Luxations of the carpal joint are of rare occurrence, and very few cases of this kind are on record.  Walters[18] reports a case of carpometacarpal luxation in a pony wherein reduction was spontaneous and an uneventful recovery followed.  His reason for reporting the case, as he states, is its rarity.

Symptomatology.—­Fractures of the carpal bones as they usually take place are diagnosed without difficulty.  Because of their usually being comminuted, abnormal movement of the joint is possible.  Such movement is not restricted and flexion of the leg at the carpus in any direction is possible.  Crepitation is readily detected and frequently these fractures are of the compound-comminuted variety.

In fracture of the accessory carpal bone (trapezium) or in fracture of any other single bone when such exists, there is no increase in the movement of the joint.  The accessory carpal bone may be readily manipulated and when fractured, its parts are more or less displaced.  Recognition of fracture of any other single carpal bone must be done by detecting crepitation unless it be a compound fracture, whereupon probing is of aid in establishing a diagnosis.

Carpal luxation when present is to be recognized by finding the apposing carpal bones joined in an abnormal manner—­that is, out of position.  There is restricted or suspended function of the joint, and in the cases recorded, no difficulty has been experienced in making a diagnosis.  The carpometacarpal portion of the articulation is the part which is usually affected.

Prognosis and Treatment.—­There is no chance for complete recovery in the usual case of carpal fracture because of the fact that there results sufficient arthritis to destroy articular cartilage beyond repair.  In the average instance, because of arthritis which persists for a considerable length of time, more or less ankylosis results.  At best, one can only hope for partial recovery, that is to say, the member may regain its usefulness as a weight-supporting part, but because of restricted or abolished joint function, locomotion is more or less difficult.  Exostoses, articular and periarticular, occur and the carpus usually becomes a large immobile articulation.  There is danger of infection resulting in simple carpal fractures and, needless to say, in a compound-comminuted fracture of the carpus, infection usually occurs and a fatal outcome is probable.

When treatment is instituted, antiseptic precautions are taken in handling the compound fractures, and in any case immobilization of the parts is sought.  Here, as has been previously pointed out, it is best to employ leather splints, so that a maximum degree of rigidity with a minimum of distress and inconvenience to the patient will result.  The leg must be bandaged from the hoof upward, making use of a sufficient amount of cotton to ensure against pressure-necrosis.  The leather splints are placed mesially and laterally and, of course, need to extend as high as the proximal end of the radius.  Subjects must be kept in slings until union of bones has become established, and as a rule there will then exist marked ankylosis.