KINEMATIC MRI OF THE SHOULDER

Objective: Clinical evaluation of shoulder pain can be difficult. Pain in the shoulder is often dynamic/positional, and it can often be elicited only during specific activity or function. Soft tissue deforms or changes in shape through motion. These complex interrelationships at the glenoid humeral joint require dynamic studies to accurately evaluate normal anatomy and abnormal pathology. The objective of our study was to evaluate the use of a dynamic cyclic cine imaging to evaluate the glenoid humeral joint. Materials and Methods: Kinematic MRI was performed using axial 5 mm sections of the gradient echo and dedicated shoulder surface coil. The patient's arm was placed in the Bonutti cine shoulder system and allowed fixed incremental rotational movement of the shoulder at 10-degrees intervals. Images were reformatted onto a dynamic cine motion by oscillating from internal to external rotation then back to internal rotation. A total of 24 asymptomatic shoulders and 35 symptomatic painful shoulders were studied. Results: Normal variations in the glenoid labrum were readily identified. The glenoid labrum in external rotation is taunt and triangular with well-identified capsular attachments. In neutral rotation the labrum often has increased signal and the middle glenoid humeral ligament occasionally blends with the labrum, making identification difficult. In maximum internal rotation the labrum is rounded and occasionally infolded. Variations in signal through the labrum are not indicative of tears. Capsular attachment must be followed from maximum internal to external rotation to identify stripping. The middle and inferior glenoid humeral ligaments often blend with labrum and internal rotation; however, in external rotation they can be identified as distinct and separate structures. Subcoracoid impingement can be identified in maximum internal rotation with a narrowing of the subcoracoid space to < 11 mm and buckling of the subscapularis and lesser tuberosity against the coracoid process. Conclusion: Accurate evaluation of the capsular/labral complex requires cine studies for accurate diagnosis. Signal changes alone or labral morphology alone varies through rotation, and static MRI does not accurately assess these morphologic changes, which vary with extremity position. Capsular attachments can be identified with cine studies accurately and reproducibly. Subcoracoid impingement can be identified with a narrowing of the coracohumeral distance to < 11 mm in internal rotation, which is suggestive of pathology.