Congenital Absence Of The Radius

Daniel C. Riordan, M.D.

Congenital absence of the radius is classified as a paraxial hemimelia in the Frantz-O'Rahilly1 terminology and may be either terminal or intercalary. This skeletal deficiency is a fairly common defect of the upper extremity, and may be hereditary. The condition occurs bilaterally in slightly over half of the reported cases. Any part of the radius may be absent, the shaft or either end; but most frequently a rudimentary upper end is present.

Since the defect involves the radial elements of the limb bud, varying defects in the carpels and metacarpal rays may also be seen. The radial bones of the carpus may be absent or fused. The thumb may be absent, partially present as a floating thumb with an absent metacarpal, or may be complete in all elements. Occasionally the index finger is absent or may be underdeveloped. The index and long fingers frequently have limited motion at the middle and distal joints.

In all cases the hand is unsupported and deviates to the radial side, frequently greater than 90 degrees. This abnormal radial deviation produces a great deal of relaxation of the finger tendons and also results in weakness and in limited motion. The ulna is short, thick, and curved radially. In most cases the humerus is also short.

Associated Defects

Absence of the radius is frequently accompanied by other congenital deformities. Some of those mentioned in the literature are: harelip, cleft palate, club-foot, hernia, kyphosis, scoliosis, torticollis, and rib deformity or fusion. Three of the cases followed here have had aplasia or underdevelopment of the lung on the affected side. This condition is usually accompanied by dextro-cardia if the defect is on the right side.

If there is total absence of the radius, the arterial system is frequently abnormal. Often the radial artery is small or absent. In such cases the nerve supply to the hand is abnormal with the radial nerve absent in its superficial branch, and the median nerve providing a dorsal sensory branch that innervates the dorsal hand surface. The ulnar nerve is usually normal.

Fanconi's syndrome should be looked for in every case. This condition is characterized by a severe, progressive, refractory macrocytic anemia, and also by a neutropenia and thrombopenia. The bone marrow is hypoplastic. There may be brown, melanin-like pigmentation of the skin, and many of the other congenital deformities mentioned earlier. This severe anemia is quite resistant to treatment and is frequently fatal. If a diagnosis of anemia is established, no surgical treatment shoulc be instituted.

Patients Treated

To date our experience has encompassed thirty-two patients with congenital radial deficiencies. In eleven of these cases, the defect was bilateral, and in twenty-one it was unilateral, adding up to a total of forty-three affected limbs. The radius was totally absent in thirty-five of these limbs and partially absent in nine.

For the first thirteen limbs treated, the surgical procedure involved a fibular graft. Subsequently, thirty limbs have been treated with a revised technique in which the hand is repositioned to center it over the ulna.

Corrective Procedure

Early correction of a radial deformity provides functional improvement, while cosmesis is markedly enhanced, thus helping to meet the emotional problems associated with the obvious deformity. Early correction is effected by means of plaster casts, with wedging or frequent changes. Long-arm casts should be used with the elbow flexed to 90 degrees, and the hand gradually brought around to line it up with the long axis of the forearm, if possible. This treatment is started in the first twenty-four hours if the child can be seen that early, and surgical treatment is started at five or six months of age. The oldest child treated in our series was four years of age.

After the hand is surgically placed in line with the long axis of the ulna, it is immobilized in plaster for two or three months, and then supported with a short-arm plastic splint. Except while the patient is bathing, this splint should be worn at all times, even during sleep. Usually, by the time the child reaches school age, the hand is stable and the support may be left off during the day, but should be worn at night until growth is completed.

Earlier Surgical Technique

The surgical treatment originally used was reported in 1955.2 (See Fig. 1 , Fig. 2 , Fig. 3 , and Fig. 4 ). This procedure consisted of a two-stage operation. First, the hand was surgically placed in its normal relationship with the distal ulna. This usually meant an approach from both ulnar and radial sides of the carpus. The position was maintained by a small pin through the carpus and distal ulna. In about two months, a second operation was performed and a fibular graft inserted in the position of the normal radius. This graft was placed against the ulna, and later into a distal osteotomy site making a "T" shaped bony structure. The hope was that the proximal fibular epiphysis would grow and contribute to bone length.

However, in thirteen fibular grafts only one showed adequate growth of the transplanted epiphysis. Review of these cases in 1958 revealed the inadequate growth of the epiphysis, and Indicated that the deformity was gradually recurring as the ulna overgrew the fibular graft.

Recent Procedures

It was noted that the ulna usually enlarged distally if it supported the hand, and several cases were then done centralizing the hand on the ulna. This made the ulna the only supporting bone and time has proven that the ulna enlarges at the distal end to become as large as a normal radius. It has provided adequate support for the hand, and no other surgical procedures have been necessary, constituting a major advantage of this method of treatment. If the operation is performed as early as five or six months, the development and distal enlargement of the ulna proceeds rapidly. Fig. 5 , Fig. 6 , Fig. 7 , Figs. 8A and 8B , Figs. 9A and 9B , and Figs. 10A and 10B depict the four-year follow-up of one of our patients. In only two cases has it been necessary to do a wrist fusion, and both cases involved revisions of earlier fibular grafts, in which the deformity had recurred. No wrist fusions have been necessary in those cases where the hand was centralized over the ulna. It is possible that wrist fusion may eventually be required in some cases, but so far the indication or necessity has not been apparent.

The Operation Described

In the surgical technique the distal ulna and carpus are first exposed from the ulnar side. The extensor carpi ulnaris and digiti quinti must be identified, freed from their tunnels dorsally, and protected. The carpus is freed from its attachment to the ulna. The radial side is then approached through a longitudinal incision.

Occasionally it has been necessary to convert this straight incision into a "Z" plasty. The carpus is exposed and freed until the ulna is visible from the radial side. If a thumb is present the exposure is more difficult, and the brachio-radialis tendon attaching to the carpus must be cut and retraction permitted. By flexing the elbow to relax the muscles, the hand is reduced over the ulna. If the muscle pull is still too great, the central carpal bone or bones are excised. Occasionally removal of the lunate and part of the capitate has been necessary. The distal end of the ulna fits into the space created. The hand is then displaced radially, exposing the distal ulna through the ulnar wound. A large Kirschner wire is then drilled from the distal ulna toward the elbow. This wire usually comes out of the ulna distal to the elbow because of the curvature. The drill is then placed on the proximal end of this wire and with the hand reduced over the distal ulna, the wire is drilled through the carpus and into the metacarpals. This usually puts the hand into a neutral position with the wire preferably in the third metacarpal. The fingers will be in moderate flexion because of the tension on the muscles after the reduction of the hand over the ulna, but they usually relax after a few weeks, so traction is not necessary.

After two months, use of the plaster cast is discontinued, but immobilization is continued by means of a short-arm plastic molded splint. This is worn day and night, until school age. Then it may be taken off during the day, but worn at night. This splint should be worn until full growth has been obtained, otherwise hand deformity will recur.

Daniel Riordan is Clinic Co-Chief Juvenile Amputee Clinic Crippled Children's Hospital New Orleans, Louisiana

(1) Frantz, Charles H., M.D. and 0'Rahilly, Ronan, M.D., "Congenital Skeletal Limb Deficiencies", The Journal of Bone and Joint Surgery (American Volume), Vol. 43-A, No. 8, December 1961. 
(2) Riordan, Daniel C., M.D., "Congenital Absence of the Radius", The Journal of Bone and Joint Surgery (American Volume), Vol. 37-A, No. 6, pp. 1129-1140, December, 1955.