Title of Invention

DISTAL TIBIAL PROSTHESIS WITH ANKLE JOINT

Abstract

DISTAL TIBIAL PROSTHESIS WITH ANKLE JOINT This invention is termed "Distal tibial prosthesis with ankle joint". It comprises of a tibial stem formed by a proximal segment and distal segment with fixing screws with washers, two collared bushes, a pivot pin, cushioning bearing pad, talar component, two counter-sunk head screws and locking setscrews. These components integrate to form a device that has a tilting hinge mechanism at its distal end, with a proximal bone-anchoring component. The distal segment of the tibial stem is adapted to mate with cushioning bearing pad on one end, the tarsal component is adapted with the counter-sunk head screws, to mate with the tarsal bones on its distal end and with cushioning bearing pad on its proximal end, also adapted to articulate with the two collared bushes with the pivot pin within it. These components form a tilting hinge mechanism that imparts a defined upward and downward rocking motion of the talar component.

Full Text

Field of invention This invention in general relates to the field of medical technology. Further, this invention relates to a novel custom-built endoprosthesis namely the Distal Tibial prosthesis with ankle joint. Principally, this invention relates to custom-built endoprosthesis - Distal Tibial prosthesis that allows normal functioning of the ankle as it provides a near normal ankle 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 the physical human body, but also a part of the personality of the patient. 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 ankle joint differs from other joint replacement prosthesis because of the complex anatomy at this site due to the ankle and subtalar joints. The prosthesis is fabricated according to the anatomical dimensions of the patient and is therefore termed as the Custom Prosthesis. The 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 tibia (ankle), elbow, distal radius, distal femur (thigh bone) and proximal tibia (leg bone). Our patent application No:897/MAS/2001, which has already been submitted, is a Proximal Tibial Prosthesis with a Pivotal Hinge Mechanism. Our patent application No:1002/MAS/2002, which has already been submitted, is a Proximal Tibial Prosthesis with a Bearing Polymer Pad Mechanism. Our patent application No: 898/MAS/2001, which has also been submitted, is a Distal Femoral Prosthesis with Pivotal Hinge Mechanism. Our 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). Our other copending application that has been filed in patent application No. 1023/CHE/2003, for the Distal Radius Prosthesis with Wrist Joint. The current application patent No: 1067/CHE/2003 is the distal tibial prosthesis with ankle joint, which replaces the distal tibial and the ankle joint. Objects of Invention It is the primary object of the invention to invent, design and construct a novel - distal tibial prosthesis with ankle joint. It is yet another object of the invention to invent, design and construct a novel endoprosthesis - distal tibial, which is unique. It is yet another object of the invention to invent, design and construct a novel, which mimics the physiological action of the distal part of the tibial bone. It is yet another object of the invention to invent, design and construct a novel endoprosthesis - distal tibial, which would retain the functional aspects of the distal tibial bone along with the ankle joint. It is yet another object of the invention to invent, design and construct a novel - distal tibial prosthesis, which would take adequate care of the functional aspect of the foot. It is yet another object of the invention to invent, design and construct a novel endoprosthesis - distal tibial, which would preserve the distal part of the tibial bone. It is yet another object of the invention to invent, design and construct a novel endoprosthesis - distal tibial, which matches, in profile, the anatomic region of the distal tibia. It is yet another object of the invention to invent, design and construct a novel endoprosthesis - distal tibial, which is economical. It is yet another object of the invention to invent, design and construct a novel endoprosthesis ~ distal tibial, which is safe in usage. It is yet another object of the invention to invent, design and construct a novel endoprosthesis - distal tibial, wherein the said device is provided with rolling hinge mechanism to impart articulating motions of the ankle joint. Description of the drawings The following specification will describe in detail with reference drawings accompanying 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. 1. Figure 1 shows an isometric view of the assembled Distal Tibial prosthesis with the major components 2. Figure 2 shows an exploded view of the Distal Tibial Prosthesis in the isometric view. 3. Figure 3 shows the side (lateral) view of the assembled Distal Tibial prosthesis with the major components 4. Figure 4 shows an exploded view of the Distal Tibial Prosthesis in the side (medial) view. 5. Figure 5 shows the exploded view of the talar component with cushioning bearing pad. FIGURE LEGEND - COMPONENTS (as per figures 1 & 2) 1. Proximal segment 2. Fixing screws 3. Distal segment 4. Collared Bushes 5. Pivot pin 6. Cushioning bearing pad 7. Talar component 8. Counter-sunk head screws 9. Locking setscrews 10. Washers DETAILED DESCRIPTION OF INVENTION The Distal Tibial Prosthesis with ankle joint is a cemented fixation device, cemented at its both ends. The special feature of this prosthesis is that it has a rolling hinge apparatus at its lower end, which simulates movements of the ankle joint in one plane, i.e., in a plane perpendicular to the coronal plane - Dorsiflexion and plantarflexion - upward and downward movement of the foot. 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 and the cushioning bearing pad, which are made of Ultra High Molecular Weight Polyethylene provided to evade metal-to-metal friction. The Distal tibial prosthesis mainly comprises of the following components: the tibial stem assembly that consists of a proximal segment (1 in figure) with an anchoring stem (la in figure 2) at its superior aspect, the lower segment of the distal segment (3 in figure 1,3 & 4) tibial component, connected to the upper segment by means of three fixing screws (2 in figure 1 & 3). The expanded malleolar portion (3d in figure 2) of the distal segment houses the rolling hinge mechanism in its inferior aspect. The proximal segment has a straight anchoring stem at its superior aspect that has a matted surface and three longitudinal troughs on its outer surface. This helps to fix the prosthesis firmly with bone cement to the remaining proximal tibial portion. The lower portion of the proximal segment forms the medial aspect of the tibial stem. The upper part of the distal segment forms the lateral aspect of the tibial stem. The inner surfaces le (in figure 2) of the proximal component and 3i (in figure 2) of the distal segment lie in close opposition when assembled. To prevent rotation of the two said components, they lock themselves (Refer figure 2) superiorly - the knob 3a of the distal segment into the pit lb of the proximal segment, inferiorly the knob Id of the proximal segment into the pit 3c of the distal segment. This locking as a result, finds the surfaces If of the proximal segment oppose with 3n of the superior aspect of the distal segment. Similarly, the surface Ig of the inferior aspect of the proximal segment lies against 3m of the distal segment. All the aforesaid surfaces (If, 3n, Ig & 3m in figure 2) are planar. The two segments, proximal and distal, when assembled, are secured to each other by three fixing screws and washers (2 in figure 2 & 10), which are driven from a lateral to medial direction into the holes 3b of the distal segment and Ic of the proximal segment. The screws are so designed to contain their heads (figure 3) within the tibial stem. The outer circumference 2a (in figure 2) lies against the inner circumference 3j (figure 2) of the bores of the distal segment. The threaded portions of the fixing screws limit themselves within the inner medial surface of the proximal segment (figure 4). The washers (10 in figure 2) made of stainless steel or titanium present adjacent to the head and the threaded portion of the screws, limits further propagation of the fixing screws beyond the inner (medial) surface of the tibial stem. The lower portion (3d in figure 2 &5) of the distal segment of the tibial stem is expanded in the medio-lateral and antero-posterior directions to simulate the normal anatomy at that level. The distal most ends of the lateral aspect of this portion extend beyond the inferior surface (3p in figure 4) of the distal segment to form a clevis type of configuration to accommodate the rolling hinge mechanism. The lower aspect of the inner walls (3e in figure 5) is formed by two cross-holes (3f in figure 5) that take in the pivot pin (5 in figures 1,2 & 3). The Pivot pin is locked in its place with the help of two locking setscrews (9 in figure 2) that go into the threaded cross-holes (3h in figure.2 that correspond to the threaded portions of the setscrews) in tip of the sidewalls of the clevis configuration. These two inferior cross-holes (3h) open into the cross-holes (31) of the sidewalls such that the non-threaded tip (9b in figure 5) of the setscrews lock the pivot pin at their corresponding pits (5c in figure 5) on either ends. The outer and inner surfaces (5a in figure 5) has a vertical slit that corresponds in line with the direction of the locking setscrews that fix the pivot pin at the pits. The inferior surface of the distal segment has a cylindrical disc-shaped pit (3g in figures 4 & 5) whose height (3k in figure 5) corresponds exactly to that of the locking disc part (6a in figure.5) of the cushioning-bearing pad (6 in figure 1,2,3 & 4). The rest of the inferior planar surface (3p in figure 4) of the distal segment lies in contact with the superior planar surface (6d in figure 4) of the cushioning bearing pad. The inferior surface (6c in figure 5) of the cushioning bearing pad is concave so that the anterior and posterior surfaces (6b in figure 5) of the bearing pad are inclined (as seen in figure 4) to the normal. The inferior concave surface (6c in figure 5) of the cushioning bearing pad has a specific radius that matches the radius of the superior surface (7c in figure 5) of the talar component. The inferior margins of the inclined anterior and posterior surfaces of the cushioning bearing pad (6b in figure 5) stop short at the superior margins of the straight anterior and posterior surfaces (7f in figure 5), in the neutral position, as seen in figure 1. The pivot pin fits snugly (the outer surface 5b in figure 5) into the bores (4c in figures 5) of the collared bushes,whose collars (4b in figure 5) are placed in the channel (7a in figure 5) of the talar component with their outer faces (4a in figure 5) face the exterior. The talar component has a channel (7a in figure 5) configuration in a reniform or bean-shape (when viewed from the side, as in figures 4 & 5), into which the collars (4b in figure 5) of the two collared bushes are assembled. Hence the inner faces of the two collars (4d in figureS) lie in opposition to the lateral and medial abutting surfaces of the rim (7 1 in figure 5). This makes the collared bushes to traverse through the channel of the talar component limited anteriorly and posteriorly at 7g and 7h respectively as well as at 7k (of figure 5) superiorly. The fit of the collared bushes into the channel is such that the outer surface of the bush (4b in figure 5) that is just adjacent to inner surfaces (4d in figure 5) articulates within the thin perimeter formed by the arching surfaces 7k and 7b (in figure 5) at the outer and inner aspects of the talar component. Due to this arrangement, the talar component gets a rocking motion that results in upward and downward tilting movements of the inferior surface (7e in figure 5), perpendicular to the coronal plane, to simulate the movements of ankle joint. There are two screwed holes (7i in figure 5) at the bottom flat serrated surface of the talar component, which house the two counter-sunk head screws (8 in figure 5). These screws get embedded into the tarsal bones with the bone cement smeared in the gap between the head (8a in figure 5) and the shaft (8b in figure 5). The serrated inferior planar surface (7e in figure 5) on this area gives sufficient grip for the bone to get anchored to the bone cement. It is to be noted that the complete specification discloses salient features of the invention, distal tibial prosthesis with ankle joint. The scope and ambit of the invention is defined in the following statement of claims. We claim 1. Distal tibial prosthesis with ankle joint comprising of a tibial stem formed by a proximal segment (1) and distal segment (3) with fixing screws (2), with washers(lO), collared Bushes (4), a pivot pin (5), Cushioning bearing pad (6), talar component (7), two counter-sunk head screws (8), and Locking setscrews (9), the said components integrated to form a device, the device having a tilting hinge mechanism (5,6,7) at its distal end, with a proximal bone anchoring component (1), containing longitudinal grooves on their surfaces, the distal segment of the tibial stem (3) being adapted to mate with cushioning bearing pad (6 ) on its distal end, the proximal segment of the tibial stem being adapted to form the bone anchoring component on the other, the talar component (7) being adapted with the counter-sunk head screws (8) to mate with the tarsal bones on its distal end and with cushioning bearing pad on its proximal end (6), also adapted to articulate with the two collared bushes (4) and the pivot pin (5) within it, forming the tilting hinge mechanism to impart defined upward and downward rocking motion of the talar component, with the pivot pins fixed in position to the distal segment of the tibial stem by locking screws. 2. Distal tibial prosthesis with ankle joint as claimed in claim 1, wherein the distal segment of the tibial stem component has a feature resembling the profile of the malleolar portion of the distal tibial bone itself. 3. Distal tibial prosthesis with ankle joint as claimed in claim 1, wherein the said cushioning bearing pad acts to minimize the impact of wear between the talar component and the distal segment giving the defined range of tilting movements of the ankle joint in the sagittal plane. 4. Distal tibial prosthesis with ankle joint as claimed in claim 1, wherein the said bushes act as bearings to minimize the impact of wear between the talar component and the pivot pin giving the defined range of movements of the ankle joint in the sagittal plane. Distal tibial prosthesis with ankle joint as claimed in claim 1, wherein the tilting hinge mechanism is formed by the pivot pin and the collared bushes being fitted to the channel of the talar component. Distal tibial prosthesis with ankle joint as claimed in claim 5, wherein the tilting hinge mechanism being formed at the channel of the talar component with collared bushes and pivot pin. Distal tibial prosthesis with ankle joint as claimed in claim 5, wherein the channel of the talar component is reinform in shape, to allow rocking movement along with the two collared bushes. Distal tibial prosthesis with ankle joint as claimed in claim 5, wherein the orientation of the cushioning bearing pad with respect to distal segment of the tibial stem. Distal tibial prosthesis with ankle joint as claimed in claim 5, wherein the orientation of the cushioning bearing pad with respect to the talar component. . Distal tibial prosthesis with ankle joint as claimed in claim 5, wherein the orientation of the collared bushes with respect to tilting hinge and the talar components. . Distal tibial prosthesis with ankle joint as claimed in claim 5, wherein the orientation of the collared bushes with respect to the shaft of the pivot pin. . Distal tibial prosthesis with ankle joint as claimed in claim 5, wherein the orientation of the collared bushes with respect to malleolar portion of the distal segment. . Distal tibial prosthesis with ankle joint as claimed in claim 1, wherein the posterior margin of the channel of the talar component acts as stopper in the position of maximum downward deviation, by butting against the outer surfaces of the collared bushes. . Distal tibial prosthesis with ankle joint as claimed in claim 1, wherein the anterior margin of the channel of the talar component acts as stopper in the position of maximum upward deviation, by butting against the outer surfaces of the collared bushes. . Distal tibial prosthesis with ankle joint as claimed in claim 1, wherein the concavity of the cushioning bearing pad mates to lie in close approximation to the convexity of the talar component. . Distal tibial prosthesis with ankle joint as claimed in claim 5, wherein the height of the channel of the talar component fits the collared bushes at any given range of movement. . Distal tibial prosthesis with ankle joint as claimed in claim 1, wherein the pivot pin is locked in position by the two locking setscrews. .Distal tibial prosthesis with ankle joint as claimed in claim I, wherein the inferior surface of the talar component is serrated to increase adhesiveness to the bone cement. . Distal tibial prosthesis with ankle joint as claimed in claim 1, wherein the inferior surface of the talar component has two screwed holes to accommodate the countersunk head screws. .Distal tibial prosthesis with ankle joint as claimed in claim 1, wherein the shape of the counter-sunk head screw is formed to provide space for the bone cement between its ^haft^nd the tarsal bone. 21. Distal tibial prosthesis with ankle joint as claimed in claim 1, wherein the extreme tip of the anchoring stem portion of the proximal segment of the tibial stem is tangentially round in section.

Documents:

1067-che-2003-abstract.pdf

1067-che-2003-claims duplicate.pdf

1067-che-2003-claims original.pdf

1067-che-2003-correspondence others.pdf

1067-che-2003-correspondence po.pdf

1067-che-2003-description complete duplicate.pdf

1067-che-2003-description complete original.pdf

1067-che-2003-drawings.pdf

1067-che-2003-form 1.pdf

1067-che-2003-form 19.pdf

1067-che-2003-form 3.pdf