| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Original Research |
1 Department of Radiology, Orthopedic University Hospital Balgrist, Forchstrasse
340, CH-8008 Zurich, Switzerland.
2 Department of Orthopedic Surgery, Orthopedic University Hospital Balgrist,
CH-8008 Zurich, Switzerland.
Received March 13, 2005;
accepted after revision May 6, 2005.
Address correspondence to M. Zanetti
(marco.zanetti{at}balgrist.ch).
Abstract
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
MATERIALS AND METHODS. Acromiohumeral distance was measured on
conventional radiographs and on MR images. Three age- and sex-matched patient
groups each including 21 patients were stratified according to acromiohumeral
distance on conventional radiographs (group 1, 
7 mm; group 2, 8-10 mm;
group 3, > 10 mm). Acromiohumeral distance was related to the presence,
location, and size of a rotator cuff tear and the degree of fatty degeneration
of the muscle assessed on MR arthrography. The relative influence on
acromiohumeral distance of the various MR arthrographic findings was assessed.
Spearman's rank correlation and stepwise regression were used for statistical
analysis.
RESULTS. In group 1 (acromiohumeral distance 7 mm)
full-thickness supraspinatus tendon tears were present in 90% (19/21) of the
patients, infraspinatus tendon tears in 67% (14/21) of the patients, and
subscapularis tendon tears in 43% (9/21) of the patients. The size of rotator
cuff tendon tears and the degree of fatty degeneration in all rotator cuff
muscles showed a significant negative correlation with acromiohumeral distance
(p < 0.05). After stepwise regression, a significant relative
influence on acromiohumeral distance remained for size of rotator cuff tear
(p < 0.0001) and for degree of fatty degeneration of the
infraspinatus muscle (p = 0.013).
CONCLUSION. Tendon tears and fatty muscle degeneration in the rotator cuff correlate with reduced acromiohumeral distance. Size of rotator cuff tear and degree of fatty degeneration of the infraspinatus muscle have the most pronounced influence on acromiohumeral distance.
Keywords: MRI • musculoskeletal imaging • orthopedic surgery • shoulder • x-ray technology
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
7 mm measured on an anteroposterior radiograph
suggests a large rotator cuff tear and the likelihood of successful outcome
after the repair is reduced [1,
2]. Some studies have shown
that narrowing of the acromiohumeral distance is associated with rotator cuff
muscle degeneration [2,
4,
5]. It is unknown whether
tendon involvement (supraspinatus vs infraspinatus), tear size, or muscle
degeneration is the most important structural change in reduced acromiohumeral
distance. The purpose of this study was to evaluate the association between
rotator cuff abnormalities and reduced acromiohumeral distance. |
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
7 mm; group 2, 8-10 mm; group 3,
> 10 mm). Imaging included conventional radiography and MR arthrography of
the shoulder in all patients. Data were collected retrospectively from the
institution's electronic database. The inclusion criteria were conventional
anteroposterior radiograph of the shoulder with the arm in neutral position
and scapular outlet view obtained; MR arthrogram of the shoulder obtained no
later than 1 month after conventional radiography at our institution according
to a standardized protocol; and no previous shoulder surgery. There were no
further exclusion criteria. The institutional review board does not require
its approval or informed consent for review of patient records or images.
Patient rights are protected by a law that requires patients to be informed
about the possibility that their charts and radiographs will be reviewed for
scientific purposes.
Imaging Protocol
Conventional radiography—Radiographic assessment included
conventional anteroposterior radiographs with the arm in neutral position. The
beam was angled 20° craniocaudally. Positioning for the supraspinatus
outlet view was performed under fluoroscopic guidance. The humeral head was
centered in the glenoid fossa, and the acromion was profiled. All radiographs
were acquired with the patient in the upright position.
MR arthrography—Twenty-eight patients underwent MR arthrography on a 1.0-T unit (Expert, Siemens Medical Solutions) and 35 patients on a 1.5-T MRI unit (Symphony, Siemens). All patients underwent MR arthrography after injection of approximately 12 mL (range, 10-14 mL) of gadopentetate dimeglumine (Magnevist, Schering) solution with a concentration of 2 mmol/L. The shoulder was placed on both MR systems in a dedicated receive-only shoulder coil with the arm in a neutral position and the thumb pointing upward.
1.0-T MRI—The following sequences were acquired with the 1.0-T MRI unit: T1-weighted spin-echo images in the coronal oblique plane with fat saturation (TR/TE, 800/20; section thickness, 4 mm; field of view, 160 x 160-mm; matrix size, 192 x 256), in the transverse plane (580/20; section thickness, 4 mm; field of view, 140 x 140 mm; matrix size, 512 x 224), and in the sagittal oblique plane (700/12; section thickness, 5 mm; field of view, 160 x 160 mm; matrix size, 256 x 192). T2-weighted fast spin-echo images (3,500/98; section thickness, 4 mm; field of view, 160 x 160 mm; matrix size, 512 x 230) and intermediate-weighted fast spin-echo images (3,500/16; section thickness, 4 mm; field of view, 160 x 160 mm; matrix size, 512 x 230) were obtained in the coronal oblique plane with fat saturation.
1.5-T MRI—The following sequences were acquired with the 1.5-T MRI unit: T1-weighted spin-echo images in the coronal oblique plane with fat saturation (792/20; section thickness, 3 mm; field of view, 160 x 160 mm; matrix size, 265 x 512), in the transverse plane (500/30; section thickness, 3 mm; field of view, 160 x 160 mm; matrix size, 256 x 512), and in the sagittal oblique plane (500/30; section thickness, 4 mm; field of view, 160 x 160 mm; matrix size, 256 x 512). T2-weighted fast spin-echo images (3,000/20; section thickness, 4 mm; field of view, 160 x 160 mm; matrix size, 256 x 512) and intermediate-weighted fast spin-echo images (2,350/20; section thickness, 4 mm; field of view, 160 x 160 mm; matrix size, 256 x 512) were obtained in the coronal oblique plane with fat saturation.
Measurement of Acromiohumeral Distance
Two blinded radiologists separately measured acromiohumeral distance on
conventional radiographs in neutral anteroposterior and supraspinatus outlet
views and on coronal oblique and sagittal oblique T1-weighted MR images.
Radiographs and MR images were randomly shown to the reviewers. Reviewer 1
specialized in musculoskeletal radiology and had 6 years of professional
experience. Reviewer 2 had no special training in musculoskeletal radiology.
The interpretations given by reviewer 2 were used only for assessment of
interobserver reliability. Acromiohumeral distance was measured electronically
with a PACS workstation (Read version 5.2.1, Image Devices). On conventional
radiographs, measurement was performed from the dense cortical bone at the
inferior aspect of the acromion to the subchondral lamina of the humeral head.
The shortest distance was measured
[4]. The same measurement was
performed by reviewers 1 and 2 on coronal and sagittal oblique T1-weighted MR
images 3 weeks later. A black line marked the inferior aspect of the acromion
at the point directly above the head of the humerus to the center. The center
of the subchondral cortex directly under the acromion marked the humeral
head.
MR Arthrographic Findings
MR arthrographic images were analyzed in consensus by two experienced
musculoskeletal radiologists (panel reviewers) without knowledge of the
radiographic acromiohumeral distance measurements. One of the panel reviewers
had 15 years of professional experience in musculoskeletal radiology and the
other reviewer, 6 years of experience. These reviewers analyzed the MR images
for presence, location, and size of rotator cuff tear, degree of fatty muscle
degeneration, and presence of muscle atrophy. The coronal extent of the tear
was measured from the insertion site at the greater tuberosity to the end of
the tendon. The sagittal extent of the tear was measured at the site with the
largest defect. Size was given in square millimeters (sagittal x coronal
extension).
Grading of muscular fatty degeneration was performed according to the classification by Goutallier et al. [6]. This classification is based on amount of fat in relation to amount of muscle. Stage 0 indicates no fatty degeneration; stage 1, some fatty streaks; stage 2, less fat than muscle; stage 3, as much fat as muscle; and stage 4, more fat than muscle. The Goutallier classification was initially described for CT and was later validated for MRI by Fuchs et al. [7]. If fatty degeneration was different in the superior and inferior parts of the subscapularis and infraspinatus muscles, the area with the highest stage was used for classification.
Muscle atrophy of the supraspinatus muscle was evaluated semiquantitatively with the so-called tangent sign. A line was drawn through the superior borders of the scapular spine and the superior margin of the coracoid [8]. The tangent sign is considered present when the supraspinatus muscle does not cross the tangent. Presence of the tangent sign indicates supraspinatus atrophy.
Statistical Analysis
Reproducibility of acromiohumeral distance— A paired
two-tailed t test was used to compare mean acromiohumeral distances.
A p value < 0.05 was considered statistically significant.
Reliability between measurements was assessed with restricted maximum
likelihood estimation (random three-way model of analysis of variance:
subject, method, reviewer).
Association between MR arthrographic findings and acromiohumeral distance—Spearman's rank correlation was performed to assess the relation between the continuous variables of acromiohumeral distance and ordinal data of fatty degeneration. Spearman's rank correlation was also used for assessing correlation between acromiohumeral distance and tear size.
Relative influence of various MR arthrographic findings on acromiohumeral distance—The relative influence of the various MR arthrographic findings on acromiohumeral distance was assessed with stepwise regression. We used SPSS 11.0.2 for Mac OS X (SPSS) to perform the statistical analysis.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
No significant interrater (p = 0.114-0.750, paired t test, two-tailed) or intramethod differences (p = 0.05-0.84, paired t test, two-tailed) were found. However, intermethod differences were significant (p < 0.0001, paired t test, two-tailed). Interrater reliability was consistently high for all methods (0.97-0.99). Intramethod reliability (conventional radiographs, 0.77; MR images, 0.91) and intermethod reliability were lower (anteroposterior radiographs vs coronal oblique MR images, 0.46; outlet view vs sagittal oblique MR images, 0.40).
Association Between Full-Thickness Tears of the Rotator Cuff and Reduced Acromiohumeral Distance
In group 1 full-thickness supraspinatus tendon tears were present in 90%
(19/21) of the patients, infraspinatus tendon tears in 67% (14/21) of the
patients, and subscapularis tendon tears in 43% (9/21) of the patients. Two
patients in group 1 had an intact rotator cuff without a tear of any tendons.
Groups 2 and 3 had a lower prevalence of full-thickness tears than group 1
(Table 1 and Figs.
1A,
1B,
1C,
1D,
1E,
2A,
2B,
2C,
2D, and
2E).
|
|
|
|
|
|
|
|
|
|
|
Association Between Tear Size and Acromiohumeral Distance
The size of tears in the rotator cuff varied from 1.3 to 38.5
cm2 (mean, 18.8 cm2) in group 1, from 4.0 to 29.5
cm2 (mean, 6.4 cm2) in group 2, and from 0.4 to 17.3
cm2 (mean, 3.3 cm2) in group 3.
Association Between Muscular Fatty Degeneration and Reduced Acromiohumeral Distance
Substantial fatty degeneration (Goutallier stages 2-4) of the supraspinatus
muscle was seen in five patients in group 1, two patients in group 2, and one
patient in group 3. Substantial fatty degeneration of the infraspinatus muscle
was found in 10 patients in group 1 and five patients in group 2. Substantial
fatty degeneration of the subscapularis muscle was present in nine patients in
group 1, three patients in group 2, and one patient in group 3
(Table 2). In group 1, nine
patients had no substantial fatty degeneration in any of the rotator cuff
muscles.
|
Association Between Supraspinatus Muscle Atrophy and Reduced Acromiohumeral Distance
Fifteen (71%) of the patients in group 1, six (29%) of the patients in
group 2, and only four (19%) of the patients in group 3 had supraspinatus
atrophy with the presence of a tangent sign. The mean acromiohumeral distance
(6.7 mm) in patients with supraspinatus muscle atrophy (tangent sign present)
(n = 25) was significantly (p < 0.001) lower than the
mean acromiohumeral distance (9.7 mm) in patients without supraspinatus muscle
atrophy (n = 36).
Association Between Various MR Arthrographic Findings and Acromiohumeral Distance
Rank correlation analysis between acromiohumeral distance on conventional
radiographs and MR images and structural changes in the rotator cuff is shown
in Table 3. A significant
(p < 0.05) negative correlation was shown between all structural
changes and acromiohumeral distance. The highest (most negative) correlation
coefficients were seen for tear size (r = -0.564 for conventional
radiographs; r = -0.646 for MR images) and fatty degeneration of the
infraspinatus muscle (r = -0.468 for conventional radiographs;
r = -0.497 for MR images). After stepwise regression, a significant
relative influence on acromiohumeral distance on conventional radiographs and
on MR images remained for rotator cuff tear size (p < 0.0001) and
for fatty degeneration of the infraspinatus muscle (p = 0.013). No
significant influence was found for location of the rotator cuff tear
(supraspinatus vs infraspinatus vs subscapularis) or for fatty degeneration of
the supraspinatus or subscapularis muscle.
|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
7 mm was proof of full-thickness tear of the
rotator cuff. Therefore, 7 mm is the cutoff value for abnormal
acromiohumeral distance. Shoulder surgeons measure acromiohumeral distance on conventional radiographs to estimate the success of a rotator cuff repair. An acromiohumeral distance < 7 mm is considered a negative factor for rotator cuff repair [11]. Unfavorable outcome in patients with a small acromiohumeral distance can be explained by the association of a short distance with large rotator cuff tear [2, 4, 5] and fatty degeneration of the infraspinatus and supraspinatus muscles [5]. Large rotator cuff tear and fatty muscle degeneration both are known to have a negative influence on outcome after rotator repair [12, 13]. Pfahler et al. [13] reported a good outcome after rotator cuff reconstruction only in patients with a cuff defect smaller than 2 x 3 cm. Goutallier et al. [14] found that fatty degeneration of both the supraspinatus and infraspinatus muscles is associated with poor structural and functional results after surgical repair. Those authors recommended that it is probably better to operate on the rotator cuff before irreversible muscular damage occurs, especially in the infraspinatus muscle.
The results of our study show that reduced acromiohumeral distance is a
reliable sign of rotator cuff tear. More than 90% of patients with an
acromiohumeral distance 7 mm had a full-thickness tear of the
supraspinatus tendon, and 67% had a full-thickness tear of the infraspinatus
tendon. The number of full-thickness tears of the supraspinatus and
infraspinatus tendons decreased considerably with an increase in
acromiohumeral distance (8-14 mm). However, compared with previous results
[10] showing an acromiohumeral
distance 7 mm was proof of rotator cuff tear, we had notable exceptions.
Two of 21 patients with an acromiohumeral distance 7 mm had an intact
rotator cuff. On the other hand, an acromiohumeral distance > 7 mm may be
associated with large rotator cuff tears. In group 2 (acromiohumeral distance,
8-10 mm), tear size was up to 29.4 cm2, and in group 3, up to 17.3
cm2.
This study also showed that reduced acromiohumeral distance is associated with atrophy and fatty degeneration of the rotator cuff muscles. Again, the correlation between reduced acromiohumeral distance and fatty degeneration of the infraspinatus muscle was less pronounced than previously shown [5]. In a CT study, Nové-Josserand et al. [5] found a 100% prevalence of acromiohumeral distance narrowing when the infraspinatus muscle exhibited fatty degeneration. In our study, normal acromiohumeral distances were seen in cases of stages 2 and 3 infraspinatus degeneration (Table 1). The differences in the results may be due to classification bias of fatty muscle degeneration in comparisons of studies conducted with different techniques.
The outliers concerning presence or absence of tendon tear or fatty muscle degeneration in both the abnormal and normal acromiohumeral distance groups indicate that reduced acromiohumeral distance on conventional radiographs gives information about the integrity of the rotator cuff but cannot be used as a single criterion for surgical decision making in rotator cuff repair.
The current study showed that acromiohumeral distance can be measured reliably on both conventional radiographs and MR images in clinical routine. No significant interrater or intramethod differences were detected. Interrater reliability was consistently high for all methods, although the experience levels of two reviewers were substantially different. The mean acromiohumeral distance on MR images was consistently smaller than the measurements on conventional radiographs. For example, the mean acromiohumeral distance on the coronal oblique MR images was 2.8 mm less than the mean acromiohumeral distance on the conventional anteroposterior radiographs. A possible explanation for this finding is that the different patient positions for MRI (supine) and conventional radiography (upright) provoked differences in muscle tension [15]. Geometric factors also may be responsible.
A limitation of the study was that although MR arthrography studies have a high accuracy (up to 95%) for rotator cuff tears [16, 17], this study lacked correlation between tears and surgery.
In summary, reduced acromiohumeral distance is associated with rotator cuff tears and rotator cuff muscle degeneration. Size of rotator cuff tear and degree of fatty degeneration of the infraspinatus muscle have the most pronounced influence on acromiohumeral distance. No significant influence was found for location of rotator cuff tear (supraspinatus vs infraspinatus vs subscapularis tendon) or for fatty degeneration of the supraspinatus or subscapularis muscle.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  U. Studler, C. W. A. Pfirrmann, B. Jost, V. Rousson, J. Hodler, and M. Zanetti Abnormalities of the Lesser Tuberosity on Radiography and MRI: Association with Subscapularis Tendon Lesions Am. J. Roentgenol., July 1, 2008; 191(1): 100 - 106. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. M. Hall Acromiohumeral Distance Am. J. Roentgenol., February 1, 2007; 188(2): W208 - W208. [Full Text] [PDF]
|
|
|
|
|
|
N. Saupe and M. Zanetti Reply Am. J. Roentgenol., February 1, 2007; 188(2): W209 - W209. [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
