The patient positioning in the MR of the shoulder: advantages and disadvantages of the internal, external and neutral rotation of the arm

Abstract

Tailoring the patient positioning in Magnetic Resonance Imaging, according to patient needs and clinical questions, is the key to successfully completing a highly diagnostic exam. This is evident in the MRI study of the shoulder in which, for clinical questions such as subacromial conflict syndrome and suspected lesions of the Rotator Cuff, is essential to obtain an accurate distension of the tendons, in order to make reporting free from doubtful or improper diagnoses. The possible arm placements for this kind of examination are: intra-rotation, extra-rotation, or neutral position. Each of them presents advantages and disadvantages that the MR radiographer must be able to assess in conjunction with the patient's conditions and the degree of cooperation. Intra-rotation is clearly the position that ensures greater comfort and stability to the patient and this results in the absence of artifacts from movement, but on the other hand it does not allow the distension of the supraspinatus tendon and the long head of the brachial biceps, it causes the overlap of supraspinatus tendon with infraspinatus one in the oblique coronal sequences, thus leading to misdiagnosis or dubious diagnosis. The arm’s neutral position is ideal for moderately collaborating patients and promotes a mild relaxation of the tendons and the absence of movement artifacts. Finally, the arm’s position in extra-rotation, obtained with variable positioning of pads under the forearm, ensures the collaboration of a substantial number of patients and tendons are well stretched and free from overlap, addressing reliable diagnoses, despite having, as the only disadvantage, a possible lower degree of cooperation of the patient.