Optimal selection of contact curves

A cutting jig and corresponding method of manufacture is provided. The jig comprises a unitary piece combining a bone cutting guide defining a cut plane and a set of fins projecting from a jig substrate and terminating in curvilinear bone-jig contact surfaces for abutting articular surface features. The curvilinear surfaces are characterized by custom patient-specific parameters derived from measurements obtained from selected image slices of a patient's joint region such that the curvilinear surfaces establish one and only one mechanical self-locking position for the unitary piece. One obtains a series of image slices of a patient's joint region, then selects a set of slices that show specified articular surface features in the joint region. Patient-specific parameters obtained from measurements of the slices specify curvilinear bone-jig contact surfaces and a cut plane. The contact surfaces at the ends of the fins may be extruded as stepped set of line segments that follow curves along the articular surface features.