Abstract: The present invention regards a synthesis plate (1), particularly for pelvic osteotomy; the present invention also regards an instrument (101) and a method for the application of the same. According to the invention, said plate (1) is composed of two distinct, separate modular components (3,5) that can be connected and fixed to each other, such that it is possible to adjust the relative angle (CC) between said two components of the modular plate as required, and then fix and integrally join them together in the desired angular position. Advantageously, with the plate (1) according to the invention and the suitable tool (101) for the application thereof, the adjustment and selection of the mutual angular position of said components can be carried out at any time, even during the execution of the osteotomy operation.