Abstract
An attempt has been made to describe some of the ways in which the element of rotation, which is so important a part of the function of the normal forearm, has a bearing upon the mechanism and treatment of forearm injuries. In particular, distinction is drawn between those injuries in which the shaft of the radius remains in continuity, and those in which there is a complete fracture of the bone. In the former, rotation of the hand in the reduction will be transmitted to the upper end of the radius, and extremes of rotational movement may safely be used to obtain and hold a reduction. In the latter there is likely to be a rotational deformity between the two radial fragments, and the lower radial fragment must be placed in accurate rotational alignment with the upper. In the first group reduction, and in certain cases immobilisation, in full pronation or full supination has been shown to have a place in the treatment of those cases in which a rotation violence has shaped the pattern of the injury. Soft tissues may be used to guide and hold a reduction in a rotational injury, just as in injuries of other types. An injury caused by forced pronation should logically be treated in full supination, for only thus are the intact soft tissues on the "pronation side" of the limb used to the best advantage.
In the mechanism of injuries caused by rotation violence it is emphasized that vertical compression is usually the basic force, to which a rotation force may be added by the direction of momentum of the body weight. Such injuries may be grouped into forced rotation injuries (in which the violence applied has taken the limb beyond the normal ranges of rotational movement), and injuries occurring while the limb is pronating or supinating. In the latter group the rotational element determines the pattern of the injury: pronation and flexion are closely allied, and a fracture occurring while the forearm is pronating will develop a backward angulation: so also a supination injury will produce a forward angulation.
On the basis of these considerations injuries of the forearm may be classified as follows:
Injuries in which the shaft of the radius remains in continuity
Forced proiiation injuries:
1) Forward dislocation of the head of the radius.
2) Backward dislocation of the lower end of the ulna.
3) The anterior Monteggia fracture-dislocation.
These injuries should be reduced and immobilised in full supination to prevent recurrence of deformity. The lateral and posterior Monteggia injuries are probably variants of dislocation of the elbow and are not caused by rotation violence. In general it is considered that all dislocations of the head of the radius are best treated in full supination.
Pronation injuries:
Greenstick fractures of the radius, and of both bones of the forearm, with backward angulation. Reduction of deformity is most easily obtained by manipulating into full supination. Certain fractures may with advantage be immobilised in this position.
Supination injuries:
Greenstick fractures of the forearm with forward angulation. Reduction is best obtained by full pronation.
Injuries in which the shaft of the radius is in two separate fragments
This group includes all complete fractures of the shaft of the radius and of both bones of the forearm. There is nearly always a rotational deformity between the two radial fragments and its correction is a dominant factor in the treatment.
