Dynamic Sonography Evaluation of Shoulder Impingement Syndrome

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1 Sonography of Shoulder Impingement Syndrome Musculoskeletal Imaging Clinical Observations A C M E D E N T U R I C A L I M A G I N G AJR 2006; 187: X/06/ American Roentgen Ray Society Y O Nathalie J. Bureau 1 Marc Beauchamp 2,3 Etienne Cardinal 1 Paul Brassard 4 Bureau NJ, Beauchamp M, Cardinal E, Brassard P F Keywords: dynamic sonography, impingement, musculoskeletal imaging, shoulder, supraspinatus tendon DOI: /AJR Received March 24, 2005; accepted after revision May 30, Radiology Department, CH Université de Montréal, Hôpital Saint-Luc, 1058 Saint-Denis St., Montreal, QC, H2X 3J4 Canada. Address correspondence to N. J. Bureau (nathalie.bureau@umontreal.ca). 2 Orthopedic Department, CH Université de Montréal, Hôtel Dieu de Montréal, Montreal, QC, H2W 1T8 Canada. 3 Present address: Médiclub, Montreal QC, H3S 2W1 Canada. 4 Division of Clinical Epidemiology, McGill University Health Center, Royal Victoria Hospital, Montreal, QC, H3A 1A1 Canada. Dynamic Sonography Evaluation of Shoulder Impingement Syndrome OBJECTIVE. Our aim was to characterize shoulder impingement syndrome using dynamic sonography. CONCLUSION. Dynamic sonography allows direct visualization of the relationships between the acromion, humeral head, and intervening soft tissues during active shoulder motion and can provide useful information regarding potential intrinsic and extrinsic causes of shoulder impingement syndrome. ubacromial impingement syndrome S is a clinical entity that was proposed by Neer in 1972 [1]. This syndrome is the result of chronic irritation of the supraspinatus tendon against the undersurface of the anterior one third of the acromion, the coracoacromial ligament, and the acromioclavicular joint. It is often difficult to diagnose because the clinical presentation may be confusing and clinical tests lack specificity [2]. Although the morphology of the acromion has been shown to be an important factor in the occurrence of subacromial impingement and rotator cuff tears [3], assessment of the shape of the acromion on radiography is sensitive to minor changes in radiographic technique and to the MR section viewed on MRI and shows high interobserver variability [4, 5]. MRI is a reliable technique for the evaluation of the rotator cuff tendons, but it provides only a static evaluation of the shoulder joint and can only indirectly suggest the diagnosis of subacromial impingement because most findings are nonspecific. Studies have investigated the value of dynamic MR evaluation of the shoulder with open MRI [6, 7]. The major limiting factors of dynamic MRI are the restricted availability of open magnets and the fact that the MR technology, at this time, only allows sequential imaging of single-plane shoulder motions that do not entirely reproduce physiologic shoulder motion. In 1990, Farin et al. [8], using dynamic sonography, described bursitis, fluid distention, and pooling of fluid lateral to the subdeltoid bursa as signs of early-stage subacromial impingement. In our experience, a wider range of abnormalities can be observed on dynamic sonography in the presence of subacromial impingement. The purpose of this study was to describe a method of dynamic sonography evaluation and to characterize the spectrum of abnormalities of subacromial impingement using dynamic sonography. Subjects and Methods Our institutional ethics committee approved this study, and written informed consent was obtained from all patients. Sonography examination of both shoulders was performed prospectively in a convenience sample of 13 patients (six men, seven women; mean age, 46 years; age range, years) presenting with a clinical diagnosis of subacromial impingement. The diagnosis of subacromial impingement was established by an orthopedic surgeon specializing in upper extremity management. Patients were selected from the surgeon s clinical practice over a period of 6 months on the basis of strict inclusion criteria (age range, years; shoulder pain of more than 6 months duration; positive impingement test) and exclusion criteria (shoulder surgery, history of acromioclavicular joint dislocation, fracture to the shoulder girdle, glenohumeral instability, osteoarthritis of the glenohumeral joint, inflammatory arthritis, diabetes, congenital anomaly, tumor of the shoulder girdle, radiation therapy to the shoulder) and after standardized clinical evaluation of both shoulders that included the Jobe, Neer, Hawkins, and Speed tests [9]. In addition, the orthopedic surgeon performed a subacromial injection test (impingement test) using 10 ml of lidocaine hy- 216 AJR:187, July 2006

Sonography of Shoulder Impingement Syndrome drochloride 2% (Xylocaine, Abbott Laboratories).

impingement [10]. The sonography examinations were performed independently by either of two musculoskeletal radiologists with 9 and 10 years experience in musculoskeletal sonography, using either a 7.

First, a complete standard comparative sonography evaluation of both shoulders was performed with the patient sitting on a stool. A dynamic sonography examination was also performed in all patients.

2 Sonography of Shoulder Impingement Syndrome drochloride 2% (Xylocaine, Abbott Laboratories). The marked relief of pain and an almost total improvement in passive or active shoulder range of motion 10 min after the subacromial injection were considered positive findings for subacromial impingement [10]. The sonography examinations were performed independently by either of two musculoskeletal radiologists with 9 and 10 years experience in musculoskeletal sonography, using either a 7.5-MHz or a 5 13-MHz high-resolution transducer (Sonoline Elegra, Siemens Medical Solutions). First, a complete standard comparative sonography evaluation of both shoulders was performed with the patient sitting on a stool. A dynamic sonography examination was also performed in all patients. The position A B in which the dynamic sonography evaluation was performed was based on the MR study by Brossmann et al. [11] that used cadavers and showed that subacromial impingement was best seen at 60 forward flexion, 60 abduction, and internal rotation. This maneuver is also similar to the impingement test described by Neer [10]. Hence, during the dynamic sonography evaluation, the patient was instructed to elevate the arm halfway between flexion and abduction with the hand in pronation and the elbow extended while the ultrasound probe was positioned in the coronal plane along the long axis of the supraspinatus tendon, between the acromion and the greater tuberosity of the humerus. The active movement could be repeated a few times. Fig. 1 Sonograms of normal shoulder and shoulders with impingement. (See also Figs. S1A S1C, videos, in supplemental data online.) A, 37-year-old man with normal dynamic sonography evaluation. Coronal sonography view of left asymptomatic shoulder, during active elevation of arm halfway between flexion and abduction with hand in pronation, shows unobstructed passage of greater tuberosity (T) of humeral head and supraspinatus tendon (S) underneath acromion (A). B, 49-year-old man with soft-tissue impingement during dynamic sonography evaluation of shoulder. Coronal sonography view of left shoulder with subacromial impingement, during active elevation of arm halfway between flexion and abduction with hand in pronation, shows pooling of fluid in lateral aspect of subacromial subdeltoid bursa (arrow) and mild impingement of supraspinatus tendon (arrowhead) as greater tuberosity (T) of humeral head approximates anterior one third of acromion (A). Note that humeral head remains in anatomic position, below acromion. C, 43-year-old man with upward migration of humeral head during dynamic sonography evaluation of shoulder. Coronal sonography view of left shoulder with shoulder impingement syndrome, during active elevation of arm halfway between flexion and abduction with hand in pronation, shows abnormal upward migration of humeral head (H) in regard to acromion (A), preventing its passage underneath acromion. There is mild distention of subacromial bursa (arrowhead). S = supraspinatus tendon. The relationships between the acromion, the humeral head, and the intervening soft tissues namely, the subacromial bursa and supraspinatus tendon were assessed during active shoulder motion. All dynamic sonography examinations were videotaped (Fig. S1, available at and static images were obtained from the cine loop showing impingement when it occurred. There was no evidence of impingement if the humeral head passed easily and freely underneath the acromion during shoulder motion (Fig. 1A). Softtissue impingement was described when pooling of fluid in the lateral aspect of the subacromial subdeltoid bursa occurred or when alteration of the normally convex surface of the subacromial bursa alone or of the subacromial bursa and of the su- C AJR:187, July

3 praspinatus tendon occurred when the greater tuberosity of the humeral head passed underneath the acromion (Fig. 1B). Osseous impingement was reported when the greater tuberosity of the humeral head migrated upward and prevented its passage underneath the acromion (Fig. 1C). All dynamic sonography studies were retrospectively reviewed by the two radiologists who performed the studies, and the type of impingement was determined by consensus. In addition, during the dynamic sonography examination, the patient was asked to report whether the movement was painful or not. Based on the sonography findings and the presence or absence of pain felt by the patient during the dynamic sonography examination, we created a four-grade classification system to characterize subacromial impingement on dynamic sonography (Table 1). Results Twenty-six shoulders in 13 patients were examined. There were 12 asymptomatic shoulders and 14 shoulders with the clinical diagnosis of subacromial impingement. In the group of shoulders with a clinical diagnosis of subacromial impingement, 14% (2/14) were diagnosed on dynamic sonography examination as a case of grade 0 impingement; 29% (4/14), grade 1; 7% (1/14), grade 2; and 50% (7/14), grade 3. By contrast, in the group of asymptomatic shoulders, 75% (9/12) were grade 0 cases; 17% (2/12), grade 1; 0% (0/12) grade 2; and 8% (1/12), grade 3. Discussion The acromiohumeral outlet is limited by the humeral head below and is formed superiorly by the coracoacromial arch, which consists of the acromion, the coracoid process, and the coracoacromial ligament, and medially by the acromioclavicular joint. During the arc of motion of the shoulder, especially forward flexion, the supraspinatus tendon and subacromial bursa may be subjected to degenerative changes because of the close relationship with these structures. In a concepts review about subacromial impingement, Bigliani and Levine [12] described intrinsic and extrinsic causes of this syndrome. Radiographic evaluation may give valuable anatomic information such as the presence of osteoarthrosis of the acromioclavicular joint or os acromiale and evidence of prior glenohumeral joint dislocation or calcific tendinosis. The supraspinatus outlet radiograph is used to determine the shape of the acromion according to the classification suggested by Bigliani et al. [3]. Acromial shape, including the lateral tilt of the acromion, can also be determined on MR studies. In addition, MRI can show the presence of rotator cuff and subacromial bursa abnormalities, degeneration of the acromioclavicular joint, and evidence of glenohumeral instability. Although this anatomic information is essential for evaluation of the patient, it does not provide information about the functional kinematics of the shoulder. Sonography has proved useful in the diagnosis of rotator cuff tears [13], rotator cuff tendinosis, calcific tendinosis, and subacromial bursitis and has become an accepted method of investigation of shoulder pathology. Dynamic sonography can provide direct visualization of the relationships between the anterior one third of the acromion, subacromial bursa, supraspinatus tendon, and greater tuberosity of the humeral head during active shoulder motion. In the absence of subacromial impingement, the motion of forward flexion of the arm halfway between flexion and abduction with pronation of the hand does not elicit any pain, and at sonography, the greater tuberosity of the humeral head glides easily beneath the anterior one third of the acromion (Fig. 2). We have found patients with grade 1 shoulder impingement who felt pain during the dynamic evaluation but in whom no evidence of anatomic impingement was shown on sonography. We hypothesize that in patients with grade 1 subacromial impingement, pain can result from impingement occurring medially on a hypertrophic degenerative acromioclavicular joint or from contact with the cora- TABLE 1: Dynamic Sonography Classification of Subacromial Impingement Grade Clinical Finding Sonography Finding 0 No pain elicited during shoulder motion No evidence of anatomic impingement 1 Pain elicited during shoulder motion No evidence of anatomic impingement 2 Pain elicited during shoulder motion Evidence of soft-tissue impingement 3 Pain elicited during shoulder motion Evidence of upward migration of the humeral head coacromial ligament. Sonography does not permit direct visualization of the relationships between the supraspinatus tendon and the acromioclavicular joint because of the osseous structures blocking the ultrasound beam. In addition, some degree of proximal migration of the humeral head may possibly occur in grade 1 subacromial impingement without provoking any visible anatomic subacromial impingement but nevertheless causing pain from irritation of inflamed tissues. Grade 2 subacromial impingement is associated with encroachment of the soft tissues between the acromion and greater tuberosity and may result from intrinsic soft-tissue abnormalities, such as tendinosis with thickening of the tendon, the presence of calcific deposits that create focal thickening of the tendon, or inflammation and distention of the subacromial bursa (Fig. 3). Primary bursitis, which is seen in inflammatory arthritis, gout, infections, and other synovial diseases, must be excluded before subacromial impingement can be implicated as the cause of soft-tissue impingement. The shape of the acromion can also cause softtissue impingement. Failure of humeral head depression during shoulder motion may also cause grade 2 subacromial impingement. In grade 3 subacromial impingement, there is failure of humeral depression resulting in upward migration of the humeral head (Fig. 4). The causes of this abnormal kinematics of the shoulder could be rotator cuff muscle fatigue, tendon tear or tendinosis, or shoulder joint instability, as described in the article by Bigliani and Levine [12]. Adhesive capsulitis, which presents with limited range of motion of the glenohumeral joint, especially abduction and external rotation, should be recognized and easily differentiated from grade 3 subacromial impingement. In this study, the majority (75%) of asymptomatic shoulders were classified as grade 0, but two shoulders (17%) were classified as grade 1 and one shoulder (8%) as grade 3 subacromial impingement. This may be the result of a selection bias because patients who suffer from subacromial impingement syndrome in one shoulder may be more at risk of having shoulder abnormalities on the contralateral side. Dynamic shoulder sonography in a cohort of subjects with both shoulders free of abnormalities might have provided different results. In the group of symptomatic shoulders, the majority (86%) were classified as grade 1, 2, or 3, but two shoulders (14%) were classified as grade 0. This should not be interpreted as two false-negative cases because this study 218 AJR:187, July 2006

this diagnosis is difficult to establish. Fig. 3 Subjective drawing (not based on cadaveric model) of subacromial impingement with soft-tissue involvement.

4 Sonography of Shoulder Impingement Syndrome did not use a gold standard. These two cases merely reflect a disparity between the diagnosis of subacromial impingement made at clinical examination and the findings on dynamic sonography evaluation and emphasize the fact that this diagnosis is difficult to establish. Fig. 3 Subjective drawing (not based on cadaveric model) of subacromial impingement with soft-tissue involvement. Drawing (coronal plane, cut section) of left shoulder during active elevation of arm halfway between flexion and abduction with hand in pronation explicitly depicts pooling of fluid in lateral aspect of subacromial subdeltoid bursa (arrow) and alteration of normally convex surface of supraspinatus tendon (arrowhead) as arm is elevated. Supraspinatus tendon is not always involved in grade 2 subacromial impingement. There is also evidence of supraspinatus tendinosis and inflammatory changes in bursa. In conclusion, dynamic sonography evaluation of subacromial impingement must be regarded as a subacromial impingement imaging test that can provide useful information to the clinician and that can be easily integrated into a routine sonography shoulder examination protocol. Sonography can show which structure is being impinged and can show upward migration of the humeral head, thus providing valuable information about the potential intrinsic and extrinsic causes of this syndrome. Fig. 2 Subjective drawing (not based on cadaveric model) of normal dynamic shoulder evaluation. Drawing (coronal plane, cut section) of left shoulder during active elevation of arm halfway between flexion and abduction with hand in pronation shows normal relationships between acromion (A), greater tuberosity (T) of humeral head, and intervening soft tissues namely, supraspinatus tendon (S) and subacromial subdeltoid bursa (arrow). D = deltoid muscle. Fig. 4 Subjective drawing (not based on cadaveric model) of subacromial impingement with upward migration of humeral head. Drawing (coronal plane, cut section) of left shoulder during active elevation of arm halfway between flexion and abduction with hand in pronation shows upward migration of humeral head in relation to glenoid cavity, which prevents passage of greater tuberosity (T) and softtissue structures of supraspinatus outlet beneath acromion. AJR:187, July

5 References 1. Neer CS 2nd. Anterior acromioplasty for the chronic impingement syndrome in the shoulder: a preliminary report. J Bone Joint Surg Am 1972; 54: Calis M, Akgun K, Birtane M, Karacan I, Calis H, Tuzun F. Diagnostic values of clinical diagnostic tests in subacromial impingement syndrome. Ann Rheum Dis 2000; 59: Bigliani LU, Morrison DS, April EW. Morphology of the acromion and its relationship to rotator cuff tears. (abstr) Orthop Trans 1986; 10: Haygood TM, Langlotz CP, Kneeland JB, Iannotti JP, Williams GR Jr, Dalinka MK. Categorization of acromial shape: interobserver variability with MR imaging and conventional radiography. AJR 1994; FOR YOUR INFORMATION 162: Peh WCG, Farmer THR, Totty WG. Acromial arch shape: assessment with MR imaging. Radiology 1995; 195: Beaulieu CF, Hodge DK, Bergman AG, et al. Glenohumeral relationships during physiologic shoulder motion and stress testing: initial experience with open MR imaging and active imaging-plane registration. Radiology 1999; 212: Graichen H, Bonel H, Stammberger T, Englmeier KH, Reiser M, Eckstein F. Subacromial space width changes during abduction and rotation: a 3-D MR imaging study. Surg Radiol Anat 1999; 21: Farin PU, Jaroma H, Harju A, Soimakallio S. Shoulder impingement syndrome: sonographic evaluation. Radiology 1990; 176: McFarland EG, Selhi HS, Keyurapan E. Clinical evaluation of impingement: what to do and what works. J Bone Joint Surg Am 2006; 88: Neer CS 2nd. Impingement lesions. Clin Orthop Relat Res 1983; 173: Brossmann J, Preidler KW, Pedowitz RA, White LM, Trudell D, Resnick D. Shoulder impingement syndrome: influence of shoulder position on rotator cuff impingement an anatomic study. AJR 1996; 167: Bigliani LU, Levine WN. Current concepts review: subacromial impingement syndrome. J Bone Joint Surg Am 1997; 79: Teefey SA, Hasan A, Middleton WD, Wright RW, Yamaguchi K. Ultrasonography of the rotator cuff. J Bone Joint Surg Am 2000; 82: A data supplement for this article can be viewed in the online version of the article at: AJR:187, July 2006

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