The ulna is composed of a body and two epiphyses - distal and proximal. The body has a triangular bone
shape, there are three edges: palmar (front), external (intercostals) and the dorsal (back) and three surfaces.
The structure of the ulna
The front edge of the bone has a rounded shape, the rear edge to the rear, and the interosseous edge has a pointed shape facing the radial bone. On the ulna is nutritious hole, leading to proximal direction nutritious tubule. On top of the front surface of the bone at the interface between the upper end and body located tuberosity. The rear surface of the bone is swung back and medial - toward the inner side of the forearm.
The proximal epiphysis is slightly thickened form and goes to the top of the olecranon. Front this process trochlear notch busy that the underside of the limited coronal ridge. On the outside of the ulnar coronoid process is cutting - the place of the articular circumference of the radial head with ulna. On the back side of the radial cutting begins instep ridge that goes down and reaches the upper edges of the body of the bone.
The distal epiphysis has a slightly rounded shape. It is clearly possible to see the head of the ulna. Its surface is smooth and concave, facing the wrist. At its periphery is articular surface - articular circumference of bones connecting with the radius. Medialnozadnyaya surface of the head goes in styloid process, which is well detectable through the skin.
Fractures of the ulna
ulna between the middle and the top of its third or in the upper third accompanied by dislocation of the radial head, which can be displaced upward and forward or up and out.
Thus, the displacement of the radial head after fracture of the ulna often causes damage to the branch of the radial nerve. Such damage often occurs as a result of a strong direct impact, such as a stick on the forearm, the exposed forward and upward. As a result of this impact fracture occurs with a significant fragment offset at an angle from the back side open to the ulnar side, and as a consequence, there is a dislocation of the radial head. Such damage is characteristic for defending a man trying to parry the blow to the head, called the damage Montedzha or parrying fracture.
As a result of the fracture back strongly curved contour of the forearm and the elbow is extended as a result of dislocation of the head. During palpation the patient feels a sharp pain, and the head of the radius bulges.
Any movement in the elbow joint (passive, active, supinatsionnye, pronation) are accompanied by severe pain, so limited. In passive elbow flexion observed springy movement.