Shoulder: Rotator Cuff and Impingement Syndromes

Abstract

Impingement syndromes are a group of abnormalities characterized by shoulder pain with the arm in certain positions, and can be divided into external and internal categories. External impingement is caused by structural changes outside of the joint and is classified as primary, secondary and subcoracoid types. Internal impingement is secondary to rotator cuff and capsular dysfunction, and is subdivided into posterosuperior (classic internal impingement), anterosuperior, anterior and entrapment of the long head of the biceps tendon subtypes. The role of imaging is to demonstrate structural findings that can corroborate a clinical impression of impingement or demonstrate findings that are suggestive of impingement, but the diagnosis of an impingement syndrome is always clinical. Primary and Secondary External Impingement SyndromesBoth primary and secondary impingement refer to compression of the subacromial-subdeltoid bursa and supraspinatus tendon due to narrowing of the supraspinatus outlet, a fibro-osseous tunnel in which the subacromial-subdeltoid bursa and supraspinatus tendon are located, and which is bounded by the humeral head inferiorly and the acromion, acromioclavicular joint and the coraco-acromial ligament superiorly (Fig. 1). In primary impingement, the narrowing is caused by anterior acromial morphology and/or degenerative changes of the acromioclavicular joint, whereas secondary impingement is caused by elevation of the humeral head as a result of glenohumeral instability.Clinically, pain can be elicited during abduction and external rotation of the arm or elevation with internal rotation. To provoke a classic Neer impingement sign on physical examination, the examiner raises the patient's arm forward while simultaneously stabilizing the scapula with another hand, causing the greater tuberosity to impinge against the acromion. If this motion is painful at 90 degrees of forward flexion, it is considered to be positive impingement. The positive result can be confirmed by injection of local anesthetic under the anterior acromion, which will relieve the pain. The Hawkins modification of the Neer maneuver reproduces impingement pain by forced internal rotation at 90 degrees of forward elevation and 30 degrees of forward flexion, which brings the greater tuberosity directly under the coracoacromial ligament, thus simulating the throwing position.

Rotator Interval

“…Extra-articular dislocation describes medial displacement of the LHBT superficial to the SSC tendon that can develop with a tear of the lateral CHL. 9,44 These basic patterns are also recognized in the more complex arthroscopic classification system suggested by Bennett (►Table 1). 45,46…”

“…8d). 9,18 In a study by Zanetti and coworkers, the overall sensitivity for detecting abnormalities of the LHBT on MR imaging was 89 to 92% and specificity was 56 to 81%. 18…”

“…As the RI capsule forms the roof of the RI, its floor is formed by the articular cartilage surface of the humeral head. [6][7][8][9] If viewed on sagittal sections (►Fig. 1c), the RI shows a quadrilateral configuration with the superior border of the SSC tendon inferiorly, the anterior border of the SSP tendon superiorly, the RI capsule anteriorly, and the humeral head posteriorly.…”

“…7,16 It can also occur as a consequence of chronic tendon instability or be observed as an isolated pathology caused by overuse in throwers or overhead athletes. 6,9,16,41 Tendinopathy typically affects the intra-articular (horizontal) portion of the LHBT. Initial intratendinous degeneration might be subtle or even invisible on inspection but might progress to fibrillation, splits, hypertrophy, or attenuation (partial tearing).…”

“…It may, however, be absent due to fibrous adherence or entrapment of the thickened tendon within the bicipital groove. 9,16 The LHBT is difficult to evaluate on MR imaging. Tendinopathy of its intra-articular portion can cause an increased caliber and a more rounded shape on sagittal oblique sections, irregular contours, and increased signal intensity on short TE images (►Fig.…”