A patient in septic shock is brought to the resuscitation area with profound peripheral shutdown. Multiple attempts at peripheral intravenous cannulation have failed, and the team leader asks you to obtain immediate intraosseous access. You choose the proximal humeral site to facilitate rapid drug and fluid delivery while definitive vascular access is being arranged.

With the patient’s hand placed palm-down over the abdomen and the elbow adducted, you palpate proximally along the anterior shaft of the humerus until you identify the greater tubercle and the anatomical neck.

What is the correct insertion landmark for proximal humeral intraosseous access?