Shoulder: one posterior view, before and after reduction

Answer a. In this view the glenoid sits medially, and the humeral head lies lateral to it. The acromion lies above the scapular spine, outside this window. The coracoid process sits at the front of the shoulder, so a posterior probe does not show it.

Answer a. An anterior dislocation moves the head forward, away from a probe on the back of the shoulder, so it lies deep. A posterior dislocation brings the head closer to the probe. In normal alignment the head sits level with the glenoid rim. A rotator cuff tear changes the tendon, not the position of the head.

Answer a. The scan confirms position and movement, so it answers the other three. It does not reliably show a fracture of the greater tuberosity, the glenoid rim or the humeral neck. Use your local imaging policy and the clinical picture to decide on an X-ray. The pre-reduction scan has already shown the direction of the dislocation.

Answer c. The posterior window lies below the scapular spine, where the probe looks straight at the back of the glenohumeral joint with the glenoid and humeral head side by side. An anterior window works but is harder to reach in a guarding patient. The outer arm and the supraclavicular fossa do not show the joint line.

Answer d. A reduced head sits level with the glenoid rim and turns in place as the arm rotates. The glenoid is part of the scapula, so it stays still. A small joint effusion does not confirm reduction. A head which does not turn with the arm suggests it is not sitting in the joint.