Dominik Nörenberg1,2, Marco Armbruster1, Yi-Na Bender2, Thula Walter2, Gerd Diederichs2, Bernd Hamm2, Ben Ockert3, and Marcus R. Makowski2,4
1Department of Clinical Radiology, Munich University Hospitals Campus Großhadern, Germany, Munich, Germany, 2Department of Radiology, Charité, Berlin, Germany, Berlin, Germany, 3Department of Trauma and Orthopedic Surgery, Shoulder and Elbow Service, Munich University Hospitals Campus Großhadern, German, Munich, Germany, 4King’s College London, Division of Imaging Sciences and Biomedical Engineering, London, United Kingdom, London, United Kingdom
Synopsis
Shoulder pain is regarded as the second most common musculoskeletal disorder in the general population. 44 % of shoulder pain syndromes are related to subacromial shoulder impingement (SAIS) due to rotator cuff tear (RCT) and glenohumeral joint arthritis. Especially subacromial spur formation is associated with SAIS and RCT. Our study demonstrates that SWMRI allows for a reliable detection and precise 3D-localization of subacromial spur formation under the coracoacromial arch in patients with SAIS and provides superior evaluation of diamagnetic spur formation compared to standard shoulder MRI using conventional radiography as a reference.Introduction
Shoulder pain is regarded as the second most common musculoskeletal disorder in the general population [1]. 44% of shoulder pain syndromes are related to subacromial shoulder impingement (SAIS) due to rotator cuff tear (RCT) and glenohumeral joint arthritis [2]. Extrinsic and intrinsic factors may cause calcified subacromial spur formation which progressively narrows the subacromial space causing SAIS and RCT [3-6]. Early detection and assessment of the exact size and location of subacromial spurs is the prerequisite for further treatment to prevent following pain syndromes. Conventional radiography (CR) and MRI are used complimentary for the clinical assessment of SAIS. Due to its excellent soft tissue contrast and high spatial resolution, fluid-sensitive T2-weighted sequences are used to characterize the inflammatory activity of associated soft tissue pathologies (e.g. tendonitis, bursitis). However, calcified subacromial spur formation cannot reliably be detected on standard shoulder MRI sequences. Therefore, 2D conventional radiography is still performed as the reference standard, despite the use of ionizing radiation. In the past, the use of susceptibility-weighted magnetic resonance imaging (SWMRI) was shown to reliably differentiate calcifications from tissue artefacts and/or haemorrhage based on their magnetic susceptibility mainly in the brain and in the prostate [7-9]. Recently, SWMRI was successfully shown to provide superior evaluation of tendon calcifications in patients with calcific tendonitis of the rotator cuff compared to standard shoulder MR [10].The purpose of this study was to compare SWMRI to standard shoulder MRI and CR for the detection of subacromial spurs in patients with clinically suspected SAIS.
Methods
44 patients with clinically suspected SAIS were included. 23 patients were positive (Figure 1) and 21 were negative (Figure 2) for subacromial spur formation. All patients underwent CR, standard T1/T2-weighted shoulder MRI and SWMRI, including magnitude and phase images. The size of subacromial spurs was measured to assess intermodality-correlations. Detection rate, sensitivity, specificity and interobserver-agreements were calculated. Linear regression was applied to determine the relationship between size measurements on CR and MRI.
Results
23 subacromial spurs were detected on CR (reference standard). The majority of these lesions (n=21, 91%) could be clearly identified as spur formation on SWMRI, using a combination of SWI magnitude and phase images (Figure 1). Standard T1/T2-imaging sequences only delineated 11 lesions (48%). On standard MRI, 5 lesions were falsely classified as subacromial spurs due to tissue artifacts. SWMRI was 98% sensitive (CI=0.92-1) and 91% specific (CI=0.788-1) for the identification of calcifications compared to CR. Standard MRI only achieved a sensitivity of 48% (CI=0.185-0.775) and a specificity of 81% (CI=0.642-0.978). Regarding the size of calcifications, SWI showed a good correlation with CR (R2=0.75; p<0.0001), while slightly overestimating lesion size (SWI=5.7±1.4mm; CR=4.3±1.2mm; mean±standard-deviation). SWI and CR achieved higher interobserver-agreements between both readers (R2=0.73; R2=0.74, p<0.0001) compared to standard MRI (R2=0.13; p<0.0001).
Conclusion
SWMRI enables the detection of subacromial spur formation in patients with SAIS with a higher sensitivity and specificity compared to standard shoulder MRI with CR as reference standard. SWMRI may add useful information to the MR based assessment of atraumatic shoulder joints.
Acknowledgements
No acknowledgement found.References
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