The instrumentation makes it possible to implant in a long bone, such as the humerus, the femur or the tibia, an implant, such as an osteosynthesis nail or a prosthetic rod, defining a longitudinal axis and including, in alignment along the longitudinal axis, two opposite terminal parts and a running part that separates the two terminal parts from one another. The instrumentation comprises a targeting ancillary tool that is adapted to target one and/or the other of the terminal parts of the implant, if applicable percutaneously, along at least one targeting axis that is transverse, or even perpendicular, to the longitudinal axis. The targeting ancillary tool is designed to be fastened laterally to the running part of the implant so as to position the targeting ancillary tool and the implant relative to one another in a predetermined configuration.