Trapeziometacarpal joint implant and associated methods

Abstract

A trapeziometacarpal joint implant includes a body defining a median plane, a metacarpal joint surface, and a trapezium joint surface. A first central region of the metacarpal joint surface is situated on an opposite side of the median plane from a second central region of the trapezium joint surface. The first and second central regions correspond to profiles of a first axial segment and a second axial segment, respectively. The first and second axial segments are one of a cylinder, a cone and a torus and are centered on a first axis and a second axis, respectively, where the first and second axes, as projected on the median plane, are substantially perpendicular to each other.

Claims

1. A method of implant interposing for a trapeziometacarpal joint, the method comprising: providing a trapeziometacarpal joint implant including a body defining: a median plane, a metacarpal joint surface having a first central region, and a trapezium joint surface having a second central region, the first central region being situated on an opposite side of the median plane relative to the second central region, wherein the first central region and the second central regions correspond to profiles of a first axial segment and a second axial segment, respectively, the first and second axial segments being each one of a cylinder, a cone and a torus and being centered on a first axis and a second axis, respectively, the first and second axes, as projected on the median plane, being substantially perpendicular to each other; accessing an articular area between a metacarpal and a trapezium of a patient; and interposing the trapeziometacarpal joint implant between the metacarpal and the trapezium in the articular area such that the metacarpal joint surface comes into direct contact and articulates with the metacarpal and the trapezium joint surface comes into direct contact and articulates with the trapezium.

2. The method of claim 1, wherein upon interposing the trapeziometacarpal joint implant between the metacarpal and the trapezium in the articular area, a tensile force is applied in a longitudinal direction of the metacarpal, then the trapeziometacarpal joint implant is positioned in the articular area while maintaining the tensile force, and then the tensile force is released to secure the trapeziometacarpal joint implant between the metacarpal and the trapezium.

3. The method of claim 1, wherein upon interposing the trapeziometacarpal joint implant between the metacarpal and the trapezium in the articular area, the body of the trapeziometacarpal joint implant separates the metacarpal and the trapezium by a thickness of less than 5 mm.

4. The method of claim 1, wherein the trapeziometacarpal joint implant is interposed between the metacarpal and the trapezium in the articular area such that the metacarpal is free to articulate against the metacarpal joint surface by tilting about the first axis and the trapezium is free to concurrently articulate against the trapezium joint surface by tilting about the second axis.

5. The method of claim 1, wherein the articular area is defined by a bone cortical layer of the metacarpal and a bone cortical layer of the trapezium, wherein the bone cortical layers of the metacarpal and of the trapezium are not completely removed before interposing the trapeziometacarpal joint implant between the metacarpal and the trapezium in the articular area, and wherein upon interposing the trapeziometacarpal joint implant between the metacarpal and the trapezium in the articular area, the metacarpal joint surface comes into direct contact and articulates with the bone cortical layer of the metacarpal and the trapezium joint surface comes into direct contact and articulates with the bone cortical layer of the trapezium.

6. The method of claim 5, wherein before interposing the trapeziometacarpal joint implant between the metacarpal and the trapezium in the articular area, the bone cortical layer of the metacarpal is not reshaped.

7. The method of claim 5, wherein before interposing the trapeziometacarpal joint implant between the metacarpal and the trapezium in the articular area, the bone cortical layer of the metacarpal is reshaped so as to match the metacarpal joint surface.

8. The method of claim 5, wherein before interposing the trapeziometacarpal joint implant between the metacarpal and the trapezium in the articular area, the bone cortical layer of the trapezium is reshaped so as to match the trapezium joint surface.

9. The method of claim 1, wherein the trapeziometacarpal joint implant is interposed between the metacarpal and the trapezium in the articular area such that the first central region of the metacarpal joint surface comes into direct contact and articulates with the metacarpal and the second central region of the trapezium joint surface comes into direct contact and articulates with the trapezium.

10. The method of claim 1, wherein upon interposing the trapeziometacarpal joint implant between the metacarpal and the trapezium in the articular area, the body of the trapeziometacarpal joint implant is oriented in the articular cavity such that the first axis extends in a frontal plane of the patient and the second axis extends in an anteroposterior plane of the patient.

11. The method of claim 1, wherein upon interposing the trapeziometacarpal joint implant between the metacarpal and the trapezium in the articular area, the body of the trapeziometacarpal joint implant is oriented in the articular cavity such that the first axis extends in an anteroposterior plane of the patient and the second axis extends in a frontal plane of the patient.

12. The method of claim 1, wherein the articular area is accessed via a posterior approach.

13. The method of claim 1, wherein the articular area is accessed via an antero-lateral approach.

14. The method of claim 1, wherein after interposing the trapeziometacarpal joint implant between the metacarpal and the trapezium in the articular area, the body of the trapeziometacarpal joint implant is not anchored in the metacarpal and the trapezium so as to retain freedom of movement in use.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an elevation view showing an implant interposed between a trapezium and metacarpal of a human hand, according to some embodiments.

(2) FIG. 2 is a perspective view of the implant of FIG. 1, according to some embodiments.

(3) FIG. 3 is an elevation in the direction of the arrow III in FIG. 2, according to some embodiments.

(4) FIGS. 4 and 5 are sections along the lines IV-IV and V-V, respectively, from FIG. 3, also showing some of the bones of the hand after the implant of FIG. 1 has been positioned, according to some embodiments.

(5) FIG. 6 is a diagram illustrating a design geometry of joint surfaces of the implant of FIG. 1, according to some embodiments.

(6) FIGS. 7 to 9 are diagrams illustrating other design geometries of joint surfaces of other implants, according to some embodiments.

(7) While the invention is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings. The intention, however, is not to limit the invention to the particular embodiments depicted. On the contrary, the invention is intended to cover all modifications, permutations, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(8) As used herein, the terms “frontal,” “antero-posterior,” and similar terms are to be understood in their anatomical sense in relation to a patient whose hand is being operated upon. With that in mind, in FIGS. 1 to 5, a trapeziometacarpal implant 1 is shown which is designed to be implanted by interposition in a trapeziometacarpal joint between a trapezium T and a first metacarpal M of a human hand, as is shown by way of example in FIG. 1.

(9) The implant 1 comprises a generally disk-shaped body 2 centered on a geometric axis Z-Z, also described as a transverse axis. The body 2 delimits a first main surface 4 and a second main surface 6, also referred to as metacarpal and trapezium joint surfaces, respectively, or primary bone contact surfaces, for example. In some embodiments, the first and second main surfaces 4 and 6 are positioned opposite each other on the axis Z-Z and separated from each other by the thickness of the body 2 along the axis Z-Z. The body 2 also includes a peripheral surface 8 that connects the first and second main surfaces 4 and 6. In some embodiments, the generatrices of the peripheral surface 8 are parallel to the axis Z-Z.

(10) As shown, the transverse profile of the body 2 is generally rectangular. In particular, in a cross section that is transverse to the axis Z-Z, the body 2 has a rectangular outer contour with rounded corners, although a variety of shapes are contemplated, including square, circular, elliptical, and others, for example.

(11) As shown, the implant 1 is formed as a single, unitary piece, consisting of the body 2 without extraneous components, such as a bone fixation component (e.g., a screw) for anchoring the body 2 in the metacarpal M or in the trapezium T. For example, in some embodiments, the body 2 is secured in position via interposition between metacarpal M and the trapezium T such that the body retains some freedom of movement to adapt its position to the stresses applied to it as a function of movements of the trapeziometacarpal joint.

(12) In some embodiments, the body 2 is formed as a single piece of graphite covered with a layer of pyrolytic carbon, which provides good biocompatibility, high mechanical strength, and resists wearing of the metacarpal and the trapezium. Although graphite and pyrolytic carbon have been referenced, other materials are contemplated, including metals such as chromium cobalt alloys and plastics, such as polyethylene, PEEK, silicone, as well as ceramics and others.

(13) As shown in FIG. 4, the first main surface 4 is concave and corresponds geometrically to a profile of an axial segment of a cylinder portion which is centered on a first axis X.sub.4 and defines a first cross section S.sub.4 that is substantially elliptic. In some embodiments, the first cross section S.sub.4 is constant along the first axis X.sub.4 and corresponds to the directrix of the first main surface 4. As shown, the first axis X.sub.4 extends perpendicular to the axis Z-Z, the axes X.sub.4 and Z-Z intersecting with one another (for reference, the first axis X.sub.4 extends in and out of the page as depicted in FIG. 4).

(14) As shown in FIG. 5, the second main surface 6 is also concave and corresponds to a cylinder portion whose second cross section S.sub.6 is substantially elliptic and which is centered on a second axis X.sub.6 perpendicular to and intersecting the axis Z-Z (for reference, the axis X.sub.5 extends in and out of the page as depicted in FIG. 5).

(15) Thus, as shown, the axes X.sub.4 and X.sub.6 extend perpendicular to each other and do not intersect. Base lines 41 (FIG. 2) and 61 (FIG. 3) belong respectively to the first and second main surfaces 4 and 6. Each of the base lines 41 and 61 extend parallel to the axes X.sub.4 and X.sub.6 and are perpendicular to each other. The base lines 41 and 61 are separated, on the axis Z-Z, by a central part 21 of the body 2. In different terms, in a median plane π of the body 2, which is perpendicular to the axis Z-Z and on either side of which the first and second main surfaces 4 and 6 are situated, the respective projections of the axes X.sub.4 and X.sub.6 are perpendicular and secant.

(16) In some embodiments, in cross section through the axis Z-Z, the body 2 has a variable thickness, the thickness being at its minimum in the central part 21 of the body and gradually increasing in the direction away from the central part 21 toward a peripheral part 22 of the body 2, as shown in FIGS. 4 and 5.

(17) The following method of fitting the implant in place between the metacarpal M and the trapezium T is accordance with some embodiments and is provided by way of example. Thus, in some embodiments, a first operating step includes a surgeon accessing the articular area between the metacarpal M and the trapezium T via a posterior or antero-lateral approach. To access the interosseous space between the metacarpal and the trapezium, the articular capsule and the ligaments surrounding the articular area are either preserved, by being retracted, or are partially incised, it being understood that the capsule and its ligaments will then be reconstructed at the end of intervention.

(18) In some embodiments, in a second operating step, the surgeon moves the metacarpal M and the trapezium T apart from each other in order to widen the interosseous space, in particular by applying a tensile force in the longitudinal direction of the metacarpal. The surgeon is then better able to prepare the bone surfaces delimited by the metacarpal M and the trapezium T, in such a way as to shape these surfaces so that they match the first and second main surfaces 4 and 6 of the body 2 of the implant 1.

(19) In practice, it will be noted that the mutually facing ends of the metacarpal M and of the trapezium T have respective surface geometries that are close to surfaces matching the first and second main surfaces 4 and 6. This is because these bone ends, in their anatomical state, have saddle shapes, which fit orthogonally one into the other. Thus, the cuts made in the bone on the mutually facing ends of the metacarpal M and the trapezium T for adapting the surface of the bones M and T to the surfaces 4 and 6 of the body 2 can be minimal, according to some embodiments. In particular, the cuts are often minimal or even unnecessary on the metacarpal M, whereas more substantial cuts may have to be made on the trapezium T. In some embodiments, preparation of the ends of the metacarpal M and/or of the trapezium T does not require any deep cutting into the bones, as cutting remains confined to the cortical bone layer.

(20) In some embodiments, in a third operating step, the tension applied to the trapeziometacarpal joint in the longitudinal direction of the metacarpal M is maintained. The surgeon positions the implant 1 in the interosseous space separating the metacarpal M and the trapezium T by interposing the body 2 between the two bones M and T in such a way that the first main surface 4 is directed toward the metacarpal M, with the first axis X.sub.4 extending in a frontal plane, while the second main surface 6 is directed toward the trapezium T, with the second axis X.sub.6 extending in an antero-posterior plane.

(21) In a variant not shown, the implant 1 is fitted in place, between the metacarpal M and the trapezium T, in a configuration tilted by 90 degrees about the axis Z-Z. The ends of the metacarpal M and of the trapezium T are prepared in advance of fitting the implant 1, according to some embodiments. Regardless, the body 2 is optionally implanted in such a way that the first and second main surfaces 4 and 6 adapt better to the ends of the metacarpal M and trapezium T of the patient being operated on, depending on the initial state of these bone ends, and/or to minimize a depth to which the bone ends are cut during preparation.

(22) Once the implant 1 has been positioned, or interposed, between the metacarpal M and the trapezium T, the axial tension applied to the trapeziometacarpal joint is released, such that the articular capsule and the ligaments surrounding the trapeziometacarpal joint move the metacarpal M and the trapezium T toward each other. In some embodiments, the body 2 of the implant 1 and/or the metacarpal M and trapezium T are adapted such that the implant 1 is held movably between the metacarpal M and the trapezium T, under the stress provided by the capsule and the ligaments. In other words, the capsule and the ligaments provide a stress whose resultant force, or a substantial component thereof, is substantially aligned with the axis Z-Z. The surgeon then closes the soft tissues around the trapeziometacarpal joint, if appropriate by reconstruction, or by ligamentoplasty, for example.

(23) The trapeziometacarpal joint thus fitted with the implant 1 exhibits a kinematic behavior similar to, or even nearly identical to the natural anatomical behavior of the trapeziometacarpal joint. For example, the implant 1 is configured such that the metacarpal M articulates against the first main surface 4 by tilting about the first axis X.sub.4 whereas the trapezium T concurrently articulates against the second main surface 6 by tilting about the second axis X.sub.6. By virtue of the implant 1, the metacarpal M and the trapezium T are articulated with respect to each other in the manner of a cardan joint, or universal joint, about the two perpendicular axes X.sub.4 and X.sub.6. These cardan joint kinematics efficiently reproduce the anatomical, saddle-type joint typically present between the metacarpal M and the trapezium T. Moreover, according to some embodiments, the first and second main surfaces 4 and 6 rest against the respective cortical bone layers of the metacarpal M and of the trapezium T, which helps prevent the body 2 from being forced into, or further penetrating one and/or the other of the metacarpal and trapezium bones M and T. By reducing the risk of this sinking effect of the implant 1 into bone, the mobility afforded by the implant 1 is longer lasting, and potentially lifelong in duration.

(24) In some embodiments, in order to promote the rolling and sliding movements of the metacarpal M and of the trapezium T against the respective central parts 42 of the first and second main surfaces 4 and 6, the first and second, elliptic cross sections S.sub.4 and S.sub.6 of the first and second main surfaces 4 and 6 have, in the central regions 42 and 62, a smaller curvature than a remainder of the cross section. In other words, the central regions 42 and 62 of the first and second main surfaces 4 and 6 are more flattened relative to the surrounding portions of the implant 1, such as the peripheral regions 43 and 63, the central regions 42 and 62 being less curved than the rest of these surfaces. In some embodiments, the difference in curvature of the first and second cross sections S.sub.4 and S.sub.6 of the first and second main surfaces 4 and 6 between the central regions 42 and 62 and the peripheral regions 43 and 63 of the implant is relatively minor, while still having the desired effect.

(25) In some embodiments, when in use, the body 2 is stabilized between the metacarpal M and the trapezium T on account of the elliptic curvature of the respective first and second cross sections S.sub.4 and S.sub.6 of the first and second main surfaces 4 and 6. In order to reinforce this stability, the first and second cross sections S.sub.4 and S.sub.6 of the respective peripheral regions 43 and 63 of the first and second main surfaces 4 and 6 have a greater curvature than the rest of the cross section. By exaggerating the curvature of the surfaces 4 and 6 in the area of their periphery, the surface cooperation of the body 2 with the metacarpal M and the trapezium T self-stabilizes the implant 1. Furthermore, the peripheral regions 43 and 63 of the surfaces 4 and 6 can thus compensate for the peripheral wear, associated with arthrosis, of the mutually facing bone ends of the metacarpal M and trapezium T.

(26) As shown, the body 2 is an implant of interposition. Thus, the thickness of the implant 1 along the axis Z-Z is limited, in the sense that the presence of the body 2 is adapted to avoid overstressing the trapeziometacarpal joint. Thus, in some embodiments, the maximum thickness e.sub.2 of the body 2 (e.g., the thickness between the peripheral regions 43 and 63 of the first and second main surfaces 4 and 6), is less than 5 mm, and preferably equal to about 1 mm, although a variety of dimensions are contemplated. Similarly, in order to adapt optimally to the interosseous space between the metacarpal M and the trapezium T, the second main surface 6 has a dimension L.sub.6, along its second axis X.sub.6, that is greater than a dimension L.sub.4 of the first main surface 4 along the first axis X.sub.4.

(27) The geometry of the first and second main surfaces 4 and 6 are optionally constructed with different shapes than described above. FIG. 6 is a diagram for visualizing a geometry of the first and second main surfaces 4 and 6 as shown in FIGS. 1 to 5. As shown in FIG. 6, the first and second main surfaces 4 and 6 correspond to profiles of axial segments, or portions, of cylinders defining the first and second axes X.sub.4 and X.sub.6, respectively. As shown, the axial segments have elliptical bases. In particular, the first and second cross sections S.sub.4 and S.sub.6 of the first and second main surfaces 4 and 6 have elliptic shapes centered on the first axis X.sub.4 and second axis X.sub.6, respectively. Thus, the geometric definition referenced above for the first and second main surfaces 4 and 6 is again shown here in a more schematic form.

(28) FIGS. 7, 8 and 9 are diagrams similar to the one in FIG. 6 showing geometric variants of the first and second main surfaces 4 and 6 of the implant 1. In FIG. 7, first and second main surfaces 104 and 106, also described as metacarpal and trapezium joint surfaces, respectively, are represented, each of which correspond to a profile of an axial segment of a cylinder that is centered on first and second axes X.sub.104 and X.sub.106, respectively, and of which the first and second cross sections S.sub.104 and S.sub.106, respectively, are circular and centered on the aforementioned axes. In other words, in some embodiments, the first and second main surfaces 4 and 6 and the first and second main surfaces 104 and 106 differ only in terms of the geometric shape of their cross section, namely elliptical for the first and second main surfaces 4 and 6 and circular for the first and second main surfaces 104 and 106.

(29) Similarly, in FIG. 8, first and second main surfaces 204 and 206, respectively, are represented, each of which corresponds to a profile of an axial segment of a cone that is centered on first and second axes X.sub.204 and X.sub.206, respectively, and of which the first and second cross sections S.sub.204 and S.sub.206, respectively, are circular. In yet another variant not depicted, the aforementioned first and second cross sections S.sub.204 and S.sub.206 are elliptic, rather than circular.

(30) Likewise, in FIG. 9, first and second main surfaces 304 and 306, respectively, are represented, each of which corresponds to a profile of an axial segment of a torus that is associated with circular, central, first and second axes X.sub.304 and X.sub.306, respectively, and of which the first and second cross sections S.sub.304 and S.sub.306, respectively, that is to say the cross section in a plane perpendicular to the applicable axis, is circular and centered on the axes X.sub.304 and X.sub.306, respectively. In other variants not depicted, the first and second cross sections S.sub.304 and S.sub.306 of the aforementioned torus is made elliptical. Similarly, and once again in a variant not depicted, the circular cross section or the elliptical cross section of the torus, instead of being constant along the first and second axes X.sub.304 and X.sub.306, respectively, optionally increases or decreases along the first and second axes X.sub.304 and X.sub.306.

(31) In still other embodiments, the curved geometry of the first and second cross sections S.sub.104, S.sub.106, S.sub.204, S.sub.206, S.sub.304 and S.sub.306 are continuously circular or elliptic or, by contrast, have substantial variations of curvature along their peripheries, for example. In particular, as has been mentioned above for the elliptic geometry of the first and second cross sections S.sub.4 and S.sub.6, the circular or elliptical geometry of the first and second cross sections S.sub.104, S.sub.106, S.sub.204, S.sub.206, S.sub.304 and/or S.sub.306 optionally have smaller curvatures in the central regions of the corresponding first and second main surfaces 104, 106, 204, 206, 304, and 306 and/or have a greater curvature in the peripheral regions of the first and second main surfaces 104, 106, 204, 206, 304, and 306 in relation to a remainder of the cross sections.

(32) FIGS. 6 to 9 thus illustrate various design geometries of the metacarpal and trapezium joint surfaces, or first and second main surfaces of the implant 1, according to some various embodiments. Depending upon the application, the various design geometries provide desirable articular mobility simulating that of the natural trapeziometacarpal joint, once the body 2 is implanted, given that the two opposite first and second main surfaces 4 and 6, 104 and 106, 204 and 206, 304 and 306 of the implant 1 are arranged orthogonal to each other. In other words, the opposite first and second main surfaces 4 and 6, 104 and 106, 204 and 206, 304 and 306 of the implant 1 are arranged in such a way that their central, first and second axes X.sub.4 and X.sub.6, X.sub.104 and X.sub.106, X.sub.204 and X.sub.206, X.sub.304 and X.sub.306 extend substantially perpendicular to one other. In embodiments with surfaces having corresponding curved axes, such as the curved, first and second axes X.sub.304 and X.sub.306, the feature of perpendicularity between the particular set of opposing first and second main surfaces is exhibited via projection of the axes in the median plane π of the body 2 of the implant 1, where the respective central regions of the first and second main surfaces 304 and 306 are arranged on either side of the plane π (as is also the case with the projections on the plane π of the rectilinear, first and second axes X.sub.4 and X.sub.6, X.sub.104 and X.sub.106, X.sub.204 and X.sub.206, which are also perpendicular to each other).

(33) Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, although various embodiments have been described with similar, angularly offset shapes for the various first and second main surfaces, it is also contemplated that the design geometry of the first main surface is the same as, with strictly identical or different dimensioning, or different than, the design geometry chosen for the second main surface of the implant. Additionally, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the above described features.