The Extensor Indicis Proprius Transposition for the Ulnar Collateral Ligament Stabilization in Thumb Hypoplasia Grades II-IIIa

Congenital upper extremity deformities are rare, the reported incidence is from 0.15% to 0.2%. The thumb is very important for a hand's functionality, as it provides up to 50% of its total performance. Proper pinch grip formation at the age of 12 to 16 months is part of normal development; however, no functional development can affect a child's psychoemotional development. Well-described techniques such as third or fourth superficial flexor transposition can be found in the literature. There is a paucity of studies on using the extensor indicis proprius (EIP) transposition for stabilization of the ulnar collateral ligament for the first metacarpophalangeal joint (MCPJ). Techniques for the usage of EIP tendon for the reconstruction of absent extensor pollicis longus tendon are more commonly practiced as they create abduction and extension for the thumb hypoplasia grade II-IIIa. We performed EIP transposition with subperiosteally fixation for the ulnar collateral ligament stabilization for thumb hypoplasia patients with a mean age of 38 months (11 to 128) and grade II (n=9), grade IIIa (n=4), and grade IIIb (n=1). Long-term follow-up (2 to 10 y) for the esthetical and functional study was performed. Patients and parents are satisfied with functional and esthetic outcomes. We believe that the EIP tendon transposition can be an alternative method for thumb hypoplasia patients grade II-IIIa reconstruction.