Trapeziometacarpal joint implant and associated methods

#Trapeziometacarpal prostheses and implants are designed to restore the strength and mobility of the anatomical joint of the thumb, between its metacarpal and the trapezium, when the joint is damaged by a degenerative or inflammatory pathological process. Many trapeziometacarpal prostheses are stem prostheses in which the metacarpal prosthetic component is anchored at one end in the metacarpal by an elongate stem while the other end of the prosthetic component is mounted pivotably either in a prosthetic component attached to the trapezium or in a cavity hollowed out in the trapezium. The implantation of these total or partial prostheses requires considerable cutting of the bone substance of the trapeziometacarpal joint and restores a ball-and-socket type of mobility which, from the point of view of kinematics, does not correspond to the mobility of the anatomical joint. Moreover, in the event of poor implantation, there are real risks of wear, luxation, or even prosthesis fracture. Some trapeziometacarpal implants without stems have also been proposed, those implants being implanted into a cavity or cavities formed in the trapezium and/or metacarpal. Often times, because of the compressive stresses applied to the implant body by the surrounding ligaments of the joint, the implant body gradually engages deeper in the bones, reducing the space between the bones and, consequently, their relative mobility.

#Some embodiments relate to a trapeziometacarpal implant that is permanently or semi-permanently implantable and provides mobility more similar to natural, anatomical mobility of the trapeziometacarpal joint. The trapeziometacarpal joint implant includes a body defining a metacarpal joint surface and a trapezium joint surface that are situated, at least in their central region, on either side of a median plane of the body. Each of the metacarpal and the trapezium joint surfaces correspond to a profile of an axial segment of a cylinder, a cone, or a torus, the axial segments of the cylinder, cone and/or torus being centered on respective axes which, as projected on the median plane, are substantially perpendicular to each other.

#Some embodiments relate to a surgical method for fitting a trapeziometacarpal joint implant in which an articular area between the metacarpal and trapezium of a patient is accessed, the cortical bone surface of the trapezium is prepared so as to substantially match the trapezium joint surface defined by a body of an implant and, if need be, the cortical bone surface of the metacarpal is prepared so as to substantially match a metacarpal joint surface defined by the body of the implant, and the body of the implant is interposed between the trapezium and the metacarpal in such a way that an axis associated with the trapezium joint surface extends in either the antero-posterior or frontal plane of the patient, while an axis associated with the metacarpal joint surface extends in the other of the antero-posterior or front planes.

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

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

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

#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.

#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.

#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.