SHOULDER IMPINGEMENT There are 2 main causes of impingement in shoulder :

1. Subacromial impingement
2. Subcoracoid Impingement

Subacromial impingement Subacromial impingement, it is one of the common pathologies causing shoulder pain. It occurs as a result of compression of the rotator cuff muscles by acromion, coracoacromial ligament and acromioclavicular joint. Repeated compression of cuff and bursa which leads to inflammation and bursitis is the primary cause of pain. Clinically provisional diagnosis is made on the basis of physical examination supported with a positive Neer impingement and Hawkins tests and is confirmed with MRI. Initial treatment is always a trial of nonsurgical measures which includes NSAIDs, physical therapy and corticosteroid injections. Arthroscopic subacromial decompression with or without acromioplasty is done in patients who fail to improve with nonsurgical modalities. Causes and Pathophysiology of Subacromial impingement Subacromial impingement occurs due to combination of extrinsic compression of the rotator cuff muscles between the humeral head andanterior part of acromion, coracoacromial ligaments, and acromioclavicular joint. Because of this compression there is intrinsic degeneration of supraspinatus muscle which results in imbalance of humeral head which in turn results in proximal migration, as a result of this narrowing of subacromial space occurs. Narrowing of subacromial space results in inflammation of the subacromial bursa because of compression between the humeral head with rotator cuff, acromion and associated structures. Subacromial impingement is always first stage of rotator cuff pathology which occurs as a result of impingement resulting in partial to full-thickness tear in future. Predisposing conditions which lead to Subacromial impingement are

• Shape of the acromion
• osacromiale
• contracture of posterior capsule
• scapular dyskinesia
• malunited tuberosity fractures

Shape of the acromion Bigliani classification of acromion morphology – it is based on a supraspinatus outlet view

• Type I – Flat
• Type II – Curved
• Type III – Hooked, Type III is most commonly associated with Subacromial impingement.

Posterior capsular contracture It causes proximal migration of humeral head which results in impingement Signs and Symptoms Pain which is gradual in onset, particularly exacerbated by overhead shoulder activities. Lifting even small objects away from the body and above shoulder precipitates pain. Patients may also have night pain which is a poor indicator of successful nonsurgical treatment. Clinical impingement tests

1. Positive Neer’s impingement sign

Rotator cuff impingement beneath the anteroinferior portion of the acromion is the cause of pain in impingement syndrome, particularly when shoulder is flexed forward and internally rotated. The pain mainly originates from inflamed bursa or the rotator cuff. The inflamed structures get stuck between the humeral head and the undersurface of acromion and coracoacromial arch. In the classic maneuver the examiner stabilizes the scapula while standing behind the patient and passively internally rotates and forward flexes the patient’s shoulder more than 90° (somewhere between flexion and abduction). The pain is reproduced in the anterolateral part of the shoulder due to approximation of GT to acromion compressing the inflamed supraspinatus and bursa.

1. Neer’s impingement test:

This is to improve the specificity of Neer’s sign. It is performed after Neer’s sign is positive. 5 mL of 1% lidocaine is injected into subacromial space and the maneuver repeated. Positive test is indicated by reduced or absent pain.

1. Hawkin-Kennedy test

Performed by flexing shoulder to 90°, flex elbow to 90°, and forcibly internally rotate driving the greater tuberosity farther under the CA ligament.The test is considered to be positive if the patient experiences pain with internal rotation. Imaging of Subacromial impingement

1. Radiographs

We recommend following views :

• True AP view of the shoulder (Grashey view): it is very useful in accessing the acromiohumeral interval. Normally it is between 7-14 mm. anything less than this predisposes to impingement.
• 30° caudal tilt view: this is a useful view in determining subacromial spurring.
• supraspinatus outlet view: very useful in accessing acromial morphology

Most common radiological findings that are associated with subacromial impingement are proximal migration of the humeral hear as seen in rotator cuff tear arthropathy, calcification of the coracoacromial ligament, osteophytes formation, cyst formation near greater tuberosity, type III acromion (hooked acromion).

1. MRI

Most commonly employed modality in evaluating subacromial impingement. Findings such as subacromial bursitis and subdeltoid bursisits are often seen. It is also useful in excluding rotator cuff and biceps pathology.

1. CT arthography
2. Ultrasound

It is also an accurate imaging technique of the rotator cuff tears and muscle bellies. Main disadvantage is user dependent. Treatment

1. Nonoperative

Physiotherphy, anti-inflammatory drugs, subacromial injections

• It is always used as first line and mainstay of treatment of isolated subacromial impingement. When it is associated with rotator cuff tear subacromial steroid injection is not indicated.
• Physiotherapy includes rotator cuff strengthening exercises and periscapular muscle strengthening and stabilization protocol.

1. Operative

Arthroscopic subacromial decompression and acromioplasty Surgery for subacromial impingement syndrome is indicated only after failed a minimum of 4-6 months of nonoperative treatment. Technique –

• surgery is performed under general anesthesia
• lateral or beech chair position is used
• first anterior acromionectomy is performed
• the anterior deltoid origin determines the extent of the acromionectomy and it must remain intact.

Open arthroscopic subacromial decompression and acromioplasty:

• Is outdated and not being used now a days.

Subcoracoid Impingement This is the impingement of the subscapularis between the coracoid of scapula and lesser tuberosity of humerus, which can cause pain over anterior shoulder and may lead to subscapularis tear. Clinical diagnosis can be made with eliciting tenderness over the coracoid. Pain gets worse when shoulder is brought to adduction, flexion and internal rotation. Diagnosis is confirmed with CT scan which shows reduction in coracohumeral interval. Initial treatment is always a course of conservative measures which includes NSAIDs, physiotherapy and corticosteroid injections. Surgery is indicated for patients who fail to respond to nonoperative measures. Etiology: Patients with congenital bone pathologies like long or more lateral placed coracoid process. Previous surgery that resulted in posterior capsular tightening can cause impingement. Maximal impingement is seen when arm is in adduction, flexion, and internal rotation. Associated conditions are combined subscapularis, supraspinatus, and infraspinatus tears. Symptoms and presentation Pain over the anterior shoulder. Pain gets worse when shoulder is brought to adduction, flexion and internal rotation. Physical exam: tenderness elicited over anterior coracoid. Maximum pain is seen at 120-130° of arm flexion and internal rotation Imaging

1. Radiographs: shows reduced coracohumeral distance.
2. CT scan:

• This is done with arms crossed over chest
• coracohumeral distance of less than 6 mm is abnormal finding
• normally coracohumeral distance is around 8.5 mm with arm adducted and 6.5 mm with arm in flexion.

1. MRI:

• This is used to access soft tissue pathology
• it shows increased signal at subscapularis muscle, sometimes may show complete tear with subluxation of biceps tendon.
• axial view can be used measure coracohumeral distance.

Treatment

1. Nonoperative

Physiotherphy, anti-inflammatory drugs, subcorocoid injections

• It is always used as first line and mainstay of treatment of isolated subcorocoid impingement. When it is associated with rotator cuff tear subacromial steroid injection is not indicated.
• Physiotherapy includes stretching exercises and periscapular muscle strengthening and stabilization protocol.

1. Operative

arthroscopic coracoplasty with or without subscapularis repair Surgery for subcorocoid impingementsyndrome is indicated only after failed a minimum of 4-6 months of nonoperative treatment. Technique –

• surgery is performed under general anesthesia
• lateral or beech chair position is used
• Resection of posterolateral part of coracoid to create a 7 mm of coracohumeral distance.
• If there is significant subscapularis tendon tear then it has to be repaired.

Open coracoplasty:

• Is outdated and not being used now a days because of advancement in arthroscopic procedures.
• Resection of lateral aspect of coracoid process and the conjoined tendon is reattached to the remaining coracoid.