Arthroscopic subacromial decompression

OVERVIEW

Chapter synopsis

Despite limited indications, arthroscopic subacromial decompression is one of the most commonly performed procedures about the shoulder.
A thorough history and physical examination are essential to confirm a diagnosis of shoulder impingement to maximize patient outcomes.
Arthroscopic acromioplasty alone or in the setting of rotator cuff repair can be performed efficiently using multiple methods, including the lateral decompression or posterior cutting block techniques.
Good to excellent clinical results can be expected in approximately 80% of patients.

Important points

All patients should undergo a minimum of 3 to 6 months of nonoperative treatment for shoulder impingement syndrome, including activity modification, physiotherapy, nonsteroidal antiinflammatory drugs (NSAIDs), and corticosteroid injections.
Absolute contraindications to subacromial decompression include the presence of rotator cuff arthropathy.

Clinical/surgical pearls

Subacromial decompression may be performed via the classic or cutting block technique.
The acromioplasty should be visualized in two planes to ensure a smooth, even resection.

Clinical/surgical pitfalls

Inadequate resection
Overresection leading to fracture
Poor portal placement leading to technical difficulties

Introduction

Although the clinical benefits of subacromial decompression have recently come into question, it continues to be one of the most commonly performed surgical procedures about the shoulder. Arthroscopic decompression, or acromioplasty, is often performed as the primary treatment for shoulder impingement syndrome. It is also used as an adjunct in arthroscopic rotator cuff repair to create an adequate working space and protect the repair construct. In itself, subacromial impingement encompasses a range of clinical entities including rotator cuff tendinosis, subacromial or subdeltoid bursitis, and frank external impingement leading to both partial- and full-thickness rotator cuff tears. This constellation of findings was first described by A.W. Meyer in 1937, who detailed an attritional process in which the rotator cuff is compressed between the humeral head and coracoacromial arch. In 1972, Neer expanded on Meyer’s work to include three successive stages of impingement ( Box 4.1 ). In all cases, subacromial impingement is characterized by anterior shoulder pain worsened with overhead activity. In some form, this is caused by an anatomic narrowing of the subacromial space and supraspinatus outlet. If left untreated this leads to progressive bursitis, tendinitis, and rotator cuff tearing. Acromial morphology most commonly accounts for this narrowing and can be classified using the Bigliani classification. Whether innate or acquired, those with anteriorly curved or hooked morphologies tend to place the rotator cuff at greater risk for impingement and arthroscopic subacromial decompression is targeted to this anatomic location.

BOX 4.1

Stages of Subacromial Impingement Syndrome

Stage I —Edema and hemorrhage of the subacromial bursa and rotator cuff
Stage IIa —Fibrosis and inflammation of the rotator cuff
Stage IIb —Partial-thickness tears of the rotator cuff
Stage III —Full-thickness tears of the rotator cuff tendons

Preoperative considerations

History

A thorough history and physical examination are typically all that is needed to make a diagnosis of subacromial impingement. The importance of the clinical evaluation cannot be overstated, because failure of subacromial decompression most often relates to diagnostic errors or missed associated pathology. Hand dominance and occupation should be noted. A thorough review of the patient’s symptoms, including duration, palliative and provoking activities, pain radiation, severity, and the character of the pain is then elicited. Any previous treatments including physiotherapy, corticosteroid injections, or pain medications should be elicited. Operative reports are obtained for any prior surgical procedures involving the shoulder.

Signs and symptoms

Classically, patients with symptoms related to impingement have anterolateral shoulder pain worsened with extremes of motion. They may report difficulty with activities of daily living that require overhead motion, such as combing hair or reaching above the level of the head. Patients often complain of night pain, worsened when lying on the affected side. One should be aware that young, overhead throwing athletes may develop secondary outlet impingement after chronic internal impingement owing to anterior capsular laxity and posterior capsular contracture. In addition, young athletes who complain of impingement-like symptoms should be closely evaluated for signs of multidirectional instability.

Physical examination

A thorough physical exam should always begin with routine inspection of the shoulder and palpation of all bony prominences. Tenderness may be found in the point of Codman, located just distal to the anterolateral corner of the acromion. The patient should have both full active and passive range of motion of the glenohumeral and scapulothoracic joints but may complain of a painful arc between 60 and 120 degrees of abduction. In the setting of isolated impingement, supraspinatus, infraspinatus, and subscapularis strength should remain intact, but pain may be elicited in more advanced processes. A number of special tests can then be used to confirm the diagnosis of impingement syndrome. The Neer impingement sign is positive when pain is elicited with internal rotation and forward elevation of the arm in the plane of the scapula. The Neer impingement test is considered positive when this pain is relieved following a subacromial injection of local anesthetic. The Hawkins test involves forward elevation of the arm to 90 degrees along with internal rotation. Virtually all maneuvers attempt to compress the rotator cuff between the greater tuberosity of the humerus and one element of the coracoacromial arch. A positive test result is defined as pain, weakness, or reproduction of symptoms. Park and colleagues reported that the combination of three positive test results—specifically the Hawkins sign, the painful arc sign, and the infraspinatus test result—had a 95% posttest probability for any degree of impingement.

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