| Abstract: |
Shoulder instability is associated with abnormalities of the joint capsule, labrum, glenohumeral ligaments, rotator cuff, and/or surrounding musculature. Magnetic resonance (MR) imaging are accurate mean of evaluating potential causes of shoulder instability .In magnetic resonance (MR) imaging of joints, diagnostic success requires delineation of complex anatomic structures and demonstration of subtle abnormalities. MR arthrography extends the capabilities of conventional MR imaging because contrast solution distends the joint capsule, outlines intraarticular structures, and leaks into abnormalities.On MR arthrography the majority of anatomic variants are easily distinguished from labral abnormalities. Articular cartilage that undercuts the labral fibrocartilage is rarely a source of diagnostic difficulty because the cartilage has lower signal intensity than the contrast solution.The aim of this work is to evaluate the role of magnetic resonance arthrography in diagnosis of patients with shoulder instability .Twenty five patients were included in this study 22 males and 3 females .Their ages ranged from 18 to 47 years .All of them were complaining from shoulder pain with history of shoulder dislocation ,20 patients had history of recurrent dislocation ,5 patients dislocated once, they were suspected clinically to have glenohumeral instability .All patients were clinically evaluated ,and then subjected for imaging modalities including plain x-ray, conventional MR, direct & indirect MR Arthrography , the diagnosis was confirmed by arthroscopy.Anterior instability was the most common finding in our study as Bankart lesion were found in 21 patient, posterior instability was deteced in one patient while superior labral lesion (SLAP lesions ) were found in 3 patients.Labral lesion: Labral tears were visualized as contour deficiencies of the labrum, filling of a torn labrum with contrast material, and opacification of the space between the detached labrum and the glenoid surface.Bankart lesion: On MR arthrograms, the Bankart lesion was visualized as a fragment of labrum attached to the anterior band of the IGHL and to the ruptured scapular periosteum floating in the anteroinferior aspect of the glenohumeral joint.Some anatomic variations that are differentiated easily by using MR arthrography present diagnostic pitfalls with conventional MRI.• Normal, intermediate-signal-intensity labral fibrocartilage at the base of the anterior labrum rarely presents a problem because the cartilage has signal intensity lower than that of the contrast medium.• Normal GHLs often can simulate torn labral fragments on conventional MRI imaging . With MR arthrography, intact GHLs can be visualized to be separate from the labral origins of the distended capsule, and these are not confused with torn fragments.• The sublabral sulci that normally fill with contrast medium remain a diagnostic pitfall and cannot be differentiated from labral tears unless the labrum is separated from the glenoid rim. Sublabral sulci involve the interface of the labrum with the articular cartilage and are located at the labral-bicipital junction or between the origins of the MGHLs and IGHLs. Complete labral detachment (sublabral hole) may also represent a normal variant.Indirect MR Arthrography takes advantages of bulk flow and the diffusion of contrast material from vascular supply into the synovial tissue lining the bursae, joint capsule, and tendon sheaths, ultimately pooling into the joint space.Indirect MR arthrography in this study has proved to be superior to conventional MR in delineating the intra-articular structures of the shoulder .Indirect MR arthrography is more effective in demonstration of glenolabral and rotator cuff injuries than is conventional MR imaging of the shoulder.Direct MR Arthrography can differentiate well between partial thickness and small full-thickness rotator cuff tears as presence of contrast at the subacromial subdeltoid bursa is diagnostic for full-thickness tear.MR arthrography accurately shows the relationship of labral lesions to the origins of the glenohumeral ligaments and helps in distinction between stable and unstable lesions.In conclusion ,MR imaging including MR arthrography ( direct&indirect) are powerful tool in the diagnosis and follow-up of patients with various shoulder pathologies. age and symptomatology should guide the choice of conventional MR imaging , indirect MR Arthrography , or direct MR arthrography .
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