20250715 Thumb polydactyly Dr Lai FJ

14-month-old boy is evaluated for duplicated thumbs. Radiographs show duplication of both proximal and distal phalanges, with a single metacarpal. Which of the following Wassel types best describes this anomaly?

• A. Type II

• B. Type III

• C. Type IV

• D. Type VI

• E. Type V

A neonate presents with unilateral thumb duplication. Which of the following best explains its embryologic cause?

• A. Ectopic SHH expression in the anterior limb bud

• B. Loss of SHH in the posterior ZPA

• C. Upregulation of BMP in the AER

• D. Mutation of HOX genes in the limb bud

• E. Ectopic SHH expression in the posterior limb bud

Which of the following statements regarding the Wassel classification for thumb duplication is correct?

• A. It is primarily based on soft tissue involvement

• B. It includes triphalangeal and triplicated thumbs

• C. It uses MRI findings for classification

• D. It is based on the level of skeletal duplication seen on radiographs

• E. It was developed after the Chung classification

A 2-year-old boy has Wassel type VI thumb duplication with deviation and global MCPJ instability. Both thumbs are of near equal size, but the ulnar thumb has better nail and alignment. What is the most appropriate initial surgical plan?

• A. Simple excision of the radial thumb

• B. Bilhaut-Cloquet procedure

• C. Resection of radial thumb with ligament and tendon transfer to the ulnar thumb

• D. Acral transposition of the ulnar nail and distal phalanx onto the radial base

• E. Delayed reconstruction until age 4 for better bone ossification

A 5-year-old girl underwent thumb duplication reconstruction at age 2. She now presents with mild residual angular deformity and a longitudinal nail ridge but no pain or functional limitation. What is the most appropriate next step?

• A. Immediate osteotomy and nailbed reconstruction

• B. Observation with yearly follow-up

• C. Excision of the nailbed

• D. Physical therapy and splinting

• E. Repeat MRI to evaluate joint structures