Bone plate internal fixation device

Abstract

This invention relates to an internal fixation device for epiphyseal shaft fixation using a bone plate, comprising a pair of retaining elements, each retaining element having a through hole configured to receive a corresponding fixation screw fixed to the bone; the internal fixation device also includes a central portion that structurally connects and constrains the retaining elements together. The central portion is resilient to allow bending and angular opening of the bone plate during the development of the epiphyseal shaft fixation surgery; the bending of the bone plate further allows relative bending between the retaining elements, wherein the fixation screws always remain coplanar with the plane containing the bending angle, and wherein the axis of each fixation screw remains perpendicular to the corresponding retaining element.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201880006072.3. That Chinese Patent Application is based on International Application PCT / EP2018 / 051237, filed on December 18, 2015, entitled "Internal Fixation Device for Bone Plate". Technical Field

[0002] This invention relates to an internal fixation device for use as a corrective device (particularly for pediatric patients). Such an internal fixation device includes a bone plate with at least a pair of through holes for receiving bone fixation screws.

[0003] The present invention particularly relates to an internal fixation device for a bone plate intended for use in epiphyseal shaft fixation surgery, for preventing natural growth or correcting limb axis deviation by limiting the natural growth of the growth plate.

[0004] This invention can be usefully applied in the field of pediatric orthopedics for epiphyseal shaft fixation surgery at the ends of deformed long bones in pediatric patients. Therefore, the following description is made with reference to non-limiting use within the scope of such art. Background Technology

[0005] Known techniques for epiphyseal diaphysis fixation surgery involve inserting devices into the bone to restrict the development of the growth plate, such as longitudinally positioned screws, nails, or bone plates. Bone plates are commonly used in techniques for epiphyseal diaphysis fixation to prevent the growth plate from developing.

[0006] Such a bone plate is applied to the bone by fixing screws, which secure it to the epiphysis and metaphysis respectively at the protruding areas of bone deformation. The metaphysis and epiphyseal portions of the bone plate have at least one through hole suitable for receiving one of the aforementioned fixing screws.

[0007] In a particular field of the present invention, problems related to patient tolerance to the aforementioned bone plates are known.

[0008] In fact, when the fixation screws of the bone plate are located above and below the growth plate, the fixation screws need to be adapted to the bending caused by the constraint of the bone plate and the changes that occur during growth.

[0009] Therefore, specific bone plates are known that are constrained to the bone by fixation screws that are easily separable from each other, in order to avoid excessive compression of the growth plate and to carefully guide the growth portion of the long bone and the natural growth process of the bone.

[0010] One solution disclosed in US Patent Document 8029507B2 relates to an angle correction plate fixation device for bone deformities, the device including a rotatable hinge arranged laterally in the plate to ensure that the plate rotates relative to the plate under the load of the fixing screws, thereby supporting bending changes that occur during growth.

[0011] However, the solution known from US Patent Document 8029507B2 presents a significant hindrance due to the presence of the hinge, which reduces the tolerance of the bone plate (especially in areas with little soft tissue coverage). Furthermore, according to known surgical techniques, the solution known from US Patent Document 8029507B2 does not further allow for adequate central reference on the growth plate for the use of Kirschner wires (for temporary fixation of the bone plate).

[0012] Another solution disclosed in US2004 / 0111089 A1 relates to a plate fixation device for controlling bone growth, and in particular for correcting bone deformities; the device includes two fixation screws that are inserted into suitable holes obtained in the bone plate.

[0013] In one example disclosed in US Patent Document 2004 / 0111089 A1, the head of each fixing screw has a spherical profile for proper rotation within an elongated seat obtained in the plate, thereby ensuring that the fixing screw is angled. For the screw shank to rotate, the spherical profile of the screw head also needs to include engagement through which the screw operates during tightening; therefore, in this known example, the screw head, as well as the bone plate (typically), is a significant obstacle in height, which may reduce the durability of the bone plate (especially in areas with little soft tissue coverage).

[0014] In another example described in US Patent Document 2004 / 01 1 1089 A1, the central connection between the holes in the bone plate is provided to be elastic, so that the fixation screw can move as the bone segment moves. Examples of elastic connections known from US Patent Document 2004 / 0111089 A1 provide: a plate with a middle section made of elastic material, a plate made of fabric surrounded by a rigid material around the opening, or using an elastic band surrounding the fixation screw instead of a plate, ultimately providing a rolled edge in the middle.

[0015] Although known implants in the prior art have partially improved the tolerance of bone plates used in patients by ensuring relative rotation of the plate ends so that the fixation screws can support changes that occur during growth, these implants have some limitations.

[0016] First, excessive elasticity of the bone plate can cause problems in fixing the bone plate in the required position.

[0017] Furthermore, even if these implants move with the bone segment, the flexible bone plate can become an obstacle in any situation (especially in terms of height), thereby promoting the outbreak of inflammatory processes in the soft tissue.

[0018] In addition, flexible bone plates may be too fragile and risk damage when subjected to stress from bone growth.

[0019] Furthermore, the configuration of elastic bone plates used in existing technologies can lead to the breakage of growth plates, thereby further reducing the tolerance of the implant.

[0020] Purpose of the invention

[0021] The purpose of this invention is to solve the problems of the prior art.

[0022] A specific object of the present invention is to provide a bone plate implant that can be optimally fixed to the bone.

[0023] Another object of the present invention is to provide a bone plate implant that is better tolerated by patients (even in tissue areas that are barely covered by soft tissue).

[0024] Another object of the present invention is to provide a stable bone plate implant suitable for epiphyseal shaft fixation applications.

[0025] Another specific object of the present invention is to provide a bone plate implant that does not interfere with the growth plate. Summary of the Invention

[0026] One potential solution of the present invention is to provide an internal fixation device for epiphyseal shaft fixation using a bone plate, comprising a pair of retaining elements, each retaining element including a through-hole for receiving a corresponding fixation screw (fixed) to the bone. The internal fixation device also includes a central portion that structurally connects and constrains the retaining elements together; the central portion is elastic to allow bending of the bone plate. Each through-hole includes a threaded surface adapted to engage with a corresponding surface of the fixation screw. The retaining elements and the central portion are provided as a combined structure.

[0027] Advantageously, the threaded surface of the through hole allows for an improved combination with the fixation screw, enabling more precise implantation into the bone while achieving a more structurally stable assembly.

[0028] Furthermore, the presence of the threaded surface of the through hole ensures that the head of the fixation screw and the bone plate can be joined with fewer obstructions (such as in terms of height) and without protrusions, thus resulting in greater tolerance (especially when the implant is applied in tissue areas with little or no soft tissue coverage).

[0029] Moreover, although the flexible central portion allows for a wide range of opening angles in the bone plate, during the evolution of epiphyseal shaft fixation surgery, the fixation screws have always remained coplanar with the plane containing the bending angle, and the axis of each fixation screw remains substantially perpendicular to the corresponding retaining element.

[0030] Internal fasteners with threaded surfaces are generally more robust and are therefore suitable for epiphyseal fastening applications, where the plate bears uniform and relevant pressure.

[0031] Furthermore, to improve tolerance, the internal fixation device is preferably characterized by: the central portion being raised relative to the bottom surface of the protective element, thereby limiting pressure on the growth portion of the long bone and preventing lateral fracture of the growth plate.

[0032] Further features and advantages of the bone plate internal fixation device of the present invention will become clearer from the following description of exemplary and non-limiting embodiments. Attached Figure Description

[0033] This description refers to the following figures, in which:

[0034] Figure 1 A perspective view of one embodiment of the internal fixation device for bone plates according to the present invention is shown;

[0035] Figure 2 It is shown in a disassembled state and from different perspectives. Figure 1 A three-dimensional schematic diagram of the fixing device in the middle;

[0036] Figure 3 A perspective view of a fixing screw for an internal fixation device for a bone plate according to the present invention is shown;

[0037] Figure 4 It shows a pair Figure 3 The fixing screws and Figure 1 Side view of the implant of the internal fixation device for the bone plate in the middle;

[0038] Figure 5 A perspective view of a second embodiment of the internal fixation device for bone plates according to the present invention is shown;

[0039] Figure 6 Showing an upward-looking perspective Figure 5 A three-dimensional schematic diagram of the fixing device in the middle;

[0040] Figure 7 A perspective view of a third embodiment of the internal fixation device for bone plates according to the present invention is shown;

[0041] Figure 8 Shown in a partially disassembled state Figure 7Fixtures in the middle;

[0042] Figure 9 Showing an upward-looking perspective Figure 7 A three-dimensional schematic diagram of the fixing device in the middle.

[0043] In different accompanying drawings, the same elements will be identified with the same reference numerals. Detailed Implementation

[0044] refer to Figure 1 The example in the illustration schematically shows a first embodiment of the internal fixing device 101.

[0045] The fixation device according to the invention is particularly suitable for use in orthopedic procedures for epiphyseal shaft fixation, i.e., treatment of long bone deformities, especially for pediatric and / or adolescent patients, by applying the fixation device through the growth portion of the long bone body in these bones. The internal fixation device 101 includes a first retaining element 102 and a second retaining element 103, each retaining element including a through-hole 104 and a through-hole 105, respectively, configured to receive corresponding fixation screws when the fixation device is implanted into the bone.

[0046] The retaining elements 102 and 103 are preferably made of a rigid and biocompatible material (e.g., titanium) and have a substantially circular shape and uniform thickness.

[0047] The retaining elements 102 and 103 are structurally interconnected by the central portion 106, which constrains the retaining elements 102 and 103 to achieve the bone plate structure. The retaining elements 102 and 103 and the central portion 106 are provided as a combined structure.

[0048] A “composite structure” is a structure made of at least two different materials or comprising at least two different material configurations exhibiting different mechanical properties (i.e., solid metal and braided metal).

[0049] In other words, the retaining element and central portion of the internal fastening device according to the invention are at least partially made of two different materials or two different configurations of materials.

[0050] Typically, retaining elements and at least a portion of intermediate sections are initially supplied as separate components of the internal fastener. These separate components are then joined together during the manufacture of the internal fastener to form a combined structure.

[0051] The central portion 106 is elastic, thereby maintaining the relative curvature between elements 102 and 103, i.e., the curvature of the bone plate. At the same time, the tensile strength of the central portion 106 ensures the structural integrity of the bone plate during the tensile-bending phase.

[0052] The bending of the bone plate corresponds to the relative rotation of the respective planes of the retaining elements 102 and 103, which results in a suitable angle change for the fixation screw, thereby supporting the angular changes that occur during bone growth and providing improved tolerance of the implant in epiphyseal fixation surgery.

[0053] Specifically, the elastic central portion 106 allows for a wide range of angular openings in the retaining elements 102 and 103 of the internal fixation device 101. In this way, the angular variations allowed by the internal fixation device 101 during bone growth in epiphyseal fixation surgery can be further improved.

[0054] The central portion 106 preferably includes a through-hole 107 configured to allow insertion of a wire guide (not shown) so that Kirschner wires can be used during implantation to center the bone plate in such a way that the central portion is properly positioned on the growth plate.

[0055] When considering retaining elements 102 and 103, each retaining element includes its own threaded surfaces 108 and 109, which are respectively located within through holes 104 and 105. Specifically, preferably, through holes 104 and 105 are substantially cylindrical and threaded surfaces 108 and 109 are the inner surfaces of the cylindrical holes. In other words, through holes 104 and 105 comprise threaded cylindrical holes formed coaxially with the through holes, and the outlet diameter and inlet diameter are substantially equal to each other. As will be further described, such threaded surfaces 108 and 109 are adapted to engage with the threaded surfaces of the retaining screws, respectively, to achieve the implant structure. Specifically, through holes 104 and 105, and threaded surfaces 108 and 109 are configured such that the retaining screws remain coplanar with the plane containing the bending angle, and the axis of each retaining screw remains substantially perpendicular to the corresponding retaining element 102 or 103.

[0056] Figure 2 The fixing device 101 is visible in its disassembled state, so as to understand the specific embodiment of the elastic center portion 106.

[0057] In this embodiment, the elastic center portion includes four elastic elements 201a, 201b, 202a, and 202b, which are arranged in pairs to constrain retaining elements 102 and 103 between retaining elements 102 and 103. In other possible embodiments, different numbers of elastic elements may be provided, such as a pair.

[0058] The elastic elements 201a, 201b, 202a, and 202b include metal wires or cables, each end of which is constrained to one of the retaining elements 102 and 103, respectively.

[0059] The quantity, size, and structure of the metal wires or cables can be adjusted according to the required flexural elasticity and tensile strength for the bone plate. The constraint or closure of the wires in the retaining element can be achieved through welding, plastic deformation (press-fitting), or other mechanical constraints. Specifically, the constraint in the retaining element occurs by tangentially placing the metal wires or cables within appropriate holes 203 in the retaining elements 102 and 103. Generally, the term "wire" refers to an elongated linear element with a cross-section of any shape, but preferably circular; such a "wire" can be made of a uniform and solid metal, a material arranged in a single strand, or other combinations thereof.

[0060] Generally, the term "rope" means an elongated linear element, preferably with a circular cross-section, made of a uniform material or a material arranged in a single strand (especially metallic or non-metallic materials).

[0061] Preferably, the elastic elements 201a, 201b, 202a, and 202b are arranged symmetrically with respect to the longitudinal axis of the fixing device 101, that is, the longitudinal axis is conceptually the center of the connecting holes 104 and 105.

[0062] Therefore, elastic elements 201a, 201b, 202a, and 202b represent a specific embodiment of the elastic center portion 106 already described.

[0063] Figure 3 An embodiment of the fixing screw 301 is shown, specifically configured for use in an internal fixation device of a bone plate according to the invention.

[0064] The fixing screw 301 is preferably made of a rigid and biocompatible material (e.g., titanium).

[0065] The fixing screw 301 includes a threaded shank 302, which preferably includes threads with a triangular profile. The fixing screw 301 also includes a tip 303, preferably self-tapping. The fixing screw 301 further includes a head 304, which has threads on its own outer cylindrical surface. The head 304 has suitable gripping means 305, such as for screwing the fixing screw 301 into a hexagonal notch in the bone.

[0066] The head thread 304 is adapted to engage with the threaded surfaces 108 and 109 (which are correspondingly threaded) of the internal fixation device to achieve an implant structure. Preferably, the threaded surfaces 108 and 109 and the corresponding head thread 304 are provided with double-start threads to simplify thread engagement during implantation applications and to ensure that the distance of advance is equal to the pitch of the thread on the rod 302.

[0067] Preferably, the pitch of the thread on the rod 302 of the fixing screw 301 is different from the pitch of the thread surfaces 108 and 109; this further helps to simplify the application of the implant. Specifically, the pitch of the thread on the rod 302 is twice the pitch of the head thread 304, which, when the head thread 304 engages with the threads 108 or 109 of the bone plate, enables proper advancement and more precise application in the terminal tightening component.

[0068] Figure 4 The illustration shows an implant for epiphyseal diaphysis fixation according to the invention, which is a kit comprising a pair of fixation screws 301 and an internal fixation device 101 for a bone plate. The fixation screws are threaded through the heads 304 into corresponding threads 108 and 109 in the through holes 104 and 105 of retaining elements 102 and 103. With the fixation screws 301, retaining elements 102 and 103 are thus adapted to be fixed to the epiphysis and metaphysis of long bones in pediatric patients, respectively, by the assembled screws, for example, bones with angular deformities to be corrected (by applying fixation device 101). The resilient central portion 106 allows for variations in the shank angle of the screws 301, which is well-tolerated by the patient even at different stages of bone growth.

[0069] As described, the internal fixation device 101 of the bone plate is configured such that each fixation screw 301 remains coplanar with the plane of the corresponding retaining element 102 or 103, thereby avoiding unnecessary pressure on the internal fixation device 101 and improving the tolerance of the implant.

[0070] The threaded surfaces 108 and 109 of retaining elements 102 and 103 are thus configured to securely bind each of retaining elements 102 and 103 together with the corresponding fixing screw 301, thereby achieving a bone plate assembly that is elastic only in the central portion 106.

[0071] The threaded engagement between the head of the fixing screw 301 and the retaining elements 102 and 103 ensures improved restraint, allowing for more precise implantation of the internal fixation device 101 and a more robust structure.

[0072] As in Figure 4 As can be understood, the presence of the threaded surfaces of the through holes in retaining elements 102 and 103 allows for engagement between the head of the fixing screw 301 and the bone plate 101 without any protrusions, and the bone plate 101 is less of an obstacle in terms of height. In fact, according to the invention, the fixing screw 301 does not need to "bump" against the bottom head surface on the retaining element; however, it is sufficient for the corresponding threads of the screw head to engage with the corresponding threads of the through hole, achieving a secure assembly.

[0073] The internal fixation device according to the invention is therefore more tolerable, especially when the implant is applied in tissue areas that are barely covered by soft tissue. Furthermore, the internal fixation device 101 with its threaded surface is generally more robust and suitable for withstanding the pressures of epiphyseal shaft fixation applications.

[0074] As in Figure 4 Understandably, to improve tolerance, the internal fixation device includes a central portion 106, which is raised relative to the bottom surface 401 of the retaining elements 102 and 103 and configured to contact the bone surface. This can thus limit pressure on the bone epiphysis and therefore prevent lateral crushing of the bone plate.

[0075] In other words, the internal fixation device 101 is substantially flat; however, the central portion 106 is raised relative to the bottom surface 401 of the retaining elements 102 and 103, and is configured to face the rod of the fixing screw 301. Therefore, it may limit pressure on the growth portion of the long bone.

[0076] refer to Figure 5 The example schematically illustrates a second embodiment of the internal fixation device 501 for bone plates.

[0077] The internal fixation device 501 includes a first retaining element 502 and a second retaining element 503, each retaining element including corresponding through holes 504 and 505, similar to the elements already described with reference to the internal fixation device 101. A central portion 506 structurally connects and constrains the retaining elements 502 and 503 together, and the central portion 506 is elastic to allow the bone plate to bend.

[0078] The central portion 506 preferably includes a central through-hole 507 configured to ensure the insertion of a wire guide (not shown) for use with Kirschner wires.

[0079] Each of the through holes 504 and 505 of retaining elements 502 and 503 includes corresponding threaded surfaces 508 and 509, respectively.

[0080] Such threaded surfaces 508 and 509 are configured to engage with the corresponding surfaces of the head of the retaining screw 301, similar to those described with reference to the internal fastener 101. The central portion 506 includes a pair of bridge elements 510a and 510b made of a resilient plastic material, separated from each other by a through-hole 507. In an alternative embodiment, the central hole 507 can be omitted since there is only one bridge element.

[0081] Typically, the bridge elements 501a and 510b are made of elastic plastic material and are arranged symmetrically with respect to the longitudinal axis of the internal fixing device 501.

[0082] Typically, polyetheretherketone (PEEK) is a plastic material with suitable resistance and biocompatibility characteristics.

[0083] Preferably, retaining elements 502 and 503 are also made of plastic material, and more preferably, these two retaining elements are integrally formed with bridge elements 510a and 510b in a single mold.

[0084] Advantageously, plastic material components can be more easily obtained through molding processes, making these embodiments less expensive than those including metal material components. Furthermore, the plastic material portions are radiolucent and, in addition to being biocompatible, ensure suitable mechanical strength and elasticity.

[0085] In an alternative embodiment, retaining elements 502 and 503 may be made of a metallic material and connected to the bridge element by a suitable coupling method. This embodiment of fixation device 501 thus envisions different elements for providing the resilient central portion 506, while maintaining the same function as the bone plate already described with respect to fixation device 101.

[0086] Figure 6 The fixation device 501 is shown from a bottom-view perspective. In this view, it can be understood that the central portion 506 includes a notch 601 on its bottom surface, which ensures that the central portion 506 is further raised and forms a preferred bending axis of the plate 501. Therefore, when the fixation device 501 is implanted, the raised central portion 506 is further adapted to restrict pressure on the long bone growth portion of the bone.

[0087] refer to Figure 7 The example schematically illustrates a third embodiment of the internal fixation device 701 for bone plates.

[0088] The internal fixation device 701 includes a first retaining element 702 and a second retaining element 703, each including a through-hole 704 and 705. A central portion 706 structurally connects and constrains the retaining elements 702 and 703 together, and the central portion 706 is elastic, allowing the bone plate to bend. The central portion 706 preferably includes a central through-hole 707 configured to ensure the direct passage of Kirschner wires, preferably without the aid of guide wires.

[0089] Each of the through holes 704 and 705 of retaining elements 702 and 703 includes corresponding threaded surfaces 708 and 709, respectively. Such threaded surfaces 708 and 709 are configured to engage with the corresponding surface of the head of the fixing screw 301, similar to the description of reference fixing device 101.

[0090] The central portion 706 includes a pair of bridge elements 710a and 710b, which realize the geometry of the through hole 707. Typically, the bridge elements 710a and 710b are arranged symmetrically with respect to the longitudinal axis of the internal fixing device 701.

[0091] Due to the different support structure, embodiments of the fixing device 701 are therefore distinguished from fixing devices 101 or 501. For example... Figure 8 As can be seen, the partially disassembled fixing device 701 includes a support frame 801 made of a single piece of plastic material. This realizes peripheral portions 802 and 803, which are part of the structure of each of the retaining elements; thus, the peripheral portions 802 and 803 of the retaining elements are integrally formed with the bridge elements 710a and 710b.

[0092] The support frame 801 is associated with a pair of annular elements 804 and 805, which are respectively implantable in peripheral portions 802 and 803. The annular elements 804 and 805 are preferably made of a high-strength material (such as a metal) and include the threaded surfaces 708 and 709 already described.

[0093] Therefore, it is possible to achieve a more robust threaded engagement structure between the screw 301 and the threaded surfaces 708 and 709 of the annular elements 804 and 805, and the frame 801 contributes to the elasticity of the central portion 706.

[0094] Therefore, the resulting fixing device 701 can improve the tolerance of size and the quality of implementation while maintaining the optimal function as described above.

[0095] The implantation of the annular elements 804 and 805 in the corresponding bases provided in the peripheral portions 802 and 803 preferably occurs through a suitable convex surface to avoid unwanted rotation of the annular elements subjected to the tightening torque of the fixing screw 301. Figure 9 The fixation device 701 is shown from a low-angle view. From this view, it can be understood that the central portion 706 includes a notch 901 on its bottom surface, which further elevates the central portion 706. Therefore, as already described, the elevated central portion 706 limits pressure on the bone epiphysis. Generally, it may be understood throughout the embodiments that the internal fixation device advantageously has rounded (for greater durability) bottom and top peripheral edges.

[0096] Specifically, the embodiments typically provide an internal fixation device for bone plates that are substantially flat and have an elliptical shape without narrowing or contraction. In this sense, the embodiments described herein differ from the typical "eight-plate" fixation devices known in the prior art.

[0097] The elastic central portion of the internal fixation device according to the invention provides multiple components, such as elastic elements or bridge elements, which are arranged tangentially relative to the periphery of the retaining element. Therefore, while ensuring proper elasticity of the bone plate, improved mechanical stability is provided. Furthermore, the elliptical shape, which does not narrow during implant placement, ensures improved surgical manipulation.

[0098] In summary, for reference Figure 4 The use of the internal fixation device for the bone plate of the present invention is described in general terms.

[0099] Once a relatively non-invasive incision is made in the skin and muscles of the patient to be implanted, the fixation device 101 is placed through the growth portion of the long bone, so that the two retaining elements 102 and 103 contact the epiphysis and metaphysis of the bone to be treated, respectively.

[0100] The fixation suture is inserted into the cartilage of the growth portion of the long bone through the central through hole in the elastic central portion 106, so that the fixation device 101 is held in place (albeit temporarily).

[0101] The fixing screw 301 is first inserted into the through hole to penetrate the corresponding part of the epiphysis and metaphysis of the bone until the head 304 reaches the threaded surface of the through hole and engages with the threaded surface of the through hole.

[0102] During the growth of the long bone growth segment, the fixation screw 301 undergoes a dragging motion that determines the angular opening throughout the treatment. This dragging motion is caused by the stretching and bending of the bone plate of the internal fixation device 101. By ensuring the bending of the bone plate 101, the angular opening of the fixation screw 301 can also be achieved after bone growth has occurred throughout the treatment.

[0103] Advantageously, the internal fixation device of the bone plate according to the invention has a flat construction and uniform thickness and no protrusions to avoid friction with the soft tissue surrounding the implant.

[0104] Furthermore, advantageously, the structural stability of the internal fixation device of the bone plate according to the invention is increased due to the constraint between the through hole and the threaded surface of the screw head, resulting in better implantation and the ability to bend with changes due to bone growth. Still advantageously, the fixation device has a rational structure and is suitable for manufacture with small tolerances.

[0105] The bone plate according to the invention solves the technical problem and achieves several advantages, including ensuring complete correction of bone deformities through single epiphyseal fixation surgery.

Claims

1. An internal fixation device for epiphyseal shaft fixation using a bone plate, comprising: A pair of retaining elements, each of the pair of retaining elements including a through hole configured to receive a corresponding fixation screw fixed to the bone; The internal fixation device of the bone plate also includes: The central portion, which structurally connects the pair of retaining elements and constrains the pair of retaining elements together, The central portion is elastic to allow bending of the internal fixation device of the bone plate and angular openings of the internal fixation device of the bone plate during the development of the epiphyseal shaft fixation surgery. The bending of the internal fixation device of the bone plate further allows for relative bending between the retaining elements, and the fixing screws always remain coplanar with the plane containing the bending angle, and the axis of each fixing screw remains perpendicular to the corresponding retaining element. The central portion further includes a notch on its bottom surface, which can further elevate the central portion and generate a preferred bending axis for the internal fixation device of the bone plate.

2. The internal fixation device for bone plates according to claim 1, wherein the central portion includes at least one bridge element made of an elastic plastic material.

3. The internal fixation device for bone plates according to claim 2, wherein the elastic plastic material is polyetheretherketone (PEEK).

4. The internal fixation device for bone plates according to claim 2, wherein the retaining element is made of plastic material.

5. The internal fixation device for bone plates according to claim 4, wherein the retaining element and the at least one bridge element are integrally formed in a single mold.

6. The internal fixation device for bone plates according to any one of claims 1-5, wherein the bending of the internal fixation device corresponds to the relative rotation of the respective planes of the retaining element, the retaining element being adapted to allow for changes in the angle of the fixation screw.

7. The internal fixation device for bone plates according to any one of claims 1-5, wherein, The bending of the internal fixation device of the bone plate further allows for the angular opening of the fixation screws after bone growth.

8. The internal fixation device for bone plates according to any one of claims 1-5, wherein the internal fixation device for bone plates is flat and wherein the central portion is raised relative to the bottom surface of the retaining element, the bottom surface being configured to face the rod of the fixing screw, the raised central portion being adapted to restrict pressure on the growth portion of the long bone body.

9. The internal fixation device for bone plates according to claim 1, wherein the retaining element and the central portion are provided as a combined structure, and wherein the central portion of the combined structure includes at least one bridge element made of an elastic plastic material.

10. The internal fixation device for bone plates according to claim 9, wherein the central portion of the combined structure includes at least one pair of bridge elements, the at least one pair of bridge elements being made of an elastic plastic material and arranged symmetrically with respect to the longitudinal axis of the internal fixation device for bone plates.

11. The internal fixation device for bone plates according to claim 9, wherein the peripheral portion of each of the pair of retaining elements of the combined structure is made of an elastic plastic material and integrally formed with the at least one bridge element, and further comprises a pair of annular elements of metallic material, each of the annular elements being implanted into a corresponding one of the peripheral portions, wherein each of the annular elements includes a threaded surface.

12. The internal fixation device for a bone plate according to claim 9, wherein the internal fixation device for a bone plate is flat and has an unnarrowed elliptical shape, wherein the central portion of the combined structure includes a member disposed tangentially relative to the periphery of the retaining element.

13. The internal fixation device for a bone plate according to any one of claims 1-5, wherein each of the through holes includes a threaded surface adapted to engage with a corresponding surface of the respective fixation screw, and wherein the threaded surface is configured to securely restrain each of the pair of retaining elements by the respective fixation screw, the internal fixation device for a bone plate providing elasticity only in the central portion.

14. The internal fixation device for bone plates according to claim 13, wherein the through hole is cylindrical and wherein the threaded surface is the inner side of the through hole.

15. The internal fixation device for a bone plate according to any one of claims 1-5, wherein the central portion further includes a central through hole configured to allow the passage of wires used for temporary fixation of the internal fixation device for the bone plate.

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