typical initial exercise program involves the use of 4 to 8 weights, with 10 to 40 repetitions performed three to five times a week.
Patients with stage II impingement may require a formal physical therapy program. Isometric stretches are useful in restoring range of motion. Isotonic (fixed-weight) exercises are preferable to variable weight exercises. Thus, the shoulder exercises should be done with a fixed weight rather than a variable weight such as a rubber band. Repetitions are emphasized, and a relatively light weight is used. Sometimes, sports-specific techniques are useful, particularly for strengthening the throwing motion, the serving motion or swimming motions. In addition, physical therapy modalities such as electrogalvanic stimulation, ultrasound treatment and transverse friction massages can be helpful.[20]

Treatment 

The treatment depends on age, activity level and general health of the patient. The goal is to reduce pain and regain function.Conservative treatment[22,23,26]
Is used at the beginning, for several weeks to months until improvement and return tot function are noticed.
Rest: or avoiding overhead activities
NSAID’s to reduce pain and swelling
Physical therapy (see above)
Steroid injection: when the resources above don’t help relieving pain. Often cortisone because of its anti-inflammatory and pain reducing effect.[26,27]

Non-conservative treatment[26]
Is recommended when the conservative treatments don’t reduce the pain.
Sugery is performed and followed by physical therapy.[26]

Neer defined three stages of impingement (see above). Regarding those three stages, the treatment is different.
• Stage I: Often is conservative treatment sufficient. This involves resting and not doing the provocative activity. Pain can be relieved by applying ice (20 minutes, 3 times/day) and using NSAID’s (nonsteroidal anti-inflammatory drugs).
Physical therapy is also part of the treatment.
• Stage II: Physical therapy[21]

Presentations

Alice Thompson. Shoulder Impingement An insight into the causes, clinical presentation, assessment and treatment of shoulder impingement. A reference for physiotherapists. 2012

Recent Related Research (from Pubmed)

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• Arthroscopic tuberoplasty for subacromial impingement secondary to proximal humeral malunion

References

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