Electric intramedullary nails for bone lengthening or repositioning

Abstract

An electrically powered intramedullary nail (1) for bone lengthening or transport comprises: a tubular portion (2) extending along the main axial direction (x) of the intramedullary nail (1); a rod-shaped portion (3) sliding within the tubular portion (2) and along the longitudinal axis (x), including an abutment element (31); an electric motor (4) for driving the rod-shaped portion (3); characterized in that it further comprises: a sleeve (5) inserted into the tubular portion (2) and spaced proximally along the longitudinal axis (x), adapted to form an inner shoulder, which serves as the end of the stroke of the abutment element (31).

Description

Technical Field

[0001] This invention relates to the field of orthopedic technology. Specifically, it relates to an electrically powered intramedullary nail for long bone lengthening or repositioning, comprising an abutment element.

[0002] Such intramedullary nails, for example, allow for limb lengthening without the use of external fixators; in addition, they can be used for optimal transport and alignment of bone segments, and even for joint locking required for post-traumatic or therapeutic purposes. Background Technology

[0003] In this particular technical field, electrically powered intramedullary nails are known, which especially allow for the lengthening of long limbs. In particular, one type discussed, called Fitbone... TM The system is well-known; it was originally developed by Professor Rainer Baumgart, a world-renowned expert in the field.

[0004] This system is primarily used for the lengthening of individual limbs that require intervention due to trauma or congenital malformations, or for the lengthening of limbs whose length has not yet fully developed.

[0005] Furthermore, with adequate preoperative planning, the previously referred type of intramedullary nail allows for axial and torsional correction as part of limb lengthening.

[0006] The nail known and mentioned in the prior art comprises two parts: a first fixed part and a second sliding part that can extend telescopically within the first fixed part; in addition, a drive electromechanical device for controlling the extension of the sliding part is provided.

[0007] Document WO2021032823 A1 relates to an intramedullary nail for lengthening long bones, comprising a first tubular body and a second tubular body inserted into and sliding therein, and a small electric motor connected by gears, the motor allowing axial translation relative to the first tubular body.

[0008] Another type of nail in the prior art is known from document US 2016 / 0183994 A1.

[0009] In intramedullary nail designs based on existing technology, a key issue stems from the risk that the sliding portion may pull out of the fixed portion when the device is implanted in the patient's body.

[0010] To avoid the aforementioned risks, it is necessary to provide some type of stop, such as a physical stop, to block the sliding portion at the end of the stroke. However, to avoid complex, if not impractical, tooling, creating such a stop would require coupling a section of a telescopically coupled tubular portion.

[0011] However, it is well known that coupling two tubular elements, such as through welding, can weaken the structural integrity of the device and increase the risk of it breaking during use.

[0012] Therefore, the technical problem upon which this disclosure is based is to economically achieve mechanical blocking between the aforementioned telescopic portions without compromising the structural integrity of the intramedullary nail. Summary of the Invention

[0013] The concept upon which this invention is based is that a (possibly elastic, biocompatible) abutment portion, for example made of a sleeve, is contained in the distal portion of the tubular portion, adapted to properly stop the movement of the abutment element contained in the rod-shaped portion that slides due to electromechanical means.

[0014] Based on this solution concept, this disclosure relates to an electrically powered intramedullary nail for bone lengthening or transport, comprising:

[0015] The tubular portion extending along the main longitudinal axis of the intramedullary nail, including the proximal and distal ends;

[0016] A rod-shaped portion that slides telescopably and retracts along the longitudinal axis within the tubular portion includes an abutment element;

[0017] An electric motor device used to drive the rod-shaped part.

[0018] In particular, the invention is characterized in that it further includes a sleeve that is fixedly inserted into the tubular portion and spaced apart from the proximal end along the longitudinal axis, adapted to form an inner shoulder that serves as the end of the travel of the abutment element.

[0019] More specifically, the sleeve may be radially elastic so as to be pressed into the tubular portion by frictional engagement.

[0020] Furthermore, it should be noted that the aforementioned sleeve may include at least one longitudinal slit for better adaptation and thus better friction against the inner surface of the tubular portion. Preferably, the longitudinal slit extends along the entire extension of the sleeve; however, it is not excluded that the elasticity of the element is achieved through one or more shorter slits.

[0021] The sleeve is preferably made of a biocompatible and / or elastic material, such as PEEK.

[0022] Preferably, the electromechanical device for an electrically driven intramedullary nail used for bone lengthening or repositioning includes a lead screw drive, which in turn includes a worm and a nut, the nut being translatable relative to the worm, the rod-shaped portion being integrally connected to the nut during translation, and the tubular portion being integrally connected to the worm during translation, and vice versa.

[0023] In the first of the two aforementioned determinations, the tubular portion includes a guide section for the nut having a non-circular inner cross-section, which is proximal to the receiving section of the sleeve. Specifically, the non-circular inner cross-section can be a polygonal cross-section with chamfered or unchamfered corners, such as a quadrilateral portion. The non-circular inner cross-section can be obtained by forming one or more flat portions on the inner cylindrical surface.

[0024] Preferably, the inner radius of the sleeve when inserted into the tubular portion is adjacent to the guide section of the tubular portion. Therefore, the maximum diameter of at least one circle circumscribed in the non-circular cross-section is greater than the inner diameter of the sleeve when installed. Preferably, the minimum diameter of the circle inscribed in the non-circular cross-section is smaller than the inner diameter of the sleeve, such that a shoulder is formed only at certain points along the circumference of the non-circular cross-section.

[0025] Advantageously, the abutting element can be defined by the distal face of the nut.

[0026] Furthermore, the sleeve can preferably have a structure with at least two layers, and more preferably three layers. This configuration allows for the selection of a material with a high elastic modulus as the core of the sleeve, while providing a material with a high coefficient of friction for the layers.

[0027] The features and advantages of the electrically powered intramedullary nail according to this disclosure will become apparent from the following description of embodiments thereof, given by way of non-limiting example with reference to the accompanying drawings. Attached Figure Description

[0028] Figure 1 A three-dimensional schematic diagram of the intramedullary nail according to the present invention is shown;

[0029] Figure 2 A three-dimensional schematic diagram of the tubular portion and sleeve of the intramedullary nail according to the present invention in a separate configuration is shown;

[0030] Figure 3 A three-dimensional cross-sectional view of the tubular portion of the intramedullary nail according to the present invention is shown;

[0031] Figure 4 A side view of the sleeve of the intramedullary nail according to the present invention is shown;

[0032] Figure 5 A schematic side view showing the fully retracted stroke end configuration of the rod-shaped portion inside the tubular portion of the intramedullary nail according to the invention;

[0033] Figure 6 A schematic side view showing the rod-shaped portion of the tubular portion of the intramedullary nail according to the invention fully extending to the end of its travel;

[0034] Figure 7 Show Figure 6 Enlarged view of detail A in the middle;

[0035] Figure 8 A perspective view of the tubular portion of the intramedullary nail according to the present invention is shown;

[0036] Figure 9 A front cross-sectional view of the sleeve of the intramedullary nail according to the present invention is shown. Detailed Implementation

[0037] Refer to these accompanying figures, especially Figure 1 The example, shown in its entirety and schematically, illustrates an intramedullary nail 1. Nail 1 is essentially a nail that can be extended by activating an electromechanical drive mechanism that inserts the nail itself.

[0038] The rotator-type intramedullary nail 1 is particularly suitable for the femur, which extends from the proximal portion 6 (preferably inclined relative to the main longitudinal x-direction of the nail itself) to the distal portion 7 (preferably extending along the same longitudinal x-direction).

[0039] The intramedullary nail 1 includes an electromechanical device 4, as will be described in detail below, which allows for alteration of the nail's longitudinal length. The electromechanical device 4 includes a motor unit 42 housed in the proximal portion 6, which is powered via a bipolar power line 8 and covered by a housing adapted to protect it. Figure 1 As shown, reference numeral 42 will indicate both the motor unit and the housing suitable for protecting it.

[0040] The intramedullary nail 1 also includes external control electronics, a transmitter, and a connector at its proximal portion 6 suitable for conveniently connecting the bipolar power line 8 to the electromechanical device 4. These components, which are known per se, will not be described further.

[0041] The distal portion 7 of the intramedullary nail 1 includes a tubular portion 2 extending in the longitudinal x direction, and a rod-shaped portion 3 that still slides within the tubular portion 2 in the longitudinal x direction.

[0042] exist Figure 2 , Figure 3 and Figure 9 The tubular portion 2, which is visible separately, includes a hollow cylindrical shell in which a rod-shaped portion 3 (also preferably tubular) is telescopically mounted.

[0043] In the proximal portion 6 and / or the distal portion 7, proximal transverse holes 9 and distal transverse holes 32 are respectively arranged to constrain axial sliding, for example by transverse bone screws. As for the distal transverse hole 32, it is preferably located at the most distal portion of the rod-shaped portion 3 along the longitudinal x-direction, such as... Figure 1 , Figure 5 and Figure 6 As shown, they can also be inserted in the middle of the rod-shaped part 3 itself.

[0044] The electric motor 4 is configured to move the rod-shaped portion 3 within the tubular portion 2 axially with millimeter-level precision.

[0045] Preferably, in addition to the motor unit 42 described above, the electromechanical device 4 also includes a lead screw drive device 41. For example... Figure 5 and Figure 6 As shown, the lead screw drive device 41 is formed by a worm gear 411 and a nut 412 coupled thereto. The worm gear 411 is rotatably mounted inside the tubular portion 2, and is integrally connected and coaxial with it during translation. The nut 412 is integrally connected to the end of the rod-shaped portion 3 and slides within a guide section 21 of the tubular portion 2, which prevents relative rotation. The motor unit 42 coupled to the worm gear 411 is configured to rotate it, thereby facilitating the displacement of the nut 412 and the rod-shaped portion 3 integrally connected thereto in the longitudinal x-direction.

[0046] For the sake of explanation, Figure 5 and Figure 6 The more compact starting stroke position and the thus more extended stroke end position of the rod-shaped portion 3 are shown respectively due to the implementation of the electromechanical device 4 as described above.

[0047] More specifically, the tubular portion 2 comprises four distinct sections from its proximal end 23 to its distal end 24: the proximal connecting section 25; the aforementioned guiding section 21; the receiving section 22; and the distal connecting section 26.

[0048] The proximal connecting section 25 has a relatively short extension length and an outer diameter larger than the rest of the tubular portion 2. It houses the bearing supporting the worm gear 411 and a coupling that allows it to be mechanically coupled to the proximal motor unit 42.

[0049] The subsequent guide segment 21 has a smaller diameter both internally and externally than the proximal connecting segment 25. Its longitudinal extension is substantially greater than that of the proximal connecting segment 25. The inner cross-section of the guide segment 21 is complementary to the outer contour of the parts constituting the nut 412, allowing only translational movement and restricting its rotational degrees of freedom. Therefore, the inner cross-section is not circular; in the embodiment shown in the figures, as... Figure 8 It is clearly visible that it has a quadrilateral outline with rounded corners.

[0050] The subsequent receiving section 22 has a circular cross-section, the diameter of which is larger than the diameter of the circumference of the inner cross-section surrounding the guide section 21. Its longitudinal extension length is comparable to that of the guide section 21.

[0051] The inner cross-section of the final distal coupling segment 26 is slightly larger than that of the receiving segment 22, while its longitudinal extension length is comparable to that of the proximal connecting segment 25. At the receiving segment 22, a tip 27 is integrally coupled, the tip having an opening for the telescopic extension of the rod-shaped portion 3.

[0052] A sleeve 5 is installed within the aforementioned receiving section 22 to reduce the inner diameter of the section and provide a shoulder 52, which serves as the end of the travel of the abutment element 31 disposed on the rod-shaped portion 3. Specifically, the abutment element 31 is defined by the distal end face of the nut element 412. As previously described, the nut element 412 slides within the non-circular cross-section of the guide section 21 through a form fit. The sleeve 5 reduces the diameter of the receiving section 22 to a value less than the maximum circumference circumferential to the non-circular cross-section. Furthermore, the reduced diameter is preferably greater than the diameter inscribed in the minimum circumference of the non-circular cross-section. Therefore, the result is that the shoulder 52 is formed only in certain portions of the non-circular cross-section circumference: in the illustrated example, the abutment surface of the shoulder 52 is located at the junction of the quadrilateral profile.

[0053] like Figure 2 , Figure 5 and Figure 6 As shown, the sleeve 5 preferably has radial elasticity so that it can be pressed into the tubular portion 2 by friction fit.

[0054] In particular, Figure 4 In the preferred embodiment shown, the sleeve 5 has a longitudinal cut 51 that extends along the entire extension of the sleeve 5. Thus, the sleeve 5 has an undeformed configuration (where its outer diameter is larger than the inner diameter of the receiving section 22) and a deformed configuration (where it collapses relative to the longitudinal cut 51 to an outer diameter equal to the inner diameter of the receiving section 22).

[0055] Obviously, to achieve the desired result, various cutting patterns can be made on the relevant sleeve 5, for example, providing at least one longitudinal slit whose extension length is less than the length of the sleeve 5 in the longitudinal x direction. The elastic deformation of the sleeve 5 defines a radial force, which significantly increases the friction between the element and its seat, thereby creating a stable coupling between the two.

[0056] As previously stated, sleeve 5 allows the forward movement of the lead screw drive 41 to be stopped, thereby avoiding serious problems associated with the rod-shaped portion 3 dislodging from the tubular portion 2.

[0057] like Figure 9 As shown, the sleeve 5 preferably has a layered internal structure, including an outer layer 55, a middle layer 54, and an inner layer 53. Therefore, the middle layer can be made of a different material (e.g., a metal material) than the outer and inner layers, which are made of, for example, synthetic plastic materials.

[0058] Other components of the electric intramedullary nail 1 are also made of synthetic plastic materials, such as silicone, thermoplastic resin, PEEK, and preferably, the tubular portion 2 is made of metal or a biocompatible metal alloy.

[0059] The main advantage of this invention is that it creates the abutment at low cost, prevents the rod-shaped portion 3 from coming out of its seat, and does not introduce a weak point in the device structure.

[0060] All components are easy to manufacture and have a particularly low cost.

Claims

1. An electrically powered intramedullary nail (1) for bone lengthening or transport, comprising: A tubular portion (2) extending along the main longitudinal axis (x) of the intramedullary nail (1) includes a proximal end (23) and a distal end (24). The rod-shaped portion (3) that slides telescopically along the longitudinal axis (x) within the tubular portion (2) includes an abutment element (31). Electric motor (4) for driving the rod-shaped part (3); Its characteristic is that it further includes: A sleeve (5) is inserted into the tubular portion (2) in a fixed connection manner and spaced apart from the proximal end (23) along the longitudinal axis (x). The sleeve is adapted to form an inner shoulder (52), which serves as the end of the stroke of the abutment element (31).

2. The electrically powered intramedullary nail (1) for bone lengthening or transport according to the preceding claim, wherein, The sleeve (5) is radially elastic so as to allow for frictional engagement inside the tubular portion (2).

3. The electrically powered intramedullary nail (1) for bone lengthening or transport according to the preceding claim, wherein, The sleeve (5) includes at least one longitudinal slit.

4. The electrically powered intramedullary nail (1) for bone lengthening or transport according to the preceding claim, wherein, The at least one longitudinal cut extends along the entire extension of the sleeve (5).

5. The electrically powered intramedullary nail (1) for bone lengthening or transport according to any one of the preceding claims, wherein, The sleeve is made of a biocompatible material, such as PEEK.

6. The electrically powered intramedullary nail (1) for bone lengthening or transport according to any one of the preceding claims, wherein, The electric motor device (4) includes a lead screw drive device (41), which includes a worm (411) and a nut (412). The nut (412) is capable of translational movement relative to the worm (411). The rod-shaped portion (3) is integrally connected to the nut (412) during translation, and the tubular portion (2) is integrally connected to the worm (411) during translation, or vice versa.

7. The electrically powered intramedullary nail (1) for bone lengthening or transport according to the preceding claim, wherein, The rod-shaped portion (3) is integrally connected to the nut (412) during translation, and the tubular portion (2) is integrally connected to the worm (411) during translation, wherein the tubular portion (2) includes a guide section (21) of the nut (412) having a non-circular inner cross section and being proximal to the receiving section (22) of the sleeve (5).

8. The electrically powered intramedullary nail (1) for bone lengthening or transport according to claim 7, wherein, The inner radius of the sleeve (5) when inserted into the tubular portion (2) is adjacent to the guide section (21) of the tubular portion (2).

9. The electrically powered intramedullary nail (1) for bone lengthening or transport according to claim 6 or 7, wherein, The abutting element (31) is defined by the distal end face of the nut (412).

10. The electrically powered intramedullary nail (1) for bone lengthening or transport according to any one of the preceding claims, wherein, The sleeve (5) has at least two layers (53, 54, 55) made of different materials.

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