PROSTHETIC IMPLANT OF THE ESR TYPE AND METHOD FOR ADJUSTING THE PROSTHETIC IMPLANT

A prosthetic implant of the ESR (energy-storing-and-returning) type, includes an upper assembly and a lower assembly, configured to define a foot and including a lower blade, an intermediate blade and an upper blade. The upper blade, the lower blade and the intermediate blade are fastened stably to each other at at least one connecting point located in the front region or in the middle region of the foot. An articulated joint is interposed between the lower assembly and the upper one to allow relative motion between them. The implant includes a connector having a first end that is connected to the upper assembly and a second end that is connected to the intermediate blade of the lower assembly. At least one between the first and the second end of the connector is movable along a movement direction to vary the force applied on the intermediate blade of the lower assembly.

TECHNICAL FIELD

This invention relates to a prosthetic implant of the ESR (energy-storing-and-returning) type and to a method for adjusting a prosthetic implant of the ESR type which is widely used in the medical field.

In particular, this invention is widely used in the field of lower limb prostheses and, more specifically, in the field of foot prostheses.

BACKGROUND ART

As is known, during walking, the foot undergoes a load cycle, depending mainly (but not only) on the conditions of the ground, the person's weight, a load being carried, if any, and the walking speed, to which the foot reacts by adapting its rigidity.

To date, therefore, there is a particularly strongly felt need to ensure that amputees have their ambulating functions restored almost entirely to the conditions existing prior to amputation. To meet this need, various different prosthetic implants are available as substitutes which aim to replicate as faithfully as possible the complexities of the force-deformation curve representing a patient's natural gait cycle.

In other words, the aim, to date, is to create a prosthetic implant that is capable of providing a mechanical reaction to different ground types, different obstacles and, generically, different loads, that is as close as possible to the mechanical reaction of a natural foot.

In this situation, various different prosthetic implants have been developed which, by varying the stiffness of the implant itself, allow the patient to walk not only on flat ground, but also on irregular surfaces such as, for example, footpaths, uneven ground, stairs, ramps and the like.

An example of such prosthetic implants is disclosed in U.S. Ser. No. 10/034,782B2. That patent document discloses an implant comprising an elongate prosthetic foot element in the form of a blade provided with a longitudinal slot. The implant also comprises a tongue portion configured to flex independently of the foot element. The prosthetic implant also includes a selectively actuated mechanism to operatively connect/disconnect the tongue portion to/from the foot element. More in detail, when the tongue portion is operatively connected to it, the foot element exhibits greater stiffness, and when the tongue portion is operatively disconnected from it, the foot element exhibits lower stiffness.

In other words, coupling and uncoupling the tongue portion and the foot element to and from each other allows varying the stiffness of the implant so as to adapt it to the patient's ambulation requirements.

Disadvantageously, actuating the mechanism which connects/disconnects the tongue portion is particularly complex and difficult, especially if the mechanism needs to be actuated when the prosthetic implant is in use.

Another disadvantage is due to the fact that in the prosthetic implant described in U.S. Ser. No. 10/034,782B2, the variable stiffness is limited to the foot element only. That means the implant is less flexible and less adaptable to the patient's ambulation requirements in that it does not allow varying and adjusting the torsional stiffness of the ankle portion of the implant.

This drawback is at least partly overcome by the prosthetic implant disclosed in U.S. Pat. No. 9,289,316B2. That patent document discloses an implant comprising a main body (or ankle) coupled to a foot by an articulated system. The articulated system acts as a variable lever arm for adapting the response of the implant to the patient's movement.

In particular, the articulated system comprises a spring having one end hinged to the main body at a fixed hinge point and another end engaged with the foot by a mounting block that is slidable along a horizontal direction (parallel to the patient's direction of movement).

When the patient walks, the sliding of the mounting block causes a variation of the length of the lever arm defined by the articulated system. Adjusting the lever arm makes it possible to control the torsional stiffness of the articulated system. More specifically, the torsional stiffness is linked to the linear stiffness of the spring and to the length of the lever arm. Thus, changing the position of the mounting block has the effect of changing the torsional stiffness of the prosthetic implant.

Disadvantageously, since the torsional stiffness of the prosthetic implant depends on a spring with linear stiffness, the prosthetic implant of U.S. Pat. No. 9,289,316B2 is unable to precisely and reliably mimic the non-linear trend of the force-deformation curve representing the patient's natural gait cycle. This drawback is at least partly overcome by prosthetic implants whose torsional stiffness can be varied by a system of shock absorbers operating with thickening fluids which, by varying their viscosity, allow the prosthetic implant to respond adaptively.

In other words, depending on the phase of the load cycle the prosthetic implant is subjected to (that is, depending on which phase of their gait cycle the patient is in), the viscosity of the thickening fluids varies to allow the implant to react in an optimal manner.

Disadvantageously, these prosthetic implants also have drawbacks. In particular, as the patient walks, for the prosthetic implant to respond adequately to load variations due, for example, to stairs, uneven ground, obstacles and the like, the response reaction of the implant with the shock absorber system needs to be well calibrated. That means that the energy that might be accumulated in an unloading phase of the cycle (known as “stance phase”) is lost and thus cannot be used by the patient in the step that follows (in what is known as the “push-off phase”). In this situation, prosthetic implants that exploit the viscosity variation of thickening fluids are uncomfortable to use and have a considerable fatiguing effect on the patient.

Other examples of foot prostheses are known from patent documents EP3128958A1 and US2020/375764A1. EP3128958A1 involves varying the length of the element that connects the top plate assembly to the blades. Even these solutions, however, do not allow the stiffness to be adjusted in a simple and precise manner.

Also known are fully actuated prostheses which can vary the stiffness but which require the actuating motor to work at each step the patient takes. This has an enormous impact on mobility.

The technical purpose of this invention, therefore, is to provide a prosthetic implant of the ESR (energy-storing-and-returning) type and a method for adjusting a prosthetic implant of the ESR type to overcome the above mentioned disadvantages of the prior art.

DISCLOSURE OF THE INVENTION

The aim of this invention, therefore, is to provide a prosthetic implant of the ESR (energy-storing-and-returning) type, but also of the semi-active ESR and active ESR type, capable of replicating as faithfully as possible the force-deformation curve representing the patient's natural gait cycle.

Another aim of this invention is, therefore, to provide a prosthetic implant of the ESR (energy-storing-and-returning) type that is comfortable for the user and reliable in use.

The technical purpose indicated and the aims specified are substantially achieved by a prosthetic implant of the ESR (energy-storing-and-returning) type and a method for adjusting a prosthetic implant of the ESR type, comprising the technical features set out in one or more of the appended claims. The dependent claims correspond to possible embodiments of the invention.

More specifically, the technical purpose claimed and the aims specified are achieved by a prosthetic implant of the ESR (energy-storing-and-returning) type. The prosthetic implant comprises an upper assembly configured to be connected to a patient's lower limb, and a lower assembly configured to define a foot.

The foot has a front region, a middle region and a rear region. The lower assembly includes a lower blade, extending along a main direction between a heel end and a toe end.

According to an aspect of the disclosure, the lower blade, along the main direction, has a curved shape that replicates the curvature of a sole of a foot.

According to another aspect of the disclosure, the lower blade is provided, along the main direction, with a longitudinal slot extending from the toe end substantially up to the middle region of the foot.

The slot divides the toe end into two rounded portions defining a “forefoot portion” (that is, the part defining the toes of the foot).

The lower assembly also comprises an intermediate blade that is partly superposed on the lower blade, preferably in the middle region of the foot. In the preferred embodiment, the intermediate blade has a first straight stretch extending from a toe end of the intermediate blade and at least partly superposed on the lower blade.

In the preferred embodiment, the intermediate blade also has a second straight stretch extending at an angle to the first stretch. The second stretch extends from the first stretch towards a heel end of the intermediate blade. According to an aspect of the disclosure, the intermediate blade also has a longitudinal slot, extending from the heel end to a middle zone of the intermediate blade itself.

The lower assembly also comprises an upper blade that is partly superposed on the intermediate blade, preferably in the middle region of the foot.

In the preferred embodiment, the upper blade is substantially rectilinear in shape.

The upper blade, the intermediate blade and the lower blade are superposed on each other substantially in the middle region of the foot. More precisely, the upper blade, the intermediate blade and the lower blade are superposed on each other between the middle region and the front region of the foot.

The upper blade, the intermediate blade and the lower blade are fastened stably to each other at at least one connecting point located in the front region or in the middle region of the foot.

In a possible embodiment, the connecting point comprises two parallel pins extending from the upper blade to the lower blade through the intermediate blade.

The upper, lower and intermediate blades diverge from each other away from the connecting point towards the rear region of the foot.

The upper, lower and intermediate blades are laminated springs made from composite material. In this situation, the upper, lower and intermediate blades have a non-linear elastic behaviour.

The prosthetic implant also comprises an articulated joint, interposed between the lower assembly and the upper one to allow relative motion between the lower assembly and the upper one.

The articulated joint acts as a ball joint allowing the patient to walk, that is to say, to mimic an ankle joint.

In a possible embodiment, the articulated joint includes a ball that is stably fixed to the upper assembly and faces towards the lower assembly. The articulated joint also includes a receiving body that is fixed to the lower assembly and faces towards the upper assembly to receive the ball. The receiving body is fixed to the upper blade in the proximity of its heel end.

In a possible embodiment, the receiving body is distinct from the lower assembly, and more specifically, from the upper blade, and is fastened to the lower assembly by, for example, screws or the like.

Alternatively, the receiving body is made as a single part with the upper blade.

The ball and the receiving body define a ball and socket joint.

Alternatively, the ball and the receiving body define a universal joint or a simple hinge.

In an example, the ball and the receiving body are made from composite material. Alternatively, the ball and the receiving body may be made from a material customarily used to make prostheses.

The prosthetic implant also comprises a connector having a first end that is connected to the upper assembly, and a second end that is connected to the intermediate blade of the lower assembly to apply a force on the intermediate blade of the lower assembly.

The connector acts substantially as a tendon element configured for transmitting a force between the upper assembly and the lower assembly. In a possible embodiment, the connector comprises a first portion which extends from the first end and a second portion which extends from the second end and which is configured to be connected to the first portion.

The first and the second portion define a lead nut and screw connection.

According to an aspect of this disclosure, the connector is a rigid element of adjustable length.

According to a possible example embodiment, the length of the connector is adjustable manually. According to another embodiment, the length might be adjustable automatically by means of a motor.

According to another aspect of this disclosure, at least one between the first and the second end of the connector is movable along a movement direction to vary the force applied on the intermediate blade of the lower assembly. In this situation, it is possible to vary the stiffness of the foot by adapting it easily and precisely to the different loads the patient is subjected to and/or to the different types of ground the patient walks on. The connector is elongated along a connection axis. The movement direction is inclined with respect to the connection axis. The movement direction is also inclined with respect to the longitudinal direction. Preferably, the movement direction is perpendicular to the longitudinal direction. The inclination angle between the movement direction and the connection axis varies with the changing position of the movable end of the connector; for example, the angle might be ninety degrees (or slightly greater); more generally speaking and by way of example, the angle might vary between 70 (or 90) and 130 degrees. It should be noted that the change in position (displacement) of the at least one between the first and the second end of the connector along a movement direction does not, in itself, involve any change of length of the connector (the connector might even be of fixed length). Preferably, it is the first end of the connector that is movable along the movement direction (that is, along a movement axis).

More in detail, being able to control the change in the connector fastening position where the force is exchanged between the lower assembly (comprising the blades, which have non-linear behaviour) and the upper assembly makes it possible to vary the point where the force is applied. In this situation, the lever arm of the force relative to the centre of rotation of the ankle changes, hence the transmitted torque also changes. By so doing, the variation in the torsional stiffness obtained can be attributed to the entire foot and is a non-linear variation, that is, a variation that replicates the natural behaviour of a foot in a highly faithful manner.

In an embodiment, the upper assembly extends along a longitudinal direction between a hook-up end, where it is operatively connected to the patient's lower limb, and a fixing end, where it is fixed to the articulated joint. The first end of the connector is slidably movable relative to the upper assembly and the movement direction is transverse to the longitudinal axis. More specifically, the movement direction is perpendicular to the longitudinal axis.

In the preferred embodiment, when the first end of the connector is slidably movable relative to the upper assembly, the second end of the connector is articulated to the intermediate blade of the lower assembly.

More specifically, the second end of the connector is hinged to the intermediate blade of the lower assembly so that a sliding movement of the first end of the connector corresponds to a rotational movement of the connector about the second end.

According to an aspect of the disclosure, the prosthetic implant comprises a slider that is extractable or retractable relative to the upper assembly along the movement direction through a plurality of equilibrium positions.

The first end of the connector is pivoted to the slider to adjust the position of the first end itself between a most extracted position, where the first end is distal to the upper assembly, and a least extracted position, where the first end is proximal to the upper assembly.

At the most extracted position, the slider is extracted and the connector is rotated about the second end so that the first end is distal to the upper assembly. In this situation, the prosthetic implant exhibits a high value of stiffness.

At the least extracted position, the slider is retracted and the connector is rotated about the second end so that the first end is close to the upper assembly. In this situation, the prosthetic implant exhibits a lower value of stiffness.

The slider might also be partly extracted from the upper assembly to occupy an intermediate position between the most extracted position and the least extracted position. The intermediate position corresponds to a walking state of the patient.

Instead of the slider, the prosthetic implant might, for example, comprise a cam capable of varying the position of the first end of the connector as described above. In use, therefore, by controlling (by extracting or retracting the slider) the position of the fastening point (that is, of the first end) of the connector, where the force is exchanged between the lower assembly and the upper assembly, it is possible to vary the point where the force is applied. This also changes the lever arm of the force relative to the centre of rotation of the ankle (articulated joint), thus varying the transmitted torque, hence the torsional stiffness of the entire foot. Since the blades have a non-linear elastic behaviour, the variation in the stiffness obtained is non-linear and such as to better replicate the force-deformation curve of a natural foot subjected to different states of stress and/or loads (for example, uneven ground, weights lifted, and so on).

In the preferred embodiment, the slider is coupled to the upper assembly by a prismatic coupling.

Alternatively, the slider may be coupled to the upper assembly by any other coupling that allows translational motion in the desired direction and is constrained in the other translational and rotational movements.

In a possible embodiment, the first end is movable slidably via an actuator which is, for example, connected to the upper assembly.

Alternatively, the first end is movable slidably by manual operation.

In another possible embodiment, the first end of the connector may be articulated to the upper assembly—hinged to it, for example—while the second end may be movable slidably along the intermediate blade.

In this situation, the prosthetic implant comprises a slide that is slidably movable along the intermediate blade to steplessly vary the position of the second end of the connector on the intermediate blade.

The prosthetic implant also comprises an adjustment element that is activable on the slide to adjust the position of the slide on the intermediate blade. In this situation, varying the position of the second end of the connector makes it possible to vary the point where the force is applied. This also changes the lever arm of the force relative to the centre of rotation of the ankle (articulated joint), thus varying the transmitted torque, hence the torsional stiffness of the entire foot.

The technical purpose and the aims specified are also achieved by a method for adjusting a prosthetic implant of the ESR (energy-storing-and-returning) type. The prosthetic implant comprises an upper assembly configured to be connected to a patient's lower limb, and a lower assembly configured to define a foot having a front region, a middle region and a rear region. The lower assembly includes a lower blade, extending along a main direction between a heel end and a toe end.

The lower assembly includes an intermediate blade that is partly superposed on the lower blade, preferably in the middle region of the foot. The lower assembly includes an upper blade that is partly superposed on the intermediate blade, preferably in the middle region of the foot.

The blades are laminated springs made from composite material.

The upper, lower and intermediate blades are fastened stably to each other at at least one connecting point located in the front region or in the middle region of the foot and diverge from each other away from the connecting point towards the rear region of the foot.

The prosthetic implant also comprises an articulated joint—for example, a ball and socket joint, a rotoidal joint or a universal joint—interposed between the lower assembly and the upper assembly to allow relative motion between the lower assembly and the upper assembly.

The prosthetic implant also comprises a connector having a first end that is connected to the upper assembly, and a second end that is connected to the intermediate blade of the lower assembly to apply a force on the intermediate blade of the lower assembly.

More in detail, the connector acts as a rigid tendon element capable of transmitting a force between the upper assembly and the lower assembly. The method comprises a step of moving at least one between the first and the second end of the connector to vary the force applied by the connector on the intermediate blade of the lower assembly.

In the preferred embodiment, in the step of moving, it is the first end that moves, while the second end is articulated to the intermediate blade—hinged to it, for example.

In an embodiment, the upper assembly extends along a longitudinal direction between a hook-up end, where it is operatively connected to the patient's lower limb, and a fixing end, where it is fixed to the articulated joint. In this situation, the method comprises a step of sliding the first end of the connector relative to the upper assembly. In this situation, the movement direction is transverse, specifically perpendicular, to the longitudinal axis.

In other words, to vary the force applied by the connector on the intermediate blade of the lower assembly, the first end of the connector is moved slidably along the movement direction.

The prosthetic implant also comprises a slider, to which the first end of the connector is pivoted. In this situation, the method also comprises a step of extracting or retracting the slider relative to the upper assembly along the movement direction through a plurality of equilibrium positions. The method also comprises a step of adjusting the position of the first end of the connector between a most extracted position, where the first end is distal to the upper assembly, and a least extracted position, where the first end is proximal to the upper assembly.

In other words, by extracting or retracting the slider relative to the upper assembly, it is possible to change in a controlled manner the position of the first end of the slider, where the force is exchanged between the foot and the upper assembly. Changing the position of the first end of the slider, that is, the point where the force is applied, changes the lever arm of the force relative to the centre of rotation of the ankle, hence the transmitted torque. In this situation, the blades change their point of rotation with the changing of the position of the first end of the connector, thus obtaining a non-linear variation of the torsional stiffness of the entire foot, capable of faithfully replicating the behaviour of a foot when subjected to stresses due to different loads and/or different ground conditions.

Further features and advantages of this invention are more apparent in the exemplary, hence non-limiting, description of an embodiment of a prosthetic implant of the ESR (energy-storing-and-returning) type and a method for adjusting a prosthetic implant of the ESR type.

With reference to the accompanying drawings, the numeral100denotes a prosthetic implant of the ESR (energy storing and returning) type.

The prosthetic implant100comprises an upper assembly200configured to be connected to a patient's lower limb.

The upper assembly200extends along a longitudinal direction A between a hook-up end200a, where it is operatively connected to the patient's lower limb, and a fixing end200b, where it is fixed to an articulated joint500.

The prosthetic implant100also comprises a lower assembly300, configured to define a foot having a front region300a, a middle region300band a rear region300c.

The lower assembly300includes a lower blade400a, extending along a main direction M, between a heel end400a′ and a toe end400a″.

In use, the main direction M coincides with the direction of forward movement of the patient while walking.

According to an aspect of this disclosure, the lower blade400ahas a curved shape along the main direction M, where the heel end400a′ and the toe end400a″ rest on the ground, while the part of the lower blade400abetween them is at least partly raised off the ground.

In other words, the lower blade400asimulates the curvature and shape of the sole of a foot.

According to another aspect of this disclosure, the lower blade400ahas a slot I extending longitudinally on the lower blade400a. In this situation, in the proximity of the toe end400a″, the slot I divides the lower blade400ainto two rounded portions L.

The lower assembly300also comprises an intermediate blade400b, partly superposed on the lower blade400a.

More specifically, as shown, for example, inFIG.1, the intermediate blade400bis superposed on the lower blade400ain proximity to the middle region300bof the foot.

The intermediate blade400bhas a first, substantially rectilinear stretch extending from a toe end400b′ and a second stretch, lying at an angle to the first stretch and extending between the first stretch and a heel end400b″.

The intermediate blade400btoo is provided with a slot12extending longitudinally between the middle region300bof the foot and the heel end400b″ of the intermediate blade400b.

The lower assembly300also comprises an upper blade400c, partly superposed on the intermediate blade400b.

More specifically, as shown, for example, inFIG.1, the upper blade400cis superposed on the intermediate blade400bin proximity to the middle region300bof the foot.

The upper blade400chas a slight curvature extending from a toe end400c′ to a heel end400c″.

The upper blade400cis shorter in length than the intermediate blade400b. The intermediate blade400bis shorter in length than the lower blade400a. The upper, lower and intermediate blades400a,400b,400care fastened stably to each other at at least one connecting point C located in the front region300aor in the middle region300bof the foot and diverge from each other away from the connecting point C towards the rear region300cof the foot.

In the embodiment shown in the accompanying drawings, the connecting point C is located in the middle region300bof the foot.

In a possible embodiment, the connecting point C is embodied by two parallel pins extending between the upper blade400cand the lower blade400a.

Aa shown, for example, inFIGS.1and4, the upper blade400cand the intermediate blade400bare connected at the connecting point C in proximity to their respective toe ends400b′,400c′.

The lower blade400a, on the other hand, is connected to the other blades400b,400cin proximity to the middle region300bof the foot.

According to an aspect of this disclosure, the lower blade400c, the intermediate blade400band the upper blade400aare laminated springs made from composite material.

When subjected to stress, the lower blade400a, the intermediate blade400band the upper blade400chave a non-linear elastic behaviour.

The prosthetic implant100also comprises an articulated joint500, interposed between the lower assembly300and the upper one200to allow relative motion between the lower assembly300and the upper one200.

In a possible embodiment, the articulated joint500includes a ball that is stably fixed to the upper assembly200and faces towards the lower assembly300.

The articulated joint500also includes a receiving body that is fixed to the lower assembly300and faces towards the upper assembly200to receive the ball. In this situation, the ball and the receiving body define a ball and socket joint.

In the embodiment shown in the accompanying drawings, the receiving body is stably fixed to the upper blade400c, preferably in the rear region300cof the foot and in proximity to the heel end400c″ of the upper blade400citself.

The ball and socket joint500allows the upper assembly200and the lower assembly300to move relative to each other in that the ball can roll in the receiving body.

In other words, the ball and socket joint500simulates the patient's ankle articulation.

According to an aspect of this disclosure, the prosthetic implant100also comprises a connector600having a first end600athat is connected to the upper assembly200and a second end600bthat is connected to the intermediate blade400bof the lower assembly300to apply a force on the intermediate blade400bof the lower assembly300, as described in detail below. The connector600extends from the first end600ato the second end600balong a connection axis Y.

The connector600is located in proximity to the rear region300cof the foot.

According to an aspect of this disclosure, one between the first and the second end600a,600bof the connector600is movable along a movement direction X to vary the force applied on the intermediate blade400bof the lower assembly300.

The movement direction X is inclined with respect to the connection axis Y. The movement direction X is inclined (preferably perpendicular) with respect to the longitudinal direction A. Thus, the displacement of the at least one between the first and the second end along the movement direction X causes the first or the second end of the connector600to move towards or away from the longitudinal axis A.

The connector600constrains the upper assembly200and the lower assembly300to rotate in a plane defined by the longitudinal axis A and by the movement direction, as shown by the arrow inFIG.1.

In other words, the connector600causes the articulated joint500to act as a centre of rotation for the prosthetic implant100.

According to an aspect of this disclosure, the connector600is a rigid element.

According to another aspect of this disclosure, the connector600is adjustable (for example, it is variable in length).

Looking in more detail, the connector600comprises a first portion601extending away from the first end600a, and a second portion602extending away from the second end600band engaged with the first portion601.

The first and the second portion601,602are engaged with each other by a lead nut and screw coupling configured to set a length for using the connector600and to connect the first and the second portion601,602rigidly so that the connector600acts as a rigid arm of preset length.

In this situation, by changing the position of one between the first and the second end600a,600bof the connector600it is possible to obtain, through the connector600itself, a variable lever arm so as to adapt the response of the prosthetic implant100as the patient moves.

In effect, by varying the lever arm, it is possible to change the point of rotation (or of flexion) of the blades400a,400b,400c, varying their state of stress. Since the blades400a,400b,400care elastically deformable in non-linear manner, varying the lever arm makes it possible to vary the stiffness of the prosthetic implant100in non-linear manner so that the behaviour of the prosthetic implant100under stress is as close as possible to that of a natural foot.

In other words, changing the position of the point where the force is applied, changes the lever arm of the force relative to the centre of rotation of the articulated joint500, hence the transmitted torque. The variation in the torsional stiffness obtained can be attributed to the entire foot, that is to the entire lower assembly300.

In a possible embodiment shown inFIGS.1,2A-2C,3, the first end600aof the connector600is slidably movable relative to the upper assembly200. In this situation, the movement direction X is transverse to the longitudinal axis A.

In the preferred embodiment, the movement direction X is perpendicular to the longitudinal direction A.

As shown inFIGS.2A-2C, the prosthetic implant100comprises a slider700that is extractable or retractable relative to the upper assembly200along the movement direction X (that is, along a movement axis X defined by the slider700) through a plurality of equilibrium positions.

Looking in more detail, the slider700is extracted slidably in a direction that is the opposite of the patient's direction of movement while walking, and is retracted slidably in the same direction as the patient's direction of movement while walking.

The first end600aof the connector600is pivoted to the slider700—for example, hinged to it—to adjust the position of the first end600aof the connector600.

In other words, the position of the slider700along the movement direction X is adjustable (by extracting or retracting the slider700) to position the first end600aof the connector600at a predetermined distance from the upper assembly200.

More specifically, the position of the first end600aof the connector600can be adjusted between a most extracted position (FIG.2C), where the first end600ais distal to the upper assembly200, and a least extracted position (FIG.2A), where the first end600ais proximal to the upper assembly200. At the most extracted position, the prosthetic implant100exhibits a higher value of stiffness whilst, at the least extracted position, the prosthetic implant100exhibits a lower value of stiffness, as described in detail below. The first end600aof the connector600is moved to the most extracted position when, for example, the patient lifts a load or walks on uneven ground and/or runs.

On the contrary, the first end600aof the connector600is moved to the least extracted position when, for example, the patient needs to climb stairs or ramps or to walk on even ground.

Advantageously, the same prosthetic implant100is adaptable to the patient's different walking needs.

Also, the same prosthetic implant100, being variable in stiffness, can be used by patients varying widely in body weight.

As shown inFIG.2B, the slider700can also be moved in such a way that the first end600aof the connector600occupies an intermediate position between the most extracted and the least extracted position. At such an intermediate position, the prosthetic implant100is in a standard walking configuration, that is to say, under conditions allowing the patient to walk in what may be termed everyday life conditions.

According to an aspect of this disclosure, the slider700is coupled to the upper assembly200by a prismatic joint. In this situation, the slider700is made in the form of a prismatic section bar slidably extractable from, or insertable into, a housing made on the upper assembly200and shaped to match the bar.

Also, the second end600bof the connector600is articulated to the intermediate blade400bof the lower assembly300.

In the embodiment ofFIGS.1,2A-2C and3, the second end600bof the connector600is articulated to the intermediate blade400bby a hinge.

In use, therefore, for the prosthetic implant100to be able to simulate a human foot as faithfully as possible, that is to say, to replicate the force-deformation curve representing the patient's natural gait cycle, the slider700is extracted from the upper assembly200by a predetermined quantity. In this situation, the connector600varies its inclination relative to the longitudinal direction A.

For example, if the slider700is moved to the most extracted position, the connecting point (identified with the first end600aof the connector600) between the slider700and the connector600occupies a position distal to the upper assembly200and the connector600is substantially parallel to the longitudinal direction A. On the contrary, if the slider700is moved to the least extracted position, the connecting point (that is, the first end600aof the connector600) between the slider700and the connector600occupies a position close to the upper assembly200and the connector600is substantially inclined with respect to the longitudinal direction A.

According to an aspect of this disclosure, the change in position of the slider700, hence of the first end600aof the connector600along the movement direction X, is approximately 2 mm. In this situation, the stiffness of the prosthetic implant100changes by approximately 10 kg, allowing a good adjustment of its response to a change, for example, of the patient's weight. Since the blades400a,400b,400crest at least partly on each other and since they are laminated springs made from compositive material, their behaviour is a non-linear elastic behaviour. Changing the position of the first end600a, that is, of the connecting point between the slider700and the connector600, makes it possible to change the point of rotation of the blades400a,400b.400c. In this situation, depending on the position of the first end600a, the blades400a,400b,400care subjected to a different flexural state, thus allowing the elastic stiffness of the prosthetic implant100to be varied in non-linear manner.

Changing the position of the first end600aof the connector600in a controlled manner varies the point where the force exchanged between the lower assembly300and the upper assembly200is applied. In this situation, the lever arm of the force relative to the centre of rotation of the ankle (that is, of the articulated joint500) changes, hence the transmitted torque also changes.

In the embodiment ofFIG.1, the position of the first end600aof the connector600, hence the extent to which the slider700is extracted, can be adjusted manually (FIG.1A).

In this situation, by using a adjustment tool, for example, an Allen key, it is possible to adjust the extent to which the slider700is extracted from the upper assembly200, hence the position of the first end600aof the connector600along the movement direction X.

Alternatively, the prosthetic implant100comprises an actuator800, shown inFIG.3, configured to slidably move the first end600aof the connector600.

In another embodiment, shown inFIGS.4and4A, the end that is moved is the second end600bof the connector600.

In this situation, the second end600bof the connector600is slidably movable along the intermediate blade400b, while the first end600ais hinged or pivoted to the upper assembly200.

Looking in more detail, as shown inFIG.4A, the prosthetic implant100comprises a slide901that is slidably movable along the intermediate blade400bto steplessly vary the position of the second end600bof the connector600on the intermediate blade400b.

The prosthetic implant100also comprises a locking element902that is applicable on the slide901to adjust the position of the slide901on the intermediate blade400b.

According to an aspect of this disclosure, the locking element902can be applied to, and released from, the slide901to prevent or allow the slidable movement of the slide901, respectively, so that its position along the intermediate blade400bcan be adjusted.

In the embodiment shown in the accompanying drawings, the locking element902is embodied in the form of a rotatable screw oriented substantially parallel to the intermediate blade400b.

As shown inFIGS.4and4A, the first end600aof the connector600is pivoted to the upper assembly200, while the second end600bis engaged with the slide901.

Adjusting the position of the second end600bby sliding the slide901on the intermediate blade400bmakes it possible to vary the response of the prosthetic implant100so that it can adapt to different ground surface conditions in a manner almost identical to that of a natural foot.

In this situation, too, the force exchanged between the lower assembly300and the upper assembly200can be changed in a controlled manner by changing the position of the point where the force is applied, in this case the second end600bof the connector600. Changing the position of the point where the force is applied, changes the lever arm of the force relative to the centre of rotation of the ankle (that is, of the articulated joint500), hence the transmitted torque. The variation in the torsional stiffness obtained can be attributed to the entire lower assembly300.

Advantageously, the prosthetic implant100of this disclosure allows varying the stiffness of the lower assembly300non-linearly to adapt it to the patient's different walking needs.

More specifically, the lower assembly300constituting the foot is capable of faithfully replicating the force-deformation curve representing the behaviour of a natural foot when subjected to loads and/or when walking on uneven ground.

Another object of this disclosure is a method for adjusting a prosthetic implant100of the ESR (energy-storing-and-returning) type. The prosthetic implant100comprises an upper assembly200configured to be connected to a patient's lower limb, and a lower assembly300configured to define a foot having a front region300a, a middle region300band a rear region300c.

The lower assembly300includes a lower blade400aextending along a main direction M, between a heel end400a′ and a toe end400a″; an intermediate blade400bpartly superposed on the lower blade400a, and an upper blade400cpartly superposed on the intermediate blade400b.

The blades400a,400b,400care laminated springs made from composite material.

The blades400a,400b,400chave a non-linear elastic behaviour.

The upper, lower and intermediate blades400a,400b,400care fastened stably to each other at at least one connecting point C located in the front region300aor in the middle region300bof the foot and diverge from each other away from the connecting point C towards the rear region300cof the foot.

More specifically, the upper blade400cand the intermediate blade400bare connected at the connecting point C at a toe end400b′,400c′, while the lower blade400ais connected at the connecting point C in proximity to the middle region300bof the foot.

The prosthetic implant100also comprises an articulated joint500, interposed between the lower assembly300and the upper assembly200to allow relative motion between the lower assembly300and the upper assembly200.

More specifically, the articulated joint500simulates an ankle articulation.

The prosthetic implant100also comprises a connector600having a first end600athat is connected to the upper assembly200and a second end600bthat is connected to the intermediate blade400bof the lower assembly300to apply a force on the intermediate blade400bof the lower assembly300.

The connector600is rigid and preferably comprises a first and a second portion connected to each other by a lead nut and screw connection.

The method comprises a step of moving at least one between the first and the second end600a,600bof the connector600to vary the force applied by the connector600on the intermediate blade400bof the lower assembly300.

Changing in a controlled manner the position of one between the first and the second end600a,600bof the connector600, where the force is exchanged between the lower assembly300and the upper assembly200means changing the point where the force is applied, thereby changing the lever arm of the force relative to the centre of rotation of the ankle (that is, relative to the articulated joint500), hence the torque transmitted.

Since the blades400a,400b,400cinteract (by resting on each other), their points of rotation vary with the changing of the load applied to them. Changing the position of one of the ends600a,600bof the connector600varies the lever arm of the force and the points of rotation, and thus also the rigidity of the prosthetic implant100is varied in non-linear elastic manner. In this situation, the prosthetic implant100can be adapted to the user's different needs such as, for example, walking on uneven ground, carrying weights and the like.

According to an aspect of this disclosure, the upper assembly200extends along a longitudinal direction A between a hook-up end200a, where it is operatively connected to the patient's lower limb, and a fixing end200b, where it is fixed to the articulated joint500. In this situation, the method comprises a step of sliding the first end600aof the connector600relative to the upper assembly200. In this situation, the movement direction X is transverse to the longitudinal axis A.

Thanks to the step of sliding, the position of the first end600aof the connector600can be adjusted relative to the upper assembly200in such a way as to vary the stiffness of the entire prosthetic implant100.

According to an aspect of this disclosure, the prosthetic implant100comprises a slider700and the first end600aof the connector600is pivoted to the slider700.

In this situation, the method comprises a step of extracting or retracting the slider700relative to the upper assembly200along the movement direction X through a plurality of equilibrium positions, and a step of adjusting the position of the first end600aof the connector600between a most extracted position, where the first end600ais distal to the upper assembly200, and a least extracted position, where the first end600ais proximal to the upper assembly200.

At the most extracted position, the stiffness of the prosthetic implant100is less than the stiffness when it is at the least extracted position.

Varying the position of the first end600aof the connector600byextracting or retracting the slider700varies the force exchanged between the lower assembly300and the upper assembly200via the slider600. Varying the position of the first end600achanges the point of application of the force, hence the lever arm of the force relative to the centre of rotation of the ankle (that is, relative to the articulated joint500) is also varied, which in turn varies the torque transmitted.

In this situation, it is possible to adapt the foot to any type of ground and/or load which the patient needs to negotiate and/or support.

This invention achieves the preset aims and overcomes the disadvantages of the prior art.

In particular, the possibility of adjusting the position of one of the ends, specifically the first end, allows making the prosthetic implant adaptive, that is to say, it allows varying the stiffness of the prosthetic implant.

Moreover, the arrangement of the blades and their makeup allow varying the elastic stiffness of the prosthetic implant in non-linear manner, making the response of the prosthetic implant practically identical to the response of a foot of an able-bodied patient walking on different types of ground.