Glenohumeral relationships during physiologic shoulder motion and stress testing: initial experience with open MR imaging and active imaging-plane registration.

PURPOSE To test the hypotheses that open dynamic magnetic resonance (MR) imaging can (a) be used to evaluate and define normal shoulder motion in active joint motion and muscle contraction and (b) be used in conjunction with physical examination. MATERIALS AND METHODS With an open-configuration, 0.5-T MR imaging system and active image-plane tracking, 10 shoulders were studied in five asymptomatic subjects to establish normal patterns of glenohumeral motion during abduction and adduction and internal and external rotation. Preliminary studies of physical examination during MR imaging, in which a physician examiner applied mechanical force to the humeral head, were also performed. RESULTS During abduction and adduction and internal and external rotation maneuvers with active subjects muscle contraction, the humeral head remained precisely centered on the glenoid fossa in all asymptomatic subjects, which is in agreement with findings of previous radiographic studies. Application of force to the humeral head by an examiner was associated with as much as 6 mm of anterior translation and 13 mm of posterior translation. CONCLUSION Dynamic MR imaging of the glenohumeral joint is possible over a wide range of physiologic motion in vertically open systems. Use of an MR tracking coil enabled accurate tracking of the anatomy of interest. These preliminary measurements of normal glenohumeral motion patterns begin to establish normal ranges of motion and constitute a necessary first step in characterizing pathologic motion in patients with common clinical problems such as instability and impingement.