Classification for Thumb Opposition in Children with Thumb Hypoplasia.

Background: The Kapandji scale has 10 levels and includes abduction, rotation and flexion movements. Assessing children with thumb hypoplasia, this scale is poorly understood and confusing. The objective of the study is to evaluate an opposition scale simpler and understandable for children. Methods: It is a validation study of a simplified scale to qualify the opposition of the thumb, in order to asses only the abduction - rotation but not the flexion of the metacarpo-phalangeal (MP) or interphalangeal (IF) joint. The proposed classification goes from 0 to 3 degrees, where 0: No opposition, 1: The thumb touches the middle phalanx of the 2nd finger, 2: the thumb touches the pulp of the 2nd finger and 3: the thumb touches the pulp of the 5th finger. 10 patients with thumb hypoplasia were analyzed by 9 hand surgeons and 9 orthopedic surgeons. Results: The intraclass correlation coefficient shows a very good inter-observer reliability with a kappa of 0.991 (p = 0.000). When correlated by groups, the finding were very good between the hand surgeons group k = 0.980 (p = 0.000) and the orthopedic surgeons group 0.974 (p = 0.000). At 6 weeks a new evaluation was made, the intra-observer reliability was excellent k = 0.995 (p = 0.000). Conclusions: The proposed scale for the evaluation of the abductionrotation of the thumb is validated and useful in the evaluation of the results of a thumb opposition transfer with a good inter-observer and intra-observer reliability between orthopedic and hand surgeons.