Minimally invasive endoprosthetic device

Abstract

Minimally invasive endoprosthetic device (10) usable to cover an exposed end (110) of a partly amputated bone (100; 200), comprising an anchoring portion (11) having at least one intramedullary stem (12) configured to be inserted inside the medullary canal (111) of said partly amputated bone, and a load distribution portion (13) comprising a covering head (15) defining a subcutaneous load surface (16) for said exposed end (110).

Description

[0001] “MINIMALLY INVASIVE ENDOPROSTHETIC DEVICE”

[0002] FIELD OF THE INVENTION

[0003] The present invention concerns a minimally invasive endoprosthetic device usable to cover an exposed end of a partly amputated bone in order to improve the distribution of the interface load with a corresponding artificial limb that reproduces the functionality of the natural one no longer present, or part of it.

[0004] Such minimally invasive endoprosthetic device finds application both in the case of amputation of a lower limb, and also of an upper limb. BACKGROUND OF THE INVENTION

[0005] When amputating an upper or lower limb, it is known to use prosthetic devices, or artificial limbs, which replace the amputated one to return the individual to a quality of life that is as normal as possible.

[0006] Such prosthetic devices essentially comprise a rigid interface, or socket, that fits over the terminal part of the amputated limb, traditionally called a stump, a terminal component which can be an artificial hand or foot, and a component for the connection between the socket and the terminal component, which can possibly reproduce the missing joints.

[0007] A determining element in the feeling of comfort and in the consequent functionality of the artificial limb is connected to the distribution of the interface load between the stump and the socket, which depends both on the type of socket and how it is made, as well as on the anatomy of the stump, which can be suitably finalized through surgery with osteomyoplastic techniques or by implanting an exoprosthetic, or transcutaneous, or endoprosthetic device, which allow to optimize the distal area of the stump on which the load is applied.

[0008] Traditional endoprosthetic devices comprise a stem able to be inserted into the intramedullary canal of the terminal part of the stump’s bone, and a plate, external to the bone but still subcutaneous, which gives an expanded distal area for sustaining the weight of the stump’s soft tissues and for improving the distribution of the stump interface load.

[0009] Traditional endoprosthetic devices suffer from a number of disadvantages, essentially related to the excessive invasiveness caused by the sizes of the stem and the thickness and shape of the plate, and therefore of the rest surface. These sizes are directly correlated to the stability of the device, which is necessary to prevent failing in the objective of rehabilitating the individual and aiding their recovery.

[0010] There is therefore the need to perfect such a minimally invasive endoprosthetic device 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 that the Applicant intends to solve, is to optimize the sizes that characterize the components of the endoprosthetic device in order to make it minimally invasive, without compromising the stability of the connection with the bone to which it is applied, while reducing risks of infection and revision.

[0012] In particular, one purpose of the present invention is to provide a minimally invasive endoprosthetic device having characteristics that make it suitable to be used for both lower limb as well as upper limb amputations.

[0013] Another purpose of the present invention is to provide a minimally invasive endoprosthetic device, easily customizable during manufacturing or suitable for mass production, to be implanted at different amputation heights and with different geometries of the resection plane.

[0014] Another purpose of the present invention is to provide a minimally invasive endoprosthetic device capable of reducing post-operative complexities, such as infections for example.

[0015] 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.

[0016] SUMMARY OF THE INVENTION 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.

[0017] In accordance with the above purposes and to resolve the technical problem disclosed above in a new and original way, also achieving considerable advantages compared to the state of the prior art, a minimally invasive endoprosthetic device according to the present invention for covering an exposed end of a partly amputated bone comprises: an anchoring portion having at least one intramedullary stem configured to be inserted inside the medullary canal of the partly amputated bone, wherein the stem has a length and a transverse size, and a load distribution portion formed at a distal end of the stem and comprising a covering head defining a subcutaneous load surface for the exposed end, wherein the covering head has a thickness and a maximum width. The device has a first ratio between the length and the transverse size of the stem comprised between about 1 and about 6, and a second ratio between the maximum width and the thickness of the covering head comprised between about 1 and about 40.

[0018] The device also has a third ratio between the length and the thickness of the stem comprised between 3 and 60.

[0019] The Applicant has found that these ratios between the measurements of the device are particularly advantageous because they offer a high degree of reliability, understood as the ability of the device to remain in position with respect to the bone once installed, and at the same time result in a particularly small overall dimension which increases the feeling of comfort for the user, guaranteeing an interface for the artificial limb.

[0020] The proportions disclosed above proved to be functional for both lower limb (femur, radio-ulna) and also upper limb (humerus, radio-ulna) amputations.

[0021] In accordance with another aspect of the present invention, the anchoring portion and the load distribution portion form a single, continuous-material component, which comprises a support body and an interface layer which develops along a perimeter strip which contains both an external surface of the stem and also a contact surface of the covering head opposing the load surface.

[0022] In accordance with another aspect of the present invention, the support body and the interface layer are made in one piece, using additive printing technologies.

[0023] According to a variant, only the interface layer is made using additive printing technology.

[0024] In accordance with a variant of the present invention, the support body and the interface layer can be made individually and joined by gluing, snap-in assembly, extrusion or incorporation.

[0025] In accordance with another aspect of the present invention, the support body is made of compact material, with no porous structure, and the interface layer is advantageously made with a material with a reticular or porous structure, with porosity in the order of 50-2000pm and thickness comprised between 0.10 mm and 25 mm.

[0026] In accordance with another aspect of the present invention, the stem can be completely lined, that is, surrounded externally, by the interface layer, while internally it is defined by the support body without a break in continuity. According to a variant, the stem can be only partly covered by the interface layer. In this case, the external surface of the stem can, in some zones, be defined by the support body itself.

[0027] In accordance with an embodiment of the present invention, the covering head comprises an annular containing collar which develops peripherally around the stem, defining therewith a circumferential aperture for the exposed end.

[0028] In accordance with an embodiment of the present invention, a peripheral zone of the covering head can be provided with a shoulder against which an external membrane of the bone can abut. Favorably, the shoulder is made by creating a discontinuity between the interface layer and the support body.

[0029] In accordance with an embodiment of the present invention, the covering head can have an eccentric part with respect to the stem. In some embodiments, the eccentric part can be configured to cover an exposed end of a second bone, anatomically adjacent to a first bone into which the stem is able to be inserted. However, the eccentric part can also be present when the device is applied to a single bone and when the device has a single stem.

[0030] In accordance with an embodiment of the present invention, the anchoring portion can comprise a first stem able to be inserted into a first bone and a second stem able to be inserted into a second bone, anatomically adjacent to the first bone. The second stem preferably develops in correspondence with the eccentric portion.

[0031] According to a variant, the second stem can consist of a screw or other similar or comparable element.

[0032] DESCRIPTION OF THE DRAWINGS

[0033] These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein:

[0034] - fig. 1 is a section view of a minimally invasive endoprosthetic device applied to the exposed end of a bone; - figs. 2-3 are a lateral view (fig. 2) and a section view (fig. 3), respectively, of a possible embodiment of the minimally invasive endoprosthetic device;

[0035] - figs. 4-5 show possible variants of the device of fig. 1;

[0036] - fig. 6 is a section view of the device variant of fig. 5; - fig. 7 is a lateral view of another variant of the device of fig. 1 ;

[0037] - fig. 8 is a section view along the line VIII- VIII of fig. 7;

[0038] - fig. 9 is a partial section view of an embodiment of the present device;

[0039] - figs. 10-12 schematically show possible applications of the device to amputations provided on a lower limb (figs. 10-11) and on an upper limb (fig. 12), respectively. 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.

[0040] DESCRIPTION OF SOME EMBODIMENTS OF THE PRESENT INVENTION With reference to fig. 1, a minimally invasive endoprosthetic device 10 according to the present invention is usable to cover an exposed end, or bone stump, 110 of a partly amputated bone 100, so as to increase the subcutaneous load surface and improve the distribution of stresses between the stump and the artificial limb. The device 10 of the present invention can be applied both to the amputation of a lower limb (femur, tibia-fibula), and also of an upper limb (humerus, radiusulna), as schematically shown in figs. 10-12.

[0041] With reference to figs. 2 and 3, the device 10 comprises an anchoring portion 11 having at least one stem 12 configured to be inserted inside the medullary canal 111 (fig. 1) of a partly amputated bone 100.

[0042] Typically, the bone 100 may be the femur, tibia, humerus, radius or ulna.

[0043] The stem 12 has a length L and transverse size D which are variable, as described below, based on the patient’s anatomy and type of amputation (specific bone, height and resection plane).

[0044] The device 10 comprises a load distribution portion 13 formed at a distal end 12a of the stem 12 and comprising a convex covering head 15 that defines a subcutaneous load surface 16 of the bone stump 110. The load surface 16 is an advantageously convex surface.

[0045] The load surface 16 can have a central flat zone 16a and a rounded perimeter edge 16b in continuity with the flat zone 16a (figs. 2-3), or it can be an overall curved surface (figs. 4-7), this in order to prevent the presence of sharp edges in the direction of the load that could damage the user’s soft tissues. The load surface 16 is opposing a contact surface 17 of the covering head 15 which is able to go into contact with the bone stump 110 (fig. 1).

[0046] The contact surface 17 can have a smaller or larger width than the segment of bone stump 110 with which it goes into contact.

[0047] The contact surface 17, from which the stem 12 projects, essentially acts as an abutment for the bone stump 110 (fig. 1).

[0048] The contact surface 17 can be an essentially flat single surface (fig. 3).

[0049] In some embodiments, the contact surface 17 can be conformed according to the resection plane of the amputated bone 100, and therefore comprise several surface zones, for example two misaligned surface zones 17a, 17b, which can form a step between them, see for example figs. 4-6.

[0050] Similarly to the stem 12, the covering head 15 also has an axial thickness S and a maximum width W (fig.3), both variable, as described below, based on the patient’s anatomy and the type of amputation (specific bone, height and resection plane). The axial thickness S is defined by the distance between the load surface 16 and the contact surface 17.

[0051] The device 10 has a first ratio R1 between the length L and the transverse size D of the stem 12 comprised between about 1 and about 6, and a second ratio R2 between the maximum width W and the thickness S of the covering head 15 comprised between about 1 and about 40.

[0052] A third ratio R3 between the length L of the stem 12 and the axial thickness S can be comprised between about 3 and about 60.

[0053] In absolute terms, the stem 12 can preferably have a length L comprised between about 15 mm and about 120 mm, and a transverse size D comprised between about 4 mm and about 30 mm. The covering head 15 can preferably have an axial thickness S comprised between about 1 mm and about 40 mm, and a maximum width W comprised between about 10 mm and about 100 mm. According to some embodiments, the anchoring portion 11 and the load distribution portion 13 form a single, continuous-material component, which comprises a support body, or core, or nucleus C, and an interface layer A that develops along a perimeter strip which contains both the external surface of the stem 12 and also the contact surface 17 (figs. 3 and 6). The stem 12 is completely lined, or externally surrounded, by the interface layer A, while internally it is defined by the support body C.

[0054] According to other solutions, the stem 12 may only be partly covered by the interface layer A. In this case, the external surface of the stem 12 may, in some zones, be defined by the support body C. The support body C is made of compact material, with no porous structure. By compact material we mean a structure characterized by the absence of an alternation, whether regular or irregular, of solids and voids, as instead occurs in a reticular or porous structure.

[0055] The support body C defines, in direct continuity, the internal part of the stem 12 and the almost totality of the covering head 15. For example, the internal part of the stem 12 can be defined by the support body C for a portion comprised between about 15% and about 100% with respect to the length L of the stem 12.

[0056] The interface layer A is advantageously made of a material having technological and mechanical characteristics suitable for osseointegration. The interface layer A is advantageously made of a material with a reticular or porous structure.

[0057] The interface layer A can have a macro-porous three-dimensional structure with porosity in the order of 50-2000pm. The morphology of the interface layer A allows to increase the primary and secondary stability of the device 10, improve bone integration, define an elastic modulus similar to that of the bone 100 preventing fragile interfaces, and act as a “scaffold” to load soluble or non-soluble molecules, for example powders, such as antibiotics, growth factors, stimulating agents, control systems and more. The interface layer A can have a thickness comprised between about 0.10 mm and about 25 mm.

[0058] The interface layer A can have a constant thickness throughout its development or a variable thickness, depending on the zone that can be the contact surface 17 and the external surface of the stem 12.

[0059] Even the interface layer A on the external surface of the stem 12 can have a variability in thickness.

[0060] The interface layer A can be a coating deposited on the support body C using alternative or combinable technologies known by the English terms of “porous coating” and “plasma spray”. Other usable technologies can comprise electrodeposition, sol-gel, dip coating.

[0061] According to some embodiments, the support body C and the interface layer A are made in one piece, that is, integrally and without a break in continuity, using additive printing technologies. According to a variant, the support body C and the interface layer A are made individually, that is, separately, and joined in an irremovable manner by gluing, snap-in assembly, extrusion or incorporation.

[0062] In possible solutions, not shown, the stem 12 could have a completely porous structure. The density of the porous structure may be homogeneous or increasing toward the axis of the stem 12, to confer greater stiffness.

[0063] According to the present invention, the support body C and the interface layer are made of metallic, polymeric or ceramic material, or with a combination of such materials, as described below.

[0064] The chosen metallic material can be comprised in a group consisting of titanium, cobalt-chromium alloy, steel alloys, Tantalum.

[0065] The chosen polymeric material can be comprised in a group consisting of, but not limited to, PE in different molecular weight gradations (for example PE, UHMWPE), PMMA, generally materials with elastic modulus comprised between 200 and 6000 Mpa. The chosen ceramic material can be comprised in a group consisting of, but not limited to, ceramic oxides, purely based on Alumina, Zirconia, Zirconium, possibly reinforced.

[0066] According to possible embodiments, the support body C and the interface layer A can be made of a single metallic material or more than one metallic material, the latter possibly being the same for both, or of different types.

[0067] According to a variant, the support body C and the interface layer A can both consist of a polymeric material with no porous structure. According to other variants, the support body C can consist of a polymeric material while the interface layer A can be made of a metallic material with a porous structure.

[0068] According to another variant, the support body C and the interface layer A are both made of a ceramic material. According to other variants, the support body C can be made of a ceramic material while the interface layer A is made of a metallic material with a porous structure.

[0069] According to another variant, the support body C can be made of a ceramic material while the interface layer A can be made of a polymeric material. The stem 12 has a substantially cylindrical shape (figs. 2-3) whereby the transverse size D is a diameter. In this case, the diameter D is essentially constant from the distal end 12a to an opposing proximal end 12b, the latter being that of insertion into the medullary canal 111. We must clarify that the stem 12 can also have sections that are not circular, for example elliptical, finned or others. In any case, the shape of the stem 12 is a substantially anatomical one, in the sense that it can be correlated to the shape of the bone to which it is applied.

[0070] In some embodiments, the stem 12 can have a conical (figs. 4-7) or cylindrical- conical shape. The cylindrical-conical shape provides a first segment of stem 12 with a cylindrical shape and a second segment, closer to the proximal end 12b, with a conical shape.

[0071] In any case, the proximal end 12b can advantageously have a slightly smaller transverse size than that of the distal end 12a and be rounded to facilitate insertion and prevent tip load traumas.

[0072] According to other embodiments, the stem 12 can have a shape defined by more than one taper.

[0073] The proximal end 12b can have a smooth surface finish, again in order to facilitate the insertion of the stem 12 into the medullary canal 111. The stem 12 can have a completely smooth external surface, or be provided with anchoring elements such as fins, projections, ribs, hollows, recesses, to promote the attachment and increase the stability with the bone 100. The smooth surface does not exclude a porous or reticular surface finish.

[0074] In some embodiments, the covering head 15 can comprise an annular containing collar 19 (figs. 3, 5-6) which develops peripherally around the stem 12 and protrudes axially from the side of the contact surface 17 defining, together with the stem 12, a circumferential aperture 20 (figs. 3 and 6) able to accommodate a terminal part of the bone 100. The annular containing collar 19 comprises, on the side facing the stem, the contact surface 17. The axial thickness SI of the annular containing collar 19, measured with respect to the contact surface 17 (fig. 3), can be comprised between about 0 mm, which corresponds to the case in which the containing collar 19 is absent, and about 20 mm. This axial thickness S 1 is favorably a function of the other sizes of the device 10. The circumferential aperture 20 can have a cylindrical (fig. 3) or slightly conical

[0075] (fig. 6) shape so as to define a condition of self-clamping with the bone 100.

[0076] The annular containing collar 19 can have a complete circumferential extension, that is, of an angle equal to 360°, or a partial circumferential extension, that is, of an angle smaller than 360°. The annular containing collar 19 can be defined circumferentially in segments.

[0077] According to some embodiments, a peripheral zone of the covering head 15 can be provided with a shoulder, or relief, 21 against which the membrane 112, called periosteum, which externally covers the bone 100, can abut. In this case, the shoulder 21 can be obtained by creating a discontinuity between the interface layer A and the support body C (fig. 9).

[0078] As shown in figs. 4-6, the covering head 15 can be provided with holes 24, 25, seatings, or hollows for the application of clamping elements such as screws 26, wires, clips, to increase the primary and secondary stability of the device 10, but also to suture soft tissues and anchor them to the device 10 and / or to the underlying bone.

[0079] In accordance with a first embodiment, which can be combined with all the previously described embodiments and variants, there is a single stem 12 and it is essentially centered with respect to the covering head 15, as shown in figs. 2-3. According to another embodiment, which can be combined with all the previously described embodiments and variants, the covering head 15 can have an eccentric part 23 with respect to the stem 12 configured to cover an exposed end, or bone stump, of a second partly amputated bone 200, anatomically adjacent to the bone 100, fig. 4. The second bone 200 can be the fibula or the ulna.

[0080] According to another embodiment, which can be combined with all the previously described embodiments and variants, in addition to the first stem 12, the anchoring portion 11 can optionally comprise a second stem 22 able to be inserted into the medullary canal of the second bone 200, figs. 5-8. The presence of the second stem 22 essentially depends on the position / height of the amputation’s resection.

[0081] In the example of figs. 7-8, only the second stem 22 can be provided with the containing collar 19. According to a variant, both stems 12, 22 are provided with their own containing collar 19. The second stem 22 can have a conformation similar to what described above for the stem 12, but with smaller sizes. It can also be made, internally, of compact material and have, externally, the interface layer A, and in general all the embodiments and variants described above with reference to the stem 12 are valid.

[0082] The second stem 22 can develop in correspondence with the eccentric portion 23.

[0083] According to possible variants, the second stem 22 can consist of a screw or other similar or comparable element.

[0084] It is clear that modifications and / or additions of parts may be made to the device 10 as described heretofore, without departing from the field and scope of the present invention, as defined by the claims.

[0085] 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 minimally invasive endoprosthetic device, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

[0086] 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. Minimally invasive endoprosthetic device (10) usable to cover an exposed end (110) of a partly amputated bone (100; 200), comprising:- an anchoring portion (11) having at least one intramedullary stem (12), with a length (L) and a transverse size (D), configured to be inserted inside the medullary canal (111) of said bone (100, 200),- a load distribution portion (13) formed at a distal end (12a) of said stem (12) and comprising a covering head (15), with a thickness (S) and a maximum width (W), defining a subcutaneous load surface (16) for said exposed end (110), characterized in that a first ratio (Rl) between said length (L) and said transverse size (D) is comprised between 1 and 6, and in that a second ratio (R2) between said maximum width (W) and said thickness (S) is comprised between 1 and 40.

2. Endoprosthetic device (10) as in claim 1, characterized in that said anchoring portion (11) and said load distribution portion (13) form a single, continuous- material component, which comprises a support body (C) and an interface layer (A) which develops along a perimeter strip which contains both an external surface of said stem (12) and also a contact surface (17) of said covering head (15) opposing said load surface (16).

3. Endoprosthetic device (10) as in claim 2, characterized in that said support body (C) and said interface layer (A) are made in one piece, said interface layer (A) or both being made using additive printing technologies.

4. Endoprosthetic device (10) as in claim 2, characterized in that said support body (C) and said interface layer (A) are made individually and joined by gluing, snap-in assembly, extrusion or incorporation.

5. Endoprosthetic device (10) as in any claim from 2 to 4, characterized in that said support body (C) is made of compact material, with no porous structure, and in that said interface layer (A) is made with a material with a reticular or porous structure, with porosity in the order of 50-2000pm and thickness comprised between 0.10 mm and 25 mm.

6. Endoprosthetic device (10) as in any claim from 2 to 5, characterized in that said stem (12) is completely lined, that is, surrounded externally, by said interface layer (A), while internally it is defined by said support body (C) without a break in continuity.

7. Endoprosthetic device (10) as in any claim from 2 to 6, characterized in that said covering head (15) comprises an annular containing collar (19) which develops peripherally around said stem (12) defining therewith a circumferential aperture (20) for said exposed end (110).

8. Endoprosthetic device (10) as in any claim from 2 to 7, characterized in that a peripheral zone of said covering head (15) is provided with a shoulder (21) against which an external membrane (112) of said bone (100) can abut, wherein said shoulder (21) is made by creating a discontinuity between said interface layer (A) and said support body (C).

9. Endoprosthetic device (10) as in any claim hereinbefore, characterized in that said covering head (15) has an eccentric part (23) with respect to said stem (12).

10. Endoprosthetic device (10) as in any claim hereinbefore, characterized in that said anchoring portion (11) comprises a first stem (12) able to be inserted into a first bone (100) and a second stem (22) able to be inserted into a second bone (200) anatomically adjacent to said first bone (100).

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