Radial Hemimelia

A rare congenital limb malformation characterized by partial or total absence of the radius.

Epidemiology

The disorder occurs in 1/5,000-30,000 live births, and is slightly more common in males than in females (sex ratio of 3:2).

Clinical description

The disorder is bilateral in 60% of cases and the right side is more commonly involved than the left. The degree of malformation varies greatly. In mild cases, only a minor shortening of the radius is present. In the most severe cases in contrast, the radius is completely absent (including presence of aberrant muscles, nerves, tendons, ligaments and blood vessels). The disorder is thus characterized by varying degree of deficiencies of the radius, carpal bones, and the thumb that produces radial deviation of the hand and marked shortening of the forearm. There may also be underdevelopment or absence of the thumb, and malformation of the elbow joint with restricted motion. Radial longitudinal deficiency is frequently (67%) associated with other congenital anomalies or syndromes, including chromosomal anomalies (trisomy 13, 18 and 21), Holt-Oram syndrome, Roberts syndrome, Rothmund-Thomson syndrome, thrombocytopenia-absent radius (TAR) syndrome, Townes-Brocks syndrome, VACTERL association and Fanconi anemia.

Etiology

The etiology remains unknown. The deformities are believed to develop early in pregnancy, between the 26th and 52th day of gestation. The disorder is being caused by reduction in FGF function.

Diagnostic methods

Diagnosis is based on clinical examination and X-rays. In utero, prenatal ultrasound may potentially detect this malformation and thus be a valuable imaging modality for early diagnosis.

Antenatal diagnosis

Prenatal diagnosis is possible using ultrasound, 3D-ultrasound or fetal magnetic resonance imaging.

Genetic counseling

Approximately 5-10% of cases are familial. Routine genetic counseling is recommended for these cases.

Management and treatment

Management aims at reducing the functional deficit. Initial therapy consists of straightening of the hand and stabilization of the wrist by serial splinting or casting that should be undertaken shortly after birth. Various surgical methods of correction have been described, such as soft tissue releases with or without ulnar osteotomy, soft tissue distraction to distalize the hand, centralization and radialization, pollicization, microvascular epiphyseal transfer and forearm lengthening.

Prognosis

The prognosis is generally good. If an early individualized treatment plan is followed a good clinical outcome can be achieved. However, the more extensive the radial longitudinal deficiency type, the more impaired is the finger function and mobility.