Abstract: A femoral head prosthesis is a multilayer composite having a metal neck stem component thread or press fit into a hollow rigid shell of metal or ceramic, a polymeric core filling the interior volume under the hollow rigid shell and around a forward part of the neck stem, and a smooth, void-free polymeric articulation layer of at most 12 mm over the exterior of the shell. The prosthesis is formed by a polymeric molding process wherein polymerizing resin or heated thermoplastic material is flowed in a mold through a set of holes through the hollow shell into the interior volume and around the shell's exterior. Once the resin has cured or the thermoplastic cooled, the stem, core, shell and articulation layer collectively form an integral prosthesis of a desired head diameter matching a patient's anatomy.

Abstract: A computer-aided pre-operative planning tool with interactive surgeon interface for total knee replacement implements a method that allows implant size selection, implant positioning, and surgical cut planes estimation (with construction of corresponding surgical jig), based upon a series of coronal, axial and sagittal image slices of a patient's leg. Limb alignment and corresponding surgical cut planes are defined based upon joint anatomical-matching analysis to minimize joint wear and restore a pre-arthritic alignment (rather than an always fully neutral alignment). Using the interface, a surgeon has the option to adjust the varus/valgus alignment within recommended bounds between the pre-arthritic and fully neutral alignments. Implant size may be selected based on a best fit to the patient's leg obtained from analysis of the images.

Abstract: A knee prosthesis for total knee replacement has femoral and tibial joint components. The femoral component has a medial condyle, a lateral condyle and an intercondylar recess between the condyles. The condyles in sagittal profile both have spiral outer surfaces, wherein the increasing anterior-to-posterior radii of curvature for the medial condyle is smaller than the corresponding radii of curvature for the lateral condyle. The tibial component has shallow concave medial and lateral condyle surfaces for receiving corresponding condyles of the femoral component as bearing surfaces when the femoral and tibial components are biased together under applied tension by ligaments. Posterior portions of each femoral condyle that contact the corresponding tibial condyle up to 90° flexion are substantially spherical in shape, with gradually increasing radii in coronal profile as flexion increases, while the anterior portions beyond 90° flexion are substantially elliptical in shape in coronal profile.

Abstract: A knee prosthesis for total knee replacement has femoral and tibial joint components. The femoral component has a medial condyle, a lateral condyle and an intercondylar recess between the condyles. The condyles have in sagittal profile a spiral outer surface with increasing anterior-to-posterior radii of curvature, such as radii that follow a Fibonacci sequence ratio per every quadrant. The tibial component is lateral-medial mirror symmetric in coronal profile and has shallow concave medial and lateral condyle surfaces for receiving corresponding condyles of the femoral component as bearing surfaces when the femoral and tibial components are biased together under applied tension by ligaments. The shallow concave condyle surfaces in sagittal profile have sharp radii of curvature near anterior and posterior ends of the condyle surfaces that can accommodate up to 5° anterior and up to 6° posterior misplacement error and up to 4° rotational mismatch between the femoral and tibial components.

Abstract: 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.

Abstract: Jigs for guiding femur and tibia resectioning in knee surgery contain bone-jig contact surfaces and a cutting guide as a single unitary piece. Contact surfaces are curvilinear surfaces formed into ends of projections from a jig base. Each jig has three pairs of contact surfaces selected to abut low-wear, lateral and medial, articular surface features, such that only one self-locking position against the bone (or cartilage) is possible and the integral cutting guide will define only one cut plane for the resectioning. An improved rotational transformation that converts scan views into desired proper axes is based on projections of rotated coordinates onto the plane of rotation to produce parameters that closely correspond to the joint surfaces in the desired jig coordinates.

Abstract: Surgical jigs for guiding bone resectioning in knee replacement surgery, one for the femur and another for the tibia, contain both the various bone-jig contact surfaces and the cutting guide as a single unitary piece. The contact surfaces are curvilinear surfaces formed into ends of planar fins that project from the jig base or substrate. Each jig has three (3) pairs of contact surfaces selected to abut low-wear, lateral and medial, articular surface features, such that the jig has one and only one possible self-locking position against the bone (or cartilage) and so the jig's integral cutting guide will define one and only one cut plane for the bone resectioning. The presence of osteophytes generally does not adversely impact the proper fit of the jigs.