Classification for Thumb Opposition in Children with Thumb Hypoplasia

Area of Science:

• Orthopedics
• Hand Surgery
• Pediatric Orthopedics

Background:

• The existing Kapandji scale for thumb assessment is complex and poorly understood in pediatric cases.
• Assessing thumb hypoplasia requires a more accessible and reliable evaluation method.

Purpose of the Study:

• To validate a simplified, child-friendly scale for evaluating thumb opposition.
• To assess abduction and rotation movements, excluding metacarpophalangeal (MP) and interphalangeal (IP) joint flexion.

Main Methods:

• A new 0-3 degree scale was developed, focusing on thumb-to-finger contact points.
• Ten pediatric patients with thumb hypoplasia were evaluated by 18 surgeons (9 hand, 9 orthopedic).
• Inter-observer and intra-observer reliability were assessed using intraclass correlation coefficients (ICC).

Main Results:

• The simplified scale showed very good inter-observer reliability (kappa = 0.991) and excellent intra-observer reliability (kappa = 0.995).
• High reliability was consistent within both hand surgeon (kappa = 0.980) and orthopedic surgeon (kappa = 0.974) groups.
• The scale proved highly reliable for assessing thumb abduction and rotation.

Conclusions:

• The proposed simplified thumb opposition scale is validated and reliable for clinical use.
• This scale offers a practical and understandable tool for evaluating thumb opposition in children with hypoplasia.
• It is particularly useful for assessing outcomes after thumb opposition transfer surgery.