SONOGRAPHIC EVALUATION
OF SUBACROMIAL SPACE
Azzoni Roberto, Cabitza Paolo, Parrini Matteo
Orthopaedic Dept., State University of Milan – 20097 San Donato Milanese (Milan) 30, via Morandi, Italy.
(E-mail: [email protected])
Aim of the study: The size of the subacromial space
varies in relation to anatomy (Fig.1) and gender. Some
pathologies of rotator cuff can be due to a reduction in
subacromial space, which is usually measured by means
of radiography using the antero-posterior and
supraspinatus outlet views. The aim of this study was to
verify the value of sonographic measurements of
subacromial space, and their variations in relation to
anatomy, age, gender and rotator cuff pathologies.
Fig. 1: Types of acromion by Wuh and Snyder (Orthop. Trans. 1992-93;
16:767-772)
Groups
Numbers
cases
of
Sonographic
Measurement
Radiographic
Measurement
Groups
1
1
70
10,5
11,0
2
54
14,4
13,9
2
3
4
20
26
10,0
08,6
10,1
09,0
Tab. I: US Vs X-Ray measurement of
subacromial space (value in mm.)
3
4
Materials and Methods: Between 1 January and 31 July 2001, we prospectively examined 200
consecutive painful shoulders using the sonography, and measured the subacromial space in all cases
using our own method (see below).
The measurements of subacromial space were made using coronal axis views of the shoulder. The
patient was in a sitting position with the upper limb hanging in backward flexion and internal rotation
(Fig. 2). The measurement reference points were the acromion itself and the head of the humerus at
the level of the greater tuberosity, which allows optimal visualisation of the long axis of the
supraspinatus. The sonographic measurement calipers were positioned on the lowest echo from the
external and inferior margin of the acromion, and the nearest point of the surface of the humeral head,
thus giving the smallest distance. The 200 shoulders were divided into four groups on the basis of
rotator cuff conditions: sonographically normal shoulders (group 1), shoulders with tendinopathy but
without cuff tears (group 2), shoulders with partial tears limited to the supraspinatus (group 3), and
shoulders with complete tears of the rotator cuff (supraspinatus and subscapular) (group 4).
Before or after sonography, all of the subjects underwent an X-ray examination of the affected shoulder
using anteroposterior, transaxiallary and supraspinatus outlet views in order to study the morphology of
the acromion and any osteoarthritic alterations in the acromioclavicular joint, and to measure the
subacromial space.
A comparison was made of the results of radiographic and sonographic measurements of subacromial
space.
Acromion type B
Acromion type C
Sonographic measurement
09,4
08,5
Radiographic measurement
10,0
07,7
Sonographic measurement
10,5
09,4
Radiographic measurement
11,0
09,3
Sonographic measurement
10,0
07,2
Radiographic measurement
10,3
06,5
Sonographic measurement
10,5
07,8
Radiographic measurement
09,8
07,0
groups
median males
median females
median in group
1
11,3
9,8
10,5
2
11,3
10,7
11,5
3
13,3
11,5
12,4
4
8,6
8,6
8,6
Tab. II: Comparison to US and X-Ray measurement in relation to the types of
acromion (value in mm.)
Tab.III: US subacromial space in relation
to sex (value in mm.)
Results: Group 1 consisted of 38 females and 32 males aged 20-62 years (median 47.5 years) whose painful shoulder showed a normal sonographic
rotator cuff image, and a subacromial space of between 6.9 and 16.6 mm (median: 10.52 mm). The median X-ray measured subacromial space was
11.02 mm. (Fig. 3)
Group 2 consisted of 22 females and 32 males aged 33-80 years (median 55 years) whose painful shoulder showed a sonographic picture of rotator
cuff tendinopathy without any sure signs of tears, and a subacromial space of between 9.6 and 17.4 mm (median: 14.4 mm). The median X-ray
measured subacromial space was 13.9 mm. (Fig. 4)
Fig. 2: Patient’s position
Group 3 consisted of 14 females and 6 males aged 53-76 years (median 64 years) whose painful shoulder showed an echographic image of a partial
during sonography
supraspinatus tendon tear and a subacromial space of between 6.5 and 13.1 mm (median: 10.8 mm). The median X-ray measured subacromial space
was 10.1 mm. (Fig. 5)
Finally, group 4 consisted of 10 females and 16 males aged 45-73 years (median 63.2 years) whose painful shoulder showed a sonographic image of a
complete (supraspinatus and subscapular) tear of the rotator cuff, and a subacromial space of between 6.1 and 12.9 mm (median: 8.6 mm). The
median X-ray measured subacromial space was 9.0 mm.. (Fig. 6)
The radiographic pictures in group 1 indicated type B acromonial
morphological abnormalities in 24 shoulders (with sonographic
and radiographic subacromial spaces of respectively 9.45 and
The variations in subacromial space in relation to age were not significant: the median measurement was 9.55 mm
10.0 mm) and type C abnormalities in 12 (sonographic and
between the ages of 40 and 50 years (lowest within-group value) and 11.18 mm between the ages of 30 and 40
radiographic subacromial spaces of respectively 8.55 and 7.79
years (highest within-group value); the median value between the age groups was 10.53 mm.
mm); none of the radiographic images suggested the presence of
The variations in subacromial space in relation to gender were more significant: in all of the rotator cuff pathology
acromioclavicular osteoarthritis.
groups, the median subacromial space was smaller among the females.
Group 2 included 18 cases with a radiographic type B acromion
Fourteen patients in group 3 and 11 in group 4 underwent surgical acromioplasty according to Neer with cuff
(with sonographic and radiographic subacromial spaces of
reconstruction; six patients in group 3 underwent arthroscopic disimpacting acromioplasty.
respectively 10.57 and 11.05 mm) and 14 with type C
(sonographic and radiographic subacromial spaces of
respectively 9.48 and 9.30 mm); there were radiographic signs of
acromioclavicular osteoarthritis in three cases.
Group 3 included two radiographic type B acromions (with
sonographic and radiographic subacromial spaces of respectively
10 and 10.33 mm) and six type C (sonographic and radiographic
subacromial spaces of respectively 7.26 and 6.56 mm); there were
radiographic signs of acromioclavicular osteoarthritis in one case.
Finally, group 4 included four radiographic type B acromions (with
sonographic and radiographic subacromial spaces of respectively
10.55 and 9.81 mm) and 20 type C (sonographic and radiographic
subacromial spaces of respectively 7.82 and 7.09 mm); there were
radiographic signs of acromioclavicular osteoarthritis in one case.
There was a highly significant correlation between the sonographic
and radiographic measurements of the subacromial space (p =
0.8, Student’s t test), as well as between these and the X-ray typed
acromion itself.
Fig. 3: Normal supraspinatus tendon and
subacromial space (mm. 12,2).
Fig. 4: Tendinopathy od supraspinatus, without tears,
subacromial space normal (mm. 11,3)
Discussion and Conclusions: Sonography measurements are sure and
precise, and sonographic examinations of the shoulder can be usefully
completed by measuring subacromial space. When
beginning the diagnosis of painful shoulder, subacromial space measurement
can avoid the need for a radiographic examination, thus reducing costs and
patient radiation exposure. It is inexpensive, non-invasive and already widely
used for the diagnosis of rotator cuff pathologies, and our technically simple and
rapid method of using it to measure subacromial space during the course of a
routine sonographic examination of the shoulder is reliable. Method is
reproducible since we have execute 24 measures of 25 healthy subjects by two
different operators, gaining median values of measure with per cent difference of
1,5% and statistical meaning with p=0,5 (t Student test).
Fig. 5: Partial tear of supraspinatus, subacromial
space reduced (mm. 10)
Fig. 6: Complete tear of supraspinatus, climb of humeral
head, subacromial space indeed reduced (mm. 5,3)
Keywords: Shoulder, Subacromial space, sonography, impingement syndrome.