GB2269752A - Anatomic wrist - Google Patents

Abstract

An implantable wrist prosthesis comprises an assembly of components 21, 22, 30 for use as a replacement for a disfunctional wrist joint. A carpal component assembly 21 comprises a capitate replacement spur 23, which is implanted into the two adjacent second and third metacarpal bones, and an intermediate component, which is connected to the spur 23 by a ball and socket connection. A radial component 22 which is inserted into the radius 10, includes a pair of ellipsoidal grooves for articulation with a pair of mating ellipsoidal convex surfaces on said intermediate component. In addition, a joint of a ball and socket configuration 30, 33 provides a connection between a stem for affixation into the ulnar 11 and the radial component 22. <IMAGE>

Description

Anatomic Wrist This invention relates to prosthesis medical devices, and more particularly it relates to an implantable anatomic wrist component and to an implantable wrist prosthesis which incorporates an improvedd assembly of components for use as a replacement for a dysfunctional wrist joint.

Several prosthesis have been constrained as hinges and have resulted in loosening.

A European model by Mueli and an American model by Hamas produced by Zimmer are simple ball and socket joints.

The problem with these wrist joints was reproducing the center of rotation of the wrist which is, in fact, at the capitate. These wrists would frequently go into imbalance.

There was an additional problem with a loosening in the bones since the Llamas was fixed in only a single metacarpal.

The present Beckenbaugh Mayo Clinic wrist and the present Biomet wrist fix only a third metacarpal and are therefore subject to loosening. They also do not allow for adjustment in the length of the prosthesis which is a definite limitation to the surgeon and the patient.

Finally, they do not capture the instant center of the wrist at the capitate but rather give the patient an elliptical articulation which the surgeon hoped would approach the center of the wrist.

The following cited patents provide some indication of prosthetic wrist joints which have been conceived. however, neither these joints nor the joints known in the prior art as lamas joints or the Mueli joint presently in use, provide the various desirable features which have been incorporated in Applicant's wrist prosthesis.

Yout et al US 4,229,841 Weber US 4,307,473 Green et al US 4,352,212 Beckenbaugh et al US 4,784,661 U. S. Patent to Weber, No. 4,307,473 and U. S. Patent to Green et al, No. 4,352,212 each show a cylindrical head of the metacarpal component received within a semi-cylindrical recess of the radial component.

The Youm et al patent, No. 4,229,841 relates to a wrist prosthesis with a proximal component affixed to the radius of the forearm. A distal component is affixed to the hand.

Both are connected by a joint which prevents axial rotation between the components relative to the forearm axis. They provide relative movement of the axis for radial-ulnar hand movement and flexion-extension hand movement. This prosthesis structure differs substantially from the structure of the instant invention which will be described subsequently.

The Beckenbaugh et al U. S. Patent No. 4,784,661 is the only pertinent patent of the prior art known to the inventor. It relates to an endo-prosthetic wrist replacement device comprising two components which have means for intramedullary implantation in the radius and a metacarpal bone, respectively.

The radial component is provided with a distal head in which there is a distally facing transversely extending groove trough of generally semi-cylindrical configuration.

The metacarpal component has a proximally located ovoid ball head of generally oval shape in cross section which is received within the head of the radius component.

It is shaped in the proximal-distal direction to conform to the semi-cylindrical groove trough in a transverse direction allowing flexion and extension and radial and ulnar deviation as the oval metacarpal component moves within the radial trough. The ovoid ball does not duplicate the instant center of the wrist at the capitate and the single stem of the metacarpal component is prone to loosen.

In the specification of Beckenbaugh, there is an adequate description of prior art joint prosthesis patents and this description by Beckenbaugh is hereby incorporated by reference into this patent application. It also includes some indication of a prosthetic wrist joint which has been conceived, and is considered to be the most pertinent prior art. However, none of the prior art joints provide the various desirable features which have been incorporated in the wrist prosthesis.

These artificial wrist joints use methylmethacrylate, an acrylic bone cement used to secure the prosthetic stems or spurs to the bones. The metal components are fabricated from a biologically inactive metal, Vitallium and high density polyethylene.

These materials are utilized to minimize friction between metal and plastic parts and thereby maximize wear life.

Viewed from one aspect the present invention provides an anatomic wrist implantable component for implantation with the adjacent metacarpal bones and radius bone of a human hand and wrist to provide an artificial wrist joint, comprising, an assembly of a pair of interconnected adjacently disposed means configured for implantation in the adjacent metacarpal bones of a human hand and terminated by a frictional surface means for engagement and relative movement with respect to another component of a wrist prosthesis, means providing a ball and socket connection, said implantable component being interconnected to said frictional surface means by said means providing said ball and socket connection.

In a preferred embodiment of this invention, flexion or extension simulating the normal motion of the human wrist is provided by a biconvex joint portion similar to that of Beckenbaugh which is received in a biconcave longitudinal spur portion provided in the radius.

The novel preferred configurations for the components of the bearing portions of the joint movement component provide an accurate reproduction of the movement required in the activities of daily living.

The normal human wrist comprises attachments and actuations of three sets of bones. The forearm, comprising the radius and ulnar is one set, the carpals as a second set, and the metacarpal bones comprise the third set. The carpals are the bones most closely associated with the motion of the wrist.

As aforestated, in the forearm, there are two bones, the radius and the ulnar. In the wrist there are eight carpals, which are divided into rows, the proximal and the distal. The proximal row includes a navicular, a lunate, a triguetrum and a pisiform. The distal row includes a trapezium and a trapezoid, a capitate and a hamate. There are five metacarpals consecutively arranged from the thumb through the last or little finger.

Wrist movement is divided between the radiocarpal and mid-carpal joints of the wrist, in a relatively complex manner. ' The configuration of each row of bones changes according to the position of the hand. Although both joints contribute to all hand motions, palmar flexion is predominately a mid carpal motion. In dorsiflexion, it is radiocarpal.

Ulnar deviation also occurs at the radiocarpal joint, while radial deviation takes place at the mid-carpal radial level. In the anatomic wrist, the motion is simplified preferably allowing prosthetic 35 degrees dorsiflexion and 35 degrees palmar flexion at the radiocarpal component junction and 15 degrees radial and 15 degrees ulnar deviation at the metacarpal capitate - carpal component.

Deterioration or destruction of the carpal bones, or loss of integrity of their ligaments with secondary stiffness and pain affects the joint and results in wrist disability.

The carpal bones are held together by ligaments.

Collateral ligaments provide lateral support of the wrist, while palmar radiocarpal and dorsal radiocarpal ligaments maintain support of the carpal area. These ligaments define a symmetrical pattern due to insertions into the scaphoid lunate, triquetrum and capitate bones. It is important that the integrity of the radiocarpal and ulnar carpal bands of ligaments as well as the dorsal and volar capsule be maintained in carpal bone surgery and that these tissues not be interfered with or impinged on by the implant.

Currently, there are a number of devices available for either total or partial prosthesis of the wrist joint.

These devices use one or more of the possible types of mechanical articulations available, which are the hinge, ball and socket, or anatomic spacers.

Most devices use intramedullary stems and methyl methacrylate bone cement to secure the prosthesis to the bone. Presently available prosthesis have components constructed from several types of biologically inactive metals and they are designed to articulate with other components constructed from a plastic such as high density polyethylene.

Several methods or techniques are used to insure that the components remain articulated, and these methods include the use of soft tissue existent at the time of implantation, the use of pins or screws to hold the articulate surface together and the use of band type locks. Certain types of available prosthesis are quite simple while other types comprise complex mechanical systems, with both types having attendant or inherent disadvantages.

The principal disadvantage of the simple prosthesis is that they may not reproduce an adequate, stable range of motion of the joint and frequently distort it, while the principal disadvantage of the complex prosthesis is the potential difficulty of surgery and increased failure.

Finally, existing prosthesis do not center the anatomic axis properly as no other includes the distal ulnar as part of the component.

Severely arthritic wrists are presently still preferentially treated by wrist fusion. This procedure leaves the patient unable to place the hand where he needs to place it for the activities of daily living wherein 70 degrees of flexion and extension are routinely used.

This anatomic wrist invention relates to a mechanical device for surgical replacement of certain bones and joints, in a diseased or otherwise damaged human wrist. In preferred embodiments there is provided a total wrist prothesis providing maximum correspondence of the provided motion with that of the human wrist.

Total wrist arthroplasty involves prosthetic replacement of the wrist by an artificial joint designed to simulate normal wrist motion. Prosthetic replacement of the wrist requires careful consideration of both anatomic and mechanical factors, together with application of the skilled surgical techniques of implant fixation and recognition of soft tissue balance across the wrist.

The surgically implantable wrist prosthesis of the illustrated embodiments of the present invention incorporates an improved assembly of components which is particularly well adapted and intended-for use in replacement of the dysfunctional wrist joint.

There are three components to this implantable prosthesis.

The metacarpal component comprises a capitate replacement from which two spurs insert into the medullary canal of the adjacent, stable, second and third metacarpal bones. A radial component inserts into the adjacent radius.

In the illustrated embodiments, the carpal component preferably comes in three adjustable thicknesses to attach to the capitate as a ball and socket "pop ball" joint where it is allowed to move in a radial ulnar deviation plane and articulate with the radial component as a biconvex articulation with the biconcave radial component where it is 'allowed to flex and extend.

There is an additional and optional ulnar component which allows articulation from the radial component to the distal ulna. This is preferably comprised of an ulnar cap which captures an ulnar head ball. It then receives an ulnar stem which is in turn, preferably inserted into the patient's distal ulna by a flex lock peg. Free movement of the ulnar ball within the ulnar cap, and free motion of the ulnar stem within the ball allows full and stable pronation and supination.

The kinematics of the wrist are very complex in the motions thereof. In the past the wrist motions could not be simply reproduced and incorporated in the design of joint prosthesis. Based on experience of previous wrist arthroplastesis and anatomic and kinetic principles found in the literature, a successful compromise is achieved in at least preferred embodiments of the present invention.

The studies which have been directed to normal wrists of healthy individuals have led to the finding that the center of rotation of the wrist is located within the head of the capitate. In the case of radialulnar deviation, the center of rotation has been found to lie toward the ulnar side of the axis of the third metacarpal and the axis of the distal radius.

The center of flexion-extension motion of the wrist was known to be offset toward the palm or volar from the axis of the third metacarpal of the additional radius also located in the head of the capitate. Pronation and supination are rotational movements of the arm about the longitudinal axis of the distal ulna. The wrist does not rotate significantly in relation to the radius, hence the wrist has been described as a biaxial joint with two degrees of freedom.

The index finger or second metacarpal is stable in its attachment with the capitate and lesser multiangular (trapezoid), function with very little motion occurring between these bones during all natural positions of flexion-extension motion or radial-ulnar deviation.

Also, the head of the capitate contains the rotation of both of the aforementioned motions. The capitate-third metacarpal fixed unit is likewise stable, therefore the logical position choice for the metacarpal component of the wrist prosthesis is fixation between these stable index and long fingers (second and third) metacarpals, a single metacarpal fixation having proven unstable and quick to loosen.

The anatomic wrist preferably captures the instant center exactly with the capitate metacarpal component.

It allows radial ulnar deviation at that point and allows flexion and extension at the radiocarpal joint preferably within the 70 degrees of motion that patients historically have found necessary for the activities of daily living.

Previous ball and socket joints which have allowed 100 to 110 degrees of motion have been known to reduce to the 70 degrees of motion over time as that seems to be the motion that the patient uses in the activities of daily living. Finally, the incorporation of an ulnar component to this wrist is a first and allows stability on the ulnar side of the joint in patients whose distal radial ulnar joint is destroyed by the same disease that has destroyed the radiocarpal joint.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein: Fig. 1 is an illustration of a posterior-anterior view of a skeleton of a right wrist and hand; Fig. 2 is an illustration of a lateral view of the skeleton of the wrist with a number of 'bones being omitted for purposes of clarity; Fig. 3 is a diagrammatic posterior-anterior view of the skeleton of the right hand with a prosthesis according to a first embodiment of the present invention inserted therein; ; Fig. 4 is a diagrammatic view of the skeleton of a wrist, with a second embodiment of prosthesis inserted therein which embodiment is similar to Fig. 3 incorporating the prosthesis of Fig. 3, yet additionally including a stem implant for the ulna, which as illustrated has an additional ball and socket joint coupler for the provision of a certain amount of control of wrist movement and is further characterized in that the spurs disposed respectively in the radius and the ulnar reside in a common plane; Fig. 5 is a left side elevation view of the metacarpal-capitate component with elements of the prosthesis shown in their assembled relationship; Fig. 6 is a bottom plan view of the metacarpal-capitate subassembly of Fig. 5 of the prosthesis in carpal component;; Fig. 7 is a right side elevation view of a trough socket and stem portion of the radial prosthesis which receives and mates with the subassembly illustrated in Figs.

5 and 6 with the stem portion thereof configured for insertion into the radius bone; Fig. 8 is a frontal oblique perspective view of the subassembly of components of Fig. 7; Fig. 9 is an assembled side elevation view of the preferred embodiment of the prosthesis of Fig. 4: Fig. 10 is partially sectional elevation view of the subassembly of Fig. 6; Fig. 11 is a front end elevation view of the portion of the implant which includes the implantable stem for the radius bone of the embodiment of Fig. 3; Fig. 12 is a top plan view of the element of Fig. 11; Fig. 13 is a front end elevation view similar to Fig.

11, but further illustrating the ball and socket joint for the ulnar implant portion of Fig. 4: Fig. 14 is a top plan view of the element of Fig. 13: Fig. 15 is a left side elevation view similar to Fig.

7, but additionally illustrating details of a flex lock peg disposed at the terminal end of the stem for implantation and fixation in the ulnar bone; and Fig. 16 is a detail illustration of the ulnar stem which is received in the bore of the captive ulnar ball.

In order to better promote an understanding of the principals of the invention, reference is now made to the two preferred embodiments illustrated in the drawings.

Specific and consistent language is used throughout the description to describe variations between the two embodiments (as illustrated in the drawings), wherein the same or like reference characters are used for the same purpose throughout the various Figs. of the drawings.

Specific language relating to wrist anatomy is used to describe the drawings.

It is to be understood that no limitation of the scope of the invention is intended, although alterations and further modifications of the two illustrated embodiments of the wrist prosthesis devices may come to mind or be made.

Such further and/or structurally simplified applications of the principals of radius bone embodiment are herewith not suggested. The more complex preferred radius and ulna embodiment of the invention are contemplated to the extent that would normally occur to one skilled in the art to which the invention relates without resorting to the exercise of invention.

Referring now to Fig. 1, a showing is made in profile of a healthy right wrist skeleton. The hand is supported by two bones, the radius 10 and the ulnar 11. These bones bear upon each other at their distal extremities and the distal face of the radius comprises an important articular surface indicated at 12.

Additionally, Fig. 1 illustrates the bones in the hand including the second metacarpal 13 and the third metacarpal 14 which are just behind the index 15 and middle finger 16, respectively. Eight carpal bones (carpus) are shown between the articular surface 12 of the radius and the metacarpals.

The capitate 17 is fixed, relatively, to the third metacarpal 14. These two bones move as a unit to define the plane of the hand in both flexion-extension and radial-ulnar-deviation.

Disposed at the base of the second metacarpal 13 is a carpal known as the trapezoid.

The two axis of wrist motion are known to pass through an area known as a head 17A of the capitate 17. In Fig. 1, the radial side of the wrist is the side on which the radius 10 is located, while the ulnar side is the side in which the ulnar 11 is located.

Fig. 2 of the drawings illustrates the dorsal side of the wrist which is the side corresponding to the back of the hand while the volar or palmar side of the wrist is at the side corresponding to the side of the palm of the hand.

Referring to Figs. 3 and 4 of the drawings, there is illustrated the basic structural assembly of component elements of the two embodiments of a wrist prosthesis as implanted in a reconstructed wrist. One wrist prosthesis embodiment, Fig. 3, is for the radius bone 10 and an alternative more elaborate construction, Fig. 4, which further includes a ball and socket joint and stem for the ulnar bone 11.

The illustration is made with portions thereof not shown for purposes of clarity, which may be construed either as a second embodiment of the invention or as an intermediate component comprising a portion of Fig. 3 prosthetic wrist joint with the ulnar assembly not being shown and thereby illustrating a somewhat pictorial side view of the hand with the prosthesis of either of two embodiments incorporated therein.

Referring now, more particularly to Figs. 3 and 4, there is illustrated a pair of wrist prosthesis embodiments 20 positioned within the human wrist. Basic procedures employed in the implantation of either of the wrist prosthesis configurations or embodiments of the present invention is well known in the art and does not differ substantially from other procedures applicable with prior art devices known to those skilled in the art to which this prosthesis pertains.

Since these procedures are known to practitioners skilled in the art, and do not form a part of the present invention, details of the procedure are not considered necessary to a full understanding of the description of the present invention and are not provided herein. As can be noted from Figs. 3 and 4, in locating the prosthesis in position certain of the carpals are removed from the wrist and the distal radius 10 and ulnar 11 are resected. This removal of the carpi and resectioning of the distal radius and ulnar is similar to that carried out in other wrist prosthesis operations.

By reference to Fig. 3 of the drawings, it will be observed that the wrist prosthesis 20 includes a metacarpal-capitate component 21 and a radial component 22.

The metacarpal-capitate component 21 has a fixation spur and stem combination 23 which is of a dual nature and is located through the capitate 17 and into the medullary cavity at 24 of the second and third metacarpals as indicated at 14. The radial component 22 also has a fixation spur 26 which is located in the medullary cavity at 27 of the radius 10.

As shown with respect to the preferred embodiment of Fig. 4, the metacarpal component 21 has a convex ball shaped articulating surface 19 which extends from the base portion of the metacarpal component. It is pivotally received within a hemispherically concave ball shaped socket in the carpal component which then provides an articulating surface for the radial component 22 when the device is inserted in the wrist.

The details of the preferred embodiment of the metacarpal component 21 of the prosthesis 20 will be more particularly described with respect to Figs. 5 and 6. The metacarpal component 21 includes dual fixation stems indicated at 23 attached to a head portion 25 wherein the head portion 25 defines a semi-spherical articulating surface at 28. The capitate stem provides a third point of fixation for the metacarpal-capitate component thereby further decreasing the chance of loosening of this component.

The metacarpal-capitate component is seen with a central stem which inserts in the stable third metacarpal and a shorter second stem which inserts in the second metacarpal. This position, angulation arc and length allows for easy surgical insertion into the two metacarpals simultaneously with maximum stabilization in the second metacarpal while allowing minimal difficulty with its insertion.

The ball portion of this metacarpal component matches the size and position of the patient's capitate. In the event of collapse of the capitate, it can still substitute for the prior position by removal of less bone.

The carpal component duplicates the joint surfaces of the scaphoid and lunate which have been removed. It comes in three sizes, increasing at 2mm. increments which allows adjustment of the carpal height or muscle tension across the artificial wrist joint.

The radial component 22 duplicates the scaphoid and lunate fossa in the normal radius. It allows 70 degrees of motion in flexion-extension while being totally unconstrained. The radial ulnar deviation occurs at the metacarpal-capitate component 21 allowing 15 degrees of radial and 15 degrees of ulnar deviation which is required for activities of daily living.

The flexion and extension occurs in an unconstrained manner at the radio-carpal junction. however, because it is unconstrained, it relieves any constraint on radial ulnar deviation in the metacarpal carpal component.

The radial component 22 is fixed to the distal end of radius 10 by the radial stem 26 which is held with methylmethacrylate glue. The metacarpal component stems are likewise, held in the metacarpals with methylmethacrylate glue.

In the event that an ulnar component is desired, the ulnar head is replaced with a cap not shown, but located at 29 and ball 30 which receives the ulnar stem 31. The ulnar stem 31 is glued into the ulna 11 and held at proper length by the flex lock peg. The shank end of stem 31, as illustrated in Fig. 16, which is a loose or slip fit in ball 30 to provide for a desirable longitudinal movement in fitting the ulnar stem relative to the ball, which receives the cylindrical shank end thereof. As the radial component 22 is inserted, it is received in the radial head ball 19 and this allows stable support of the radial component 22.

It allows full pronation and supination and is yet, unconstrained in distraction to protect from loosening.

The stem 26 portion as shown in Figs. 7, 8, 9 and 12 illustrates the portion implanted in the distal end of radius 10 as aforementioned. Fig. 13 shows the addition of a laterally disposed socket 33 which receives a ball 30 as shown in Fig. 14 and which is a view looking toward the longitudinal groove of Fig. 11 and the rear portion of -the half-socket of Fig. 13.

Fig. 14 is a plan view which shows an assembly of the socket 33 and ball element 30 of the stem 31 for the ulnar implantation. It shows a flex-lock peg 32 locking arrangement also shown in Figs. 9, 14 and 16 which retains this stem in the bone structure. The locking end is comprised of a plurality of circular disc-like elements which will deform as the implant is inserted in the ulna bone 11, and which thereafter resists longitudinal movement in the opposite direction thereby preventing loosening of the connection with the bone.

The details of the spur stems and ball and socket joint are indicated in further detail in Figs. 5, 6 and 7 wherein the stem 23 also includes a depending spur 34 which is implanted in the carpal. The plan view in Fig. 6 shows the configuration of the surface of the intermediate member which as shown incorporates the socket portion of the ball and socket connection.

The capitate ball is captured by the carpal component in Fig. 5 by the flexibility of the high density polyethylene.

The ulnar head 33 captures the ulnar ball 30 by reducing the balls size by freezing. The ball 30 once expanded to room or body temperature, will turn freely but is not easily dislocated from the ulnar head.

The configuration can possibly be described in a manner more readily understood by indicating that a portion of this would be in the shape of the knuckles of two fingers, that is, they have a round configuration in plan but are somewhat cylindrical in elevation as shown by Fig. 10.

Fig. 7 shows the curved view in which the vitallium portions of Fig. 6 may articulate in the general configuration of the intermediate portion contained in the socket as shown in the cross section in Fig. 10. The major portion of the sub-assembly of Fig. 6 would ride without mechanical restraint at the right inside portion thereof in grooves of longitudinal trough like semi-cylindrical cross sectional configuration with generally spherical ended portions of the grooves as shown in the view of Fig. 8.

The two units are assembled as shown in Fig. 9 and a distally extending spur 23 shown in Fig. 7 is implanted in the metacarpal while the proximally extending spur 26 is implanted in the radius. Fig. 11 is a view looking directly into the dual grooves of the left hand portion of Fig. 7 while Fig. 12 is a plan view incorporating the grooves of Fig. 11 therein.

It is considered to be apparent from the foregoing description that the illustrated embodiments provide a metacarpal-capitate component constructed anatomic divergence of the second, third metacarpal stems to give maximum stability, while allowing ready insertion in the human hand.

Attention is directed to the fact that adjustable components allow adjustment of carpal length at surgery.

It is invisioned that carpal components varying in size by increments of approximately 2mm will accommodate this adjustment capability at surgery. Also prosthesis sizes may vary by about 20 percent between the sizes respectively between male and female patients.

In the case of female patients with large hands, the larger male size may suffice.

It is also considered to be apparent that the availability of the ulnar component and its adjustability resulting from the slip fit of the ulnar stem in its ball further enhances the utility of the prosthesis to provide advantages not heretofore known in the prior art.

Thus, in at least preferred embodiments there is provided a new and novel implantable wrist joint prosthesis design wherein the design concerns in use, the ability of the surgeon to adjust carpal height; and the fixation of the prosthesis device to two metacarpals parts, thereby further obviating loosening of the fix, and by allowing inclusion of and fixation to the distal ulna thereby directed to the interaction of a plurality of components in the prosthesis, which afford a movement and degree of freedom similar to those 'of the natural wrists; and there is provided a carpal component of varying height which allows adjustable tension and length at the time of surgery; and there is provided an improved wrist prosthesis design which overcomes and/or obviates substantially all of the shortcomings or disadvantages of prior implantable wrist prosthesis devices and which wrist prosthesis represents the most anatomic replacement of the wrist joint to date and is a significant advance over existing implantable components; and there is provided a laterally extending plurality of components comprising a ball and socket joint, which is configured to provide for a certain degree of and arranged for connection with the ulnar to provide desired wrist rotation; and there is provided an implantable wrist prosthesis having a unique metacarpal attachment, anatomic in design allowing stability while being easily insertable.

Aspects of the invention have been described in detail with reference to two somewhat different embodiments, the choice of which in practice, is determined by the surgeon to fit the needs of patients.

Accordingly, the preferred illustrated embodiment thereof which as a wrist joint prosthesis is the more complex of the two embodiments in that it incorporates the first ulnar component device.

It is intended that reference to this second embodiment as an additional embodiment shall not limit the scope of the invention relative to a first prosthesis embodiment, i.e. not providing an ulnar implant device for rotational movement of the wrist, as some patients require only the radius bone implant.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that having regard to the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

Claims (28)

CLAIMS:

1. An anatomic wrist implantable component for implantation with the adjacent metacarpal bones and radius bone of a human hand and wrist to provide an artificial wrist joint, comprising, an assembly of a pair of interconnected adjacently disposed means configured for implantation in the adjacent metacarpal bones of a human hand and terminated by a frictional surface means for engagement and relative movement with respect to another component of a wrist prosthesis, means providing a ball and socket connection, said implantable component being interconnected to said frictional surface means by said means providing said ball and socket connection.

2. The anatomic wrist implantable component of claim 1, a pair of spur means, with the ball of said ball and socket connection assembly being integrally attached to the rearward portion of said pair of spur means, and the socket portion of said ball and socket assembly being secured to the forward portion of said frictional surface means.

3. The anatomic wrist implantable component assembly for an anatomic wrist prosthesis of claim 1, wherein the socket of said ball and socket assembly is fixedly attached to the rearward end of said stem assembly and the ball is secured to the forward end of said frictional surface means.

4. An anatomic wrist implantable component for an anatomic wrist prothesis of claim 1,2 or 3, comprising a forward portion having a frictional engagement surface means and a radius bone stem means disposed at the opposite end thereof.

5. The anatomic wrist implantable prosthesis component for an anatomic wrist prosthesis of claim 4, further having a laterally disposed ball and socket assembly, the ball of said socket assembly having a diametrical bore therethrough for reception of a pin means of a ulnar bone spur means.

6. The anatomic wrist structure for an anatomic wrist prosthesis of claim 5, further including a stem for implantation in the ulnar bone, said means having a rod element for slidable reception in the diametric bore of the ball of the laterally disposed ball and socket assembly of the radius bone stem means, thereby providing for length adjustability of said ulnar bone stem means in the bore of said ball.

7. The anatomic structure for an anatomic wrist prosthesis of claim 6, further comprising the incorporation of a flex-lock means at the implantable terminal end of the stem for the ulnar bone.

8. An anatomic wrist implantable component for an anatomic wrist prosthesis comprising an assembly of a pair of interconnected adjacently disposed stems configured for implantation in the adjacent metacarpal bones of a human hand and terminated by a frictional surface element for engagement and relative movement with respect to another component of a wrist prosthesis, said implantable component being interconnected to said frictional surface element by means providing a ball and socket connection.

9. The anatomic wrist implantable component of claim 8 being further characterized by the ball of said ball and socket connection assembly being integrally attached to the rearward portion of said pair of stems and the socket portion of said ball and socket assembly being secured to the forward portion of said frictional surface element.

10. The anatomic wrist implantable component assembly of claim 8, wherein the socket of said ball and socket assembly is fixedly attached to the rearward end of said stem assembly and the ball is secured to the forward end of said frictional surface element.

11. An anatomic wrist implantable component for an anatomic wrist prothesis of claim 8, 9 or 10, comprising a forward portion having a frictional engagement surface and a radius bone stem portion disposed at the opposite end thereof.

12. The anatomic wrist implantable prosthesis component of claim 11, further having a laterally disposed ball and socket assembly, the ball of said assembly having a diametrical bore therethrough for reception of a pin of a ulnar bone spur.

13. The anatomic wrist structure of claim 12, further including a stem for implantation in the ulnar bone, said stem having a rod element for slidable reception in the diametric bore of the ball of the laterally disposed ball and socket assembly of the radius stem, thereby providing for length adjustability of said ulnar stem in the bore of said ball.

14. The anatomic structure of claim 13, further comprising the incorporation of a flex lock peg at the implantable terminal end of the stem for the ulna bone.

15. An anatomic wrist prosthesis for implantation respectively with adjacent metacarpal bones and radius bone of a human hand and wrist to provide an artificial wrist joint, comprising, in combination, a dual stem portion component for implantation into two adjacent metacarpal bones, terminated at a portion thereof remote from the implantable portions of said dual stem portion component with a substantially spherical ball, an intermediate component of said prosthesis having a hemispherical socket concavity for reception and moveable retention of said ball of said dual stem portion component, said intermediate component having the aforementioned receptacle portion, further defining ellipsoidal male dual-convex portions at the rear portion of said component remote from said first mentioned hemispherical socket concavity, said portion being configured and adapted to be received for movement in a third component of said prosthesis, said third component incorporating as a head portion thereof, a stem for implantation in the radius bone of a human arm, said third portion having a pair of ellipsoidal grooves at the head end thereof configured as semi-circular in cross section to receive and allow for linear movement of the intermediate component in said longitudinal ellipsoidal grooves, providing a concave articulating surface shaped complimentary to the ellipsoidal convex articulating surface of said intermediate component, first affixation means for affixing a first fixation stem portion and a second fixation stem portion thereof respectively to one of the adjacent metacarpal bones of said human hand, and further having a spur of smaller dimensions disposed below said dual stems to be implanted into a carpal bone, an additional fixation stem means providing for fixation in the radius bone.

16. The anatomic wrist prosthesis of claim 15, being further characterized in that the ellipsoidal convex articulating surface of said first intermediate component is substantially convex with the ellipsoidal concave mating articulating surface portion of the adjacently disposed receiving portion thereof, there being only a non-mechanical, frictional connection between these two articulating surface portions when mutually engaging one another.

17. The anatomic wrist prothesis of claim 15or 16, in which said first component is provided with a laterally disposed semi-socket for captive engagement reception of a ball disposed therein to provide a limited ball and socket type movement configuration, an additional component comprising a ball disposed thereon, having an axial bore therethrough and having a rod like shaft portion dimensioned to provide a sliding fit of one end thereof in the bore of said ball disposed thereon and further terminating in an opposite end portion including a stem for implantation and fixation in the ulhar bone.

18. The anatomic wrist prosthesis of claim 17, further including fixation means for retention of the last mentioned stem in the ulnar bone.

19. The anatomic wrist prosthesis of claim 18, wherein said fixation means for the ulnar bone includes a deformable locking component at the terminal end thereof remote from said ball, which is readily inserted, but after implantation, provides a locking means disposed and arranged to prevent loosening or ready removal of said fixation means thereof.

20. The anatomic wrist prosthesis of claim 19, further characterized in that the deformable locking member is a flex-lock peg.

21. The anatomic wrist prosthesis of claim 20, wherein the flex-lock peg comprises a plurality of uniformly spaced disc like elements disposed in a longitudinal arrangement along the terminal end of said ulnar stem.

22. An anatomic wrist prosthesis of any of claims 17 to 21, further characterized by having only a nonmechanical frictional connection existent between the rear engagement surfaces of the intermediate component and the mating surfaces of the forward portion of the radius stem.

23. An anatomic wrist prosthesis comprising an assembly of a pair of interconnected adjacently disposed means configured for implantation in the adjacent metacarpal bones of a human hand and terminated by a frictional surface means for engagement and relative movement with respect to another wrist prosthesis component, said adjacently disposed means being interconnected to said frictional surface means by means providing a ball and socket connection.

24. An anatomic wrist prosthesis as claimed in claim 23, further comprising a radial component having a radial stem for implantation in the radius bone of a human wrist and a frictional engagement surface for engagement with said frictional surface means.

25. An anatomic wrist prosthesis as claimed in claim 24, further comprising an ulnar bone stem for implantation in the ulnar bone of a human wrist and ball and socket means connecting said ulnar bone stem to said radial component.

26. An anatomic wrist implantable component for an anatomic wrist prosthesis substantially as hereinbefore described with reference to Figures 3 to 6, 9 and 10 of the accompanying drawings.

27. An anatomic wrist prosthesis substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.

28. An anatomic wrist prosthesis substantially as hereinbefore described with reference to Figures 4 to 16 of the accompanying drawings.