A customized patient-specific orthopaedic instrument for facilitating implantation of an acetabular cup prosthesis in a coxal bone of a patient includes a customized patient-specific acetabular reaming guide. The customized patient-specific acetabular reaming guide includes a longitudinal passageway for an acetabular reamer and a plurality of arms with attached feet. Each foot of the reaming guide is positioned relative to the body based on the contours of the coxal bone of the patient and a predetermined degree of version and inclination angles of the acetabular cup prosthesis when implanted in the patient's coxal bone.
