A 28-year-old male athlete presents to the emergency department with severe left shoulder pain after a collision during a football match. He reports his arm was abducted and externally rotated at the moment of impact. On examination, the shoulder has a "squared-off" contour with loss of normal deltoid roundness, and the patient holds his arm in slight abduction and external rotation. An AP shoulder X-ray is obtained. The structure marked **A** (humeral head) is noted to be displaced antero-inferiorly. Before attempting reduction, which of the following is the MOST critical clinical action to perform?

Explanation

## Why "Test axillary nerve function by assessing sensation over the lateral deltoid (regimental badge area) and document the findings" is right The glenohumeral joint is the most mobile joint in the body, sacrificing stability for mobility. Anterior shoulder dislocation (95% of all dislocations) occurs when the humeral head **A** is forced into antero-inferior displacement, typically via abduction and external rotation. Axillary nerve injury is a common complication of anterior shoulder dislocation, usually presenting as neurapraxia. The critical clinical imperative is to test axillary nerve function BEFORE reduction and document the baseline status. This protects the clinician from liability for nerve injuries caused by the dislocation itself, and establishes whether any post-reduction nerve deficit is attributable to the reduction procedure or the original injury. Sensation over the lateral deltoid (regimental badge area) is the standard bedside test for axillary nerve integrity (Gray's Anatomy 42e Ch 47; Apley 10e). ## Why each distractor is wrong - **Obtain an MRI to rule out associated rotator cuff tears before reduction**: While rotator cuff tears are indeed associated with anterior dislocation (especially in older patients), MRI is not performed before reduction. Reduction is urgent and should not be delayed for imaging. MRI is obtained post-reduction if clinical suspicion for rotator cuff injury is high. - **Perform immediate closed reduction using the Kocher technique to minimize soft tissue damage**: Although closed reduction is appropriate and Kocher is a valid technique, this is NOT the most critical action before reduction. Neurovascular assessment must precede the reduction procedure to establish baseline status and medico-legal documentation. - **Administer intravenous antibiotics to prevent infection at the dislocation site**: There is no indication for prophylactic antibiotics in a closed dislocation. Antibiotics are reserved for open dislocations or when there is skin breach. **High-Yield:** Always document axillary nerve function (lateral deltoid sensation) BEFORE shoulder reduction to avoid medicolegal liability for iatrogenic nerve injury. [cite: Gray's Anatomy 42e Ch 47; Apley 10e]