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Radial ray defect refers to a spectrum of congenital anomalies affecting the preaxial (radial) side of the forearm, characterized by hypoplasia or aplasia of the radius, often accompanied by abnormalities of the thumb, carpal bones, and sometimes the humerus.
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Etiopathogenesis
Embryology:
- Upper limb buds form in the 4th week of gestation.
- The radius and thumb develop along the preaxial border.
- Disruption of mesenchymal differentiation or vascular supply → radial ray malformations.
Causes:
- Sporadic / isolated (most common).
- Syndromic associations:
- Holt–Oram syndrome (cardiac septal defects + radial anomalies).
- TAR syndrome (Thrombocytopenia with Absent Radius, thumb usually present).
- Fanconi anemia (radial anomalies + aplastic anemia).
- VACTERL association (vertebral, anal, cardiac, tracheoesophageal, renal, limb defects).
- Roberts syndrome, trisomy 18, etc.
- Environmental/teratogenic: thalidomide, maternal diabetes.
Classification
| Type I |
Minor hypoplasia of thumb |
| Type II |
Hypoplastic radius, shortened |
| Type III |
Partial absence of radius |
| Type IV |
Complete absence of radius (most severe) |
Clinical Features
- Shortened forearm with radial deviation of hand (“radial club hand”).
- Absent/hypoplastic thumb.
- Limited elbow/wrist motion.