Treatment of defects of the ulna in children by establishing cross-union with the radius.

When one growing forearm bone is destroyed by disease, develops imperfectly or lacks stability because of a pseudarthrosis or dislocation at either end, the effect is not usually confined to the abnormal bone, because secondary structural changes in the other are likely to follow. The consequences may be serious when stability is impaired, because normal function of the hand is largely dependent upon this property of the forearm. This stability is provided at the elbow by the ulna and at the wrist by the radius, stress being transmitted from radius to ulna through the interosseous membrane. When the ulna is defective distal to the humero-ulnar joint this mechanism commonly fails in spite of stability at the elbow and a radius which is at first normal. This very normality of the radius is the factor responsible, because its growth is unimpaired and it soon outstrips its partner. Bowing is followed by dislocation of the radial head so that even this stabilising influence is lost (Figs. 1 and 8). Stress directed upward from the hand now forces the unsupported radial head still more proximally, being no longer transmitted to the ulna and thence through the elbow to the shoulder. The grip is inevitably weakened and dexterity impaired. Furthermore, as the radial head continues to migrate, shortening increases and elbow flexion and forearm rotation decrease, thus aggravating the situation. This unfortunate sequence may be interrupted if bony union is achieved between the ulna proximally and the radius distally. The immediate effect is to restore stability and enable growth in length to continue from the epiphysis at either end of the now conjoined forearm bone. Rotation is unavoidably sacrificed, but since it is diminished already, little is lost provided the forearm is reconstructed in neutral rotation. The dislocated radial head with its epiphysis is of no further value and may be excised with impunity if it obstructs elbow flexion. This principle is attributable to Hey Groves (1921), who employed it in the treatment of recalcitrant non-union of radius and ulna. Vitale (1952) described two patients in whom the method was applied for defects of the ulna in growing children, and Lowe (1963) presented his experience with similar patients in whom either the ulna or the radius was involved. Both authors reported satisfactory results and emphasised the dangers of neglect in such patients. Although the need to perform this operation is becoming less frequent as treatment for fractures and osteomyelitis becomes more effective, it seems timely to report three patients in whom the operation was indicated and performed with satisfaction. In one further patient a disabling pronation deformity due to a combination of obstetric paralysis and cerebral palsy was managed similarly and the outcome was, within the limits ofthe underlying cause, a success.