Impingement Syndrome of the Shoulder

Abstract

Background: Shoulder pain is the third most common musculoskeletal complaint in orthopedic practice. It is usually due to a defect of the rotator cuff and/or an impingement syndrome.

Methods: This review is based on pertinent literature retrieved by a selective search of the Medline database.

Results: Patients with shoulder impingement syndrome suffer from painful entrapment of soft tissue whenever they elevate the arm. The pathological mechanism is a structural narrowing in the subacromial space. A multiplicity of potential etiologies makes the diagnosis more difficult; it is established by the history and physical examination and can be confirmed with x-ray, ultra - sonography, and magnetic resonance imaging. The initial treatment is conservative, e.g., with nonsteroidal antiinflammatory drugs, infiltrations, and patient exercises. Conservative treatment yields satisfactory results within 2 years in 60% of cases. If symptoms persist, decompressive surgery is performed as long as the continuity of the rotator cuff is preserved and there is a pathological abnormality of the bursa. The correct etiologic diagnosis and choice of treatment are essential for a good outcome. The formal evidence level regarding the best treatment strategy is low, and it has not yet been determined whether surgical or conservative treatment is better.

Conclusion: Randomized controlled therapeutic trials are needed so that a standardized treatment regimen can be established.

FIGURE 1

Overview of causes of primary subacromial impingement syndrome (SIS) and rotator cuff (RC) degeneration. The RC can be damaged by both intrinsic and extrinsic factors, which can lead to RC rupture and to an abnormally high position of the head of the humerus. This, among other factors, can cause a non-outlet SIS. Primary SIS, in turn, leads to CAL ossification and acromial osteophyte formation. Primary SIS is to be distinguished from rarer types of shoulder impingement (gray-shaded boxes). AC, acromioclavicular; CAL, coraco-acromial ligament

Figure 2

Anatomical overview of the shoulder (left, above), showing the mechanism of subacromial impingement with painful entrapment of soft tissues (arrows, right, above) on elevation of the arm, due to pathological contact of the humeral head with the roof of the shoulder joint, particularly the anterolateral portion of the acromion (below). From: Habermeyer P: Schulterchirurgie, 4th ed., 2010 (1). Reproduced with the kind permission of Elsevier GmbH, Urban & Fischer, Munich, Germany

Figure 3

Acromial shapes as classified by Bigliani and Morrison: type I (flat), type II (curved), type III (hooked)

Figure 4

Critical shoulder angle and acromiohumeral index a) Critical shoulder angle (CSA): the angle (black lines) is measured from the inferior pole of the glenoid between the glenoid plane and the lateral border of the acromion. A wide CSA is a risk factor for rotator cuff lesions. b) Acromiohumeral index (Al): this is the quotient of the distance from the glenoid surface to the lateral end of the acromion (GA, dotted arrow) and the distance from the glenoid surface to the lateral end of the humeral head (GH, black arrow): by definition, AI = GA/GH. A high AI is also a risk factor for rotator cuff lesions

Figure 5

Subacromial decompression in a patient with an anterolateral bone spur. a) Bone spur on the anterolateral portion of the acromion (above the red line) in an arthroscopic view from posterior, with an electrosurgical probe and bursa fragments at the lower edge of the image. c) The spur (red line) can also be seen on an anteroposterior (AP) shoulder x-ray. b) The same operative field after arthroscopic decompression: the lateral extension of the acromion is now flat (above the red line). A bone drill can be seen at the lower edge of the image. d) The x-ray shows the surgically widened subacromial space and the flat lower edge of the acromion (red line)