1. A method of manufacturing a custom arthroplasty guide, the guide including a mating region configured to matingly receive a portion of a patient bone associated with an arthroplasty procedure for which the custom arthroplasty guide is to be employed, the mating region including a surface contour that is generally a negative of a surface contour of the portion of the patient bone, the surface contour of the mating region being configured to mate with the surface contour of the portion of the patient bone in a generally matching or interdigitating manner when the portion of the patient bone is matingly received by the mating region, the method of manufacture comprising: a) using a medical imaging system to obtain first data, wherein the first data is associated with the portion of the patient bone; b) providing second data, wherein the second data is associated with a bone other than the patient bone; c) employing a computer to use the first data to modify the second data into third data; d) employing the computer to use the third data to generate a three dimensional computer model of the portion of the patient bone; e) employing the computer to use the three dimensional computer model to generate design data associated with the custom arthroplasty guide; and f) using the design data in manufacturing the custom arthroplasty guide.