AUTHOR=Wu JianPing , Shi WeiZhe , Lin XueMei , Li JingChun , Yuan Zhe , Zhu Mingwei , Liu YuanZhong , Li YiQiang , Canavese Federico , Xu HongWen 

TITLE=Epidemiological characteristics and distribution of congenital thumb duplication in south China: An analysis of 2,300 thumbs in 2,108 children

JOURNAL=Frontiers in Pediatrics

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/pediatrics/articles/10.3389/fped.2022.1027243

DOI=10.3389/fped.2022.1027243

ISSN=2296-2360

ABSTRACT=Objective: The objective of this study was to evaluate epidemiological and anatomical characteristics of children with congenital thumb duplication (CTD).
Methods: We retrospectively reviewed 2108 children with CTD. Data regarding sex, age at the surgery, laterality, uni- or bilateral involvement, and dominant side were retrieved from the medical charts. Plain radiographs were used to classify all CTD according to Wassel-Flatt, Rotterdam and Chung classification systems and to evaluate the patho-anatomy of the duplication as well as the presence of associated anomaly.
Results: A total of 796 girls and 1312 boys with CTD (n=2300 thumbs) met the inclusion criteria. The male to female and unilateral to bilateral ratio were 1.6:1 and 10:1, respectively. Associated anomaly was found in 302/2300 thumbs (13.1%), and the middle phalanx deformity of the 5th finger was the most common one. A dominant thumb, larger and more developed, was on the ulnar side in 2270/2300 cases (98.7%). 
According to the Wassel-Flatt classification, type IV (40.2%) was the most common deformity and the extra thumb was connected to the main thumb by a joint in most cases (437/780); overall, 15.7% of thumbs (n=360) did not fit the Wassel-Flatt classification. 
According to the Rotterdam classification, type IV (51.3%) was the most common form; in most cases (363/1180) the thumb was hypoplastic or floating. Overall, 3/2300 thumbs (0.1%) could not be classified according to Rotterdam classification. 
According to the Chung classification, type A was the most common subtype (44.1%); in most cases (716/1015) the duplication was at the level of the metacarpal bone. Overall, 2/2300 thumbs (0.1%) did not fit the Chung classification. 
Conclusions: In patients from southern China, CTD shows male and right-sided predominance with ulnar-dominant thumb. Abnormalities of the middle phalanx of the 5th finger are more frequent in patients with associated anomaly. The development of a simple and comprehensive classification system is needed to guide treatment and to adequately assess the epidemiological characteristics of patients with CTD in order to facilitate comparison between different patients’ populations.