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Arthroscopic Subacromial Decompression
Lateral Approach
Neer proposed three stages of progression of impingement syndrome: stage I, reversible changes with edema and hemorrhage; stage II, irreversible tendonitis and fibrosis; and stage III, tendon degeneration and tearing. Neer developed the open anterior acromioplasty, and in 1985 Ellman presented comparable results using the arthroscope for subacromial decompression. He showed 88% excellent or good ratings at 1 to 3 years follow-up. Since then, multiple authors have reported similar results using arthroscopic techniques. The primary advantage of arthroscopic subacromial decompression is less surgical morbidity and quicker rehabilitation because the deltoid is not detached from the acromion. Visualization of the glenohumeral joint, biceps tendon, and labrum enable one to diagnose other possible abnormalities.
Indications
1. Stages I and II often respond to conservative treatment, gentle exercises, nonsteroidals, and corticosteroid injections.
2. Refractory stage II disease and stage III disease should be treated surgically with bursectomy and subacromial decompression with debridement or repair of the rotator cuff.
Contraindications
1. Deficient deltoid
2. Previous infection
Mechanism of Injury
Impingement syndrome is a result of compression of the rotator cuff, particularly the supraspinatus tendon, between the humerus and the anterior aspect of the acromion or against the coracoacromial (CA) ligament. It may also be caused by an inferiorly directed hook on the anterior acromion, bony spurs projecting from the undersurface of the acriomioclavicular (AC) joint, or malunion of a greater tuberosity fracture. Repetitive crushing and abrasion of both the rotator cuff and the subacromial bursa lead to local inflammation and pain.
Clinical Evaluation
1. Impingement syndrome is a clinical diagnosis.
2. Patients often present with complaints of insidious onset of pain particularly with activities at shoulder height or higher.
3. Pain is worse at night and may prevent them from getting to sleep or may wake them from sleep.
4. Pain is typically localized to the proximal lateral aspect of the humerus.
5. Crepitation is often palpable in the subacromial region with active range of motion.
6. Classic tests for impingement have been described by Neer and Hawkins:
a. The Neer impingement sign is performed by elevating the patient’s arm in the forward plane then internally rotating the humerus while stabilizing the scapula with the opposite hand. This maneuver causes pain as the rotator cuff is compressed against the under surface of the acromion.
b. The Hawkins test is performed by flexing the shoulder forward 90 degrees and then forcibly internally rotating the shoulder. This drives the greater tuberosity against the coracoacromial ligament reproducing impingement symptoms.
7. Diagnostic injection of the subacromial space with 1% xylocaine results in complete resolution of impingement symptoms to confirm the diagnosis.
Imaging
1. Plain radiographs are the mainstay for evaluation of acromial morphology.
a. Supraspinatus outlet view
i. Bigliani described three types of acromion. Type I is a flat acromion, type II is curved inferiorly at the anterior aspect, and type III is hooked anteriorly; best appreciated on this view.
b. True anteroposterior (AP) view of scapula view
i. Obtained for evaluation of glenohumeral joint space, the AC joint, and humeral head position.
c. Axillary view
i. Demonstrates early changes in the glenohumeral joint and presence of an os acromionale.
d. Zanca view, 20-degree AP cephalic-tilted view
i. Provides the best view of the AC joint.
2. Magnetic resonance imaging (MRI) and computed tomography are not routinely indicated.
a. MRI is utilized if there is question of a possible partial thickness, or small full-thickness rotator cuff tears.
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