The humerus is the largest bone in the upper extremity. The proximal humerus relates to the upper part of the humerus that articulates with the scapula, comprising the shoulder joint. Proximal humerus fracture repair, therefore, is a very common problem for many people.
The articular surface of the proximal humerus approximates the hemisphere. This is known as the humeral head. Three identifiable columns that blend into the long shaft, or diaphysis, of the bone, support the humeral head.
The muscles about the shoulder are divided into a deep set of muscles, referred to as the rotator cuff, and a more superficial set of muscles, such as the deltoid and the pectoralis. The muscles of the rotator cuff insert into the proximal humerus at prominences known as tuberosities and are key to the proper functioning of the shoulder joint. The large muscle that envelops the shoulder joint is the deltoid. Certain injuries can interrupt the blood supply to the humeral head, leading to bone infarction or avascular necrosis.
The bone infarct or avascular necrosis of the humeral head may be only partial, such that the bone may recover and heal uneventfully.