BIO-mechanical finger prosthesis

Abstract

Bio-mechanical finger prosthesis (10) comprising a proximal portion (11) for coupling to a person's hand (100), and at least both a proximal phalanx (13) which can be associated with a stump (111) of a finger, an intermediate phalanx (14) and a distal phalanx (15) articulated together in succession, and also a transmission unit (25) configured to determine an articulated rotation of said phalanges (13, 14, 15).

Description

[0001] “BIO-MECHANICAL FINGER PROSTHESIS

[0002] FIELD OF THE INVENTION

[0003] The present invention concerns a bio-mechanical prosthesis for a whole finger that can be fitted onto the hand of a person who has suffered the loss of one or more fingers starting from a transphalangeal amputation, that is, at the level of the first phalanx. In particular, the prosthesis of the present invention is applied in cases in which the finger’s metacarpophalangeal joint is still present and functional, or at least still has at least some residual mobility.

[0004] BACKGROUND OF THE INVENTION

[0005] It is known that the loss of a finger or part of it compromises the hand’s performance, preventing a person from carrying out some of daily life’s activities, ranging from gripping an object with force to more precise actions such as gripping thin or small objects, or exerting pressure with a finger or making small movements with precision.

[0006] Not only do fingers allow to perform precise actions, but they also offer greater ability to handle objects. When holding an object in one hand, the weight of the object is distributed across all fingers. By varying the force exerted by each of the hand’s fingers, the hand is able to manipulate the object in a myriad of ways. However, if all or even only a part of one or more fingers are missing, the ability and the number of ways to manipulate an object drastically decrease.

[0007] Currently, partial finger replacement generally involves an aesthetic type of solution, that is, one that can only offer a realistic shape without the possibility of restoring any functionality lost with the physical impairment.

[0008] Electrically powered solutions are also known, offering a certain degree of functionality recovery, but with significant weights and overall dimensions, as well as being fairly difficult to use.

[0009] Other known solutions provide the movement of the prosthetic finger through the movement of the human residue, that is, the finger stump. These solutions offer a decent recovery of dexterity, at the expense of a large exoskeletal structure.

[0010] There is therefore the need to perfect a bio-mechanical finger prosthesis that can overcome at least one of the disadvantages of the state of the art.

[0011] One purpose of the present invention, which corresponds to the technical problem to be resolved, is to hyperextend the distal phalanx of the bio-mechanical prosthesis so as to allow thin objects to be gripped. This action normally reproduces the act of pinching or clamping a tapered object.

[0012] Another purpose of the present invention is to improve the precision and dexterity of a bio-mechanical finger prosthesis when gripping objects.

[0013] Another purpose of the present invention is to provide a bio-mechanical finger prosthesis that has at least one, preferably two, degrees of freedom.

[0014] Another purpose of the present invention is to provide a bio-mechanical finger prosthesis that is particularly compact.

[0015] Another purpose of the present invention is to provide a bio-mechanical finger prosthesis that is easily activated by the human residue of the person using it.

[0016] The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

[0017] SUMMARY OF THE INVENTION

[0018] The present invention is set forth and characterized in the independent claim. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.

[0019] In accordance with the above purposes and to resolve the technical problem described above in a new and original way, also achieving considerable advantages compared to the state of the prior art, a bio-mechanical finger prosthesis according to the present invention comprises a proximal portion for coupling to a person’s hand, and at least:

[0020] - a proximal phalanx which can be associated with a stump of a finger of such hand, an intermediate phalanx and a distal phalanx articulated together in succession,

[0021] - a transmission unit configured to determine an articulated rotation of the phalanges, which is formed by a cable transmission element constrained at ends thereof to the proximal portion and to the distal phalanx, respectively, and by return elements on which the cable transmission element is returned.

[0022] In accordance with one aspect of the present invention, the proximal portion comprises a hooking member provided with elastic retention means which, in response to an extension movement of the distal phalanx, allow an elongation of the cable transmission element so as to allow a hyp erextension of the distal phalanx.

[0023] Doing so achieves at least the advantage of being able to hyperextend the distal phalanx in a particularly simple manner, and therefore allow an excellent grip even of small and tapered objects. This essentially occurs with an interaction between the distal phalanx and the thumb of the hand which, by exerting pressure on the distal phalanx, allows it to hyperextend, allowing the prosthesis to reproduce the act of pinching or clamping a tapered object.

[0024] In accordance with another aspect of the present invention, the elastic retention means are housed in a seating of the hooking member and comprise both a first elastic element and also a first of the ends of the cable transmission element which is conformed to cooperate with the first elastic element, determining a compression thereof in response to the extension movement.

[0025] In accordance with another aspect of the present invention, the proximal portion can comprise a glove having a dorsal surface to which the hooking member is attached.

[0026] In accordance with another aspect of the present invention, the first elastic element can be a first spring capable of working in compression. The cable transmission element passes coaxial through the body of the first spring.

[0027] In accordance with another aspect of the present invention, the intermediate phalanx is rotatably articulated to the proximal phalanx by means of a first hinge and to the distal phalanx by means of a second hinge.

[0028] In accordance with another aspect of the present invention, respective torsion springs can be advantageously keyed to the first hinge and to the second hinge.

[0029] In accordance with another aspect of the present invention, the transmission unit comprises a guide channel made in the proximal phalanx and through which the cable transmission element passes, the guide channel having an entry end and an exit end which are misaligned and develop into a first segment and into a second segment, inclined with respect to the first segment by a certain angle of inclination.

[0030] In accordance with another aspect of the present invention, the certain angle of inclination can be comprised between approximately 115° and approximately 125°, preferably it is of approximately 120°.

[0031] In accordance with another aspect of the present invention, the return elements comprise a first return element stably associated with the proximal phalanx and a second return element associated with the intermediate phalanx. The second return element can be associated elastically with the intermediate phalanx.

[0032] In accordance with another aspect of the present invention, the cable transmission element is advantageously a cable or wire having an inextensible length.

[0033] In accordance with another aspect of the present invention, the prosthesis comprises a socket, optionally annular, associated with the proximal phalanx and conformed so as to contain the stump, during use.

[0034] In accordance with another aspect of the present invention, the prosthesis comprises aesthetic shells coupled to the intermediate and distal phalanx, respectively, by means of suitable attachment members, the aesthetic shells defining, on a palmar side of the intermediate and distal phalanx, a hollow space in which the cable transmission element is positioned.

[0035] In accordance with another aspect of the present invention, the first and second return elements are located on a palmar side of the proximal and intermediate phalanx.

[0036] DESCRIPTION OF THE DRAWINGS

[0037] These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of an embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

[0038] - fig. 1 is a three-dimensional view of a bio-mechanical finger prosthesis according to the present invention;

[0039] - fig. 2 is a view of the prosthesis of fig. 1 with separated components;

[0040] - fig. 3 is a longitudinal section view of the prosthesis of fig. 1 in which the phalanges of the prosthesis are shown in the extended position;

[0041] - fig. 4 is a longitudinal section view of the prosthesis of fig. 1 in which the distal phalanx of the prosthesis is shown in the hyperextended position.

[0042] We must clarify that the phraseology and terminology used in the present description, as well as the figures in the attached drawings also in relation as to how described, have the sole function of better illustrating and explaining the present invention, their purpose being to provide a non-limiting example of the invention itself, since the scope of protection is defined by the claims. To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can be conveniently combined or incorporated into other embodiments without further clarifications.

[0043] DESCRIPTION OF AN EMBODIMENT OF THE PRESENT INVENTION

[0044] With reference to fig. 1, a bio-mechanical finger prosthesis 10 according to the present invention can be suitable to replace any finger of the hand, even more than one, in cases where the natural finger’s metacarpophalangeal joint is still present and functioning, or at least it still has even residual mobility.

[0045] The prosthesis 10 shown in figs. 1-4 is, by way of example, a replacement for the index finger.

[0046] The prosthesis 10 comprises a proximal portion 11 for coupling to a hand 100 of a person, and a distal portion 12 essentially reproducing the anatomical structure of the natural finger.

[0047] The distal portion 12 comprises a proximal lever or phalanx 13 able to be associated with a person’s finger stump 111, an intermediate lever or phalanx 14 and a distal lever or phalanx 15 which are articulated together in succession so as to rotate on a common plane of rotation R.

[0048] In figs. 3 and 4 the plane of rotation R is identified, by way of example, as the x-z plane of a Cartesian reference system (x, y, z) in which the x-axis is aligned in the direction of the length of the finger. In anatomical terms, placing the hand in an open position, that is, in complete supination, the frontal plane is defined as the plane passing through the axis of the middle finger and parallel to the open palm, and the sagittal plane, which corresponds to the plane of rotation R, is defined as the plane passing through the axis of the middle finger and orthogonal to the frontal plane.

[0049] The proximal phalanx 13 is rotatably articulated to the intermediate phalanx 14 by means of a first hinge 16 around a first axis of rotation Y1 (fig. 1). The first hinge 16 is able to recreate the proximal interphalangeal joint (PIP).

[0050] In fig. 2, the first hinge 16 comprises a first pin 16a, possibly formed by two halves, which can be associated with the facing ends of the proximal 13 and intermediate 14 phalanx, which are conformed as a fork.

[0051] The intermediate phalanx 14 is in turn rotatably articulated to the distal phalanx 15 by means of a second hinge 18 around a second axis of rotation Y2 (fig. 1). The second hinge 18 is able to recreate the distal interphalangeal joint (DIP).

[0052] In fig. 2, the second hinge 18 comprises a second pin 18a, possibly formed by two halves, which can be associated with the facing ends of the intermediate 14 and distal 15 phalanx, which are conformed as a fork.

[0053] The first axis of rotation Yl is parallel to the second axis of rotation Y2 of the second hinge 18. The axes of rotation Yl, Y2 are orthogonal to the plane of rotation R. In fig. 1, the axes of rotation Yl, Y2 are parallel to the y-axis of the Cartesian reference system (x, y, z).

[0054] The first hinge 16 and the second hinge 18 are at opposing ends of the intermediate phalanx 14.

[0055] The bio-mechanical finger prosthesis 10 of the present invention therefore has two degrees of freedom of rotation. The two degrees of freedom - PIP and DIP - are activated by acting on a single degree of freedom that corresponds to the rotation of the metacarpophalangeal joint, referred to in the sector by the acronym MCP.

[0056] The first and second hinges 16, 18 can comprise friction reduction elements such as bearings 19 and washers 20, visible in the exploded view of fig. 2.

[0057] Respective torsion springs 21, 22 are keyed to the first hinge 16 and the second hinge 18.

[0058] The torsion springs 21, 22 are able to accumulate rotational energy when the distal 15 and intermediate 14 phalanx are flexed, and produce a corresponding rotational torque when gripping needs to cease and the distal 15 and intermediate 14 phalanx return to their extended position.

[0059] The prosthesis 10 also comprises a socket 23 associated with the proximal phalanx 13 and conformed to contain the stump 111, during use. The socket 23 can, for example, be a ring 24 (figs. 1-4) or a component capable of also wrapping around the tip of the stump 111, as a kind of cup.

[0060] The prosthesis 10 comprises a transmission unit 25 configured to determine the articulated rotation of the phalanges 13, 14, 15, figs. 3 and 4.

[0061] The transmission unit 25 is formed by a cable transmission element 26 constrained, respectively, to the proximal portion 11 with a first end 26a and to the distal phalanx 15 with a second end 26b, and by return elements 27, 28 on which the cable transmission element 26 can insist.

[0062] The distal phalanx 15 is provided with a recess 46 (figs. 3-4) in which the second end 26b of the cable transmission element 26 is stably attached, by means of an attachment dowel 47 (fig. 2).

[0063] The cable transmission element 26 is a cable or wire with a substantially inextensible length.

[0064] The articulated rotation of the phalanges 13, 14, 15 occurs on the plane of rotation R following an activation rotation, that is, a flexion or an extension, transmitted by the stump 111 contained in the socket 23.

[0065] The return elements 27, 28 comprise a first return element 27 stably associated with the proximal phalanx 13 and a second return element 28 elastically associated with the intermediate phalanx 14, the cable transmission element 26 being able to insist on the return elements 27, 28, figs. 3 and 4.

[0066] The first return element 27 can be a cylindrical peg 27a attached to the proximal phalanx 13 near the first hinge 16 and parallel to the first axis of rotation Y1 thereof. The cable transmission element 26 is partly returned around the peg 27a.

[0067] With reference to figs. 3 and 4, the transmission unit 25 also comprises a guide channel 30 defining a constrained path for the cable transmission element 26 within the proximal phalanx 13.

[0068] The guide channel 30 develops longitudinally through the proximal phalanx 13 between an entry end 31 , facing toward the proximal portion 11 , and an exit end 32, facing toward the intermediate phalanx 14, which are misaligned.

[0069] The guide channel 30 develops into a first segment 30a and into a second segment 30b, wherein the second segment 30b is inclined with respect to the first segment 30a by a certain angle of inclination a. The angle of inclination a can be comprised between approximately 115° and approximately 125°. In the example of figs. 3-4, the angle of inclination a is approximately 122°.

[0070] The guide channel 30 causes the cable transmission element 26 to be directed from a dorsal side of the proximal portion 11 toward a palmar side of the proximal phalanx 13, in the direction of the first return element 27.

[0071] The first return element 27 is positioned facing the exit end 32 of the guide channel 30 and the cable transmission element 26 is partly wrapped around it, directed toward the second return element 28. According to the present invention, figs. 3 and 4, the proximal portion 11 comprises a hooking member 33 provided with elastic retention means 34 which in response to an extension movement of the distal phalanx 15 allow an elongation, or rather a sliding, of the cable transmission element 26, so as to allow a hyperextension of the distal phalanx 15.

[0072] An extension movement is defined as the opening movement of the finger on the sagittal plane, that is, on the plane of rotation R.

[0073] The hooking member 33 is provided with a seating 35 in which the elastic retention means 34 are inserted, which comprise both a first elastic element 36 and also the first end 26a of the cable transmission element 26 which is conformed to cooperate with the first elastic element 36, determining a compression thereof in response to the extension movement.

[0074] The first elastic element 36 can be a first spring 36a, through the body of which the cable transmission element 26 passes coaxial, the first spring 36a being capable of working in compression.

[0075] The proximal portion 11 comprises a glove 37 conformed to be fitted on the hand 100 and having a dorsal surface 37a to which the hooking member 33 is attached.

[0076] The hooking member 33 can be suitably glued to the dorsal surface 37a in a position substantially aligned with the stump 111.

[0077] Operationally, the first end 26a of the cable transmission element 26, when the latter is stressed by a corresponding movement of the stump 111 to hyperextend the distal phalanx 15, slides in the seating 35 compressing the first elastic element 36. The first elastic element 36, in turn, being compressed allows a recall movement of the cable transmission element 26 when the stress exerted by the stump 111 ceases. In other words, by exerting an extension torque on the distal phalanx 15, a negative rotation (arrow F in fig. 4) is achieved on the plane of rotation R. The negative rotation is made possible by the elongation of the cable transmission element 26 thanks to the compression of the first elastic element 36.

[0078] According to some embodiments, the second return element 28 is associated with the intermediate phalanx 14 and is provided with elastic positioning means 38 which, in response to a flexion movement of the distal phalanx 15 and of the intermediate phalanx 14, determine a position of the cable transmission element 26 such as to increase a tightening torque as the flexion movement increases.

[0079] A flexion movement is defined as the closing movement of the finger on the sagittal plane, that is, on the plane of rotation R.

[0080] In particular, the elastic positioning means 38 allow the cable transmission element 26 to move away from the first and second hinge 16, 18.

[0081] The elastic positioning means 38 comprise a sliding pin 39 and a second elastic element 40, which are inserted in a seating 41 made through in the intermediate phalanx 14, and a guide element 42 attached to the sliding pin 39 and through which the cable transmission element 26 passes.

[0082] The second elastic element 40 can be a spring 40a coaxial to the sliding pin 39 and capable of working in compression.

[0083] The seating 41 is made in a central zone of the intermediate phalanx 14.

[0084] The sliding pin 39 is conformed to be inserted in the seating 41 and has a first end to which the guide element 42 is attached, and an opposing second end conformed to cooperate with the second elastic element 40, compressing it inside the seating 41 as the flexion movement increases.

[0085] The guide element 42 can be a plate provided with a hole or a slot for the passage of the cable transmission element 18.

[0086] Operationally, the flexion of the stump 111, suitably constrained in the socket 23, leads to the traction of the cable transmission element 26 with the flexion of the distal phalanx 15 and subsequently to the flexion of the intermediate phalanx 14.

[0087] The suitable assembly of the cable transmission element 26 during the flexion of the distal phalanx 15 entails the movement of the cable transmission element 26 away from the second hinge 18, with a first increase in the tightening torque.

[0088] The subsequent flexing phase of the intermediate phalanx 14 is characterized by the away movement of the guide element 42 as a direct consequence of the traction of the cable transmission element 26 with the sliding of the sliding pin 39 in the seating 41.

[0089] This entails a second movement of the cable transmission element 26 away from the second hinge 18, with a subsequent increase in the tightening torque.

[0090] With reference to figs. 1-4, the prosthesis 10 can also comprise aesthetic shells 43, 44 able to be coupled by means of suitable attachment members 45 to the corresponding intermediate 14 and distal 15 phalanges. The aesthetic shells 43, 44 can each be made into two half-shells to facilitate their application.

[0091] It is clear that modifications and / or additions of parts may be made to the biomechanical finger prosthesis 10 as described heretofore, without thereby departing from the field and scope of the present invention, as defined by the claims.

[0092] It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art will be able to achieve other equivalent forms of bio-mechanical finger prosthesis, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

[0093] In the following claims, the sole purpose of the references in brackets is to facilitate their reading and they must not be considered as restrictive factors with regard to the field of protection defined by the claims.

Claims

CLAIMS1. Bio-mechanical finger prosthesis (10) comprising a proximal portion (11) for coupling to a hand (100) and at least:- a proximal phalanx (13), an intermediate phalanx (14) and a distal phalanx (15) articulated together in succession,- a transmission unit (25) configured to determine an articulated rotation of said phalanges (13, 14, 15), which is formed by a cable transmission element (26) constrained with ends (26a, 26b) thereof to said proximal portion (11) and to said distal phalanx (15), respectively, and by return elements (27, 28) on which said cable transmission element (26) is returned, characterized in that said proximal portion (11) comprises a hooking member(33) provided with elastic retention means (34) which, in response to an extension movement of said distal phalanx (15), allow an elongation of said cable transmission element (26) to allow a hyperextension of said distal phalanx (15).

2. Prosthesis (10) as in claim 1, characterized in that said elastic retention means(34) are housed in a seating (35) of said hooking member (33) and comprise both a first elastic element (36) and also a first of said ends (26a) of said cable transmission element (26) which is conformed to cooperate with said first elastic element (36), determining a compression thereof in response to said extension movement.

3. Prosthesis (10) as in claim 1 or 2, characterized in that said proximal portion (11) comprises a glove (37) having a dorsal surface (37a) to which said hooking member (33) is attached.

4. Prosthesis (10) as in any claim hereinbefore, characterized in that said first elastic element (36) is a first spring (36a) through the body of which said cable transmission element (26) passes coaxial, the first spring (36a) being capable of working in compression.

5. Prosthesis (10) as in any claim hereinbefore, characterized in that said intermediate phalanx (14) is rotatably articulated to said proximal phalanx (13) by means of a first hinge (16) and to said distal phalanx (15) by means of a second hinge (18).

6. Prosthesis (10) as in claim 5, characterized in that respective torsion springs (21, 22) are keyed to said first hinge (16) and to said second hinge (18).

7. Prosthesis (10) as in any claim hereinbefore, characterized in that said transmission unit (25) comprises a guide channel (30) made in said proximal phalanx (13) and through which said cable transmission element (26) passes, said guide channel (30) having an entry end (31) and an exit end (32) which are misaligned and develop into a first segment (30a) and into a second segment (30b), inclined with respect to said first segment (30a) by a certain angle of inclination (a).

8. Prosthesis (10) as in claim 7, characterized in that said certain angle of inclination (a) is comprised between 115° and 125°, preferably it is of 120°.

9. Prosthesis (10) as in claim 1, characterized in that said return elements (27,28) comprise a first return element (27) stably associated with said proximal phalanx (13) and a second return element (28) elastically associated with said intermediate phalanx (14).

10. Prosthesis (10) as in any claim hereinbefore, characterized in that said cable transmission element (26) is a cable or wire having an inextensible length.

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