An assembly of instruments for installing an implant on a bone having a pair of pins (40) placed in known patient specific postioning relative to the bone, the assembly of instruiments comprising: a reaming instrument (60) habing a first tube (61) configured to be slid onto one of the pins, and a second tube (65) spaced from the first tube to be aligned with the other one of the pins； and a cannulated reamer (80) having a reamer end (81) configured to ream the bone, and a hollow shaft (82) supporting the reamer end and configured to be driven, the hollow shaft concurrently received in the second tube of the reaming instrument and mounted onto the other of the pins, for the reaming instrument to guide movement of the cannulated reamer when reaming bone.
