Abnormal systemic arterial morphology Posterior humeral circumflex artery occlusion 2026-02-24T07:41:49Z The axillary artery can be compressed by the humeral head owing to abduction and external rotation of the shoulder joint caused by overhead motion, as typified by pitching. Blockage of the posterior circumflex humeral artery (PCHA), which arises from the third part of the axillary artery and supplies the shoulder joint and a number of its associated muscles. The lesion can be ascertained angiographically, whereby dye is injected both with patient's humerus at the side of the body and again with shoulder held in abduction and external rotation. Test is positive if there is evidence of PCHA occlusion with arm in abduction and external rotation but artery is patent when arm is held at the side.