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Innervation of the muscles in the posterior compartment of the arm and forearm is provided by the radial nerve. The vascular supply can be disrupted if there is considerable displacement of shaft fragments. The blood supply to the humeral shaft is supplied by the axillary and brachial artery, the latter branches to form the radial and ulnar artery ( figure 5 and figure 6 and figure 7). The tendon of the long head of the biceps brachii muscle passes between the lesser and greater tuberosities as it courses from its origin on the superior portion of the glenoid to its insertion on the radius ( figure 4). The biceps brachii and triceps muscle groups attach further distally. The pectoralis major muscle inserts on the proximal shaft while the deltoid muscle attaches to the midshaft. The humeral shaft supplies the attachment for a number of powerful muscles ( figure 3). For the purposes of fracture classification, the lesser tuberosity marks the boundary between the proximal humerus and the midshaft. The lesser tuberosity of the humerus is located on the anterior surface of the humerus and provides the attachment for the subscapularis muscle. The greater tuberosity, located lateral to the humeral head and on the superior aspect of the humerus, provides the attachment for three of the rotator cuff muscles: supraspinatus, infraspinatus and teres minor ( figure 2). The distal humerus articulates with the radius and ulna at the elbow. The muscles and tendons of the rotator cuff, the acromion, and ligamentous attachments such as those between the coracoid process of the scapula and the acromion, serve to both stabilize the glenohumeral articulation and provide for a wide range of motion of the shoulder joint. The proximal humerus articulates with the glenoid of the scapula to form the shoulder joint ( figure 1). (See "Stress fractures of the humeral shaft" and "Proximal humeral fractures in adults".)ĬLINICAL ANATOMY - The humerus is the largest bone in the upper extremity. Stress fractures of the humeral shaft and proximal humeral fractures are discussed separately. Nonstress fractures of the midshaft (diaphysis) of the humerus will be reviewed here.

The majority of both proximal and midshaft humerus fractures are nondisplaced and can be treated conservatively (nonsurgically). INTRODUCTION - Fractures of the humerus can occur proximally, at the shaft, or distally.