Triphalangism in thumb polydactyly: an anatomic study on surgically resected thumbs

Area of Science:

• Hand surgery
• Congenital hand anomalies
• Developmental biology

Background:

• Preaxial polydactyly is a common congenital hand anomaly.
• Triphalangeal thumb is a frequent manifestation, impacting hand function.
• Understanding thumb morphology is crucial for surgical planning.

Purpose of the Study:

• To anatomically classify triphalangeal thumbs in preaxial polydactyly.
• To correlate radiological findings with surgical dissection.
• To define morphologic and clinical criteria for classification.

Main Methods:

• Anatomic dissection of surgically resected thumbs from preaxial polydactyly cases.
• Radiological assessment of thumbs with metacarpophalangeal joint duplication.
• Classification based on phalangeal number and osteocartilaginous joint structures.

Main Results:

• Thumbs were categorized into three groups based on phalangeal count and joint formation.
• Group 1: Three phalanges, absent metacarpophalangeal joint.
• Group 2: Three phalanges, two well-formed joints.
• Group 3: Three phalanges, one interphalangeal joint.

Conclusions:

• Established a classification system for triphalangeal thumbs in preaxial polydactyly.
• Highlighted variations in joint formation and phalangeal structure.
• Provides a basis for understanding clinical presentation and surgical management.