Prosthetic interface device

Abstract

The present invention relates to an interface device (1) configured to control the movement of mobile elements comprised in a prosthesis (P) applied at the stump of a limb of a subject with amputation. The device (1) includes at least a pulley (4) comprising a portion of annular crown configured to engage connection means (7) connecting mechanically a pair of agonist-antagonist muscles so that a linear displacement motion of such connection means (7), associated with a contraction-stretching motion of the pair of agonist-antagonist muscles, causes a corresponding rotation of the pulley (4). The device (1) further comprises an angular position transducer (8) associated with the pulley (4), configured to generate an electrical control signal of the motion of the mobile components of the prosthesis (P) as a function of the rotation of the pulley (4).

Description

[0001] PROSTHETIC INTERFACE DEVICE

[0002] DESCRIPTION

[0003] Technical field of the invention

[0004] The present invention relates to an interface device configured to emit a signal capable of controlling automatically the movement of mobile elements included in a prosthesis, in particular applied at the stump of a limb of the same subject.

[0005] The proposed device accomplishes the task of interfacing mechanically the musculoskeletal system of an amputated subject with an external prosthesis worn by the latter, which represents a device, in itself and interchangeable, provided, of course, that it is arranged to receive the control signal emitted by the interface device of the invention.

[0006] The interface device comprises a rotational element, for sake of simplicity a pulley, configured to transform the linear motion of the muscles of the amputated limb into a rotational motion. Such rotational motion of the pulley is transformed into a signal (a digital or analogical signal, depending on the type of used electronics) usable to control a degree of freedom of the prosthesis worn by the amputated subject. The pulley moves passively thanks to the activity of the muscles of the amputated subject. The motion of the pulley is tracked and transformed into a control signal for the mobile components of the prosthesis, for example a hand prosthesis.

[0007] Background

[0008] The loss of a limb represents a devastating event involving inevitably a disability for the affected subject. Whether it is a lower or upper limb, the quality of life of the amputated individual is affected significantly, both depending on the seriousness of the amputation itself, and depending on the solutions which are afterwards adopted to try to recover the lost functionality.

[0009] War injuries and infections cause the higher number of amputations in developing countries, whereas oncological and cardiovascular diseases are the main factors in the Western world, together with the road and workplace accidents. If one considers the latter only, currently in Italy there are 3,391 (December 2021 census) individuals recorded at the National Institute for Insurance against Accidents at Work (INAIL) with a degree of disability caused by amputation from 65% to 100%, indicative percentage of disability from very severe to absolute. Previous statistics from the Ministry of Health show a total of about 5600 cases of amputation or congenital disease of the upper limb. As to the lower limbs instead, the amputation discharge rate reported for the year 2009 is 4.2 for 100,000 residents if one considers the major amputation operations only (that is the amputations above the foot level) after a diabetic pathology, with a rate twenty times higher than the one of the healthy population, not at risk.

[0010] With respect to the lower limb, the challenge of restoring the lost function to an upper limb amputee through prosthetic systems is more difficult, especially since the hand motor skills are very difficult to replicate and control.

[0011] The upper limb, in fact, does not act only as an ideal tool to operate within the surrounding environment, but also represents sophisticated means of social interaction. The recovery of its functionality then results to be fundamental. Above all, it is complex to determine how to capture the user motion intentions to control the prosthesis and how to give the user the feedback on the interaction of the prosthesis with the external environment.

[0012] To this purpose, the options currently on the market can be divided into three big categories of prosthesis: cosmetic, body-powered, and myoelectric (or prosthesis with myoelectric control). The cosmetic prostheses aim at restoring, mostly, the aesthetics of the lost limb and, despite the low technological level, they are often the ones preferred by the amputated subject. Apart from providing a realistic replica of the limb, some of them are equipped with passive spring mechanisms capable of offering a simple grip. The so-called body- powered prostheses, instead, are functional devices which transmit mechanically, through a cable, the force produced by the motion of a healthy joint (typically the shoulder contralateral to amputation) and a hook end effector.

[0013] The myoelectric prostheses are capable of releasing the user from the need for wearing cables and harnesses, since they use the electrical signal generated by the contraction of the muscles remaining on the stump of the amputated subject for controlling one or more degrees of freedom. The most common myoelectric control device provides electrodes integrated in the socket to record the electrical signal, directly from the skin surface, to be used as input signal to the control of one single degree of freedom (for example opening and closing of the prosthetic hand grip).

[0014] As to the functional prostheses, then body-powered and myoelectric prostheses, conflicting results in terms of performances have been collected over the years. If on one side the control of the mechanical prostheses is less intuitive with respect to that of a myoelectric prosthesis, on the contrary, these bulkier systems are also more robust and, thanks to the biomechanical connection due to the presence of the transmission cable, allow the user to have moderately realistic feedback on the interaction between prosthesis and external environment. This provides the subject partial kinesthetic (position and motion) and load information which instead is almost completely absent when using a myoelectric device.

[0015] Moreover, to improve the features of the user-prosthesis interface, it is possible to follow surgical remodelling of the stump. The Targeted Muscle Reinnervation (TMR), the Regenerative Peripheral Neural Interface (RPNI), the Agonist-antagonist Myoneural Interface (AMI), osteointeg ration, cineplastics, are all examples of how the human body can be modified to facilitate interaction between the subject and the prosthesis. TMR provides to transfer the nerves previously dedicated to the hand control towards new healthy muscle groups (for example from the flexor muscles of the forearm to the pectoralis major). Thanks to this “transfer” of motor intention, the subject succeeds in controlling the muscle recipient of the nerve naturally, as if it were the one originally innervated. The procedure thus allows to produce an EMG signal adequate to control a myoelectric prosthesis. The rational behind RPNI is similar, since the nerve, which is transferred in the TMR, in this case is implanted inside a muscle tissue graft in itself, which wounds it wholly. This tissue then acts as electrical signal amplifier, recorded as EMG in a more or less invasive way, with the same goal of providing a control input to the prosthetic device.

[0016] In both just described scenarios, however, since a real joint is lacking where intrinsic forces (of the same muscles) and extrinsic forces (resistances opposed by external elements) could act, also each type of proprioceptive feedback, both of position and load, is absent.

[0017] In presence of adequate conditions, this problem is faced by implementing an AMI, experimental technique which provides the surgical connection of two muscles acting on the joint ifself and belonging to an agonist-antagonist pair. After amputation, in fact, to restore the “biomechanical dependence” of the pair means to recover the physiological model therefore if one of the two muscles contracts, the other one is stretched and vice versa. In this way, thanks to the normal operation of the muscle receptors, the subject receives the normal flow of proprioceptive information linked to the contraction of one of the two muscles, coming from the stretching of the respective antagonist. Within this system, not only it is possible to collect the EMG signal of both muscles, useful to the myoelectric control, but it has also been hypothesized to artificially cause the contraction thereof through electric stimulation, so as to provide a resistance to the voluntary motion of the not stimulated muscle, thus simulating the presence of a load. The modification of the limb can go further, until putting the subject’s skeleton in physical communication with the prosthesis and the external environment, with all risks associated thereto. Osteointegration, for example, guarantees a quite safe and comfortable connection between the residual limb of the subject and the prosthesis thanks to a real artificial extension of the bone. The part implanted in the latter is brought to outside the stump and acts as attack for the prosthesis, thus allowing to avoid the use of the socket, whose exchange of force with the skin is often reported among the main reasons for discomfort by the amputee. In past it was also proved, but with little success, the use of the tendons of the remaining muscles of the stump, both to implement directly the prosthetic joint and to return possible forces exerted on the latter.

[0018] Considering the represented state of art, it is clear that the currently available prosthetic technology is still far from being able to be defined satisfying. There are different needs that the various types of prosthesis succeed in satisfying, but the benefits of a choice are inevitably accompanied by the weaknesses associated thereto. Although myoelectric prostheses currently represent the most advantageous solution, the operation of the latter, even if intuitive, requires a specific training and it is affected by possible changes, even minimum, in the interface between the recording electrode and the source of the activity. Moreover, the myoelectric devices on the market do not yet provide integrated solutions aimed at returning sensory information allowing the amputated subject to use the prosthesis dexterously, without the need for paying constant attention to it.

[0019] The myoelectric prostheses use the electromyographic signal (EMG) produced by the voluntary contraction of the muscles of the amputated subject to control the engine of the device and thus to generate a corresponding torque. In order to be able to produce effectively this type of signal, a long training phase is required for the amputated subject. The signal trend, moreover, is not exactly proportional or linearly related to the effort that the subject applies, or to the force produced by the contracting muscle. The myoelectric control of a prosthesis suffers from the introduction of several intermediate variables between the subject’s real effort that the final torque application, which require more or less sophisticated algorithms for processing the signal and controlling the effector. The origin of the signal is distance from the recording electrode and does not consist of one single active unit, but of several components (motor units, composed of muscle fibres innervated by one single motor neuron). For these two reasons, the spatial resolution of the signal is very low and produces a little selective signal, generally used for a proportional control of one single degree of freedom.

[0020] Moreover, it is required that the position and the conditions of the recording electrode remain stable while using the device, therefore a small displacement, as well as any alteration of the interface, such as increased sweating, can significantly compromise the signal quality. The one based on EMG is then a not very robust motor intention decoding system.

[0021] Moreover, the myoelectric prostheses do not allow to return any type of information on the joint state, both kinesthetic (position and motion) and load, disappeared with amputation, which eliminated the connection between the agonist-antagonist muscles acting on the lost joint.

[0022] The users, then, succeed in controlling one or more degrees of freedom of a prosthetic device only under careful visual control.

[0023] The only solution explored so far for the recovery of load feedback during AMI consists in the functional electrical stimulation of the muscle antagonist to the one responsible for the ongoing motion, thereto is then imposed a resistance. The use of the electrical stimulation, however, could not be optimum for two reasons: the interference with the EMG signal, currently only option available for controlling the prosthesis, and the short-and long-term effects which the electric stimulation causes (for example, dynamics of muscle fatigue worse than the one linked to a voluntary contraction). GB2445869A describes a transcutaneous prosthetic device. The device comprises at least a fixing device for soft tissues adapted to be fixed to the musculotendineous soft tissues of a residual limb and a transcutaneous anchor for an external prosthesis which is coupled in a fixed way, directly or indirectly, to the bone of the residual limb in use. The device comprises even means for transmitting signals between the fixing device and an external prosthesis, which signals are related to the contraction and / or relaxation of the muscle of the residual limb. The connection between the the fixing device for soft tissues and the external prosthesis in use can include a mechanical or electric connector, preferably a sealed connection within the transcutaneous component, to provide an effective barrier between the internal and external environments

[0024] EP1955679A1 describes an assistance device which includes a detection part and an actuation part. The detection part includes a sensor, a first transmitting / receiving circuit, a first data processing circuit, a first charging circuit and a first battery. The part for actuating the assistance device includes an actuation part, a second data processing circuit, a second transmitting / receiving circuit, a second charging circuit and a second battery. The electromagnetic waves are transmitted by the second transmitting / receiving circuit provided in the actuation part to the first transmitting / receiving circuit provided in the detection part. The induced electromotive force generated at this time is input to the first charging circuit through the first data processing circuit provided in the detection part and the first battery provided in the detection part is charged.

[0025] US11278235B2 describes a prosthetic device comprising foot and ankle elements connect for a motion of two degrees of freedom relative to each other, by allowing the rotation thereof. Two linear actuators connect the foot and ankle elements. The actuation of the actuators in the same direction causes the rotation around the ankle axis and the actuation of the actuators in opposite directions causes the rotation around the subtalar axis. A processor receives sensory information from a sensor and actuates the actuators to control an equilibrium position of the in-series elastic elements.

[0026] Summary of the invention

[0027] The technical problem placed and solved by the present invention is then to provide an improved solution to implement the automatic control of a prosthesis, or more generally of a mobile device, by a subject, which allows to obviate the drawbacks mentioned above with reference to the known art.

[0028] Such problem is solved by an interface device as defined in claim 1. It is also protected a prosthesis comprising such device.

[0029] The proposed device implements, in use, an interface between a subject and a device to be implemented, in particular a prosthesis worn by the subject. The interface device to this purpose incorporates a transduction mechanism for converting the linear motion of a pair of agonist-antagonist muscles of the subject in a control signal of mobile components of the prosthesis.

[0030] In other words, the interface device is configured to allow the transmission of the motor intention from an amputated subject to the mobile components of the prosthesis, capable of reproducing one or more degrees of freedom and corresponding functionalities of the missing limb. In particular, the interface device allows to control the movement of the mobile components through the exercise of the tendons associated with the pair pf agonist-antagonist muscles responsible for carrying out the above-mentioned functionalities in a healthy subject.

[0031] To this purpose, the interface device comprises a transduction mechanism of the movement of the above-mentioned tendons or a residual portion of the pair of muscles in an electrical signal by a mechanical coupling with a rotating disk, therefore the rotation of the disk causes the generation of an electrical signal for actuating the mobile elements of the prosthesis, as it will be better illustrated hereinafter. The transduction mechanism includes an implantable passive device, preferably exploited in combination with the already described surgical technique of agonist-antagonist myoneural interface (Agonist-antagonist

[0032] Myoneural Interface, AMI).

[0033] The invention thus allows to extract from the mechanical activity produced by the muscle contraction of the stump of an amputated limb of the subject, a signal useful for controlling one or more degrees of freedom of a device, for example a prosthetic device configured to implement one or more of the functionalities of the amputated limb.

[0034] The principle underlying the invention is to be able to generate the control signal of a degree of freedom by tracking the motion of a rotating body, depending in a mechanical and passive way on the activation and contraction state of a pair of antagonist muscles associated to the considered degree of freedom. This can be implemented by combining (or re-adapting) the AMI surgical technique performed after a limb amputation, with an implantable mechanical device which constitutes the real innovation. The AMI consists in implementing the mechanical connection of the muscles’ tendons belonging to an agonist-antagonist pair, so as to restore their functional contractionstretching relationship physiologically present, but lost following amputation.

[0035] In other words, by connecting the two muscles through suture (or through the tendons when still present) the physiological biomechanical model is restored therefore if one of the muscles contracts, the other one is stretched, aimed at finding again the proprioreceptive feedback relating to the articulation implemented by the subject pair of muscles.

[0036] According to a first aspect of the invention, the ‘single tendon’ created by suturing the two interrupted tendons is housed like a belt in the crown of a rotative or rotating element, which is engaged with respect to a fixed rotation axis. The rotating element is passive, connected surgically and mechanically to both muscles, and it can rotate freely in both directions based upon the muscle which contracts, by producing at the same time a stretching in the antagonist muscle of the pair and then the activation of the muscle receptors and the corresponding proprioceptive feedback.

[0037] Apart from the rotating element, for sake of simplicity indicated in a simplifying way as a pulley hereinafter in the present exposition, the proposed device consists of additional two parts: an angled bracket acting as frame element and axis for the rotation of the pulley and the anchor to the stump bone, and a rotative encoder, that is an angular position transducer, broken down into a passive marker (or more than one), integral to the pulley, and a tracking sensor (tracker) which can be arranged externally to the subject’s skin, and which can be integrated in the socket of the prosthesis.

[0038] In general terms, a rotative encoder is an electromechanical device which converts the mechanical angular position of its own rotating axis into a digital and / or analog electrical signal. Connected to suitable electronic circuits and appropriate mechanical connections, the encoder is capable of measuring angular displacements, rotation speeds and accelerations. The encoders can be classified in different categories, thereamong optical and magnetic. Moreover, the encoders can be of two types: incremental, when the output signals are proportional in incremental way to the performed displacement, or absolute, when a well-defined value corresponds to each position of the rotating element.

[0039] The main new aspect of the invention consists in transforming the linear shortening / stretching of the pair of agonist-antagonist muscles into a rotational motion of the pulley, on the crown thereof the agonist-antagonist connection is housed. Such rotational motion can be easily measured through the rotative encoder and used to control the position of the prosthesis, by faithfully reproducing the physiological control in the position of the muscles on the motions of a joint in an healthy subject. The possibility of tracking the motion of the passive rotational markers present on the pulley thanks to an encoder external to the skin solves the needs for having to extract motion signals from the inside of the stump and to bring the power supply to possible active devices, through transcutaneous through-cables, which would constitute an infective risk important for the user.

[0040] With the purpose of obtaining to control the position of the prosthesis and to return one or more degrees of freedom to the same, as anticipated an angular position transducer is used.

[0041] Several strategies and technologies can be adopted to track the motion of the pulley, with the passive traceable element implanted inside the tissues, whereas the active tracking one always remaining externally can be integrated in the socket of the prosthetic device. The mutual positioning of tracked and tracking element has to be kept for a correct operation of the interface, therefore it is preferred to position stably the socket of the prosthesis associated to the interface device. It is important to refer on the skin surface the position of the implanted pulley, which remains unchanged thanks to the fixing on the bone by means of the bracket. The surface reference, for example, can be provided graphically with an indicator tattooed on the subject’s skin, or through Led indicator or acoustic sound which appear when active and passive part result to be aligned.

[0042] The tracking of the pulley is not affected by the presence of material obstacles (that is biological tissues or biocompatible coatings) present between the latter and the tracking sensor. However, it can depend upon the distance between the two, which then becomes a factor to be taken into consideration for the interface design (that is disk positioning, sensor power, and so on).

[0043] In the light of the preceding considerations, preferred variants of the invention provide the use of magnetic rotative encoders which exploit the Hall effect, or optical encoders.

[0044] The magnetic encoders use a system for detecting the signals based on the variation in the magnetic flow generated by a permanent magnet (characterized by one or more polar pairs) placed in rotation in front of a sensor configured to record the corresponding variation in the magnetic field, to sample it and transform it into an electric pulse which defines the magnet position. The Hall effect is a physical phenomenon according thereto in a conductor (Hall element) crossed by electric current in longitudinal direction, in presence of a magnetic field in perpendicular direction, the moving charges result to be subjected to the Lorentz Force by generating a potential difference in the direction transversal to the ends of the Hall element, which is called Hall potential.

[0045] It is possible to use in the proposed device a magnetic encoder which exploits the so-called Hall effect, which comprises a permanent magnet, characterized by the alternation of North and South poles, housed integrally to the rotating element (for example above the pulley or incorporated in the latter). The magnetic field generated thereby is detected by a Hall sensor, which can be housed on its own printed circuit board (Printed Circuit Board, PCB), arranged externally to the patient’s skin and preferably integrated in the prosthetic device, for example in the socket. Also, the maximum distance, in use, between the permanent magnet and the Hall sensor, depends upon the intensity of the magnetic field generated by the magnet.

[0046] According to additional aspects of the invention, the permanent magnet comprises a coating with biocompatible material when not incorporated inside the pulley. The permanent magnet does not require any type of power supply and / or data communication. The magnetic field, differently from the electrical one which is acquired for controlling the myoelectric prostheses, can cross several levels of biological tissue by decreasing intensity, but not being distorted, even in case of very low intensities.

[0047] As far as the type of rotative optical encoder is concerned, instead, the operating principle of the latter is based upon the rotation of a graduated disk with a radial grating, formed by opaque lines alternated with transparent spaces. This is illuminated by an infrared-ray source, arranged perpendicularly with respect to the sensor. The graduated disk thus projects its image on the surface of the receivers passing through a collimator. The receivers detect the light variations occurring while moving the disk, caused by the alternation between opaque lines and transparent spaces, by converting them into corresponding electrical pulses.

[0048] The usable optical scanning technology can be: transmissive, if the receiver is placed diametrally opposite with respect to the infrared-ray source, or reflective, if the light source and the receiver are on the same side of the device.

[0049] Advantageously, the device variants according to the invention which use optical or magnetic encoder according to what illustrated above allow to track the rotational motion of the pulley in a wholly not invasive way, since they do not require a physical connection between rotating portion and recording components, specifically magnetic or optical components. In this way, it is possible to isolate the elements implanted inside the stump and to avoid leaving openings in the tissues.

[0050] An additional important aspect of the invention is the passive operation of the interface device, without the need for power and wiring for transmitting the signal outside the tissues.

[0051] Advantageous aspects of the invention provide the additional possibility of adjusting actively the resistance to rotation of the pulley, like a brake acting on a wheel, and of enriching with load information the proprioceptive feedback deriving from the bionic system which has formed.

[0052] Other advantages, features and the use modes of the present invention will result evident from the following detailed description of some embodiments, shown by way of example and not for limitative purposes. Brief description of figures

[0053] The Figures of the enclosed drawings will be referred to, wherein:

[0054] ■ Figure 1 shows a lateral perspective view of a first preferred embodiment of the device according to the present invention;

[0055] ■ Figure 2 shows a schematic view of several preferred embodiments of an angular transductor according to the present invention;

[0056] ■ Figures 3 and 4 show lateral perspective views of a preferred embodiment of the device according to the present invention comprising a magnetic encoder, in static condition and dynamic condition, respectively;

[0057] ■ Figures 5 and 6 show lateral perspective views of a preferred embodiment of the device according to the present invention comprising an optical encoder, in static condition and dynamic condition, respectively;

[0058] ■ Figures 7 and 8 show lateral perspective views of additional preferred embodiments of the device according to the present invention, respectively comprising two pulleys for controlling two degrees of freedom of the device itself; and

[0059] ■ Figure 9 shows a lateral perspective view of a still additional preferred embodiment of the device according to the present invention, comprising a braking system for returning a load feedback to the user.

[0060] The thicknesses, the proportions and the curvatures represented in the above-mentioned Figures are meant as purely exemplifying, are generally magnified and are not necessarily shown in proportion.

[0061] Detailed description of preferred embodiments

[0062] Various embodiments and variants of the invention will be described hereinafter, and this with reference to the above-mentioned Figures.

[0063] Analogous components are designated in the several Figures with the same numeral reference. The several embodiments and variants described hereinafter are likely to be used in combination, where compatible.

[0064] The present invention provides a new interface device suitable for controlling a prosthesis (more generally, of any electromechanical device provided with mobile elements). A first preferred embodiment of the interface device is shown schematically in Figure 1 , where it is designated with the numeral reference 1.

[0065] The device 1 is configured to transform the motor intention which the user shows by contracting one of the muscles M of a pair of agonist-antagonist muscles, in a control signal for a degree of freedom of a prosthesis P, of which the socket 2 only is shown.

[0066] The device 1 includes a transduction mechanism of the motion of a pair of agonist-antagonist M muscles associated to the missing limb in a motion of one or more mobile components of the prosthesis P (not shown in the enclosed Figures), preferably capable of reproducing functionally a degree of freedom associated with the missing limb. The device 1 is at least partially implantable inside the stump, where under stump the set of all bone tissues and soft tissues remaining proximally after a limb amputation operation is meant.

[0067] The device 1 consists of three main components, thereamong a rotating element or pulley 4, configured to be installed inside the stump, on the external crown of which a connecting member or segment 7 between the pair of agonistantagonist M muscles, is housed like a belt, which can be implemented by muscle fibers (then a biological tissue) or a suture artificial element which can be implemented surgically, and which represents the means for transmitting the motion from the pair of agonist-antagonist M muscles to such pulley 4.

[0068] The device 1 further comprises a frame element 5 configured to be fixed to the bone stump 3, in particular an anchoring structure comprising an angled bracket, which provides the rotation axis of the pulley 4. At last, the device 1 includes a rotative encoder 8, that is an angular position transducer, which can be provided as broken down into a passive component to be implanted inside the tissues, integrated and integral with the rotating element, and an active component intended to remain outside the tissues, in particular integrated in the prosthetic device P associated with the interface device 1.

[0069] By specifically referring to Figure 2, the rotative encoder 8 consists of a passive marker 12, arranged so as to result to be integral to the pulley 4, and a tracking sensor 9 configured to be arranged externally to the skin, for example integrable in the socket 2 of the prosthesis P, programmed to generate the control electrical signal for actuating its mobile components as a function of the detected rotation of the pulley 4.

[0070] With reference to a first encoder variant shown in Figure 2 and in Figures 3 and 4, the angular position transductor is a magnetic encoder 8a, therefore it comprises a permanent magnet 12a integrated in the pulley as passive marker, characterized by the alternation of one or more polar pairs, whereas for the active component it comprises a sensor 9a configured to record the variation in the magnetic field generated by the magnet 12a and caused by the rotation of the pulley.

[0071] With reference to the second variant shown in Figure 2 and in Figures 5 and 6, the angular position transductor is an optical encoder 8b, in particular of reflective type, therefore the pulley comprises a graduated disk 12b as passive marker, characterized by the alternation of opaque and transparent lines, whereas the active component includes a source emitting infrared-ray light, such as a LED, and one or more receiving sensors 9b, wherein the source is preferably arranged perpendicularly with respect to the receiving sensor 9b. When it is illuminated by the lighting source, the graduated disk projects its image on the surface of the receiving sensors, passing through a possible collimator. The receiving sensors detect the light variations occurring due to the disk rotation (due to the alternation between opaque lines and transparent spaces), by converting them into corresponding electrical pulses. Specifically, Figures 3 and 5 relate to a static condition of the device 1 , wherein the contraction state of the two muscles is in equilibrium, in the variants 1a and 1b comprising magnetic encoder 8a and optical encoder 8b, respectively. The pulley results to be still since there is no shortening and respective stretching of the pair of involved muscles, so as to produce a rotation of the passive element. The receiving means, then, do not codify any position variation of the pulley.

[0072] Figures 4 and 6, instead, respectively relate to the same device variants of Figures 3 and 5, but in dynamic condition, wherein one of the two muscles of the pair is contracted and the other one is stretched. The pulley is put in rotation since, considering the pair of muscles put in conjunction through the tendons, while one contracts the other one is stretched, so as to generate a pair of forces which puts in rotation the passive element. According to such configurations, the receiver of the respective encoder then detects the variations in magnetic field or light caused by the rotation of the pulley, by converting them into a corresponding signal useful for controlling the prosthesis.

[0073] It is confirmed that the mechanical activity of the single pair of agonistantagonist muscles which determines the shortening of one of the two muscles along its own axis is then transformed into rotational motion of the single pulley 4 and, additionally, into electrical signal to be used for controlling a degree of freedom of the prosthesis P. Within the present explanation, under number of degrees of freedom the number of independent variables required to determine univocally the position of a material point in space is meant, whereas the number of degrees of freedom of a system is meant to be equal to the number of generalized coordinates required to describe its motion within the space of the configurations.

[0074] In order to produce the connecting segment between the two involved muscles, so as to stretch one of the two when the other one contracts and vice versa, the AMI surgical technique can be advantageously used. The so- implemented connecting segment 7 is then housed on the external surface 6 of the circular crown of the pulley 4 like a rope that engages in a respective pulley, with the purpose of translating the linear motion of the muscles in rotational motion of the pulley 4. It is preferable to avoid that the connecting segment 7 slides with respect to the external surface 6, so as to guarantee that the whole muscle contraction is really translated into rotation.

[0075] To this purpose, the surface 6 in contact with the connecting segment can be implemented suitably and uniformly rough, then with high roughness, so as to maximise the friction force which the force of the linear motion transmits to the pulley 4. The sliding absence, apart from guaranteeing the motion transmission, minimizes the damages to the tissues. Additionally, one or more biocompatible and permanent fixing points S, can be applied to fix the segment (which can be biological) to the artificial surface of the crown 6.

[0076] The sizes of the pulley 4, as those of the bracket fixed element 5, can be determined for each specific application, as a function, for example, of the space available inside the stump, of the sizes and functionalities of the muscle tissue, of the motion resolution which one wants to obtain, and of the technical features of the sensor selected for detecting the rotation of the pulley and for generating the control signal for actuating the mobile components.

[0077] In fact, it is necessary to consider that, the pulse (force over time) generated by each one of the two muscles of the agonist-antagonist pair in conjunction being equal, the rotation frequency of the pulley increases as the radius of the pulley itself decreases. Reduced sizes then involve that with a minimum muscle contraction a small linear displacement is produced, but a rotation in much greater proportion of the pulley. Therefore, even in case of lack of residual muscle tissue or a poor functionality of the same, reduced sizes of the pulley allow to guarantee a sufficient spatial sensitivity for decoding the motor intention and then a substantially complete covering of the motion range of the degree of freedom controlled by the interface device. With still reference to Figure 1 , the first preferred embodiment of an interface device according to the present invention designated as a whole with 1 will be now described more in details, in association with a prosthesis P controlled thereby. The prosthesis P can include a socket element 2 suitably shaped to be worn by the amputated subject.

[0078] As anticipated, the interface device 1 is configured to generate a control signal which can be received by the prosthesis P which can be applied at the residual limb portion in an amputated subject, in particular at the bone stump 3, the presence thereof is required for an optimum fixing of the herein proposed interface device 1.

[0079] The prosthesis P includes one or more mobile components configured to be able to move mutually, according to at least a degree of freedom.

[0080] The device 1 implements a new mechanism for controlling such mobile components of the prosthesis P, configured to convert the movement of a pair of agonist-antagonist M muscles associated to the functionality of the limb or portion of missing limb, in a corresponding motion of the mobile components which aims at reproducing such functionality (for example, opening and closing the mobile components to reproduce the functionality of opening and closing the fingers of a hand with the purpose of grasping an object). In particular, the mechanism uses an angular position transducer (for example absolute or incremental magnetic / optical encoder) capable of translating the rotation of the pulley into an electrical signal for actuating the mobile elements.

[0081] The mechanism for controlling the interface device 1 first of all comprises a pulley 4 revolvingly connected to a bracket 5, configured to be fixed to a portion of bone stump 3. The bracket 5 can include a pin element around which the pulley can rotate, in particular around a rotation axis R which is then fixed with respect to the bone stump 3 once the bracket 5 is fixed.

[0082] The bracket 5 can be fixed to the bone part of the stump 3 by already known orthopaedical surgical techniques, for example those commonly used to repair fractures by using screws and / or plates made of biocompatible metal. Despite each case of amputation is a unique case, in itself, with specific features, problems and requirements, it is possible to indicate some guidelines fundamental for the system.

[0083] The materials used for the system inside the stump, generally defined biomaterials (that is ceramic, polymer, metal and composite materials) have to meet the principles of biocompatibility, non-toxicity, non-immunogenicity and they must be neither biodegradable nor bio-absorbable. Such biomaterials are devised to interface with the biological systems, characterized both by a considerable chemical inertia and by a high range of mechanical stresses. If there is a need for using immunogenic materials, these have to be coated with additional material which increases the biocompatibility thereof.

[0084] The fixing sizes are decided based on the available tissue, both bone tissue for the real anchoring, and soft tissue for housing the whole device. The indication is to guarantee to the rotating part a stable and lasting-over-time support. Moreover, the fixing sizes have to guarantee the correct positioning of the rotating element, whose angular position is transduced near the skin surface, where the prosthesis and the sensors tracking the disk are housed.

[0085] The fixing structure has to respond to very specific structural mechanical properties, thereamong: stability, robustness, resistance to possible external trauma, resistance to friction (which could be detected between the rotating element and the pin belonging to the structure itself), low thermal conductivity.

[0086] The pulley 4 can further be coated with bio-compatible material. The pulley 4 can be a full pulley, or a disk with openings or hollow portions; it is essential that it includes at least a portion of circular crown comprising an external lateral surface 6, preferably continuous and / or parallel to the rotation axis R of the pulley 4, for coupling with the connection means 7. The external lateral surface 6 has to be configured to engage directly or indirectly the connection means 7 configured to be inoculated inside the limb stump to connect mechanically the pair of agonist-antagonist muscles, or to engage the tendons associated with such pair of muscles, if still present.

[0087] The engagement of the connection means 7 (or of the tendons) with the pulley 4 is so that a linear displacement motion of such connection means 7 (or tendons) associated with a contraction-stretching motion of the pair of agonistantagonist muscles causes a corresponding rotation of the pulley 4 with respect to the bracket 5, for example according to a predetermined proportionality law.

[0088] The device 1 further comprises an angular position transducer 8 associated with the pulley 4, configured to generate an electrical control signal of the mobile components of the prosthesis P as a function of the rotation of the pulley 4. More specifically, the angular position transductor 8 comprises a position sensor 12, integral to the pulley 4, and a tracking sensor 9 arranged in a fixed position with respect to the bracket 5, configured to receive or detect from the position sensor 12 data associated with the position of the pulley 4 and to generate the signal for controlling a degree of freedom of the prosthesis P as a function of such data. Preferably, the tracking sensor 9 is fixed in the socket element 2 of the prosthesis P.

[0089] According to already illustrated preferred variants of the invention, the position sensor can be a permanent magnet, and the tracking sensor a Hall sensor which is preferably housed on its own printed circuit. According to such variant, the materials to be used for the components of the device have to avoid altering the magnetic field generated by the permanent magnet, by preferring diamagnetic materials.

[0090] An additional embodiment of the invention provides the use of a system of reflective optical scanning for the detection of the displacement of the pulley and the generation of the corresponding control signal of the mobile elements, according to what already described. According to such solution, the pulley is a graduated disk with a first radial grating, formed by the alternation of opaque and transparent lines. The device further comprises an infrared-ray source configured to illuminate the pulley, and receiving means comprising a second radial grating having the same pitch of the first grating.

[0091] The pulley is interposed between the infrared-ray source and the second radial grating, and the receiving means is configured to generate an electrical control signal of the mobile elements of the prosthesis, in function of the variations in the light projected by the infrared-ray source through the first grating on the second radial grating, caused by the displacement of the pulley. The infrared rays generated by the source hit the pulley and thus project the image of the first grating on the surface of a plurality of receivers, suitably masked by the other grating (or collimator grating). The receivers, which can be integrated in the prosthesis, are configured to detect the light variations which occur while displacing the pulley, by converting them into corresponding variations in one electrical quantity. The light source and / or the receiving means can be integrated in the socket of the prosthesis and are preferably positioned in the same side of the socket to reduce the sizes of the prosthesis.

[0092] Moreover, the device 1 can comprise a unit for regulating the resistance to rotation of the pulley 4 as a function of the external load detected at a joint portion of the prosthesis P. According so such embodiment variant, the device allows to control actively the mechanical resistance to the rotation of the pulley as a function of the external load applied to the robotic joint. For example, in a prosthetic elbow, a load acting in extension of the forearm with respect to the arm is translated into a resistance to the rotation of the pulley of the interface device, induced by the contraction of the biceps. This allows the user to feel the load acting on the robotic elbow of the prosthesis.

[0093] The control of the resistance of the pulley as a function of the load can be implemented through a braking system, for example a braking system 15 by friction of the type shown in Figure 9, wherein an additional preferred embodiment of the interface device designated with 1’ is represented.

[0094] The braking system 15 is operatively connected with the rotating element 4, around which a pair of the tendons 7 are wound. The braking system 15 can comprise at least two pistons configured to abut on opposing portions of the pulley, so that at least a piston is operative at each one of the two external planar surfaces (and circular in case of full pulley) of the same. Alternatively to the pistons, in order to reduce to the minimum the wear and heat produced due to friction electromagnetic brakes can be used, which allow to avoid the contact with the pulley, and to re-use the induced currents. The link between external load and resistance to rotation can be scaled, so as to keep a proportionality ratio, by optimizing the ratio between the informative value of the feedback and the energy consumption, the produced heat and the magnitude of the not wished forces applied to the pulley.

[0095] The braking system 15 can be configured so that the pressure exerted by the pistons against the pulley increases as the load to the joint of the prosthetic device worn by the subject increases, which is controlled by the rotation of the pulley itself. In this way, the braking system 15 fulfils the functionality of translating the load into mechanical resistance to the rotation of the pulley.

[0096] The signal to be used for the active control of the resistance can be acquired by additional sensors integrated onboard the prosthesis, and has to be transferred to the braking system which is implanted inside the stump. Such transmission can preferably take place according to a wireless mode, without through-cables, by exploiting short-distance communication devices, for example Bluetooth devices. According to such variant, it is necessary to implant an additional device for the power supply of the resistance element or, in case, to exploit the induction power supply, as long as the correct operation of the encoder is not compromised.

[0097] Alternatively, a wired transmission mode can be provided to conduct both the control signal and the power supply, exploiting cables passing through the stump. However, the presence of through-cables would involve the disappearance of characteristics such as passivity and complete isolation of the implanted elements, and the need for braking down the tracking system into internal and external components: it would be possible to implant the whole rotative encoder inside the stump and to improve the technical specifications thereof (resolution, sizes, power), by further increasing the possibility of using several pulleys and several encoders in the same space, each one for each degree of freedom to be controlled.

[0098] The control of the resistance of the pulley as a function of the load can be further integrated with an osteointegration system (for example the Bone- integrated Human-Machine Gateway), allowing the physical hooking of the prosthesis to the stump without using socket, by creating the possibility of making the cables to pass from the outside to the inside of the stump through the device itself. Such cables are configured to bring to the implanted pulley the load information and the power supply. The proprioceptive feedback in its totality is then recomposed thanks to the contraction-extension coupling which allows to produce an afferent signal (from the stretched muscle) informing on the positional status of the artificial joint, and thanks to the possibility of regulating the resistance of the pulley additional means is available to return load feedback (in addition to the one already adopted in AMI). The link between external load and resistance to rotation can be scaled, so as to keep the proportionality, by optimizing the ratio between the information value of the feedback and the energy consumption, the produced heat and the magnitude of the not wished forces applied to the pulley.

[0099] With reference to the additional variants of Figures 7 and 8, embodiments of the device of the invention configured for controlling more than a degree of freedom of the prosthesis are illustrated, thanks to the use of a mechanism comprising a corresponding plurality of pulleys. To this purpose, a plurality of pairs of muscles can be preliminarily obtained through the AMI surgical technique, with the purpose of restoring a corresponding plurality of degrees of freedom to be controlled independently from one another.

[0100] According to the variant of interface device 10 of Figure 7, configured to control a prosthesis having two degrees of freedom, the tendons (or the connecting segment) of each one of the two muscle pairs associated to the device 10 are housed around distinct pulleys 40, therefore each one is used for controlling a respective degree of freedom of the prosthesis. Such two pulleys 40 can have different sizes, in particular diametres. The respective active components, which characterize the encoders 80a and 80b associated with each pulley, are preferably arranged on one side and on the other one of the bone stump 3, each one aligned to the respective passive component. The encoders used in this solution can be both optical and magnetic, as represented in Figure 7.

[0101] Moreover, the two pulleys 40 are preferably arranged in diametrally opposite position with respect to the bone stump 3, and still more preferably they have the same rotation axis R, so as to be able to share one single fixed bracket element 50.

[0102] With reference to the embodiment of Figure 8, the pulley is broken down into several sub-units, meant as a plurality of mutually concentric and coaxial pulleys 41 stacked on top of each other, wherein each pulley is connected to a specific agonist-antagonist muscle pair, all involved muscle pairs being arranged at the same side of the bone stump 3. The individual management of the single sub-units or single pulleys 41 and of the respective encoders 81 allows to track the single motions of the muscle pairs independently from one another. It is then possible to check, with one single interface device 11 , several degrees of freedom of one single prosthesis (for example the single fingers of a hand prosthesis can be controlled independently by using several pairs of agonist-antagonist muscles).

[0103] It is possible to combine several pulleys concentrically even in case of reduced space of the available tissues, and then to associate each degree of freedom to the single pulleys. This can be implemented by creating several pairs of agonist-antagonist muscles originally active on the same or on different joints or, alternatively, by dissecting the remaining muscle tissue in separated bundles, specularly between agonist muscle and antagonist muscle, controlled independently through nerve bundles separated too.

[0104] For this specific variant, it is necessary to use methods for tracking disks compatible to each other, for example to guarantee that the magnetic fields of several magnetic encoders do not interfere with each other, or at least that the interaction can be interpreted both at level of the processed signal and then also functional to the control. An alternative is to use pulley or rotating, concentric disks, having different sizes, tracked optically, as for the variant of Figure 8. Also, different combinations of rotative (magnetic and optical) encoders can be implemented to guarantee an optimum control of the degrees of freedom of the prosthesis.

[0105] An additional variant for controlling a plurality of degrees of freedom of the prosthesis provides the use of spring pulleys, therefore instead of constituting with two muscles the agonist-antagonist pair, each one of the two muscles is connected singularly, mechanically, to a respective spring pulley, configured to keep the muscle in stretched condition when it is at rest. In this way, each single muscle associated with the respective spring pulley is used to control independently a degree of freedom of the mobile components by a respective encoder associated with the specific pulley, according to the already described modes.

[0106] The present invention has been sofar described with reference to preferred embodiments. It is to be meant that other embodiments belonging to the same inventive core may exist, as defined by the protective scope of the here below reported claims.

Claims

CLAIMS1. An interface device (1), for controlling a prosthesis (P) comprising one or more mobile components, which device (1) comprises:• a bracket (5) configured to be fixed to a portion of bone stump (3);• a pulley (4) comprising a portion of annular crown, the pulley (4) being rotatably connected to said bracket (5), wherein said portion of circular crown comprises an external lateral surface (6) configured: to engage connection means (7) configured to mechanically connect a pair of agonist-antagonist muscles, or to engage the tendons associated with a pair of agonist-antagonist muscles, the connection being such that a linear displacement motion of such connection means (7) or tendons, associated with a contraction-stretching motion of the pair of agonist-antagonist muscles, causes a corresponding rotation of said pulley (4);• an angular position transducer (8) associated with said pulley (4), configured to generate an electrical control signal capable of controlling the movement of the aforementioned mobile components as a function of the rotation of said pulley (4).

2. The device (1) according to claim 1, wherein said angular position transducer (8) comprises a position sensor (12) integral to said pulley (4) and a tracking sensor (9) arranged in a fixed position with respect to said bracket (5) and configured to receive or detect from said position sensor (12) data associated with the position of said pulley (4) and to generate said electrical control signal based on said data.

3. The device (1) according to any one of the preceding claims, wherein said external lateral surface (6) is parallel to the axis of rotation (R) of said pulley (4).

4. The device (1) according to any one of the preceding claims, wherein said pulley (4) is coated with bio-compatible material.

5. The device (1) according to one of claims 2 to 4, wherein said position sensor (12a) is a magnet, and said tracking sensor (9a) is a Hall sensor.

6. The device (1) according to one of claims 1 to 4, wherein said pulley (4) comprises a graduated disk (12b) which includes a first radial grating, formed by the alternation of opaque and transparent lines, wherein said device (1) further comprises an infrared-ray source configured to illuminate said pulley (4), and receiving means (9b) comprising a second radial grating having the same pitch as said first grating, wherein said pulley (4) is interposed between said infraredray source and said second radial grating, wherein said receiving means (9b) is configured to generate an electrical control signal of the mobile elements in function of the variations in the light projected by said infrared-ray source through said first grating on said second radial grating, caused by the rotation of said pulley (4).

7. The device (1) according to any one of the preceding claims, comprising a unit for regulating the resistance to rotation of said pulley (4) as a function of the load detected at a joint portion of the prosthesis (P), said regulating unit comprising a braking system (15) of said pulley (4).

8. The device (10; 11) according to any one of the preceding claims, comprising a plurality of said pulleys (41), mutually arranged concentrically and coaxially, wherein each pulley (41) is configured: to engage respective connection means (7) configured to mechanically connect a respective different pair of agonist-antagonist muscles, or to engage tendons associated with a respective different pair of agonist-antagonist muscles.

9. The prosthesis (P) comprising a socket element (2) and a device (1; 10; 11) according to any one of the preceding claims, wherein said tracking sensor (9) is fixed to said socket element (2).

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