Page:Structure and functions of the body; a hand-book of anatomy and physiology for nurses and others desiring a practical knowledge of the subject (IA structurefunctio00fiskrich).pdf/186

 in cases of fracture their relative position is of considerable importance as showing the amount of deformity.

The two forearm bones are more frequently broken together than separately and generally by direct violence, the lower fragment being usually drawn up by the action of the flexor and extensor muscles and producing a swelling on the palmar surface of the forearm. Indirect violence usually causes fracture of the radius only. In both cases, but especially in fracture of both bones, there is a tendency for membrane to get between the fragments, so the arm is put up in splints with the hand midway between pronation and supination in order to separate the bones as far as possible. Care must be taken not to have the bandage too tight or gangrene of the fingers may result. In most fractures of the arm it is put up bent, but in fracture of the olecranon it is put up fully extended, as the fragment is sure otherwise to be displaced by the pull of the triceps. In fact, the olecranon is sometimes fractured by the muscular force of the triceps, though usually its fracture, which is frequent, is due to direct violence. The ulna is also often fractured in the middle by direct violence or the styloid process may be broken. Fracture of the neck or shaft of the radius is very common, the most important arm fracture being that of the lower end of the radius or Colles' fracture. This and the corresponding fracture in the leg, Pott's fracture, are two of the commonest fractures. In dislocation of the wrist the normal relation of the two styloid processes remains unchanged, but in Colles' fracture the lower fragment often projects on the back of the hand, making a typical deformity called the silver fork deformity.

The bones of the wrist and hand had best be described before the forearm muscles are taken up, as the muscles of the forearm are distributed largely to the fingers.

The Wrist.—The wrist or carpus is made up of eight bones arranged in two rows of four each. In the first