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Radial hemimelia is a congenital longitudinal deficiency of the radius bone of the forearm characterized by partial or total absence of the radius.
- Congenital longitudinal deficiency of the radius
- Radial clubhand
- Radial longitidinal meromelia
- Radial ray agenesis
- Prevalence: 1-9 / 100 000
- Inheritance: -
- Age of onset: Infancy, Neonatal
- ICD-10: Q71.4
- OMIM: -
- UMLS: -
- MeSH: -
- GARD: 225
- MedDRA: -
It occurs in 1/30,000-100,000 live births, and is slightly more common in males than in females (sex ratio of 3:2).
Radial hemimelia is bilateral in 50% of cases and the right side is more commonly involved than the left (with a ratio of 2:1). The degree of malformation varies. In the most severe cases, the radius is completely absent, and the entire arm is shorter with marked curving of the forearm and stiffness of the elbow and fingers. This is the most common variant of radial hemimelia, in which hand, finger and elbow function is significantly impaired. In the majority of cases with complete absence of radius, the soft tissues of the forearm (including the muscles, nerves, tendons, ligaments and blood vessels) are also abnormal. There may also be underdevelopment or absence of the thumb, and fusion or malformation of the elbow joint with restricted motion. In the mildest cases, the radius is slightly smaller than the ulna, with minimal deviation at the wrist. Radial hemimelia is frequently 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 (in which characteristically the thumb is present), Townes-Brocks syndrome, VACTERL association and Fanconi anemia (see these terms).
The etiology remains unknown. The deformities are believed to develop early in pregnancy, between the 28th and 56th day of gestation. Maternal drug use (cocaine, thalidomide or valproate), compression of the uterus and vascular injury have been suggested to play a role in the etiopathogenesis of this condition, but these theories have not been proven.
Diagnosis is based on clinical examination and X-rays. Further tests and a complete physical examination are required in case of additional anomalies. Radial hemimelia can be detected by prenatal ultrasound scan at 20 weeks of gestation.
Approximately 5-10% of radial hemimelia cases are familial.
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. Intensive stretching exercises and physical therapy are required to achieve a passive extension of the wrist and elbow into a normal position. More severe cases require corrective surgery, usually performed at around one year of age. Surgical approaches involve realigning the ulna bone through osteotomy and use of external fixators, and centering the wrist on the remaining ulna. In case of thumb absence, corrective shifting the index finger to the position of the missing thumb (pollicisation) is used to make the hand functional.