Management

The management of ulnar dysplasia depends on the severity of the deformity. Patients must be assessed for the infrequent concomitant anomalies in the musculoskeletal system. Early splintage and physiotherapy can be useful for mild anomalies. Surgical intervention is indicated for syndactyly, thumb hypoplasia, a narrow first web with inability to grip, or progressive bowing of the radius with growth. Most procedures tend to be done to correct deformities of the hand eg:

• syndactyly separation
• widening of the first web space
• rotational osteotomies of the first metacarpal to bring it out of the plane of the hand
• removal of rudimentary digits or parts of additional fingers
• pollicizations of the index finger

The wrist deformity can be addressed by excision of the cartilaginous ulnar anlage if there is severe or progressive ulnar deviation of the hand and bowing of the radius. In these cases, the tendons of flexor carpi ulnaris and extensor carpi ulnaris can be transferred to the radial side to increase the forces for radial deviation. A mildly short ulna can be addressed with distraction osteogenesis to provide some lengthening. If the radial head is subluxed or dislocated, it can be excised if there is an otherwise stable elbow and forearm with reasonable ulna length.

If the ulna is short proximally and the forearm is unstable, it may be necessary to create a one-bone forearm. In this procedure, the connections between radius and ulna are divided, the fibrous anlage is resected and the proximal parts of the radius and ulna are fused. Distraction osteogenesis can be combined with the creation of a one-bone forearm to bring the radial head into a better position. There is loss of all forearm rotation and this has functional implications.

In a synostosed ulnar dysplasia (type IV deformity), the extremity is often malpositioned. It is short, dorsally angulated and the forearm is pronated. This is described as a 'hand-on-flank' deformity. Generally, the limb is useless for most functional activities. A corrective osteotomy can be carried out to rotate and anteriorly angulate the forearm giving a hand anterior to the trunk with the elbow flexed and the forearm in midrotation.

Increasingly, distraction osteogenesis can be used as a valuable adjunct in the revision treatment of a child with ulnar dysplasia.