Background:The predominant method for Manske type ⅢB and Ⅳ thumb hypoplasia is pollicization.However,for those who are not willing to sacrifice the index finger,a method that could reconstruct a functionally capable and aesthetically acceptable thumb remains desirable.This study aimed to investigate and assess the functional and radiographic outcomes of utilizing a reversed vascularized second metatarsal composite flap for thumb reconstruction as a new altative.Methods:From May 2014 to January 2017,15 patients with Manske type ⅢB or Ⅳ thumb hypoplasia who were admitted to the Department of Hand Surgery,Beijing Jishuitan Hospital were included in this study.An osteocutaneous flap containing a section of second metatarsal and its distal head was transferred in reversed position to reconstruct carpometacarpal joint.The donor site was reconstructed by a split half of the third metatarsal.Various functional reconstructions were commenced at second stage.The reconstructed thumbs were evaluated using the Kapandji score,pinch force,and the capacities of performing daily activities through a detailed questionnaire.Results:Among these 15 patients (seven type ⅢB and eight type Ⅳ),there were ten boys and five girls with median age of 4.2 years (range:2.0-7.0 years).There were seven right,three left,and five bilateral thumbs for whom only the right thumb received surgery.There were 14 metatarsal flaps survived (14/15).With an average follow-up of 19.2 months,the reconstructed thumbs had acceptable functional and aesthetic outcomes and the donor foot presented in decent appearance without signs of impaired function.All 15 children have improved the Kapandji score (from 0 to an average of 6.7),pinch force (from 0 to an average of 1.5 kg),with ability of grip and pen holding.X-ray indicated continuous bone growth.Patients and parents had good acceptance of the new thumb.Conclusions:Reconstruction of an unstable hypoplastic thumb (Manske type ⅢB and Ⅳ) with use of a vascularized metatarsal is an effective strategy.It offers an altative solution for parents insisting on saving the thumb.