Is MRA an unnecessary expense in the management of a clinically unstable shoulder? A comparison of MRA and arthroscopic findings in 90 patients.

Abstract

In detection of glenoid labrum pathology, MR arthrography (MRA) has shown sensitivities of 88-100% and specificities of 89-93%. However, our practice suggested that there may be a higher frequency of falsely negative reports. We assessed the accuracy of this costly modality in practice.
We retrospectively reviewed MRA reports of 90 consecutive patients with clinical shoulder instability who had undergone shoulder arthroscopy. All had a history of traumatic anterior shoulder dislocation and had positive anterior apprehension tests. All underwent arthroscopy and stabilization during the same procedure. We compared the findings, using arthroscopic findings as the gold standard in the identification of glenoid labrum pathology.
83 of the 90 patients had glenoid labrum tears at arthroscopy. Only 54 were correctly identified at MRA. All normal glenoid labra were identified at MRA. This gave a sensitivity of 65% and a specificity of 100% in identification of all types of glenoid labrum tear. 74 patients had anterior glenoid labral tears that were detected at an even lower rate of sensitivity (58%).
The sensitivity of MRA in this series was substantially lower than previously published, suggesting that MRA may not be as reliable a diagnostic imaging modality in glenohumeral instability as previously thought. Our findings highlight the importance of an accurate history and clinical examination in the management of glenohumeral instability. The need for MRA may not be as high as is currently believed.

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Acta Orthopaedica 2012; 83 (3): 267–270 267
Is MRA an unnecessary expense in the management of a
clinically unstable shoulder?
A comparison of MRA and arthroscopic findings in 90 patients
Sam C Jonas1,2, Michael J Walton1,2, and Partha P Sarangi1,2
1Department of Orthopaedics, University Hospital Bristol; 2Avon Orthopaedic Centre, Southmead Hospital, Bristol, UK
Correspondence: Sam.jonas@doctors.org.uk
Submitted 11-04-11. Accepted 11-11-01
Open Access - This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use,
distribution, and reproduction in any medium, provided the source is credited.
DOI 10.3109/17453674.2012.672090
Background and purpose In detection of glenoid labrum pathol-
ogy, MR arthrography (MRA) has shown sensitivities of 88-100%
and specificities of 89-93%. However, our practice suggested that
there may be a higher frequency of falsely negative reports. We
assessed the accuracy of this costly modality in practice.
Patients and methods We retrospectively reviewed MRA
reports of 90 consecutive patients with clinical shoulder instabil-
ity who had undergone shoulder arthroscopy. All had a history of
traumatic anterior shoulder dislocation and had positive anterior
apprehension tests. All underwent arthroscopy and stabilization
during the same procedure. We compared the findings, using
arthroscopic findings as the gold standard in the identification of
glenoid labrum pathology.
Results 83 of the 90 patients had glenoid labrum tears at
arthroscopy. Only 54 were correctly identified at MRA. All
normal glenoid labra were identified at MRA. This gave a sensi-
tivity of 65% and a specificity of 100% in identification of all types
of glenoid labrum tear. 74 patients had anterior glenoid labral
tears that were detected at an even lower rate of sensitivity (58%).
Interpretation The sensitivity of MRA in this series was sub-
stantially lower than previously published, suggesting that MRA
may not be as reliable a diagnostic imaging modality in glenohu-
meral instability as previously thought. Our findings highlight the
importance of an accurate history and clinical examination in the
management of glenohumeral instability. The need for MRA may
not be as high as is currently believed.


Bankart (1923) first described damage to the anterior glenoid
labrum as being a cause of recurrent anterior dislocation.
Labral lesions are known to lead to higher rates of instabil-
ity. Open surgical stabilization is effective, and modern
arthroscopic techniques with suture anchors have similar suc-
cess rates (Hobby et al. 2007). Arthroscopic techniques have
the advantage of not violating the subscapularis tendon and
allow a diagnostic evaluation of the joint and capsulo-lig men-
tous structures prior to reconstructive surgery.
Various imaging modalities have been used to identify gle-
noid labral lesions, including arthrography, CT arthrography,
MRI, and MRI arthrography (MRA). MRA has proven to be
the most sensitive (Chandnani et al. 1993, Palmer et al. 1994).
Studies evaluating the sensitivity of MRA in the detection of
glenoid labral lesions, using arthroscopy as the gold standard,
have found high sensitivity (88–100%) and high specific-
ity (91–93%) (Flannigan et al. 1990, Chandnani et al. 1993,
Palmer et al. 1994, Palmer and Caslowitz 1995, Tirman et
al. 1997, Waldt et al. 2005, Holzapfel et al. 2010, Iqbal et al.
2010).
MRA is, however, more invasive than conventional MRI.
This has implications such as increased cost, longer waiting
list times, and an increased number of potential risks associ-
ated with the procedure (Newberg et al. 1985). Normal varia-
tions in anatomy may also reduce sensitivity (Beltran et al.
1997).
The high reported accuracy of standard 1.5-T MRA has lead
to it being integral to the pathway for many patients with ante-
rior instability, possibly at the expense of an accurate history
and clinical examination by a specialist shoulder surgeon. We
have therefore assessed the accuracy of MRA in a group of
patients undergoing anterior stabilization for clinical instabil-
ity. Our hypothesis was that 1.5-T MR arthrography is not as
sensitive as previously believed.
Patients and methods
90 consecutive patients (78 men) undergoing arthroscopic
anterior stabilization surgery were identified over a 3-year
period. Mean age was 27 (15–53) years. All patients had a his-
tory of traumatic anterior shoulder dislocation with persistent
symptoms of instability. 41 had dislocated twice or less, 47

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268 Acta Orthopaedica 2012; 83 (3): 267–270
had dislocated more than twice, and 2 had a history of per-
sistent subluxation. At clinical examination, all patients had
a positive anterior apprehension test. They all had a preopera-
tive MRA; this was thought to help in surgical planning.
52 of 90 arthrograms were performed and interpreted by
4 consultant radiologists with more than 10 years of mus-
culoskeletal experience. The remainder were performed and
interpreted by 3 other consultant radiologists with varying
musculoskeletal experience. Under fluoroscopic guidance,
using local anesthetic, 14 mL of iodinated contrast (contain-
ing dilute gadolinium: 1:200) was injected into the glenohu-
meral joint. Using dedicated shoulder coils, the following
sequences were obtained on a Siemens Avanto 1.5 Tesla MRI
scanner: axial T1 weighted gradient echo (high resolution,
thin slice thickness), axial TSE T1 weighted, sagittal oblique
and coronal oblique fat-suppressed SE T1 weighted, and cor-
onal oblique TSE T2 weighted images. The performing radi-
ologist then interpreted the MRI arthrograms. The criterion
used for the detection of glenoid labral pathology was that of
an obvious change in morphology or detachment visualized
in the labrum, or a change in signal intensity that would be
consistent with such a change. Only 1 radiologist interpreted
each MR arthrogram.
We performed an examination under anesthesia in all cases
before surgery. Arthroscopy was performed in the lateral decu-
bitus position with longitudinal traction. A posterior soft-spot
portal was created and a diagnostic arthroscopic evaluation of
the glenohumeral joint was performed with probing of the gle-
noid labrum via an anterior portal. Stabilization procedures,
including anterior labral repair and capsular imbrication, were
performed as required. A single consultant orthopedic shoul-
der surgeon with more than than 10 years of experience per-
formed all procedures.
This work was registered and approved by the North Bris-
tol NHS Trust clinical audit department (registration number
1414).
Statistics
Sensitivities, specificities, positive and negative predictive
values, and their respective 95% confidence intervals (CIs)
were calculated in the detection of glenoid labrum pathology
using SPSS software version 16.
Results (Table)
83 of the 90 patients had a glenoid labrum tear identified at
arthroscopy. These were all described as having substantial
labral damage, 74 with avulsion of the anteroinferior labrum
consistent with a Bankart lesion, 4 with avulsion of the pos-
terior labrum, and 7 with avulsion of the superior anterior
to posterior labrum consistent with a SLAP lesion. Of the
remaining 7 cases, 2 were described as having a mobile labrum
with a degree of anterior capsular laxity but no labral detach-
ment, 3 were described as cases of medial subluxation, and 2
were described as having an essentially normal but anteriorly
scuffed labrum. All patients underwent arthroscopic stabiliza-
tion of the shoulder.
MRA allowed correct identification of the 2 normal labra,
the 3 cases of medial labral subluxation, and the 2 cases of
capsular laxity. Of the 83 cases with labral avulsion, 43 were
correctly identified as having anterior tears, 3 were correctly
identified as having posterior tears, and 5 were correctly iden-
tified as having SLAP lesions. 1 was reported as having a pos-
terior tear and 2 were reported as having a SLAP lesion, all 3
of which had anterior tears at arthroscopy. 29 patients were
reported as having a normal labrum: 28 had an anterior tear
and 1 had a posterior tear.
Overall 54 of 83 patients with some sort of labral pathol-
ogy were identified at MRA, giving a sensitivity of 65% (CI:
0.54–0.74) and a specificity of 100% (CI: 0.65–1.00). Most
patients (74 of 83) with labral pathology were found to have
anterior tears. Of these, 43 were correctly identified at MRA,
giving a sensitivity of 58.1% (CI: 0.47–0.69) and a specificity
of 100% (CI: 0.81–1.00) in detection of anterior labral tears.
Discussion
Although several studies have examined the sensitivity of the
MR arthrogram in detecting glenoid labral lesions, the major-
ity had small sample size and identified the patient group at
the time of arthroscopy—retrospectively evaluating those
with proven labral lesions rather than prospectively includ-
ing all clinically unstable shoulders that were indicated for
surgery (Chandnani et al. 1993, Palmer et al. 1994, Waldt et
al. 2005).
Sensitivity and specificity of MRA with arthroscopy findings as gold standard
Finding at arthroscopy

No. found
at MRA
No. found at
arthroscopy
True
positive
True
negative
False
positive
False
negative
Sensitivity of MRA

Specificity of MRA

Anterior labral tear
Posterior labral tear
Slap lesion
Any labral tear
Normal labrum
43
4
7
54
36
74
4
5
83
7
43
3
5
54
7
16
85
83
7
54
0
1
2
0
31
1
0
29
0
0.58 (0.47–0.69)
0.75 (0.30–0.95)
1.00 (0.56–1.00)
0.65 (0.54–0.74)
1.00 (0.65–1.00)
1.00 (0.81–1.00)
0.98 (0.94–0.99)
0.97 (0.91–0.99)
1.00 (0.65–1.00)
0.65 (0.54–0.74) 29

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Acta Orthopaedica 2012; 83 (3): 267–270 269
Palmer and Caslowitz (1995) and Waldt et al. (2005) are cur-
rently the largest published studies (n = 121 and n = 104). The
subjects were identified at arthroscopy and the MRAs were
reviewed retrospectively. Waldt et al. showed sensitivities of
88% for detection of labro-ligamentous damage and 77% for
correct diagnosis of specific lesion types. Palmer and Caslow-
itz showed sensitivity and specificity of 92% for identification
of labral lesions. Other, smaller studies have had sensitivities
ranging from 91% to 100% (Flannigan et al. 1990, Chandnani
et al. 1993, Palmer et al. 1994, Waldt et al. 2005, Holzapfel
et al. 2010, Iqbal et al. 2010). These smaller studies included
subjects with shoulder instability similar to what we describe
here, but several used other indicators for inclusion such as
shoulder pain, which we did not use.
Our aim was to assess the sensitivity of the preoperative
MRA in those patients who were indicated for arthroscopic
stabilization on clinical grounds. We found substantially lower
sensitivity (65%) in detection of labro-ligamentous damage
found at arthroscopy than has been reported in other published
studies (Flannigan et al. 1990, Chandnani et al. 1993, Palmer
et al. 1994, Palmer and Caslowitz 1995, Tirman et al. 1997,
Waldt et al. 2005). This difference may be explained by the
fact that the 2 largest published studies (Palmer and Caslowitz
1995, Waldt et al. 2005) were performed by experienced and
specialized musculoskeletal radiologists. The reliability of
interpretation of MRA may be more accurate in their hands.
However, our series—and most surgeons’ practices—rely on
MRAs being reported by many different radiologists of varied
experience and expertise. This lower sensitivity may be a more
accurate reflection of routine clinical practice.
With a specificity of 100%, the presence of a normal MRA
in conjunction with a normal examination would appear to be
reassuring confirmation of one’s clinical acumen. However,
bearing in mind the sensitivity (65%), a “normal” MRA should
not be used as a rationale for not operating on a symptomatic
individual. Most of our patients had anterior labral tears. Thus,
the results may not be applicable to the interpretation of MRA
in detection of other types of glenoid lesions.
Recent studies by Magee and Williams (2006) and Magee
(2009) have shown that 3-T MR arthrograms may have higher
levels of sensitivity in the detection of glenoid labrum lesions
(95–98%) than those using 1.5-T, which is the general conven-
tion. This would make this modality a much more attractive
diagnostic tool. However, until such MRAs are in general use,
we should consider 1.5-T MRA as our everyday standard.
Although our study has a similar sample size to those
reported previously, it has several shortcomings that could
not be altered due to the retrospective nature of the study
design. All the arthroscopies were performed by a specialist
shoulder surgeon, but the MR arthrograms were performed
by 7 different radiologists, only 4 of whom were musculo-
skeletal specialists. None of the images were checked by a
second radiologist to confirm the result. This difference in
level of radiologist training and experience may explain some
of the reduced sensitivity and reflects practice in a standard
hospital. This is consistent with work previously published by
Theodoropoulos et al. (2010). Sample populations from pre-
vious studies included normal shoulders, but our study only
included patients who had clinical symptoms severe enough to
warrant a surgical intervention. These patients were therefore
more likely to have pathology when examined at arthroscopy.
Our findings highlight the importance of an accurate history
and a clinical examination by a specialist shoulder surgeon in
the management of glenohumeral instability. Indeed, in these
hands, the need for costly investigations such as MRA might
be reduced and the pathway of the patient might be made
faster and more efficient.
SCJ: main author; data collection and analysis. MJW: contribution to writing
and editing of paper. PPS: supervising consultant; initiator of study; contribu-
tion to editing of paper.
We thank Charles Wakeley, consultant radiologist, University Hospital Bris-
tol, for providing technical advice and for performing many of the original
investigations.
No competing interests declared.

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