Defining postoperative stability in children with radial polydactyly.

Area of Science:

• Orthopaedic surgery
• Paediatric hand surgery
• Congenital hand differences

Background:

• Limited data exists on paediatric metacarpophalangeal (MCP) joint instability following radial polydactyly reconstruction.
• Understanding normal MCP joint mobility and alignment in children is crucial for evaluating surgical outcomes.

Purpose of the Study:

• To establish fundamental data on thumb MCP joint mobility and alignment in healthy children.
• To compare joint stability parameters between healthy paediatric thumbs and those reconstructed for Wassel-IV radial polydactyly.
• To aid in the postoperative evaluation of MCP joint instability in children.

Main Methods:

• Evaluated 27 healthy paediatric thumbs (Group A) and 12 thumbs post-Wassel-IV reconstruction (Group B).
• Measured MCP joint radial and ulnar deviation on stress testing.
• Assessed MCP and interphalangeal (IP) joint alignment using posterior-anterior radiographs.

Main Results:

• Operated thumbs (Group B) showed greater mean ulnar deviation (35°) and radial deviation (30°) on stress testing compared to healthy thumbs (Group A: 25° and 30°).
• Group B exhibited significantly greater mean ulnar deviation (10°) on radiographs than Group A (5°) (p=0.029).
• Mean radial alignment of the IP joint was significantly higher in Group B (15°) than Group A (0°) (p=0.221).

Conclusions:

• Physiological thumb MCP joint mobility in children requires consideration during postoperative assessment.
• MCP joint instability may be indicated by >30° deviation with a lack of endpoint on stress testing.
• Comparing joint stability to the healthy contralateral hand is recommended for accurate diagnosis of pathological instability.