Sunday 26 June 2016

Humerus-Fractures of the Proximal End of the Humerus-Humeral Head Fractures-Greater Tuberosity Fractures-Lesser Tuberosity Fractures-Surgical Neck Fractures-Fractures of the Shaft of the Humerus-Fractures of the Distal End of the Humerus-

Humerus
The humerus articulates with the scapula at the shoulder joint and with the radius and ulna at the elbow joint. The upper end of the humerus has a head, which forms about one third of a sphere and articulates with the glenoid cavity of the scapula. Immediately below the head is the anatomic neck. Below the neck are the greater and lesser tuberosities, separated from each other by the bicipital groove. Where the upper end of the humerus joins the shaft is a narrow surgical neck. About halfway down the lateral aspect of the shaft is a roughened elevation called the deltoid tuberosity. Behind and below the tuberosity is a spiral groove, which accommodates the radial nerve The lower end of the humerus possesses the medial and lateral epicondyles for the attachment of muscles and ligaments, the rounded capitulum for articulation with the head of the radius, and the pulley-shaped trochlea for articulation with the trochlear notch of the ulna. Above the capitulum is the radial fossa, which receives the head of the radius when the elbow is flexed. Above the trochlea anteriorly is the coronoid fossa, which during the same movement receives the coronoid process of the ulna. Above the trochlea posteriorly is the olecranon fossa, which receives the olecranon process of the ulna when the elbow joint is extended

Fractures of the Proximal End of the Humerus
Humeral Head Fractures
Fractures of the humeral head can occur during the process of anterior and posterior dislocations of the shoulder joint. The fibrocartilaginous glenoid labrum of the scapula produces the fracture, and the labrum can become jammed in the defect, making reduction of the shoulder joint difficult
Greater Tuberosity Fractures
The greater tuberosity of the humerus can be fractured by direct trauma, displaced by the glenoid labrum during dislocation of the shoulder joint, or avulsed by violent contractions of the supraspinatus muscle. The bone fragment will have the attachments of the supraspinatus, teres minor, and infraspinatus muscles, whose tendons form part of the rotator cuff. When associated with a shoulder dislocation, severe tearing of the cuff with the fracture can result in the greater tuberosity remaining displaced posteriorly after the shoulder joint has been reduced. In this situation, open reduction of the fracture is necessary to attach the rotator cuff back into place.

Lesser Tuberosity Fractures
Occasionally, a lesser tuberosity fracture accompanies posterior dislocation of the shoulder joint. The bone fragment receives the insertion of the subscapularis tendon, a part of the rotator cuff.

Surgical Neck Fractures
The surgical neck of the humerus , which lies immediately distal to the lesser tuberosity, can be fractured by a direct blow on the lateral aspect of the shoulder or in an indirect manner by falling on the outstretched hand.

Fractures of the Shaft of the Humerus
Fractures of the humeral shaft are common; displacement of the fragments depends on the relation of the site of fracture to the insertion of the deltoid muscle. When the fracture line is proximal to the deltoid insertion, the proximal fragment is adducted by the pectoralis major, latissimus dorsi, and teres major muscles; the distal fragment is pulled proximally by the deltoid, biceps, and triceps. When the fracture is distal to the deltoid insertion, the proximal fragment is abducted by the deltoid, and the distal fragment is pulled proximally by the biceps and triceps. The radial nerve can be damaged where it lies in the spiral groove on the posterior surface of the humerus under cover of the triceps muscle.


Fractures of the Distal End of the Humerus
Supracondylar fractures are common in children and occur when the child falls on the outstretched hand with the elbow partially flexed. Injuries to the median, radial, and ulnar nerves are not uncommon, although function usually quickly returns after reduction of the fracture. Damage to or pressure on the brachial artery can occur at the time of the fracture or from swelling of the surrounding tissues; the circulation to the forearm may be interfered with, leading to Volkmann’s ischemic contractureThe medial epicondyle (Fig. 9.10) can be avulsed by themedial collateral ligament of the elbow joint if the forearm is forcibly abducted. The ulnar nerve can be injured at the time of the fracture, can become involved later in the repair process of the fracture (in the callus), or can undergo irritation
on the irregular bony surface after the bone fragments are
reunited
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