A cutting guide assembly is provided for resecting a head of a bone. The cutting guide assembly includes an elongate support rod and at least one cutting plate couplable to the support rod, the at least one cutting surface defining a cutting surface arranged such that when coupled to the support rod, the bone can be cut to form a resection surface by aligning a cutting tool with the cutting surface. The support rod is configured to be partially disposed in and rotatable within a cavity extending into the head of the bone, defines a longitudinal axis and including a reference formation.
