Review Question - QID 4422

The artery labeled 4 on the arteriogram is the posterior humeral circumflex artery, which is the primary blood supply to the humeral head, and most likely to lead to AVN when injured.

While previous literature suggested that the anterior humeral circumflex artery provided the main blood supply to the humeral head, more current literature supports the posterior circumflex humeral artery as the predominant blood supply. Despite the anterior humeral circumflex artery being disrupted in approximately 80% of proximal humeral fractures, the occurence of resultant osteonecrosis is still infrequent. This inconsistency suggests a greater role for the posterior humeral circumflex artery.

Hettrich et al. performed a cadaveric study assessing the vascularity of the proximal part of the humerus. They injected gadolinium into the axillary artery proximally, and then either the anterior humeral circumflex artery or the posterior humeral circumflex artery was ligated. MRI was then performed and the specimens were dissected to determine the dominant blood supply. They found that the posterior humeral circumflex artery provided 64% of the blood supply to the humeral head, whereas the anterior humeral circumflex artery supplied 36%. The posterior humeral circumflex artery also provided significantly more of the blood supply in three of the four quadrants of the humeral head.

Hertel et al. assessed predictors of humeral head ischemia after fractures of the proximal humerus. Their results concluded that the most predictive factors for humeral head ischemia included the >8mm length of the dorsomedial metaphyseal extension, disrupted integrity of the medial hinge, and the complicated and communited fracture types.

Crosby et al. used tetracycline labeling as a measure to study humeral head viability after 3- or 4-part proximal humerus fractures taken at the time of hemiarthroplasty. Their findings showed that the vascular supply was preserved in all of the resected specimens including displaced three- and four-part proximal humerus fractures especially in younger patients. They recommended that with intact vascularity to the humeral head, head-preserving techniques utilizing stable, site-specific fixation and minimal dissection should be considered in the treatment of displaced three- and four-part proximal humerus fractures.

Illustration A shows a labeled arteriogram of the blood vessels near the shoulder.