Biphasic bone plate

Abstract

1. A bone plate (1) having a lower surface (2), an upper surface (3), a maximum thickness measured between the lower surface and the upper surface, a left side surface (4), a right side surface (5), a longitudinal axis (6), and a plurality of plate holes (7) extending from the lower surface to the upper surface, and further having a slot (8) in the lower surface (2) extending from the left side surface to the right side surface and having a width measured in a plane parallel to the longitudinal axis and a midplane (16) between the sides, wherein (i) the hollow space defined by the slot extends from the left side surface to the right side surface in the form of a straight cylinder, and (ii) the slot has an undercut feature (9) that limits the opening of the slot when the bone plate is bent vertically in a direction that attempts to widen the slot.

Description

Technical Field

[0001] 1. Field of the Invention The present invention relates to a bone plate according to the preamble of claim 1 and a method for manufacturing a bone plate according to the preamble of claim 10.

Background Art

[0002] Bone plates that exhibit biphasic stiffness behavior promote secondary bone healing. These bone plates allow for interfragmentary movement required at low functional loads (flexible phase) and limit said movement maximally when the slot closes at higher magnitudes of functional load (rigid phase). Thus, these bone plates provide a controlled movement to the fracture that is largely independent of the magnitude of the functional load. Thereby, (i) healing complications caused by mechanically adverse conditions can be avoided, and (ii) the average time until bone union can be shortened.

[0003] It has been found that an interfragmentary movement of 0.5 mm (0.2 - 1 mm) results in good healing outcomes for different fracture sizes (1, 2, and 6 mm cover most of the fractures). Known bone plates with optimized slot widths avoid overstimulation of the fracture and thereby can result in healing complications such as hypertrophic healing delay and nonunion.

[0004] 2. Description of the Related Art The biphasic bone plate is known from WO 2017 / 024416. To provide tensile strength and resistance to bending in valgus of the bone plate, this known bone plate comprises a slot having a lower section that extends from the lower surface to the upper surface of the bone plate and that extends across the bone plate along the shape of a "W" in a view towards the lower surface of the bone plate. This W-shape is formed by a nose having a free end that protrudes and expands from one of the rigid sections of the bone plate along the longitudinal axis of the bone plate and by an adjacent end formed in the concave shape of the other rigid section, the concave shape forming an enclosure for the nose, whereby movement of the nose relative to the enclosure is restricted in both directions along the longitudinal axis of the bone plate. Further, the central section of the slot has a width that increases towards the upper section of the slot, and the upper section of the slot has two curved legs that extend in the direction of the longitudinal axis of the bone plate. The lower section of the slot has a substantially cylindrical shape that has a base in the shape of a "W" on the lower surface of the bone plate and a peripheral surface that extends vertically, i.e., orthogonally to the lower surface of the bone plate. In contrast, the central section and the upper section of the slot each have a substantially cylindrical shape with their bases on the side surface of the bone plate, while their peripheral surfaces extend transversely, i.e., parallel to the transverse axis of the bone plate that extends orthogonally to the longitudinal axis between the two side surfaces of the bone plate. Due to the fact that the central axis of the cylinder of the central section and the upper section of the slot extends orthogonally to the central axis of the cylinder of the lower section of the slot, the lower section as well as the central section and the upper section have to be manufactured in a separate subsequent working process that results in a complex and expensive manufacture of the slot.

[0005] The window size of the plate according to WO 2017 / 024416 is determined only by the width W of the slot feature at the lower surface of the plate. Thus, it is intuitive that not only the closing but also the opening of the slot is restricted by the undercut feature located at the lower plate surface (as disclosed in the prior invention).

Prior Art Documents

Patent Document

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a method for manufacturing a biphasic bone plate that enables the manufacture of a bone plate in a single manufacturing step without reducing the resistance of the biphasic bone plate to tensile force and valgus bending. A further object of the present invention is the possibility of manufacturing a small slot width (less than 0.3 mm) without the need to assemble different plate components.

Means for Solving the Problems

[0008] The present invention solves the problems brought about by a bone plate having the features of claim 1 and a method for manufacturing a bone plate having the features of claim 10.

[0009] The advantages of the bone plate according to the present invention are essentially - Straight slots can be formed in a single manufacturing step from a single workpiece using a standard wire erosion or water jet cutting process, Thereby reducing manufacturing time, complexity, and thus manufacturing costs, and - Preventing catastrophic failure (valgus bending) of the bone plate under non-physiological loading conditions.

[0010] Furthermore, the idea of the present invention of shifting the undercut feature (open limiter) away from the lower plate surface to different positions and orientations provides the following further unexpected advantages. · The possibility of forming slots including undercut features in a single manufacturing step involving established robust manufacturing processes such as wire erosion. · The formability of slots including undercut features having a desired slot width of less than 0.3 mm. Other manufacturing processes, such as sink erosion, cannot produce such narrow slots. Another assembly from different parts can be avoided. · The contact area on the lower plate surface when the slot is closed becomes a flat surface over the entire width of the bone plate, thereby enabling uniform and distributed contact and limiting the occurrence of particle wear. Non-linear but curved slots (e.g., omega) do not allow for uniform slot closure due to the non-uniform bending lines of the bone plate.

[0011] The bone plate according to the present invention shows a significant increase in strength [ultimate load (eccentric axial compression) exceeding twice that for fracture] and fatigue performance (cycles exceeding four times that for fracture) compared to standard bone plates. Thereby, the risk of clinical implant fracture is significantly reduced.

[0012] Further advantageous embodiments of the present invention can be described as follows.

[0013] In a particular embodiment, the width W of the slot measured in a plane parallel to the central plane between the longitudinal axis and the side surface is variable. This configuration allows the advantage that the slot width can significantly expand in a T-shape towards the upper surface, for example, to form stress distribution characteristics.

[0014] In other embodiments, the undercut feature has an S-shape, a Z-shape, or a W-shape in a plane parallel to the central plane between the longitudinal axis and the side surface. Due to the S-shape, Z-shape, or W-shape of the undercut feature, two adjacent protrusions are formed that further provide resistance to the torsion of the bone plate.

[0015] In a further embodiment, the dimensions of the undercut feature are selected such that when the bone plate is bent longitudinally in the direction in which it attempts to widen the width of the slot, the extension of the lower surface is limited to a maximum of 3 mm, preferably a maximum of 1 mm.

[0016] In a further embodiment, the slot has a width W in the range of 0.1 to 1.3 mm, preferably in the range of 0.15 to 0.30 mm, measured on the lower surface of the bone plate in the direction of the longitudinal axis.

[0017] In a further embodiment, the slot is configured in the shape of a "T" or an "L" at the upper part of the bone plate, and the free end of the vertical leg of the "T" or "L" extends into the undercut feature of the slot, and the two horizontal legs of the "T" or the horizontal leg of the "L" extend in the direction of the longitudinal axis of the bone plate and are preferably curved.

[0018] In yet another further embodiment, the walls of the slot on the lower surface of the bone plate are angled with respect to each other such that they are parallel when the slot is closed. The slot is deformed by the bending of the bone plate which originally results in an inclination of the parallel walls and thus a line contact of the slot when closed. This too, as before, can result in significant metal wear in the contact area. The formation of the angled slot to compensate for the inclination increases the contact area and thus reduces wear.

[0019] In another embodiment, the dimensions of the slot are selected such that when the slot is fully closed on the lower surface of the bone plate, the length of the lower surface is shortened by a maximum of 1 mm, preferably a maximum of 0.3 mm, so that the width W measured on the lower surface becomes equal to 0.

[0020] In another embodiment, the slot allows the plate to bend vertically by at least an amount of 1.0°, preferably at least 1.5°.

[0021] In a further embodiment, the bone plate comprises two or more slots.

[0022] In another embodiment, the bone plate further comprises means for attaching a bone healing sensor, preferably in the form of screw holes suitable for receiving fasteners.

[0023] In other embodiments, the bone plate is configured such that when the width W of the slot measured on the lower surface of the bone plate is greater than 0, the bending stiffness of the flexible section is reduced by 75% compared to a conventional bone plate without a slot, and when the width W of the slot measured on the lower surface of the bone plate under compression in the eccentric axis direction is equal to 0, the bending stiffness of the flexible section is increased by 75% compared to a conventional bone plate without a slot. The aforementioned increase in bending stiffness of about 75% compared to a conventional bone plate without a slot depends greatly on the loading mode and can be significantly higher.

[0024] In other embodiments, the dimensions of the slot are selected such that the bone plate can bend, in addition to the inherent bendability of the plate without slots vertically, by an amount of up to 20°, preferably up to 10°.

[0025] In other embodiments, the width W of the slot measured on the lower surface of the bone plate in the direction of the longitudinal axis is greater than 0.25 mm, preferably greater than 0.20 mm.

[0026] In yet other embodiments, the width W of the slot measured on the lower surface of the bone plate in the direction of the longitudinal axis is less than 0.30 mm, preferably less than 0.25 mm.

[0027] In a further embodiment, the bone plate has a maximum thickness in the range of 6 mm to 13 mm.

[0028] In a further embodiment, the bone plate has a thickness in the range of 10 mm to 12 mm, preferably for use on the femur.

[0029] In a further embodiment, the bone plate has a thickness in the range of 4 mm to 9 mm, preferably for use on the humerus or tibia.

[0030] In other embodiments, the bone plate has a width in the range of 14 mm to 22 mm, preferably in the range of 17 mm to 21 mm, measured on the lower surface perpendicular to the longitudinal axis at the position of the slot.

[0031] In other embodiments, a force in the range of 50 to 400 N, preferably in the range of 100 to 300 N, acting substantially parallel to the longitudinal axis of the bone plate with an offset of 10 mm to 30 mm from the lower surface of the bone plate, is sufficient to close the slot at the lower surface of the bone plate such that the width W becomes equal to zero.

[0032] In a further embodiment, the slot has a curved shape as seen in the longitudinal cross-section of the bone plate, and the curved shape expands from the lower surface towards the upper surface.

[0033] Preferably, the plate thickness T gradually decreases towards both ends of the bone plate from the slot.

[0034] In a further embodiment, at least one of the plurality of plate holes is configured to receive an angular stability locking screw at a predetermined angle.

[0035] In a further embodiment, at least one of the plurality of plate holes is configured to receive a variable angle locking screw.

[0036] In other embodiments, the plate holes have different sizes to receive bone screws of different diameters.

[0037] Preferably, the bone plate is formed from titanium or a titanium alloy, preferably stainless steel.

[0038] Preferably, the bone plate is used for the treatment of fractures.

[0039] In a further embodiment, the slot is completely or partially covered by an elastic biocompatible membrane, which is preferably impermeable to micro and nano metal wear particles. This can achieve the advantage of being able to confine potential wear particles generated by intermittent slot closing contact within the membrane.

[0040] In a further embodiment, the bone plate is pre - contoured to a statistically derived shape of a particular anatomical region.

[0041] According to a further aspect of the present invention, there is provided a method for manufacturing a bone plate according to the present invention, wherein the slot is formed using a wire erosion or water jet cutting process.

[0042] Preferably, the slot is generated by passing an erosion or cutting tool through one of the sides of the bone plate and guiding the tool straight towards the opposite side, thereby forming a through - slot.

[0043] Hereinafter, with reference to the following attached drawings, special embodiments of the present invention will be described as an example.

Brief Description of the Drawings

[0044]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0045] Figs. 1 to 6 show typical embodiments of the bone plate 1 according to the present invention. The bone plate 1 includes a lower surface 2, an upper surface 3, a maximum thickness T measured between the lower surface and the upper surface 2, 3, a left side surface 4, a right side surface 5, a longitudinal axis 6, and a plurality of plate holes 7 extending from the lower surface 2 to the upper surface 3. Further, the bone plate 1 is provided with a slot 8 extending from the left side surface 4 to the right side surface 5 on the lower surface 2. The slot 8 has a width W of 0.15 mm measured in a plane parallel to the longitudinal axis 6 and the central plane 16 between the side surfaces 4, 5. The hollow space defined by the slot 8 forms the shape of a straight cylinder (also called a right cylinder) and extends from the left side surface 4 to the right side surface 5. The slot 8 is provided with an undercut feature 9 that limits the opening of the slot 8 when the bone plate 1 is bent longitudinally in a direction in which the bone plate 1 attempts to widen the width of the slot 8.

[0046] Typically but not limited to, the undercut feature 9 of the slot 8 has an S-shape in a plane parallel to the longitudinal axis 6 and the side surfaces 4, 5, whereby two complementary protrusions 13a, 13b (Fig. 5) are formed by two arcuate portions of the S-shape. The undercut feature 9 of the slot 8 is located in the lower part of the bone plate 1, that is, a part of the bone plate 1 closer to the lower surface 2 of the bone plate 1.

[0047] The S shape is configured as an "S" standing upright in the direction of the longitudinal axis 6 such that one arcuate portion of the "S" extends into the vertical section of the slot 8. The slot 8 extends from the lower surface 2 of the bone plate 1 towards the upper surface 3 of the bone plate 1 and has a width W measured at the lower surface 2 of the bone plate 1 in a plane parallel to the longitudinal axis 6 and the central plane 16 between the side surfaces 4, 5. The complementary protrusions 13a, 13b formed by the S-shaped slot 8 are spaced apart from each other by a width of the slot 8 that may be smaller than or slightly larger than the width W of the slot 8 measured at the lower surface 2 of the bone plate 1 in the case of the unloaded bone plate 1. Thereby, when the bone plate 1 is bent, the two protrusions 13a, 13b engage with each other from the left side surface 4 to the right side surface 5 so as to lock against further bending of the bone plate 1 in this direction and against torsion about the longitudinal axis 6 of the bone plate 1 as tensile forces are generated on the lower surface 2 of the bone plate 1.

[0048] In the embodiment shown in FIGS. 1-6, the slot 8 is configured with a "T" shape in the upper part of the bone plate 1, i.e., in the portion of the bone plate 1 closer to the upper surface 3 of the bone plate 1. Thereby, the free end of the vertical leg of the "T" extends into the S-shaped portion of the slot, and the two horizontal legs of the "T" are curved and extend in the direction of the longitudinal axis 6 of the bone plate 1.

[0049] Due to slot 8, the flexural rigidity (also called bending rigidity) of bone plate 1 is significantly reduced in the region of slot 8, whereby the bone plate 1 is divided into three longitudinal sections, namely, a flexible section 10 in the region of slot 8 and two rigid sections 11a, 11b, and each rigid section extends to one side end of the bone plate 1. The plate holes 7 are positioned in the rigid sections 11a, 11b such that bone fasteners extending through the plate holes 7 and fixed to bone fragments are disposed in the rigid sections 11a, 11b of the bone plate 1. Therefore, the load acting on the bone plate 1 due to the patient's body weight or the force exerted by the patient is applied to the rigid sections 11a, 11b of the bone plate 1. In the flexible section 10, the bone plate 1 is formed as a beam-shaped cross-bridge portion 12 that is vertically restricted by the upper side, that is, by the horizontal leg of the "T" shape of slot 6 and the upper surface 3 of the bone plate 1.

[0050] Since the bending rigidity of the cross-bridge portion 12 is lower compared to the rigid sections 11a, 11b of the bone plate 1, the bone plate 1 first bends in the flexible section 10. Under the bending load applied in this way, compressive and tensile forces are developed in the direction of the longitudinal axis 6, and these forces cause stress in the bone plate 1. When the influence of the bending moment caused by the applied bending load tends to close slot 8, the maximum compressive stress is seen above slot 6, while the maximum tensile stress is seen on the upper surface 3.

[0051] The upper side 14 of the slot 8 extends along the two horizontal legs of the "T". Since the deflection of the bridging portion 12 depends more on the length of the bridging portion 12 than on the stress imposed on the bridging portion 12 by the bending moment, the shape of the flexible section 10 of the bone plate 1 can be optimized with respect to the desired deflection required to close the slot 8 at the lower surface 2 of the bone plate 1 and with respect to the maximum stress occurring in the bridging portion 12. Furthermore, due to the curved shape of the two horizontal legs of the "T", the height of the bridging portion 12 measured between the upper side 14 of the slot 8 and the upper surface 3 of the bone plate 1 varies along the length of the bridging portion 12 from the minimum height of the longitudinal mid-plane of the bridging portion 12 to the maximum height at the transition of the bridging portion 12 of the bone plate 1 to the rigid sections 11a, 11b. The bending stiffness of the bridging portion 12 at a specific position along the longitudinal axis 6 depends on the height of the bridging portion 12 at this position, whereby the bridging portion 12 can be configured with a variable bending stiffness that particularly adapts the change in bending stiffness to optimize the stress distribution of the bridging portion 12.

[0052] Alternatively, an effect similar to that of the T-shaped slot 8 can be achieved by a form of the slot 8 having an "L" shape in the upper part of the bone plate 1, i.e., the part of the bone plate 1 closer to the upper surface 3 of the bone plate 1. Thereby, the free end of the vertical leg of the "L" extends into the S-shaped portion of the slot 8, and the horizontal leg of the "L" is straight and extends in the direction of the longitudinal axis 6 of the bone plate 1 (FIG. 7).

[0053] According to Euler-Bernoulli bending theory, the curvature of the neutral axis of the bridging portion 12 is proportional to the bending moment and inversely proportional to the bending stiffness (flexural rigidity), and the bending stiffness is defined as the product E*I, where E is also called the modulus of elasticity or Young's modulus, and I is the second moment of area of the cross-section of the bridging portion 12.

[0054] Regarding the narrowing and closing of the slot 8, only the deflection of the bridging portion 12 is relevant, and the final bending deformation of the rigid sections 11a, 11b of the bone plate 1 can be ignored.

[0055] The transition from the flexible phase to the rigid phase of the bone plate 1 occurs when the slot 8 closes on the lower surface 2 of the bone plate 1, and thus, as described above, depends on the bending moment, the bending rigidity of the cross-bridge portion 12, and the deflection of the cross-bridge portion, which is a function of the length of the cross-bridge portion 12 measured in the direction of the longitudinal axis 6 of the bone plate 1.

[0056] Typical but not limiting, the embodiments of the bone plate 1 according to the present invention shown in FIGS. 1-6 are configured for application to metaphyseal fractures such as the distal femur, proximal humerus or distal / proximal tibia. One rigid section 11b of the bone plate 1 is spoon-shaped, and the slot 8 is disposed near the spoon-shaped rigid section 11b. Further, the plate holes 7 of the spoon-shaped rigid section 11b are disposed in an enlarged portion disposed at the end on the bone plate 1, while the plate holes 7 of the other rigid section 11a are disposed along the longitudinal axis 4 of the bone plate 1 and are equally spaced from each other (FIG. 6). By these means, the bone plate 1 is pre-contoured to a statistically derived shape of a specific anatomical region.

[0057] Typically, but not limited thereto, the bone plate 1 is formed from stainless steel. In another embodiment, the bone plate 1 may be formed from titanium or a titanium alloy. The bone plate 1 has a plate thickness T that gradually decreases from the region having the slot 8 towards both ends of the plate 1. For a specific application of the bone plate 1 to the humerus or tibia, the thickness T in the region of the slot 8 is typically about 8 mm, but is not limited thereto. Further, the bone plate 1 typically but not limitingly has a width of about 17 mm measured on the lower surface 2 perpendicular to the longitudinal axis 6 at the position of the slot 8. Alternatively, for use on the femur, the bone plate 1 may typically but not limitingly have a plate thickness T of about 12 mm in the region of the slot 8.

[0058] The bone plate 1 has a biphasic stiffness behavior in order to promote secondary bone healing, i.e., to allow for interfragmentary motion required at low functional loads (flexible phase) and to maximally limit this motion when the slot closes at higher magnitudes of functional load (rigid phase). The bending stiffness of the flexible section 10 is reduced by 75% compared to a conventional bone plate without slots when the width W of the slot 8 measured at the lower surface 2 of the bone plate 1 is greater than 0 (flexible phase), and is increased by 75% compared to a conventional bone plate without slots when the width W of the slot 8 measured at the lower surface 2 of the bone plate 1 in eccentric axial compression is equal to 0 (rigid phase).

[0059] The plate holes 7 can be configured as variable angle holes. Alternatively, one or more of the plate holes 7 can be configured to receive an angle stable locking screw at a predetermined angle. For this purpose, one or more of the plate holes 7 can be conical or can comprise a conical female thread. The bone plate 1 further comprises under-sized threaded holes 15 suitable for receiving fasteners so as to provide means for attaching a bone healing sensor. In another alternative embodiment, the plate holes 7 may have different sizes for receiving bone screws of different diameters.

[0060] Typical but not limiting, slot 8 has a width W of approximately 0.3 mm as measured on the lower surface 2 of bone plate 1 in the direction of longitudinal axis 6. The width W of slot 8 is such that bone plate 1 can bend up to approximately 10° in addition to the inherent bendability of a plate without similar slots in the longitudinal direction, and such that the width W measured at lower surface 2 becomes equal to 0. It is selected to enable the length of lower surface 2 to be shortened by a maximum of approximately 1 mm when slot 8 is completely closed at lower surface 2 of bone plate 1. Thereby, a force of approximately 200 N acting substantially parallel to longitudinal axis 6 of bone plate 1 with an offset of approximately 20 mm from lower surface 2 of bone plate 1 is sufficient to close slot 8 at lower surface 2 of bone plate 1 such that width W becomes equal to 0. The slot dimensions in the region of undercut feature 9 are such that the extension of lower surface 2 is typically but not limited to a maximum of 2 mm when bone plate 1 is bent longitudinally in a direction to widen the width of slot 8.

[0061] Figures 9 to 12 show another embodiment of the bone plate 1 according to the present invention, which differs from the embodiment of FIGS. 1 to 6 only in different forms of the slot 8 seen in a plane parallel to the central plane 16 between the sides 4 and 5. Thereby, FIG. 10 shows a zigzag undercut feature 9 in a plane parallel to the longitudinal axis 6 and the central plane 16 between the sides 4 and 5, rather than an S-shape, and FIG. 9 shows a W-shaped undercut feature 9 in a plane parallel to the longitudinal axis 6 and the central plane 16 between the sides 4 and 5. This W-shaped undercut feature 9 forms a nose portion 17 that protrudes from one of the rigid sections 11a (FIG. 3) of the bone plate 1 along the longitudinal axis 6 and has an enlarged free end, and the adjacent end of the other rigid section 11b (FIG. 3) of the bone plate 1 that forms the nose portion 17 is formed in a concave shape so as to form a surrounding portion 18 that receives the nose portion 17 such that the movement of the nose portion 17 relative to the surrounding portion 18 is restricted in both directions along the longitudinal axis 6 of the bone plate 1. In the non-deformed state of the bone plate 1, the slot 8 extends between the nose portion 17 and the surrounding portion 18 with a width W measured at the lower surface 2. The surrounding portion 18 surrounds the nose portion 17 by more than 180° in a field of view orthogonal to the central plane 16 between the sides 4 and 5. Thereby, the bending of the bridging portion 12 is restricted in both directions, that is, in a first direction in which the maximum tensile force occurs on the upper surface 3 and in a second direction in which the maximum compressive force occurs on the upper surface 3, so as to provide resistance to tensile force and valgus bending. Due to the S-shape, Z-shape or W-shape of the undercut feature, two adjacent protrusions are formed to further provide resistance to the torsion of the bone plate. FIG. 11 shows a slot 8 that is configured in the same manner as the slot 8 of FIGS. 1 to 6 having a "T" shape in the upper part of the bone plate 1, that is, the part of the bone plate 1 closer to the upper surface 3 of the bone plate 1, but one arcuate portion of the "S" extends in, and the free end of the vertical leg of the "T" extends into the S-shaped portion of the slot 8 such that the vertical section of the slot 8 extending from the lower surface 2 to the upper surface 3 of the bone plate 1 is located at the center between the two horizontal legs of the "T". A further alternative embodiment is shown in FIG. 12, which differs from the embodiment of FIG. 11 only in that the walls of the slot 8 on the lower surface 2 of the bone plate 1 are angled with respect to each other by an angle α such that they are parallel when the slot 8 is closed.As a result, when a load is applied to the bone plate 1, the contact area between the walls of the slot 8 increases when the slot 8 closes, thereby reducing metal wear in the contact area.

[0062] As described above, the width of the slot 8 can extend significantly, for example, in a T - shape, towards the upper surface 3 of the bone plate 1 in order to form the stress distribution feature portion. In another embodiment of the bone plate 1 shown in FIG. 8, the width W of the slot 8 measured in a plane parallel to the central plane 16 between the longitudinal axis 6 and the side surfaces 4, 5 is significantly enlarged along the horizontal leg of the T - shaped slot 8. Thereby, the flexible section 10 of the bone plate 1 comprises a chamber 19 extending from the upper side 14 of the slot 8. The chamber 19 is open on the lower surface 2 of the bone plate 1 via the slot 8. The chamber 19 is preferably suitable for accommodating one or more sensors (not shown) for measuring strain, displacement, load or pressure or temperature. Alternatively, or in addition, the chamber 19 is suitable for accommodating one or more actuators, for changing the mechanical properties of the implant, or for storing drugs for controlled release, or for providing a space for callus growth.

[0063] In yet another alternative embodiment, the slot 8 is completely or partially covered by an elastic biocompatible membrane that is impermeable to micro - and nano - metal wear particles so that potential wear particles generated by intermittent slot - closing contact can be trapped by the membrane. Alternatively, the slot 8 may be filled with a softer material to reduce the "dead space" and bind the wear particles.

[0064] According to the method for manufacturing the bone plate 1 according to the present invention, the slot 8 is formed using a wire erosion or water jet cutting process to generate the slot 8 by passing a water jet cutting tool through the bone plate 1 towards one of the side surfaces 4, 5 and guiding the tool straight towards the opposite side surface, thereby forming the through - slot 8.

[0065] Although the present invention has been described in conjunction with its specific embodiments, it will be apparent to those skilled in the art that many alternatives, modifications, and variations are possible. Accordingly, it is intended to embrace all such alternatives, modifications, and variations that fall within the scope of the appended claims.

[0066] It will also be understood that the specific features of the present invention described in connection with separate embodiments may be provided in combination in a single embodiment. Conversely, the various features of the present invention described in connection with a single embodiment may be provided separately or in any suitable partial combination or in any other described embodiment of the present invention as appropriate. Specific features described in connection with various embodiments should not be considered essential features of those embodiments unless the embodiments cannot operate without those elements.

Claims

1. A bone plate (1) having a lower surface (2), an upper surface (3), a maximum thickness T measured between the lower and upper surfaces (2, 3), a left side surface (4), a right side surface (5), a longitudinal axis (6), and a plurality of plate holes (7) extending from the lower surface (2) to the upper surface (3), the bone plate (1) further having a slot (8) with an opening in the lower surface (2), the slot extending through the bone plate from the left side surface (4) to the right side surface (5) and having a width W measured in a plane parallel to the central plane (16) and the longitudinal axis (6) between the left side surface (4) and the right side surface (5), (i) the slot (8) has an inner surface defining a hollow space that extends through the bone plate from the left side surface (4) to the right side surface (5) and through which a straight line can pass without contacting the inner surface of the slot, (ii) the slot (8) comprises an undercut feature (9) that limits the opening of the slot (8) when the bone plate (1) is bent longitudinally in a direction in which the bone plate attempts to widen the width of the slot (8), characterized in that it is a bone plate (1).

2. The bone plate (1) according to claim 1, characterized in that the width W of the slot (8) measured in a plane parallel to the central plane (16) between the longitudinal axis (6) and the side surfaces (4, 5) is variable.

3. The bone plate (1) according to claim 1 or 2, characterized in that the undercut feature (9) has an S-shape, a Z-shape, or a W-shape in a plane parallel to the central plane (16) between the longitudinal axis (6) and the side surfaces (4, 5).

4. The bone plate (1) according to any one of claims 1 to 3, characterized in that the dimensions of the undercut feature (9) are selected such that when the bone plate (1) is bent longitudinally in a direction in which the bone plate attempts to widen the width of the slot (8), the extension of the lower surface (2) is limited to a maximum of 3 mm.

5. The bone plate (1) according to any one of claims 1 to 4, characterized in that the slot (8) has a width W in the range of 0.1 to 1.3 mm measured in the lower surface (2) of the bone plate (1) in the direction of the longitudinal axis (6).

6. The slot (8) is formed in the upper part of the bone plate (1) in the shape of a "T" or an "L", and the free end of the vertical leg of the "T" or the "L" extends to the undercut feature (9) of the slot (8). The two horizontal legs of the "T" or the horizontal leg of the "L" extend in the direction of the longitudinal axis (6) of the bone plate (1). The bone plate (1) according to any one of claims 1 to 5, characterized in that.

7. The walls of the slot (8) on the lower surface (2) of the bone plate (1) are angled with respect to each other so as to be parallel when the slot (8) is closed. The bone plate (1) according to any one of claims 1 to 6, characterized in that.

8. The dimensions of the slot (9) are selected such that when the slot (6) on the lower surface (2) of the bone plate (1) is completely closed, the length of the lower surface (2) is shortened by at most 1 mm so that the width W measured on the lower surface (2) is equal to 0. The bone plate (1) according to any one of claims 1 to 7, characterized in that.

9. The slot (8) is characterized in that it allows the plate (1) to bend vertically by an amount of at least 1.0°. The bone plate (1) according to any one of claims 1 to 8, characterized in that.

10. A method for manufacturing the bone plate (1) according to any one of claims 1 to 9, characterized in that the slot (8) is formed using a wire erosion or water jet cutting process.

Images