Radial longitudinal deficiency (RLD) has been classified into four grades depending on the degree of hypoplasia of the radius (Table 41-1). Centralization is usually performed at 9 to 12 months of age because anesthesia is safer, preliminary soft tissue distraction can be carried out, and subsequent thumb reconstruction can be done before the child develops a maladaptive pattern.

This procedure may be done first for children with type 0 or 1 deficiencies.

Children with type 2 or greater deficiencies may need preliminary serial casting or soft tissue distraction using an external fixator.

Children with RLD have anomalies involving the muscular, vascular, and nervous systems in addition to the obvious skeletal deformity.

Skeletal anomalies: The radius is either absent or partially developed, and the ulna is bowed posteriorly and shortened to two thirds its normal length. The articulation between the carpus and ulna does not form a normal joint. It is usually fibrous but can be lined by hyaline cartilage.

Muscle anomalies: The extensor carpi radialis longus and brevis may be absent or fused to the extensor digitorum communis (EDC). The extensor pollicis longus (EPL), extensor pollicis brevis (EPB), and abductor pollicis longus (APL) are present if the thumb metacarpal is present, or they may be fused to the surrounding tissues. The supinator is generally absent, as is the pronator quadratus. The pronator teres is absent if the radius is absent. The flexor carpi radialis longus and brevis are often absent. The flexor carpi ulnaris is usually present and normal, as is the flexor digitorum superficialis. The palmaris longus is often absent. The flexor pollicis longus is present only if the thumb metacarpal is present. If the thumb is present, the thenar muscles are usually present. The hypothenar, interosseous, and lumbrical muscles are usually normal.

Vascular anomalies: The brachial and ulnar artery are usually present and normal, but the radial artery is absent or attenuated. The interosseous arteries are usually well developed.

Nerve anomalies: The median and ulnar nerves are present, but the median nerve is the most superficial structure on the radial side of the arm and may be confused during surgical dissection with a tendinous structure. The median nerve must be identified first during the exposure. The radial nerve frequently ends at the elbow; thus, the median nerve supplies sensation to the radial side of the arm.

The procedure is performed under general anesthesia and tourniquet control. The patient is positioned supine with the affected extremity on a hand table.

The four key steps of centralization are the following:

A long-arm cast with the elbow flexed to 90 degrees is provided. The extremity is immobilized for at least 8 weeks, and the pin is kept in place for as long as possible. A long-arm Orthoplast splint to maintain wrist position is worn full-time for 3 months and then at night until skeletal maturity. Prolonged pin fixation followed by long-term splinting is necessary to minimize recurrence.

Recurrence is the most common source of failure following centralization, and the cause appears to be multifactorial. Operative causes include the inability to obtain complete correction at surgery, inadequate radial soft tissue release, and failure to balance the radial force. Postoperative reasons consist of early pin removal, poor postoperative splint use, and the natural tendency for the shortened forearm and hand to deviate in a radial direction for hand-to-mouth use.

Even a successful centralization still results in a shortened forearm segment secondary to altered growth of the ulna (60% of normal). The short forearm is both a cosmetic and functional problem for the teenager with radial deficiency. Lengthening of the ulna can be accomplished using uniplanar or multiplanar shaft-distraction devices.