DOI:10.2214/AJR.05.0528
AJR 2006; 187:216-220
© American Roentgen Ray Society
Dynamic Sonography Evaluation of Shoulder Impingement Syndrome
Nathalie J. Bureau1,
Marc Beauchamp2,3,
Etienne Cardinal1 and
Paul Brassard4
1 Radiology Department, CH Université de Montréal, Hôpital
Saint-Luc, 1058 Saint-Denis St., Montreal, QC, H2X 3J4 Canada.
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.
Received March 24, 2005;
accepted after revision May 30, 2005.
Address correspondence to N. J. Bureau
(nathalie.bureau{at}umontreal.ca).
Abstract
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.
Keywords: dynamic sonography • impingement • musculoskeletal imaging • shoulder • supraspinatus tendon
Introduction
Subacromial impingement syndrome 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, 37-58 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, 30-60 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 hydrochloride 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].
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Fig. 1A —Sonograms of normal shoulder and shoulders with impingement.
(See also Figs. S1A-S1C, videos, in supplemental data online.) 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).
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Fig. 1B —Sonograms of normal shoulder and shoulders with impingement.
(See also Figs. S1A-S1C, videos, in supplemental data online.) 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.
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Fig. 1C —Sonograms of normal shoulder and shoulders with impingement.
(See also Figs. S1A-S1C, videos, in supplemental data online.) 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.
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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 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.
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
www.ajronline.org),
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). Soft-tissue
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 supraspinatus 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).
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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.
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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 coracoacromial 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
soft-tissue impingement. Failure of humeral head depression during shoulder
motion may also cause grade 2 subacromial impingement.
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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.
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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.
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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 soft-tissue structures of supraspinatus
outlet beneath acromion.
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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 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.
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.
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Abstract
Introduction
