Artificial implant for carpometacarpal joint

An artificial implant for a carpometacarpal (CMC) joint used for replacing a CMC joint surface of the first metacarpal bone is provided and has: an insert portion having an inserting end for inserting into a bone marrow cavity exposed from an incision of the first metacarpal bone, and a front end; an articular replacement portion connected to the front end of the inserting portion and disposed outside the incision of the first metacarpal bone, and having an articular profile surface to replace the CMC joint surface of the first metacarpal bone; and an attached flange protruded from a peripheral of the articular replacement portion, attached to an outer bone surface of the first metacarpal bone adjacent to the incision, and having at least one suture hole, through which at least one suture passes for assisting to fix an abductor pollicis longus (APL) to the outer bone surface.

FIELD OF THE INVENTION

The present invention relates to an artificial implant, and more particularly to an artificial implant for a carpometacarpal (CMC) joint used with a surgical suture.

BACKGROUND OF THE INVENTION

Osteoarthritis is a disease that affects the joints. When intra-articular cartilage of the joints is damaged or worn, it causes osteoarthritis, and thus affects joint stiffness, pain and loss of function. Osteoarthritis commonly occurs in hip joint, knee joint, spinal joint and joints of the hand (such as palm and thumb joint). Among these, the carpometacarpal (CMC) joint arthritis is one of the most important issue in the degenerative arthritis disease of the upper limb. The CMC joint is located at the base portion of the thumb in anatomy, wherein a distal end of the CMC joint is a metacarpal bone, and a proximal end thereof is a trapezium close to the radial side. The CMC joint is the most activity joint of hand joints and can stretch, bend, adduct, abduct and rotate. Thus, once the CMC joint is degenerated, lesioned or wounded, it will cause great influence in daily life.

When the medicament or injection can't be effective to relieve pain and can't further deal with the degenerative arthritis of the CMC joint, the doctor generally advise the patient to be treated by a hand joint surgery. Further, the design of the artificial implant and the development of material fabrication thereof are continuously improved, so that artificial implants are applied to clinical use day by day. The injured CMC joint is replaced by arthroplasty surgery, and thus it not only reduces pain from arthritis, but also maintains the CMC joint activities and the behavior function of hand.

Briefly, the arthroplasty is a surgically method for reducing the pain from arthritis and restoring the joint function. The process of a traditional surgery for replacing an artificial CMC joint is firstly to crosscut a wound from the root of the thumb, then temporarily cut and remove the tendon of a abductor pollicis longus (APL) attached to the trapezium, open a joint capsule of the CMC joint, and abscise the damaged CMC joint surface at the proximal end of a first metacarpal to form an incision. Then, a portion of an implant is inserted into a bone marrow cavity of the first metacarpal from the incision at the proximal end of the first metacarpal. Thereafter, a surgical suture is used to reconstruct the APL tendon cut during the surgery, followed by suturing the wound.

However, during the surgery, it not only needs to temporarily cut the APL in the step of moving the APL tendon originally attached to the trapezium, but also needs to drill the first metacarpal to form two small holes for the surgical suture to pass therethrough, in order to arrange the surgical suture at both sides of the APL in advance. Thus, after the artificial implant is implanted into the bone marrow cavity, the APL tendon can be attached on the outer surface of the first metacarpal by surgical suturing. As mentioned above, the steps of cutting the APL tendon or drilling holes on the first metacarpal both are to destroy the tissue of the metacarpal or the tendon before reconstruction. In addition, the surgical suture arranged in advance is easily over-pushed into the bone marrow cavity by the artificial implant when the artificial implant is implanted into the bone marrow cavity. This causes the displacement of the surgical suture and thus it is difficult to carry out the precise positioning. Alternatively, the surgical suture arranged in advance may be destroyed by the artificial implant when the artificial implant is implanted into the bone marrow cavity, it's thus more difficult to process the reconstruction surgery for the APL tendon.

Therefore, it is necessary to provide an artificial implant for a carpometacarpal joint for solving the problems existing in the foregoing conventional technique.

SUMMARY OF THE INVENTION

A primary object of the present invention is to provide an artificial implant for a carpometacarpal (CMC) joint, wherein the artificial implant for the CMC joint has an attached flange to provide suture perforation, so as to omit the step of drilling holes on the first metacarpal. This facilitates the surgical suture to be fixed onto the artificial joint implant without destroying the tendon of the abductor pollicis longus (APL). Thus, it can simplify the surgical process to improve the surgery efficiency and increase the success rate of the arthroplasty surgery of the CMC joint.

To achieve the above object, the present invention provides an artificial implant for the carpometacarpal (CMC) joint, which is used for replacing a carpometacarpal joint surface of a first metacarpal bone and comprises:

an insert portion having an inserting end for inserting into a bone marrow cavity exposed from an incision of the first metacarpal bone, and a front end;

an articular replacement portion connected to the front end of the inserting portion and disposed outside the incision of the first metacarpal bone, and having an articular profile surface to replace the carpometacarpal joint surface of the first metacarpal bone; and

an attached flange protruded from a peripheral of the articular replacement portion, configured to be attached to an outer bone surface of the first metacarpal bone adjacent to the incision, and having at least one suture hole.

wherein an interval is formed between the attached flange and the first metacarpal bone, and at least one suture passes through the interval and the suture hole, and the suture is knotted with an abductor pollicis longus for assisting to fix the abductor pollicis longus (APL) to the outer bone surface;

wherein the articular profile surface of the articular replacement portion is elliptical and includes a major axis and a minor axis, the major axis and the minor axis are crossed at a first intersection point, one end of the major axis close to the attached flange and the peripheral of the articular replacement portion are crossed at a second intersection point, a line is defined from the first intersection point to the attached flange, and an included angle defined between the line and the major axis is 1° to 45°, so that the attached flange is positioned and offset with respect to the second intersection point based on the articular profile surface; and

wherein a ratio of the length of the major axis of the articular profile surface of the articular replacement portion and the length of the attached flange is 10:1 to 2:1.

In one embodiment of the present invention, the attached flange is integrally connected to the articular replacement portion through a tilting connection surface.

In one embodiment of the present invention, the suture hole is circular, oval or regular polygonal.

In one embodiment of the present invention, the insert portion, the articular replacement portion and the attached flange are integrated into one piece.

In one embodiment of the present invention, the material of the insert portion, the articular replacement portion and the attached flange are titanium, silica gel, zirconia or pyrocarbon.

In one embodiment of the present invention, the articular replacement portion and the attached flange are made of biocompatible metal or alloy and processed by powder injection molding and high-temperature sintering.

In one embodiment of the present invention, the articular profile surface is saddle-shaped, double parabolic concave discoid, single parabolic concave discoid, spherical, hemispherical, polygonal spherical or polygonal hemispherical.

In one embodiment of the present invention, the interval formed between the attached flange and the first metacarpal bone is equal to ½ to 5/2 of the thickness of the attached flange.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings. Furthermore, directional terms described by the present invention, such as upper, lower, front, back, left, right, inner, outer, side, longitudinal/vertical, transverse/horizontal, and etc., are only directions by referring to the accompanying drawings, and thus the used directional terms are used to describe and understand the present invention, but the present invention is not limited thereto.

Referring now toFIG. 1A, an artificial implant100for a carpometacarpal (CMC) joint used for replacing a carpometacarpal joint articular surface of a first metacarpal bone according to a preferred embodiment of the present invention is illustrated. As shown, the artificial implant100for the carpometacarpal joint comprises: an insert portion110, an articular replacement portion120, and an attached flange130, wherein the insert portion110, the articular replacement portion120and the attached flange130are made of biocompatible metal or alloy, such as titanium, silica gel, zirconia or pyrocarbon. In this embodiment of the present invention, the insert portion110, the articular replacement portion120and the attached flange130are made of biocompatible metal or alloy and processed by powder injection molding and high-temperature sintering; and the insert portion110, the articular replacement portion120and the attached flange130are preferably integrated into one piece, but not limited thereto.

Referring toFIG. 1AandFIG. 1B, according to the artificial implant100for a carpometacarpal joint according to the preferred embodiment of the present invention, the insert portion110has an inserting end111and a front end112, wherein the inserting end111is used for inserting into a bone marrow cavity exposed from an incision of the first metacarpal bone. The articular replacement portion120is connected to the front end112of the insert portion110and disposed outside the incision of the first metacarpal bone, and has an articular profile surface121to replace the carpometacarpal joint surface of the first metacarpal bone, where in the articular profile surface121can be saddle-shaped, double parabolic concave discoid, single parabolic concave discoid, spherical, hemispherical, polygonal spherical or polygonal hemispherical for being corresponding to a remote portion surface of a trapezium.

Referring still toFIG. 1AandFIG. 1C, in the preferred embodiment of the present invention, when the articular profile surface121of the articular replacement portion120is saddle-shaped or double parabolic concave discoid, the articular profile surface121includes a major axis120aand a minor axis120b, wherein the attached flange130is integrally connected to the articular replacement portion120through a tilting connection surface132. The articular profile surface121is elliptical, and the attached flange130is protruded from the peripheral of the articular replacement portion120. The major axis120aand the minor axis120bare crossed at a first intersection point120c, while one end of the major axis120aclose to the attached flange130and the peripheral of the articular replacement portion120are crossed at a second intersection point120d. A line120eis defined from the first intersection point120cto the attached flange130, and an included angle θ defined between the line120eand the major axis120ais 1° to 45°, such as 2°, 4°, 6°, 8°, 10°, 12°, 15°, 18°, 20°, 25°, 30°, 35°, 36° or 40°. Thus, the attached flange130is positioned and offset with respect to the second intersection point120dbased on the top view of the articular profile surface121. In more detail, the attached flange130is located at a position offsetting 1 to 45 degrees toward an outer side of a palm from an intersection point of the peripheral of the articular profile surface121and the major axis120aof the articular profile surface121, for being corresponding to the location of an attached portion of a tendon of a abductor pollicis longus (APL). In this embodiment of the present invention, a ratio of the length of the major axis120aof the articular profile surface121of the articular replacement portion120and the length of the attached flange130is 10:1 to 2:1, such as 5:1, but not limited thereto.

In addition, in this embodiment of the present invention, the attached flange130is protruded from an peripheral of the articular replacement portion120, and can be configured to be attached to an outer bone surface of the first metacarpal bone adjacent to the incision (i.e. corresponding to the location of the attached portion of the APL tendon), wherein the attached flange130has at least one suture hole131, such as one, two, three or four, but not limited thereto. The suture hole131is circular, oval or regular polygonal, but not limited thereto. The diameter of the suture hole131is set in accordance with at least one times of the diameter of the suture. For example, the diameter of the suture hole131can be set to be two times, three times or more of the diameter of the suture. Moreover, the attached flange130is preferred integrally connected to the peripheral the articular replacement portion120through a tilting connection surface132for increasing the connection strength with the articular replacement portion120.

Referring toFIG. 2AtoFIG. 2D, in the preferred embodiment of the present invention, the artificial implant100for a carpometacarpal joint is applied for arthroplasty surgery, for replacing the damaged carpometacarpal joint. The surgical process comprises steps, as follows:

Referring toFIG. 2A, in a first step, a wound is cut from the skin of the root of the thumb, and a portion of the APL tendon attached to the outer bone surface of the first metacarpal bone200is moved aside by a forceps for at least exposing the first metacarpal bone200and the trapezium300. The carpometacarpal (CMC) joint is located between the first metacarpal bone200and the trapezium300.FIG. 2Ais an example of a right hand direction, but the surgical process is practically not limited thereto.

Referring toFIG. 2B, in a second step, the joint capsule of the carpometacarpal joint is opened, and a damaged proximal end articular surface of the first metacarpal bone200near the carpometacarpal joint is cut and removed to form an incision201. If it is necessary to replace the proximal end articular surface of the trapezium300near the carpometacarpal joint by a corresponding implant, the proximal end articular surface of the trapezium300can be also removed at the same time to form another incision301. Further,FIG. 2Balso illustrates the other adjacent bones, such as the second metacarpal bone400, the trapezoid500and the navicular bone600, so as to facilitate a clear understanding of the relative position of the bones.

Next, referring toFIG. 2C, it only briefly illustrates the first metacarpal bone200and the trapezium300ofFIG. 2B. In a third step, the artificial implant100for the carpometacarpal joint is inserted into the bone marrow cavity202of the partially cut first metacarpal bone200through the incision201thereof in manner of the articular replacement portion120facing outward and the insert portion110facing inward. It should be noted that, before the artificial implant100for the carpometacarpal joint of the present invention is inserted into the bone marrow cavity202, it is unnecessary to drill any hole on a bone wall of the first metacarpal bone200in advance for being used as an attachment for fixing the artificial implant. Thus, the surgical process can be relatively simple. If necessary, the incision301of the trapezium300is formed in advance, and the other artificial implant302also can be embedded into the incision301.

Subsequently, referring toFIG. 2D, in a fourth step, according to the design of the artificial implant100of the present invention, the attached flange130is preferably located at the radial side of the first metacarpal bone200. That is to say, the attached flange130is located at a position offsetting 1 to 45 degrees toward an outer side of a palm from the intersection point of the peripheral of the articular profile surface121for being corresponding to the location of the abductor pollicis longus700of the first metacarpal bone200, wherein an interval133is formed between the attached flange130and the first metacarpal bone200(also as shown inFIG. 2C), and the attached flange130is used to allow at least one suture800to pass through the interval133and the suture hole131, so that the suture hole131provides a structural base for securing the suture800. In the embodiment of the present invention, the interval133formed between the attached flange130and the first metacarpal bone200is equal to ½ to 5/2 of the thickness of the attached flange130, such as 0.5, 1, 1.2, 1.25, 1.5, 2 or 2.5 times thereof; the suture800is made of biocompatible or biodegradable material and can be a single strand type, a double strand type or a multi-strand type, but not limited thereto.

In suturing, the abductor pollicis longus700attached to the outer bone surface of the first metacarpal bone200is returned by a forceps, then the suture800passes through the suture hole131and the interval133, and is knotted with the abductor pollicis longus700by Krackow suturing or other suturing techniques, wherein the attached flange130is attached and flush to the outer bone surface of the first metacarpal bone200adjacent to the incision201. Therefore, after the abductor pollicis longus700is stitched on the attached flange130by at least two sutures800, it would be beneficial to allow the abductor pollicis longus700to be attached and flush to the outer bone surface of a front side of the first metacarpal bone200in a manner of surface contact, for the purpose of reattaching the tendon of a abductor pollicis longus to the outer bone surface.

Finally, the wound of the skin is sutured to complete the arthroplasty surgery of the carpometacarpal joint. It should be noted that, during the surgery process, the abductor pollicis longus700can be sutured and fixed to the outer bone surface of the first metacarpal bone200and the attached flange130without cutting the abductor pollicis longus700, so as to simplify the arthroplasty surgery of the carpometacarpal joint.

As described above, in comparison with the traditional artificial implant for the carpometacarpal joint, it can relieve the pain of the carpometacarpal joint arthritis, but needs to drill holes on the first metacarpal bone or to cut the abductor pollicis longus before implanting the artificial implant, such that the complexity and inconvenience of the arthroplasty surgery is increased. Thus, in contrast, the artificial implant for the carpometacarpal joint of the present invention is provided with the suture hole131formed on the attached flange130of the artificial implant100for the carpometacarpal joint, which not only can omit the step of drilling holes on the first metacarpal bone but also can easily fix the surgical suture on the artificial implant without destroying the abductor pollicis longus. As a result, the present invention can simplify the surgical steps and improve surgical efficiency, thereby increasing the success rate of the arthroplasty surgery of the artificial implant for the carpometacarpal joint.