Other Thumb Deformities

Abstract The thumb accounts for approximately 40% of overall hand function, and deformities carry significant implications for pediatric hand development and quality of life. This article reviews three distinct congenital and acquired thumb deformities: pediatric trigger thumb, triphalangeal thumb, and congenital clasped thumb. Pediatric trigger thumb, an acquired condition resulting from a size mismatch between the flexor pollicis longus tendon and the A1 pulley, is staged using the Sugimoto classification and can resolve spontaneously, though surgical release of the A1 pulley reliably restores full range of motion in refractory cases. Triphalangeal thumb presents across a wide spectrum from a single extra phalanx to a five-fingered hand with absent thenar musculature and is classified by the morphology of the extra phalanx to guide surgical reconstruction. Congenital clasped thumb, a flexion–adduction deformity caused by hypoplasia or absence of the thumb extensors, can be categorized by either Tsuyuguchi's system or Mih's modification of McCarroll's system and managed initially with splinting. Surgical reconstruction is reserved for resistant or complex cases. Accurate diagnosis and classification of each condition are essential, as the natural history, associated systemic anomalies, and response to conservative versus operative intervention differ considerably across deformities.