1. A femoral neck implant comprising: a body for implantation into a femoral neck of a patient, the body having a patient-specific cross-section of variable size and shape along a longitudinal axis of the body and a patient-specific three-dimensional outer surface that closely nests and conforms complementarily to a cortical boundary surface corresponding to a cortical/cancellous bone interface surface of the femoral neck of the specific patient after removing only the cancellous bone from the femoral neck; and a neck portion extending from the body and configured for coupling with a femoral head implant.