BACKGROUND

Field

The present disclosure generally relates to systems and methods for replacement of an ankle by a prosthesis.

Description of the Related Art

Patients with certain types of ankle problems may require a total ankle replacement prosthesis. Although such devices have been used for some time, improvements are still needed in various respects, including but not limited to features that contribute to ease of implantation by a surgeon, resistance to posterior separation post-operatively, and resistance to component subsidence.

SUMMARY

Embodiments of the invention address many of the problems encountered with prostheses for various anatomical joints, including but not limited to, total ankle replacement prostheses. Many of the features of these embodiments are particularly helpful when employed using an anterior approach, as opposed to a medial-lateral approach. Posterior separation resistance is aided with the use of a wedge entirely or partially on the posterior side of the tibial component. One or more pegs can be used to provide guidance for the wedge. Preferably the surgical technique involves no bone preparation beyond initial saw cutting, although preparation for the wedge or the pegs, or both, are possible. Component subsidence resistance is aided by minimizing bone resection and by maximizing the extent that the components rest on cortical bone rim. Embodiments utilize a lateral flare to cover the anterior cortical rim of the tibia, as opposed to traditional trapezoidal or oblong footprints found in many prior art designs. This lateral flare increases the contact area of the tibial tray with the cortical rim of the anterior tibia. The lateral flare follows the anatomic tibia shape in the transverse plane by wrapping around the anterior aspect of the fibula.

An embodiment of the invention comprises a tibial implant, a talar implant and an intermediate implant, wherein the intermediate implant fixedly attaches to the tibial implant and is capable of articulating with respect to the talar implant, wherein the intermediate implant has a first edge of the articulating surface and a second edge of the articulating surface, wherein the first edge is at a different elevation from the second edge, with elevation being defined with respect to a top surface of the intermediate implant.

An embodiment of the invention comprises a kit comprising a tibial implant, a talar implant and a plurality of intermediate implants, wherein the intermediate implants attach to the tibial implant and have respective articulating surfaces that articulate with respect to the talar implant, wherein at least one of the intermediate implants has a different elevational dimension of the first end point from another of the intermediate implants or has a different elevational dimension of the second end point from another of the intermediate implants.

An embodiment of the invention comprises a tibial implant, a talar implant and an intermediate implant, wherein the intermediate implant attaches to the tibial implant and is capable of articulating with respect to the talar implant, wherein one of the tibial implant and the intermediate implant comprises a pocket and the other of the tibial implant and the intermediate implant comprises a latch, the latch and the pocket engaging with each other upon assembly, wherein the intermediate implant comprises an intermediate implant recess on an anterior edge thereof, and wherein when viewed along an anterior-posterior direction, the intermediate implant recess at least partially aligns with the pocket and the latch.

An embodiment of the invention comprises a tibial implant, a talar implant and an intermediate implant, wherein the intermediate implant attaches to the tibial implant and is capable of articulating with respect to the talar implant, wherein the tibial implant has a tibia-facing surface and a lower surface opposed to the tibia-facing surface, wherein the lower surface has a cutout region extending in from an exterior perimeter of the tibial implant, the cutout region defined by a cutout perimeter shape that demarcates the cutout region from a remainder of the lower surface of the tibial implant, wherein the cutout perimeter has a tibial dovetail configuration, wherein the tibial dovetail configuration extends along two sides and at least a portion of a remainder of the cutout perimeter, and wherein the intermediate implant comprises an intermediate implant dovetail having an intermediate implant dovetail configuration that is complementary to the tibial dovetail configuration.

An embodiment of the invention comprises a tibial implant, a talar implant, and an intermediate implant fitting between the tibial implant and the talar implant, wherein the tibial implant has a tibia-facing surface and a lower surface opposed to the tibia-facing surface, wherein the lower surface has a cutout region defined by a perimeter shape demarcating the cutout region and a non-cutout region, the perimeter shape meeting an anterior edge of the tibial implant, wherein the tibia-facing surface has at least one tibial peg protruding therefrom and attached to the tibia-facing surface at an attachment region, wherein, as viewed along a direction perpendicular to the tibia-facing surface, the attachment region partially overlies the non-cutout region and partially overlies the cutout region.

An embodiment of the invention comprises a tibial implant comprising a tibia-facing surface and an opposed surface, wherein the tibia-facing side comprises a flat surface; and two pegs protruding from the tibia-facing surface; and a fin protruding from the tibia-facing surface, wherein, in a cross-section taken perpendicular to its long direction, the fin has a wide direction and a narrow direction, the wide direction being longer than the narrow direction, and the wide direction being generally perpendicular to a direction of advancement of the tibial implant, wherein the fin has a wedge-shaped end away from the tibia-facing surface that is, wherein the pegs are at least partially axisymmetric having respective axes of symmetry, wherein an anterior edge of the tibial implant is an edge having a cutout therein and a posterior direction is a direction that is opposed to the anterior edge, and the fin is more posterior than the pegs, wherein the fin has a fin centerline and the pegs have respective peg axes of symmetry, and the peg axes of symmetry and the fin centerline are all substantially parallel to each other.

In an embodiment of the invention, the tibial implant may have an outer perimeter such that, upon proceeding counterclockwise as viewed from above, the perimeter comprises a first straight edge; the first straight edge being followed by a first convex corner that meets and is tangent to the first straight edge; the first convex corner being followed by a second straight edge or a shallow arc that meets and is tangent to the first convex corner, wherein an angle of the first convex corner is greater than 90 degrees but less than 180 degrees; the second straight edge or the shallow arc being followed by a second convex corner that meets and is tangent to the second straight edge or the shallow arc; the second convex corner being followed by a first concave curve, wherein the second convex corner transitions to the first concave curve at a first inflection point, wherein there is a tangent line that is parallel to the first straight edge and is tangent to second convex corner at a tangency point that is farther from first straight edge than is the first inflection point, wherein the first concave curve continues on to cross the tangent line so as to become farther from the first straight edge than is the tangent line; wherein the first concave curve is followed by a convex curve that proceeds from the first concave curve and returns to the first straight edge to form a complete perimeter of the tibial plate.

