Congenital synchondrosis of the scaphotrapezio-trapezoidal joint.

Incomplete cavitation of the cartilaginous precursor of the carpus during the fourth to eighth weeks of intrauterine life results in carpal synostosis or synchondrosis, which becomes radiographically apparent as the carpus ossifies. Such anomalies occur rarely, are generally believed to be asymptomatic, and are usually discovered as incidental radiographic findings. We present two cases of symptomatic, nonsyndromic congenital synchondrosis of the scaphotrapezio-trapezoidal joint, a type of carpal coalition not previously reported.