Title of Invention

A KNEE JOINT SIMULATOR.

Abstract

A knee joint simulator and in particular to a knee joint simulator system which would be cost effective, simple to manufacture1 and use. Importantly, the simulator of the invention involves Tibial Implant (TB) and Femoral Implant (FM) wherein the Femoral Implant (FM) is maintained stationary while the Tibial Implant (TB) is adapted for motion with respect to the Femoral Implant (FM) mimicking usual human joint movement. The Tibial movement is achieved involving a cam runner (CM) and stepper motor connected at an end part of the Tibia and an hydraulic actuator means (AM) connected to the other end part of Tibia, a Control Panel (CP) Ojperatively connected to a Computer System (CS) for generating controlled simulated motion for required testing of implants. The simulator takes in account the load and the displacement time histories and simulate in the best possible manner the forces that occur at the knee joint due to physiological conditions during walking and running involving the use of hydraulic actuators. Advantageously the simulator utilizes' bone model and simulates the real situation closely. The simulator is specifically adapted to provide extremely cost effective testing of implants especially involving biocompatjble materials.

Full Text

FIELD OF THE INVENTION The present invention relates to a knee joint simulator and in particular to a simulator which would be cost effective, simple to manufacture and use and more importantly also adapted to take into account the various gait cycles simulating said walking/running conditions load and the displacement time histories and simulate in the best possible manner the forces that naturally occur in joint due to physiological conditions during walking or running. Advantageously the simulator utilizes bone model and simulates the real situation closely. The simulator is specifically adapted to provide extremely cost effective testing of tibial and femoral implants especially involving biocompatible materials i.e. which are not harmful to the human body systems. BACKGROUND ART The importance of effective partial or complete joint replacement to reduce patient's suffering is well known and over the years there has been a continuous effort to improve upon the art of joint replacement. US6205411 describes methodology and experimental apparatus for replacement of hip, knee, wrist, shoulder or a foot and ankle joints. The apparatus basically includes a pre-operative geometric planner and pre-operative kinematics of a biomechanlcal Simulator. DE19746333 discloses a machine having a frame compressing horizontal or slightly angled rails with a sliding heel trolley. It is also known that a great deal of work has been carried out within probably last decade for the development of knee joint simulators. Basically such conventional simulators involve control inputs, which are time histories of flexion angle, flexion-extension forces and moment component of the foot to floor reaction along the tibial. In most cases such articulation of knee joints are provided by stepper motors or electro hydraulic actuators. However in all simulators it is important that the physiological conditions are replicated to the extent possible and force, displacement are measured for feedback considerations. Many multi station simulators are known to specifically reduce the cost and time of testing a number of artificial joints. While there may be several variants of simulators presently in use, however, such simulator are cost-extensive to obtain which make Its use limited and not readily Affordable. Such known simulators usually involve expensive actuators and complex 1 electronic control system leading to high cost of the simulators. All these limitations did not encourage the wide-scale use of the simulators. In recent years use of simulators for the development of implants with biocompatible materials with adequate mechanical and tribological concerns, has become essential. Cost effective simulators are therefore a key to not only the regular testing of standard products but also to the development of newer and safer materials for the implants. There is thus a growing need for simulators which would on one hand be cost-effective and easily affordable and on the other hand be adapted for generating near natural simulated conditions for effective testing of implants for its wide scale and advanced uses / applications for the benefit of mankind. OBJECTS OF THE INVENTION The basic objective of the invention is therefore to provide an easily affordable knee joint simulator that gives all the facilities and functions of a standard device and is adapted for developing near-natural implants for future use with least harmful effects to the body-system. Another objective of the present invention is directed to provide ease of manufacturing and operation and therefore make It user friendly. Yet another objective of the present invention is directed to provide a knee joint simulator taking into the account the load and displacement time histories such that the physiological conditions during walking and running are simulated in the best possible manner. Yet further objective of the present invention is directed to provide a simulator adapted to different Gait-Cycles to simulate effectively the walking or running conditions. Further objective of invention is directed to provide a simulator, which would achieve perfect synchronization between force and displacement in line with the gait cycle. . Yet another objective of the present invention is directed to provide a simulator that selectively and advantageously involve bone- model-configuration so that transmission of forces to the joint is done in the most realistic manner. 2 Yet further objective of the present invention is directed to provide a simulator that takes into account the instantaneous center of rotation in a moving co-ordinate system during joint articulation so that the movement is realistic whereby loads are transmitted via the real bone-model that takes into account the stiffness and damping that occurs naturally during walking or running cycle. SUMMARY OF THE INVENTION Thus according to the basic aspect of the present invention there is provided a knee joint simulator comprising: means for holding a tibial implant and a femoral implant in mutually cooperative disposition adapted to simulate the walking /running conditions; means for holding the femoral implant stationary and fixed and the tibial implant adapted for motion mimicking normal human joint movement during said walking/running conditions; said tibial implant operatively connected to a cam runner and a stepper motor at one end and to an actuator at its other end to generate related motion time history ; a control panel adapted for controlled operative motion of said tibial implant, connected to said cam runner and a stepper motor at one end and to an actuator at its other end, based on the various gait cycles simulating said walking/running conditions generated by a computer means. load cells means for continuously measuring the forces and moments in "X" and "Y" direction and related forces, and displacements at the joint during simulation for testing of implants based on said selected input force and the gait cycle. . The above disclosed knee joint simulator of the invention advantageously takes into account the load and displacement time history applicable to artificial implants when in use using hydraulic actuators and the forces that occur at the knee joint due to physiological conditions during walking and running which are simulated in the best possible manner. Importantly in the above simulator of the invention the displacements and forces are further adapted to be synchronized involving any conventionally available software means, which can be readily developed for the purpose. Load cells as sensor means 3 are used to measure forces and moment in "X" and "Y" direction and these are used either to confirm applied force -time - history or used for a feedback control system. In accordance with a preferred aspect the simulator of the invention comprises of a tibial and femoral implants, each supported with respect to a respective box support in a manner such as the femoral implant remain stationary and fixed while the tibial implant is adapted for motion with respect of said femoral implant involving a cam and follower mechanism. Two strings on either side of the tibial implant are provided to achieve the forces constraint by its co-operative action with selectively disposed pulleys, a control means and a cooperative computer means to generate various gait cycles based on the simulated conditions of joint articulation during walking/running. The synchronized load-displacement can thus be applied following standard gait-cycle and a feedback control system maintains the real walking or running sequences. Advantageously, the simulator of the invention utilizes bone model with similar elasticity and strength as that of the natural bone for transmitting forces to the joint due to which realistic forces and moment could be achieved. Importantly a string pulley arrangement for transmitting the forces and a cam and follower arrangement represent the real situation joint closely. Moreover, the articulation in the joint-simulator uses an instantaneous center of rotation (in a moving coordinate system) making the simulation close to reality. In accordance with another aspect the simulator of the invention advantageously utilizes parts of the artificial femur and tibia fitted with the implants as the test sample provides a more natural mimicking of the knee joint articulation where load is transferred to the bone via the implants. ' Thus the simulator of the invention achieves or utilizes real system for testing of implants and provides for a more reliable and authentic simulation system. This is important because if the real system is not mimicked it is difficult to maintain the instantaneous center of rotation during knee joint articulation since the center about which the rotation of femur-tibia pair occur is not a fixed point. 4 BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURE The details of the invention, its objects and advantages are explained hereunder in greater detail, in relation to non limiting exemplary illustration of the knee joint simulator of the invention as per the accompanying Figure 1. As illustrated in Fig 1. the simulator of invention basically involves a femoral (FM) implant and a tibial implant (TB) fixed in two boxes (Bl & B2) respectively. The box (Bl) containing the femoral implant (FM) kept fixed/stationary and the box (B2) supporting the tibial implant (TB) adapted for said motion using a cam (CM) and follower mechanism (FLM) with respect to said stationary femoral implant to simulate the usual walking/running conditions required for testing of the Implants. . For the purpose two strings (STG1 & STG2) means are provided at two ends of tibia! implant (TB) which as shown further pass over selectively disposed pulleys (PL) to generate forces as well as constraints. The pulleys are shown connected to the actuator means (AM). Sensor/load means (SM) preferably four such load cell means are provided to sense the force and moment measurements. A control panel (CP) provides for controlled motion of the tibial implant via the said actuator means at one end and the Cam (CM) and follower at the other end. The control panel (CP) is in turn shown operatively connected to a Computer System (CS) for generation of various gait-cycles to simulate the walking and running conditions. Similar to that in real walking the ground force are transmitted in the simulator of the invention through tibia to the knee joint and the tibial movement Is more conspicuous. Advantageously, the simulator of the invention utilizes bone model with similar elasticity and strength as that of natural bone for transmitting ground forces to the joint due to which realistic forces and moments could be achieved- Importantly the use of bone models (similar in strength and shape) and a string pulley arrangement for transmitting the forces represents the real situation closely. As shown in fig. 1, the movement at the joint is imparted using a cam and follower mechanism at the tibial end to represent the real situation. Moreover, in accordance with another aspect the knee-joint simulator achieves the instantaneous center of rotation (In a moving co-ordinate system) during joint articulation so that the movement Is realistic. As also represented the simulator of the Invention advantageously utilizes parts of the artificial femur and tibia adapted to be fitted with the implants as the test sample which provide a more natural mimicking of the knee joint articulation where load is transferred to the bone via the Implants. It is thus possible by way of 5 the above knee joint simulator of the invention to obtain a simple and cost effective knee joint simulator adapted to reproduce the desired realistic motion time history by selected use of the above system and its operative components. Advantageously, the simulator is adapted to articulate using various kind of gait-cycle involving different input to the stepper motor such as walking or running motion time-history whereby perfect synchronization can be achieved. Advantageously also since the simulator of the invention is based on bone model, impact loading can be eliminated and only soft padding can be used instead to absorb moments. The knee joint simulator of the invention would thus provide for a cost-effective, easily affordable and simple to operate and use knee joint simulator adapted for generating near natural simulated conditions for effective testing of implants for its wide scale and advanced applications as artificial implant. The simulator takes into the account the load and displacement time history such that the forces that occur at the knee joint due to physiological conditions during walking or running are simulated in the best possible manner. The bone-model concept utilized in the simulator provides for better and more natural transmission of the forces to the joint representing the real situation closely. Also, adequate consideration is given in the development of the simulator to take into account the instantaneous center of rotation in a moving co-ordinate system during joint articulation so that the movement is realistic. The simulator is thus directed to meet the growing need for simulators which would on one hand be cost-effective and easily affordable and on the other hand be adapted for generating near natural simulated conditions for effective testimg of variety of implants especially the present day need for implants of biocompatible materials for its wide scale and advanced uses/applications for the benefit of mankind. 6 WE CLAIM 1. A knee joint simulator comprising: means (Bl & B2) for holding a tibial Implant (TB) and a femoral Implant (FM) in mutually cooperative disposition adapted to simulate the walking /running conditions; means (Bl) for holding the femoral implant (FM) stationary and fixed and the tibial implant (TB) adapted (B2) for motion mimicking normal human joint movement during said walking/running conditions; said tibial implant (TB) operatively connected to a cam (CM) runner and a stepper motor at one end and to an actuator (AM) at Its other end to generate related motion time history; a control panel (CP) adapted for controlled operative motion of said tibial implant (TB), connected to said cam (CM) runner and a stepper motor at one end and to an actuator (AM) at its other end ,based on the various gait cycles simulating said walking/running conditions generated by a computer means (CS). load celts (SM) means for continuously measuring the forces and moments in "X" and "Y" direction and related forces, and displacements at the joint during simulation for testing of implants based on said selected input force and the gait cycle. . 2. A knee joint simulator as claimed in claim 1 wherein the means for fixing the tibial and the femoral implants comprise of two boxes (Bl & B2) containing the implants. 3. A knee joint simulator as claimed in anyone of claims 1 or 2 wherein the said force and displacement time histories at the joints are synchronized. 4. A knee joint simulator as claimed in anyone of daims 1 to 3 adapted for various kinds of gait-cycles using different inputs to the said stepper motor. 5. A knee joint simulator as claimed in daim 4 wherein different gait cydes can be accommodated to simulate different walking and running conditions. 6. A knee joint simulator as claimed in anyone of daims 1 to 5 comprising string means (STG1 & STG2) provided on either side of the tibial implant which 7 cooperate with selectively disposed pulleys (PL) to generate said controlled operative motion of said tibial implant. 7. A knee joint simulator as claimed in anyone of claims 1 to 6 comprising soft padding to absorb the moments. 8. A knee joint simulator as claimed in anyone of claims 1 to 7 wherein four said toad cell (SM) means are provided to measure; the said forces in "X" and "Y" direction and confirm the applied force time history and/or assist in future feedback control system. 9. A knee joint simulator as claimed in anyone of dalms 1 to 8 comprising bone models (FM/TB) and string pulley arrangements (STG1/2 & P2) for transmitting the forces to the joints and provide instantaneous center of rotation during joint articulation and thus provide most realistic testing facilities of implants. 10. A knee joint simulator as claimed In anyone of claims 1 to 9 comprising artificial femur (FM) and tibia (TB) adapted to be fitted to the implants for testing. 11. A knee joint simulator as claimed in anyone of claims 1 to 10 wherein a cam (CM) and follower mechanism (FLM) is used at the tibial end to mimic the real situation. 12. A knee joint simulator substantially as herein described and illustrated with reference to the accompanying figure 1. A knee joint simulator and in particular to a knee joint simulator system which would be cost effective, simple to manufacture1 and use. Importantly, the simulator of the invention involves Tibial Implant (TB) and Femoral Implant (FM) wherein the Femoral Implant (FM) is maintained stationary while the Tibial Implant (TB) is adapted for motion with respect to the Femoral Implant (FM) mimicking usual human joint movement. The Tibial movement is achieved involving a cam runner (CM) and stepper motor connected at an end part of the Tibia and an hydraulic actuator means (AM) connected to the other end part of Tibia, a Control Panel (CP) Ojperatively connected to a Computer System (CS) for generating controlled simulated motion for required testing of implants. The simulator takes in account the load and the displacement time histories and simulate in the best possible manner the forces that occur at the knee joint due to physiological conditions during walking and running involving the use of hydraulic actuators. Advantageously the simulator utilizes' bone model and simulates the real situation closely. The simulator is specifically adapted to provide extremely cost effective testing of implants especially involving biocompatjble materials.

Documents:

00493-kol-2004 abstract.pdf

00493-kol-2004 claims.pdf

00493-kol-2004 correspondence.pdf

00493-kol-2004 description(complete).pdf

00493-kol-2004 drawings.pdf

00493-kol-2004 form-1.pdf

00493-kol-2004 form-13.pdf

00493-kol-2004 form-18.pdf

00493-kol-2004 form-2.pdf

00493-kol-2004 form-3.pdf

00493-kol-2004 letters patent.pdf

00493-kol-2004 p.a.pdf

00493-kol-2004 reply f.e.r.pdf

493-KOL-2004-(22-03-2012)-CORRESPONDENCE.pdf

493-KOL-2004-(22-03-2012)-FORM-27.pdf

493-KOL-2004-CORRESPONDENCE 1.1.pdf

493-KOL-2004-FORM 27.pdf