Trapezometacarpal dislocation is an uncommon traumatic lesion, especially in pediatric population, accounting for less than 1% of hand traumas. The lesion is usually due to an axial force, transmitted on a partially flexed thumb, causing the metacarpal bone to dislocate dorsally. When acute, various treatments have been described — closed reduction and cast, open or closed reduction with temporary K-Wire fixation, dorsal capsule and ligament reconstruction. In this abstract, we report a case of a 15-year-old boy who was admitted in the emergency department with a chronic post-traumatic trapeziometacarpal dislocation. The history reveals that he suffered from an thumb traumatism, by falling of a motorcycle seven months before, left untreated. By the time of the admission, he was suffering from thumb pain following a minor trauma that happened one week before. The X-rays and the preoperative CT scan showed a trapeziometacarpal dislocation, due to an untreated first metacarpal base fracture, with complete articular destruction. He underwent surgery, which consisted of an open reduction, a interposition graft of costal cartilage (9th rib) and ligament reconstruction (intermetacarpal, anterior oblique, posterior capsule). A temporary K-wire between first and second metacarpal was made followed by a cast immobilization for one month. The follow-up of the surgery showed a complete recuperation of the articular mobility and an absence of pain. Finally the X-rays revealed a reduction of the luxation.