ancillary instruments for the reconstruction of a posterior cruciate knee ligament by drilling one or two tibial canals using a surgical operation performed from the front . the instrument set includes a system for protecting the posterior surface of the upper tibia end and an aiming device for guiding at least one drill . the protection system comprises at least one bent tube removably coupled by an extension portion to a locking handle for securing the tube through the intercondylar fossa of the femur on the posterior surface of the upper end of the tibia , so that the distal end of the bent tube serves as the stop to the drill guided by the aiming device and emerging from the tibial bone canal , and the bent tube can form , together with a rectilinear wire feed - through tube disposed in the place of the drill , a continuous canal for guiding a metallic loop used to draw the prosthetic posterior cruciate knee ligament from the anterior surface of the tibia to the femur insertion point .