Title of Invention

DISTAL RADIAL PROSTHESIS WITH WRIST JOINT

Abstract

This prosthesis comprises of a radial shaft, a biplanar hinge, a carpal stabilizing component, proximal pivot screw with two collared bushes and a distal pivot screw with two collared bushes, the components when assembled forming a biplanar hinge mechanism, the radial shaft being adapted to mate with the biplanar hinge on one end and forming the bone anchoring component on the other. The biplanar hinge mates with the carpal stabilizing component on its distal end and with radial shaft on its proximal end, forming the biplanar hinge mechanism, to impart a defined radial (outer) deviation and (inner) ulnar deviation between the radial shaft and the biplanar hinge and a flexion and extension between biplanar hinge and the carpal stabilizing component. The distal end of the carpal stabilising component is adapted to accommodate the convex surfaces of the carpal bones.

Full Text

The following specification particularly describes the nature of the invention namely the distal radius prosthesis and the manner in which it is performed. Field of invention This invention relates to the Distal Radial Prosthesis with Wrist Joint in the field of medical technology. Further, this invention relates to a novel custom-built endoprosthesis namely the Distal Radial prosthesis. Principally, this invention relates to custom-built endoprosthesis Distal Radial prosthesis that allows normal functioning of the hand as it provides a near normal wrist joint. Introduction Management of patients with musculoskeletal neoplasms has always been one of the most challenging areas in oncology. Prior to 1970, almost every patient with a primary malignant tumour of musculoskeletal system would have any surgical treatment. They would not have adjuvant chemotherapy or irradiation and surgical treatment was almost an amputation with a five-year survival rate of 20%. For benign lesions such as Giant Cell Tumours, the treatment was curettage with 40-60% recurrence rate. Patients with painful metastatic lesions underwent palliative management until they were mercifully relieved by death. Prior Art Technique and Practice The conventional treatment for bone tumours over the years has been amputation, which is surgical removal of the affected part of the body. Amputation led to severe disability and psychological problems. The patient was made to lose not only part of his body, but part of his personality. By the advent of limb salvage, the technique of removing the tumour only and saving the limb of the patient was developed. The aim of limb salvage in bone tumour management is to eradicate the disease, retain the integrity of the skeletal system and preserve the limb with useful functions using metallic prosthesis. The early methods of reconstruction after limb salvage used the patient's own bone from another part of the body, but were associated with severe disability due to the lack of knee motion. The technique of endoprosthetic replacement revolutionized limb salvage by providing a method of reconstruction that provides stability and mobility. The endoprostheses that is used after excision of bone tumours around the wrist joint, differs from other joint replacement prosthesis because of the complex function that it needs to serve. The prosthesis is fabricated according to the anatomical dimensions of the patient and is therefore termed as the Custom Prosthesis. The Component custom prosthesis was designed by us to meet the anatomical and functional demands after excision of bone tumours. Different types of Custom Prosthesis have been developed by us to replace bone defects after limb salvage surgery for bone tumours of the distal radius, elbow, distal femur (Thigh bone) and proximal tibia (Leg bone). The patent application No: 897/MAS/2001, which has already been submitted, is a proximal tibial prosthesis with a pivotal hinge mechanism. The patent application No:1002/MAS/2002, which has already been submitted, is a proximal tibial prosthesis with a bearing polymer pad mechanism. The patent application No: 898/MAS/2001, which has also been submitted, is a distal femoral prosthesis with pivotal hinge mechanism. The patent application No: 707/CHE/2003, which has already been submitted, is a distal femoral prosthesis with thrust bearing polymer pad and rotating axis mechanism. Even though all these patent applications are for prostheses around the knee joint, the anatomical part replaced by patent application Nos: 897/MAS/2002 and 1002/MAS/2002 is the upper part of the leg bone (proximal tibia), whereas the patent application No: 898/MAS/2001, and patent application No: 707/CHE/2003 replace the lower part of the thigh bone (distal femur).The other CO pending application that has been filed is Patent application No: 1067/CHE/2003, which is the Distal Tibial Prosthesis with ankle Joint. The present patent application No. 1023/CHE/2003, differs from all the above applications because of the unique features of the joint replaced, namely the wrist joint. Objects of Invention It is the primary object of the invention to invent, devise and construct a novel - distal radial prosthesis with wrist joint. It is yet another object of the invention to invent, devise and construct a novel endoprosthesis - distal radial, which is unique. It is yet another object of the invention to invent, devise and construct a novel, which mimics the physiological action of the distal part of the radial bone. It is yet another object of the invention to invent, devise and construct a novel endoprosthesis - distal radial, which would retain the functional aspects of the distal radial bone along with the wrist joint. It is yet another object of the invention to invent, devise and construct a novel - distal radial prosthesis, which would take care of the functional aspect of the hand. It is yet another object of the invention to invent, devise and construct a novel endoprosthesis - distal radial, which would preserve the distal part of the radial bone. It is yet another object of the invention to invent, devise and construct a novel endoprosthesis - distal radial, which matches, in profile, the anatomic region of the distal radius. It is yet another object of the invention to invent, devise and construct a novel endoprosthesis ~ distal radial, which is economical. It is yet another object of the invention to invent, devise and construct a novel endoprosthesis - distal radial, which is safe in usage. It is yet another object of the invention to invent, devise and construct a novel endoprosthesis - distal radial, wherein the said device is provided with biplanar hinge mechanism to impart articulating motions of the wrist joint. It is yet another object of the invention to invent, devise and construct a novel, wherein the radial stem arches sideways to the right when viewed from the front side for a RIGHT configured distal radial prosthesis (Figure IB). It is yet another object of the invention to invent, devise and construct a novel, wherein the radial shaft arches sideways to the left when viewed from the front side for a LEFT configured distal radius (Figure I A). Further, the objects of the invention will be clear from the following description. Brief description of the drawings: The following specification will describe in detail with reference drawings accompa nying the specification. The nature of the invention and the manner in which it is to be performed is clearly and sufficiently described in the complete specification. The final portion of the complete specification ends with a statement of claims, which defines the invention. Figure 1 shows the ventral view of the distal radial prosthesis with the wrist joint in neutral position - LEFT configuration - 1 A, RIGHT configuration - IB. Figure 2 shows the distal radial prosthesis in ulnar deviated position (2A) and in radial deviated position (2B). Figure 3 shows the exploded view of the distal radial prosthesis in the anteroposterior plane. Figure 4 shows the expanded portion of the outlined area shown in figure 3. Figure 5 shows the lateral view (5 A) and the anteroposterior view (5B) of the distal radial prosthesis. Figure 6 shows exploded view of the outlined area shown in figure 5 A. FIGURE LEGEND (as per figure no. 3) 1. Carpal stabilizing component 2. Biplanar Hinge component 3. Distal Radial Shaft component 4. Proximal pivot screw 5. Proximal collar bushes 6. Distal pivot screw 7. Distal collar bushes DETAILED DESCRIPTION OF INVENTION The distal radial prosthesis has been aimed giving due consideration to the importance of maintaining an optimum function of the hand. The radio-carpal joint or the wrist joint serves as a base for the movements of all fingers and supports the rotational movements of the forearm at the distal radio-ulnar joint. The distal radial prosthesis described here, contains two hinge mechanisms at its distal end to enable movements at the antero-posterior or frontal plane and the medio-lateral or the sideward planes. As the proximal end of the prosthesis is fixed with PMMA cement and the distal end is secured to the carpal bones, rotational movements are restricted in this design. These facts can be better understood with the knowledge of the various parts of the distal radial prosthesis. The major components of the prosthesis include carpal stabilizing component (1), the biplanar hinge component (2) and the distal radial shaft component (3) as shown in figures 4, & 6. The minor but equally important components include two pivot screws, proximal (4) and distal (6) and four collared bushes (5 & 7) to complete the hinge mechanisms. All the components are made of surgical stainless steel of AISI - Grade 316 L or titanium of ASTM - B 348, Grade 5, except the collared bushes, which are made of Ultra High Molecular Weight Polyethylene provided to evade metal-to-metal friction during the biaxial movements and to act as effective bearings to facilitate such movements. The distal radial shaft component (Component 3 in figures 3, 4 & 5) is smoothly curved with the convexity towards the outer (lateral) aspect of the forearm as shown in figures lA and IB, so as to give the normal contour of the bone and hence of the forearm. This portion is moulded at its proximal end into a straight anchoring stem (3a in figure 3) whose surface is matted with three longitudinal troughs all to fix the stem firmly to the PMMA cement. The shaft portion (3b of figure 4) is oval in cross-section and is expanded in its distal end to form a plinth made of components - 3c, 3d, 3e, 3f, for the medio-lateral (side-to-side) hinge. This portion is ovoid in the frontal elevation with the superior (with respect to the figure) or distal (with respect to anatomical location), half (3f of figure 4) being smaller than the inferior or the proximal half (3c of figure 4). A vertically oriented semicircular groove (3g of figure 6) is fashioned in the medio-lateral plane at the distal portion of the plinth, to receive the biplanar hinge component (2). This groove also houses two collared bushes (5 in figure 6) to articulate with the proximal pivot screw (4 of figure 6). The outer diameter of the collars (5b of figure 6) of the two bushes is nearly equal to the inner diameter of the inferior hoop of the biplanar hinge component (2). The faces 5a (figure 6) of the collared bushes rest on the inner surfaces (3h of figure 6) of the groove (3g of figure 6). Hence when assembled, the inner faces of the proximal collar bushes (5d in figure 6) lie in opposition to the outer surfaces (2p in figures 4 and 6) of the inferior hoop of the biplanar hinge component; the head (4a in figure 6) of the proximal pivot screw lies in opposition to the ventral surface of the plinth; the outer surface (4b of figure 6) of the shaft lies well within the inner bore 5c (in figure 6) of both the proximal collar bushes (5). This screw is threaded at its tip (4c in figure 6) that contains itself well within the threaded portion of the plinth over the dorsal aspect. This proximal pivot screw is driven in an antero-posterior direction so as to give an axial movement in the medio-lateral plane. The excursions of the proximal pivot axis are such that the inferior surfaces 2k and 21 (figure 6) of the biplanar hinge component and the superior surfaces 3i and 3j (figure 6) of the plinth of the radial shaft component do not come into direct contact, so as to avoid metal-to-metal friction. The difference in breadths of superior and inferior halves of the distal plinth (3c, 3f of figure 4) leaves two blunted ledges (3d, 3e of figure 4) at the outer and inner surfaces, which act as stoppers for the medio-lateral movement. The outer ledge is slightly distal to the inner to give a physiological range of lesser outer (lateral/radial) deviation (Figure 2B) than inner (medial / ulnar) deviation (Figure 2 A) of the hand with respect to forearm, at the wrist. The biplanar hinge component (2) has a circular hoop (Component 2c of figure 4) in its proximal aspect, which seats in the groove of the plinth, in between the collared bushes (5) to receive the proximal pivot screw (4). This assembly leaves a small appreciable gap (as seen in figure 5 A) of a few thousands of a millimetre between the inferior hoop (2c) of the biplanar hinge and the floor of the groove of the plinth to avoid metal-to-metal contact. The superior aspect of the biplanar hinge (2 of fig.4) is devised into an antero-posteriorly oriented groove (2f of figure 4) that receives the inferior hoop (Ic of figure 4) of the carpal stabilizer component (1 of figure 3). This inferior hoop (Ic of figure 4), oriented in the antero-posterior plane, together with two more collared bushes (7 of figure 3) on its either sides, fits snugly into the groove of the biplanar hinge component and gets secured by the distal pivot screw (6 of figure 3). The faces 7a (figure 4) of the collared bushes rest on the inner surfaces (2m of figure 4) of the walls of the superior groove (2f of figure 4) of the biplanar hinge component. Hence when assembled, the inner faces of the collar bushes (7d in figure 4) lie in opposition to the outer surfaces (IJ in figure 4) of the inferior hoop of the carpal stabilizing component; This distal pivot screw (6 of fig.4) is driven from outer (lateral) surface of the biplanar hinge component through the bore le (figure 6) of the inferior hoop of the carpal stabilizing component, to the inner (medial) surface of the biplanar hinge component so as to provide the second distal axis of movement, which is in the antero-posterior plane. This arrangement leaves a gap of a few thousands of a millimetre (as seen in Fig.lA, IB, 2A, 23 & 5B), between the inferior hoop (Ic of figure 4) and floor of the superior groove of the biplanar hinge (2f in figure 4). Hence when assembled with the collar bushes through the superior hoop (2in in figure 6) of the biplanar hinge, the head (6a in figure 6) of the distal pivot screw lies in opposition to the lateral surface of the biplanar hinge component (as shown in figures (lA, IB, 2A, 2B and 5B); the outer surface (6b of figure 6) of the shaft lies well within the inner bore 7c (figure 6) of both the distal collar bushes (7). This screw is threaded at its tip (6c in figure 6) that contains itself well within the threaded portion of the superior hoop (2in in figure 6) over the inner aspect. This distal pivot screw is driven in a medio-lateral direction so as to give an axial movement in the antero-posterior plane. This distal hinge mechanism produces the antero-posterior excursions i.e., flexion and extension of the wrist. The excursions of the distal pivot axis are such that the inferior surfaces If and Ig (figure 4) of the carpal stabilizing component and the superior surfaces 2d and 2a (figure 4) of the walls of the superior groove of the biplanar hinge component do not come into direct contact, so as to avoid metal-to-metal friction. The mid-portion of the biplanar hinge component (2 of figure 4) is raised in the anterior and posterior surfaces (2g & 2h at the inner and outer aspects of the anterior surface shown in figure 4). These raised portions limit the excursion of the carpal stabilizing component on the biplanar hinge component i.e. flexion and extension. Proximally this raised portion stops abruptly at the mid-portion of either limb of the hoop (2b- outer and 2e- inner) of the biplanar hinge to limit the medio-lateral movement of the component 2, at the ledges 3d & 3e (figure 4) of the plinth (3 of figure 3) of the distal radial shaft. The distal surface of the outer wall (2a) of the groove (2f in figure 4) of the hinge component is planar whereas the inner one (2d) is tapered. These shapes accommodate the corresponding outer and inner bases (Ig & If respectively) of the carpal stabilizing component (1). The distal-most end of the carpal stabilizing component fans out on either side from its body (lb in figure 4) as outer and inner carpal supports (la). These supports are in a plane perpendicular to the antero-posterior plane and are concave distally (surface Id in figure 6) to take in the carpal bones. There are two holes (Ih in figure 4) provided in these supports for screws to fix the prosthesis distally to the carpal bones. The screws are driven from proximal to distal in a desired direction into the carpal bone that is facilitated by scooped out proximal oval surfaces to accommodate the heads of those fixing screws. All articulations of this prosthetic assembly are so constructed to allow no metal-to-metal contact between any of them. This is made possible either by the use of collar bushes or by leaving an appreciable gap between the components of hinges. The surfaces of the entire prosthesis have been moulded especially at the ledges, to eliminate sharp edges. It is to be noted that the complete specification discloses salient features of the invention. The scope and ambit of the invention is defined in the following statement claims. We claim 1. Distal radial prosthesis with wrist joint comprising of a radial shaft, a biplanar hinge component, a carpal stabilizing component, a proximal pivot screw with two collared bushes and a distal pivot screw with two collared bushes, the said components integrated to form a device, with a proximal bone anchoring component which contains longitudinal grooves on their surfaces; the device having a biplanar hinge mechanism, the radial shaft being adapted to mate with the biplanar hinge component on one end, forms the bone anchoring component on .the other, the biplanar hinge component being adapted to mate with the carpal stabilizing component on its distal end and with radial shaft on its proximal end, forming the biplanar hinge mechanism, to impart a defined radial outer deviation and inner ulnar deviation between the radial shaft and the biplanar hinge component and the mechanism to impart a defined flexion and extension between the biplanar hinge component and the carpal stabilizing component; the carpal stabilizing component adapted in its distal end to accommodate the convex surfaces of the carpal bones and distally to articulate with the biplanar hinge component. 2. Distal radial prosthesis with wrist joint as in claim 1, wherein the radial shaft component has a feature resembling the profile of the lateral curve of the radial bone itself 3. Distal radial prosthesis with wrist joint as in claim 1, wherein the radial shaft tilts to the right, when viewed from the front position for the RIGHT forearm configuration. 4. Distal radial prosthesis with wrist joint as in claim 1, wherein the radial shaft tilts to the left, if viewed from the front position for the LEFT limb configuration. 5. Distal radial prosthesis with wrist joint as in claim 1, wherein the proximal axis mechanism of the biplanar hinge component being fitted to the groove of the plinth of the radial shaft component with collared bushes and proximal pivot screw. 6. Distal radial prosthesis with wrist joint as in claim 5, wherein the said bushes act as bearings to minimize the impact of wear and give the wrist joint a frictionless range of movements in the medio-lateral plane. 7. Distal radial prosthesis with wrist joint as in claim 5, wherein the orientation of the collared bushes with respect to the biplanar hinge and the radial plinth components. 8. Distal radial prosthesis with wrist joint as in claim 5, wherein the orientation of the collared bushes with respect to the shaft of the proximal pivot screw. 9. Distal radial prosthesis with wrist joint as in claim 1, wherein the disial axis mechanism of the carpal stabilizing component being fitted to the groove of the biplanar hinge component with collared bushes and distal pivot screw. 10. Distal radial prosthesis with wrist joint as in claim 9, wherein the said bushes act as bearings to minimize the impact of wear and give the wrist joint a frictionless range of movements between the carpal stabilizing component and the biplanar hinge. 11. Distal radial prosthesis with wrist joint as in claim 9, wherein the orientation of the collared bushes with respect to the biplanar hinge and the carpal stabilizing components. 12. Distal radial prosthesis with wrist joint as in claim 9, wherein the orientation of the collared bushes with respect to the shaft of the distal pivot screw. 13. Distal radial prosthesis with wrist joint as in claim 1, wherein the outer ledge of the plinth of the radial shaft component acts as stopper in the position of maximum lateral radial deviation, by butting against the biplanar hinge component. 14. Distal radial prosthesis with wrist joint as in claim 1, wherein the inner ledge of the plinth of the radial shaft component acts as stopper in the position of maximum medial ulnar deviation, by butting against the biplanar hinge component. 15. Distal radial prosthesis with wrist joint as in claim 1, wherein the raised portions of the anterior surface of the biplanar hinge component acts as stopper in the position of maximum flexion, by butting against carpal stabilizing component. 16. Distal radial prosthesis with wrist joint as in claim 1, wherein the raised portions of the posterior surface of the biplanar hinge component acts as stopper in the position of maximum extension, by butting against carpal stabilizing component. 17. Distal radial prosthesis with wrist joint as in claim 1, wherein the concavity of the carpal stabilizing component mates to lie in close approximation to the convexity of the carpal bones. 18. Distal radial prosthesis with wrist joint as in claim 1, wherein the groove of the plinth of the radial shaft component is concentric to the proximal pivotal holes. 19. Distal radial prosthesis with wrist joint as in claim 1, wherein the groove of the biplanar hinge component is concentric to the distal pivotal holes. 20. Distal radial prosthesis with wrist joint as in claim 1, wherein the extreme tip of the radial stem component is tangentially round in section. Dated this 12th December 2003, Signatures

Documents:

1023-che-2003-abstract.pdf

1023-che-2003-claims duplicate.pdf

1023-che-2003-claims original.pdf

1023-che-2003-correspondnece-others.pdf

1023-che-2003-correspondnece-po.pdf

1023-che-2003-description complete duplicate.pdf

1023-che-2003-description complete original.pdf

1023-che-2003-drawings.pdf

1023-che-2003-form 1.pdf