Thumb hypoplasia treatment requires considering every component of the maldevelopment. Types II and IIIA hypoplasia share common features such as first web space narrowing, hypoplasia or absence of thenar muscles and metacarpophalangeal joint instability. Many surgical techniques to correct the malformation have been described. We report our surgical strategy that includes modifications of the usual technique that we found useful in reducing morbidity while optimizing the results. A diamond-shape kite flap was used to widen the first web space. Its design allowed primary closure of the donor site using a Dufourmentel flap. The ring finger flexor digitorum superficialis was transferred for opposition transfer, and the same tendon was used to stabilize the metacarpophalangeal joint on its ulnar and/or radial side depending on a uniplanar or more global instability. An omega-shaped K-wire was placed between the first and second metacarpals to maintain a wide opening of the first web space without stressing the reconstructed ulnar collateral ligament of the MCP joint. We report a clinical series of 15 patients (18 thumbs) who had this reconstructive program.