Automatic prosthesis for above-knee amputees

Abstract

A above knee prosthesis (P) applied to femoral connection ( 100 ) of an amputee that comprises a upper hinge ( 1 ) connected to femoral connection ( 100 ) of the patient, an articulation axis ( 2 ) with the function of reproducing the knee movements, a tibia-calf muscle unit ( 3 ) pivotally connected to the femoral segment ( 1 ) and a damper ( 5 ) that reproduces some functions of the calf muscle and ensures to the prosthesis (P) to brake and to allow the sequential swing and stance phases typical of the gait. The damper ( 5 ) comprises a cylinder ( 5 c ) wherein a piston ( 10 ) and a stem ( 9 ) act connected to each other and adapted to carry out a damping reaction of said damper responsive to the forces loaded on the prosthesis. In particular, a force transducer is provided in the damper ( 5 ) arranged, in particular, in the stem ( 9 ) with a microprocessor that receives a force signal from the transducer and operates means for adjusting the reaction of the damper responsive to the detected force signal. Exemplary embodiments are equipped with means for adjusting the gait parameters during a gait cycle, means for exploiting the energy dissipated by the prosthesis, means to assist the charge and the change of batteries, means to know the direction and/or the intensity of resultant forces transmitted through the prosthesis.

1 . A prosthesis for above-knee amputees, said prosthesis having a femoral segment, which can be fixed to a femoral connection, and a tibial segment pivotally connected to each other about an articulation axis that reproduces the knee movements, said tibial segment being articulated by an ankle to a foot having toes, a sole of the foot and a heel, wherein said knee movements comprise a swing phase, between bringing the toes off the ground and landing the heel, and a stance phase, comprising landing the heel, loading the sole of the foot and bringing the toes off the ground, a hydraulic damper being provided having respectively a upper hinge and a lower hinge connected respectively with said femoral segment and said tibial segment and damping the relative movement of said tibial segment with respect to said femoral segment, so that in the stance phase the tibial segment is braked with respect to the knee articulation between said femoral segment and said tibial segment, wherein the hydraulic damper comprises a cylinder-piston and a stem connected to said piston, and a microprocessor is provided for adjusting the damping reaction of said damper wherein a force transducer is provided in said stem, and the microprocessor receives a force signal from said force transducer on the stem and adjusts the damping reaction of said damper responsive to the force signal from the stem. 
     
     
         2 . Prosthesis, according to  claim 1 , characterised in that said force transducer is provided in said stem, and the microprocessor receives a force signal from said transducer on the stem and adjusts the damping reaction of said damper responsive to the detected force signal on the stem. 
     
     
         3 . Prosthesis, according to  claim 1 , characterised in that said force transducer is a ring dynamometer put in a hole made in said stem, with axis of the hole orthogonal to the axis of the stem. 
     
     
         4 . Prosthesis, according to  claim 1 , characterised in that said force transducer on the damper is a load cell arranged at said lower hinge of said damper. 
     
     
         5 . Prosthesis, according to  claim 1 , wherein a force transducer is provided in said femoral segment, selected from the group comprised of: an orthogonal force transducer, a longitudinal force transducer, a torque transducer, or a combination thereof, and said microprocessor receives a force signal from said force transducer in the femoral segment and adjusts the reaction of said damper responsive to the force signal present on said femoral segment. 
     
     
         6 . Prosthesis, according to  claim 1 , wherein a further force transducer is arranged to detect a situation of singularity in flexion by measuring the presence of overloads in bending. 
     
     
         7 . Prosthesis, according to  claim 5 , wherein a memory unit is provided for memorizing the force data of said force transducers, and means for comparing them with maximum admissible values. 
     
     
         8 . Prosthesis, according to  claim 1 , wherein a position transducer is provided at the articulation axis that reproduces the knee movements, said position transducer measuring the rotation of the knee. 
     
     
         9 . Prosthesis, according to  claim 1 , wherein said femoral segment and said tibial segment are geometrically conformed in order to be, at the beginning of a gait cycle at the end of the swing, in a condition of singularity measured by a mechanical abutment integrated in the damper, said force transducer on the damper measuring the actual load transmitted to the articulation also in the condition of singularity and the microprocessor that computes the measure can discriminate and control this step during the gait. 
     
     
         10 . Prosthesis, according to  claim 1 , wherein said damper is of hydraulic type and comprises blades arranged as check valve blade springs for opening an oil flow responsive to a speed of the stem in the cylinder. 
     
     
         11 . Prosthesis, according to  claim 1 , wherein said damper is of hydraulic type and comprises:
 a first chamber (A) and a second chamber (B), separated by said piston;   a compensation chamber;   a channel (E_ 1 ) extending from chamber B to compensation chamber, between which a check valve (VN_ 1 ) without pre-charge and an adjustment valve remote are arranged;   a channel (E_ 2 ) extending from compensation chamber to chamber (A), between which a check valve (VN_ 2 ) without pre-load is arranged;   a channel (C_ 1 ) extending from chamber (A) to compensation chamber, between which a check valve (VN_ 3 ) without pre-charge and an adjustment valve remote are arranged;   a channel (C_ 2 ) extending from compensation chamber to chamber (B), between which a check valve (VN_ 4 ) is arranged;   a channel that connects a chamber of an oil sealing chamber to chamber and is used to avoid pressure peaks in the oil sealing chamber as well as it can be used as compensation chamber and air emptying chamber in a phase of filling damper.   
     
     
         12 . Prosthesis, according to  claim 1 , wherein said prosthesis has the characteristic of being equipped, at the foot, with an insole having an array of force and position transducers whose signals are computed by said microprocessor for determining the mode of interaction of the foot of the patient with the surroundings, where the transducers located at the insole allow to determine a data selected from the group comprised of:
 a resultant load vector on said prosthesis, in its intensity, direction and position components, whereby said microprocessor can adjust most favourably the reaction of the damper;   the point of application of the resultant load vector, wherein one or more force transducers located in the artificial limb whose signals, computed with the signal generated by said insole, allow the microprocessor to determine a transmitted resultant load vector.   
     
     
         13 . Prosthesis, according to  claim 12 , wherein said artificial limb comprises a further transducer of the angular position located at the ankle and adapted to control the relative inclination between tibia and foot, said microprocessor receiving signals from said transducer of the angular position located at the ankle for determining, in association to the data on the force vector provided by the insole, the position of the ankle responsive to the vector force. 
     
     
         14 . Prosthesis, according to  claim 1 , wherein said knee articulation axis comprises a generator/motor capable of providing energy in some phases of the gait cycle and of receiving energy during other phases, an energy storage unit being provided adapted to accumulate and to release again said energy through said motor controlled by said microprocessor during the phases of the gait cycle. 
     
     
         15 . Prosthesis, according to  claim 14 , wherein force and position transducers are provided arranged according to said knee articulation, in said microprocessor program means being provided that operate responsive to signals coming from said force and position transducers arranged according to said knee articulation, said microprocessor supplying signals to said motor/generator for working respectively as motor during a leg realignment phase and as generator during a support phase. 
     
     
         16 . Prosthesis, according to  claim 15 , wherein said microprocessor directs to said energy storage unit the energy dissipated by the knee from said motor/generator with function of generator and recalls energy from said energy accumulator with a variable delay addressing it to said motor/generator with function of motor as propulsion when accelerating the tibia to ensure realignment with the femur. 
     
     
         17 . Prosthesis, according to  claim 14 , where in said damper variable pitch springs are provided that allow to have low stiffness for small angular travel between the femoral segment and the tibial segment, and high stiffness for large angular travel. 
     
     
         18 . Prosthesis, according to  claim 14 , wherein said ankle articulation between said tibial segment and said foot comprises a further motor/generator. 
     
     
         19 . Prosthesis, according to  claim 18 , wherein said ankle articulation comprises a damping element arranged in parallel to said motor/generator. 
     
     
         20 . Prosthesis, according to  claim 18 , wherein said ankle articulation comprises furthermore, force and angular position transducers connected to said microprocessor responsive to signals coming from said force and angular position transducers arranged in the ankle, sending to said energy storage unit the energy generated by the ankle during the step of support of the heel onto the ground, and recalling energy from said accumulator with a variable delay addressing it to said motor/generator on the ankle as power necessary to lift the foot, acting as motor, allowing a much easier and natural gait avoiding possible foot-ground impacts. 
     
     
         21 . Prosthesis, according to  claim 18 , wherein said microprocessor administers said motors/generators of the knee-ankle with program means adapted to recognize the phase of the gait owing to the signals coming from said force and position transducers arranged at said knee and ankle articulations. 
     
     
         22 . Prosthesis, according to  claim 18 , wherein said motor/generator on the knee and said further motor/generator on the ankle share a same energy storage unit. 
     
     
         23 . Prosthesis, according to  claim 22 , wherein said motor/generator devices associated to the joints of the knee and of the ankle and the energy accumulator are fluidic devices. 
     
     
         24 . Prosthesis, according to  claim 1 , wherein means are provided adapted to adjust the pace of the gait in a same gait cycle, said means providing functions at least of the following variables: time, relative rotation angle between tibia and femur; or, in equivalence, relative rotation angle between tibia and femur, and first derivative with respect to time for said angle; means being provided for measuring the variation of said angle and of said first derivative or speed in a gait cycle and means for causing the tibia to follow a function corresponding to that phase of the gait cycle characterized by predetermined values of the angle and of the speed. 
     
     
         25 . A prosthesis for above-knee amputees, said prosthesis having a femoral segment, which can be fixed to a femoral connection, and a tibial segment, pivotally connected to each other about an articulation axis that reproduces the knee movements, said tibial segment being articulated by an ankle to a foot having toes, a sole of the foot and a heel, wherein said knee movements comprise a phase so-called swing, between bringing the toes off the ground and landing the heel, and a phase so-called stance, comprising landing the heel, loading the sole of the foot and bringing the toes off the ground; a motor/generator, the motor being supplied by a current whose intensity is adjusted by a microprocessor to obtain a desired torque at the articulation axis so that in the stance phase the tibial segment is braked about said articulation axis, said microprocessor changing the damping reaction of said damper of said gear motor according to a predetermined force-position function, wherein means are provided adapted to adjust the pace of the gait in a same gait cycle, said means providing functions at least of the following variables: time, relative rotation angle between tibia and femur; or, in equivalence, relative rotation angle between tibia and femur, and first derivative with respect to time for said angle; means being provided for measuring the variation of said angle and of said first derivative, or speed, in a gait cycle and means for causing the tibia to follow a function corresponding to that phase of the gait cycle characterized by predetermined values of the angle and of the speed. 
     
     
         26 . Prosthesis, according to  claim 25 , wherein said means adapted to adjust the pace of the gait in a same gait cycle comprises closed curves, said microprocessor memorizing a plurality of gait modes, each mode being described by a family of said closed curves having similar shape and having different amplitude responsive to an average walking speed. 
     
     
         27 . Prosthesis, according to  claim 25 , wherein said space comprises further coordinates selected from the group comprised of:
 algebraic value of the resultant load vector acting on the limb and transmitted to the ground;   algebraic value of the moment of said resultant vector with respect to the axis of rotation of the articulation;   moment transmitted by the femur to the articulation.   longitudinal force on the femur;   orthogonal force on the femur;   second derivative of said angle of rotation,   or combination thereof.   
     
     
         28 . Prosthesis, according to  claim 25 , wherein said space comprises also the longitudinal force acting on the damper. 
     
     
         29 . Prosthesis, according to  claim 25 , wherein said means adapted to adjust the pace of the gait in a same gait cycle provides also functions at least of the following variables: relative rotation angle between tibia and foot; first derivative with respect to time for said angle set between tibia and foot; means being provided for measuring changes of said first derivative, or speed, in a gait cycle and means for causing the foot to follow a function corresponding to that phase of the gait cycle and having that speed, in order to cause the prosthesis to reproduce the features of that function. 
     
     
         30 . Prosthesis, according to  claim 25  wherein transducer means are provided adapted to measure, continuously with respect to time, or at discrete time intervals, said parameters that represent the coordinates of said space, and to memorize said parameters with respect to time, said microprocessor comprising means adapted to analyse the data determined by the transducers, comparing them with the data recorded in said memory unit, for determining, among the recorded data, the curve that is most suitable for representing the actual gait, called ideal curve. 
     
     
         31 . Prosthesis, according to  claim 30 , wherein said microprocessor adjusts the reaction of the damper and/or of the motor for minimizing errors, said errors consisting of deviations, in said n-dimensional space, between an actual point, whose coordinates are the measurements made by the transducers, and a corresponding point of the ideal curve. 
     
     
         32 . Prosthesis, according to  claim 29 , wherein said microprocessor adjusts the reaction of the damper according to variations of moment and/or force orthogonally to the femur within a gait cycle. 
     
     
         33 . Prosthesis, according to  claim 25  wherein program means are provided residing in said microprocessor adapted to measure the duration of support of the foot to ground during the gait, and for associating a parameter of confidence to each different support duration, to each parameter of confidence corresponding a measured damping stiffness imparted by said microprocessor to said damper, wherein said means for measuring the duration of support of the foot to ground during the gait measure the duration of an event double pitch cause the speed of the gait and the time for load of the limb amputed, comparing them with data recorded relative to the time for load of a missing limb, and allowing a flexion to the knee tanto higher what lower is the deviation between the time for load determined and the time for load of a missing limb. 
     
     
         34 . Prosthesis, according to  claim 1 , wherein a reduction gear is provided having a fast shaft connected to an electric motor and a slow shaft connected to the knee articulation, the motor being supplied by a current whose intensity is adjusted by said microprocessor to obtain a desired torque at the articulation axis. 
     
     
         35 . A prosthesis for above-knee amputees, said prosthesis having a femoral segment, which can be fixed to a femoral connection, and a tibial segment pivotally connected to each other about an articulation axis that reproduces the knee movements, said tibial segment being articulated by an ankle to a foot having toes, a sole of the foot and a heel, wherein said knee movements comprise a phase so-called swing, between bringing the toes off the ground and landing the heel, and a phase so-called stance, comprising landing the heel, loading the sole of the foot and bringing the toes off the ground, a reduction gear being provided having a fast shaft connected to an electric motor and a slow shaft connected to said articulation axis of the knee, the motor being supplied by a current whose intensity is adjusted by a microprocessor to obtain a desired torque at the articulation axis so that in the stance phase the tibial segment is braked about said articulation axis, said microprocessor changing the damping reaction of said damper of said gear motor according to a predetermined force-position function. 
     
     
         36 . Prosthesis, according to  claim 35 , wherein a second gear motor is provided connected to the ankle articulation having a fast shaft connected to an electric motor and a slow shaft connected to the ankle articulation, the motor being supplied by a current whose intensity is adjusted by said microprocessor to obtain a desired torque at the articulation axis. 
     
     
         37 . Prosthesis, according to  claim 35  wherein said or each gear motor acts also as generator. 
     
     
         38 . Prosthesis, according to  claim 35  wherein said fast shaft and said slow shaft connected to said articulation are orthogonal to each other, to achieve a reduced encumbrance as far as possible similar to the anatomic sizes. 
     
     
         39 . Prosthesis, according to  claim 38 , wherein said gear motor has a gear ratio between said fast shaft and said slow shaft that is higher or equal to five, on said fast shaft a first position transducer being mounted to determine the instant position of said fast shaft; on said slow shaft a second position transducer being mounted , said motor piloting said fast shaft in order to maintain a predetermined play with said slow shaft and to allow the reversibility of the motion. 
     
     
         40 . Prosthesis, according to  claim 35  wherein between said reduction gear, located at said knee articulation, and said articulation a freewheel is located adapted to free the tibia from the reduction gear during the swing phase, i.e. when the inertia of the leg is active, vice-versa the freewheel constrains the two movements to each other when the motor/brake has to act on the tibia. 
     
     
         41 . Prosthesis, according to  claim 40  where in flexion phase said microprocessor operates said motor in order to brake the movement of the tibia ensured by said freewheel when in a meshed position, whereas during the extension phase said microprocessor operates or does not operate said motor causing said freewheel to mesh or not to mesh. 
     
     
         42 . Prosthesis, according to  claim 35  wherein said shafts of the reduction gear provide two angular transducers adapted to measure the angular position of said shafts, wherein said reduction gear has backward efficiency less than a forward efficiency, said microprocessor computing the data produced by said transducers and operating the motor to limit the dissipation in the reduction gear of the kinetic energy of the leg recovering suitably play occurring in the kinematical chain. 
     
     
         43 . Prosthesis, according to  claim 35 wherein said shafts of the reduction gear provide one or more moment transducers. 
     
     
         44 . Prosthesis, according to  claim 1  wherein a rechargeable battery is provided, and means for releasably engaging with said rechargeable battery, said battery feeding electronic devices that are arranged in said prosthesis. 
     
     
         45 . Prosthesis, according to  claim 44 , wherein said battery is connected to said prosthesis in a front position with respect to the articulation axis and is accessible from the above by the patient who is in a sitting position, in a way congruent with the geometry of the limb, allowing the sitting patient to extract /position it. 
     
     
         46 . Prosthesis, according to  claim 45 , wherein a port is provided arranged to connect said artificial limb to a computer for recharging said battery that feeds the electronic devices that are arranged in said artificial limb, updating the firmware, transferring, for a deferred analysis, the data recorded by the artificial limb to the computer. 
     
     
         47 . Prosthesis, according to  claim 46 , wherein said rechargeable battery comprises a recharging circuit connectable with a supply circuit external to the limb by a primary/secondary connection of a transformer.