9 Impingement and Rotator Cuff Disease

Impingement and Rotator Cuff Disease 121 9 Impingement and Rotator Cuff Disease A. Stäbler CONTENTS Shoulder pain and chronic reduced function are frequently heard complaints in an orthopaedic outpa- 9.1 Defi nition of Impingement Syndrome 122 tient department. The symptoms are often related to 9.2 Stages of Impingement 123 the unique anatomic relationships present around the 9.3 Imaging of Impingement Syndrome: Uri Imaging Modalities 123 glenohumeral joint ( 1997). Impingement of the 9.3.1 Radiography 123 rotator cuff and adjacent bursa between the humeral 9.3.2 Ultrasound 126 head and the coracoacromial arch are among the most 9.3.3 Arthrography 126 common causes of shoulder pain. Neer noted that 9.3.4 Magnetic Resonance Imaging 127 elevation of the arm, particularly in internal rotation, 9.3.4.1 Sequences 127 9.3.4.2 Gadolinium 128 causes the critical area of the cuff to pass under the 9.3.4.3 MR Arthrography 128 coracoacromial arch. In cadaver dissections he found 9.4 Imaging Findings in Impingement Syndrome alterations attributable to mechanical impingement and Rotator Cuff Tears 130 including a ridge of proliferative spurs and excres- 9.4.1 Bursal Effusion 130 cences on the undersurface of the anterior margin 9.4.2 Imaging Following Impingement Test Injection 131 Neer Neer 9.4.3 Tendinosis 131 of the acromion ( 1972). Thus it was who 9.4.4 Partial Thickness Tears 133 introduced the concept of an impingement syndrome 9.4.5 Full-Thickness Tears 134 continuum ranging from chronic bursitis and partial 9.4.5.1 Subacromial Distance 136 tears to complete tears of the supraspinatus tendon, 9.4.5.2 Peribursal Fat Plane 137 which may extend to involve other parts of the cuff 9.4.5.3 Intramuscular Cysts 137 Neer Matsen 9.4.6 Massive Tears 137 ( 1972; 1990). 9.4.6.1 Acromioclavicular Cyst 138 The muscles of the rotator cuff, the deltoid muscle, 9.4.7 Rotator Cuff Muscles 139 and the muscles inserting at the proximal humerus, 9.4.8 Rotator Interval Tears 140 including the thoracodorsalis muscle, and the pec- 9.4.9 Incomplete and Complete Subscapularis Tears toralis muscles, control the shoulder joint. Without and Biceps Tendon Lesions 141 9.4.10 Adhesive Capsulitis 144 muscle control, a relatively free subluxation of the 9.4.11 Coracoid Impingement 144 humeral head in anterior, posterior or inferior direc- 9.5 Acromion: Anatomic Variations and tion is possible despite intact glenohumeral ligaments Associated Changes in Rotator Cuff Disease 145 and muscles. The deltoid muscle, the pectoralis major 9.5.1 Acromial Shape 146 muscle, and parts of the rotator cuff muscles center 9.5.2 Acromial Slope 147 9.5.3 Os Acromiale 148 the humeral head under the coracoacromial arch 9.5.4 Coracoacromial Ligament 149 by pulling the humeral head upwards. This force is 9.5.5 Acromioclavicular Joint 150 counteracted only by downward directed gravitation, 9.5.6 Greater Tuberosity 151 and muscles with an inferior insertion at the humeral 9.6 Impingement Syndrome and head or proximal humerus. Calcifying Tendinitis 153 References 154 Rotator cuff disease is related to various factors. A dominant mechanism seems to be upward center- ing of the humeral head with a failure to stabilize the shoulder against this muscle action. Stiffness of the posterior capsule or increased muscle tension in the posterior located cuff muscles may aggravate the A. Stäbler, MD Institute for Radiologic Diagnostic, Klinikum Grosshadern, impingement process by forcing the humeral head Ludwigs-Maximilians University, Marchioninistrasse 15, upwards against the anteroinferior acromion as the 81377 Munich, Germany arm is elevated (Fig. 9.1) (Matsen 1990). 122 A. Stäbler Fig. 9.1a, b. Stiffness of the posterior glenohumeral capsule or increased muscle tension is frequently associated with signs of impingement. A normally lax posterior capsule allows downward shift during fl exion of the arm (a). Stiffness of the posterior capsule or increased muscle tension force the humeral head upwards, causing narrowing of the supraspinatus outlet near the anterior tip of the acromion (b). (Adapted from Matsen 1990) ab Anatomic variants in the shape of the acromion, agent results in pain relief, while provoking pain with degeneration of the rotator cuff tendons with or the arm elevated (Kessel and Wat s o n 1977; Wat s o n without calcifying deposits, repetitive or severe 1989; Neer 1995). trauma, chronic overuse due to occupation or sports Any abnormality that disturbs the relationship activities, contribute to the development of rota- of the subacromial structures may lead to impinge- tor cuff pathology by increasing friction and wear ment (Bigliani et al. 1991; Bigliani and Levine against the acromion and the coracoacromial arch 1997). Several forms of impingement have been dif- (Bigliani et al. 1991; Bigliani and Levine 1997; ferentiated. Causes leading to impingement can be Hijioka et al. 1993). An increase in volume of the classifi ed as intrinsic (intratendinous) or extrinsic soft tissue in the subacromial space, for example due (extratendinous). Impingement is further charac- to swelling from mucoid degeneration of a tendon, terized as primary or secondary to another process, compromises the subacromial space and symptoms such as instability. Impingement of the supraspinatus of impingement appear because of the unyielding tendon can be caused by a primary narrowing of the nature of the coracoacromial ligament (Uthoff et supraspinatus outlet or by secondary subacromial al. 1988). bone apposition (osteophytes), bone apposition Others believe that the pathogenesis of most at the greater tuberosity, glenohumeral instability, rotator cuff tears is an intrinsic degenerative pro- including superior labrum anterior posterior (SLAP) cess of the rotator cuff, because they observed lesions, muscle imbalance with increased forces cen- such degenerative changes at the undersurface of tering the humeral head under the coracoacromial the acromion in the absence of tears (Ogata and arch, and supraspinatus hypertrophy due to occupa- Uhthoff 1990), or found specimens that had a tion or sports activities. partial tear of the rotator cuff on the articular side Impingement of the supraspinatus tendon and with an usually intact undersurface of the acromion the greater tuberosity occurs primarily against the (Ozaki et al. 1988). acromial end of the coracoacromial ligament and the anterior tip of the acromion during stretching of the ligament, which explains the presence of trac- tion osteophytes on the anterior acromion (Burns 9.1 and Whipple 1993). Biceps tendon impingement Definition of Impingement Syndrome occurs predominantly against the lateral free edge of the coracoacromial ligament (Burns and Whipple Subacromial impingement syndrome is a painful 1993). compression of the supraspinatus tendon, the sub- Coracoid impingement is a painful compression acromial–subdeltoid bursa, and the long head of the of the subscapularis tendon between the anterior biceps tendon between the humeral head and the portion of the humeral head at the level of the lesser anterior portion of the acromion occurring during tuberosity and the coracoid process. The glenoid rim abduction and forward elevation of the internally impingement occurs from repetitive posterior and rotated arm (Neer 1972). The test injection is used cranial subluxation of the humeral head in throwers to prove the presence of impingement syndrome. or tennis players with compression of the posterior Impingement syndrome is present in a painful shoul- superior labrum and subsequent degeneration of the der when subacromial infi ltration with an anesthetic labrum, frequently followed by ganglion cyst forma- Impingement and Rotator Cuff Disease 123 tion. This form of impingement is better classifi ed as Panni et al. determined the prevalence of rota- instability. tor cuff pathologies in 80 shoulder specimens Impingement, which ultimately results in degen- obtained from 40 cadavers. The mean age at death eration of the rotator cuff tendons, is a combined was 58.4 years. The rotator cuff was normal in 82.5% interaction of several elements including vascular, (66 shoulders); an articular-side partial tear was degenerative, traumatic, and mechanical or anatomic present in 5% (four cuffs); a bursal-side partial tear factors. These elements are interrelated, and each was seen in 7.5% (six cuffs); and a full-thickness tear affects the tendons in a manner that contributes to was found in 5% (four cuffs) (Panni et al. 1996). tendon weakening (Neviaser and Neviaser 1990). 9.3 9.2 Imaging of Impingement Syndrome: Stages of Impingement Imaging Modalities The changes in the supraspinatus tendon from For imaging impingement syndrome and rotator normal to complete rupture are classifi ed accord- cuff pathologies, radiographs, ultrasound, arthrog- ing to Neer in three stages (Neer 1977, 1983). The raphy, computed tomography (CT), magnetic reso- fi rst stage of impingement syndrome is edema and nance imaging (MRI) and magnetic resonance (MR) hemorrhage in the distal part of the tendon close to arthrography are used. Three radiographs compris- the insertion at the greater tuberosity. In this area, ing ‘true’ anteroposterior (AP) outlet-view and ‘Rock- called the critical zone, the nutrition of the avascular wood’ projection are obtained routinely. Ultrasound tendon is limited because of the distance from the is used frequently to get an overview of the rotator vascularized bone and the vascularized supraspina- cuff pathology. Arthrography is only rarely used as tus muscle. Unfortunately, this zone is also exposed a single method. When available, a combination of to the pressure between the upward centered humeral MRI following the distension of the joint capsule head and the anterior portion of the acromion. Stage I with fl uid is a widely used practice. is found in persons younger than 25 years, may result from excessive overhead use in sports or work, and can be reversible. 9.3.1 Repetitive mechanical trauma and stress causes Radiography fi brosis and thickening of the subacromial–subdeltoid bursa and tendonitis in the supraspinatus Imaging of the shoulder should start with radio- tendon, indicating the second stage of impingement graphs.

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