What position should the head and arm be in during Adson's test?

During Adson's test, the correct position for the head and arm involves rotating the head towards the arm while simultaneously extending and externally rotating the arm. This position is designed to assess for thoracic outlet syndrome, specifically by evaluating the relationship of the subclavian artery and the brachial plexus to structures in the thoracic outlet.

When the head is turned towards the affected arm, it narrows the space in the thoracic outlet, which can help discern if there's compression on neurovascular structures. At the same time, extending and externally rotating the arm further opens the shoulder joint and stretches the surrounding structures, allowing for a thorough assessment of signs related to thoracic outlet syndrome.

The test is positive when there is a decrease or loss of the radial pulse on the side being tested, indicating potential vascular compression. Therefore, the position characterized by rotating the head towards the arm and extending and externally rotating the arm is integral to eliciting the test’s intended response.