A new anterior locking plate for C2, C3 internal fixation

Abstract

This invention discloses a novel anterior locking bone plate specifically for internal fixation of the second and third cervical vertebrae, belonging to the field of orthopedic implant technology. The bone plate comprises an upper plate for fixation to the second cervical vertebra and a lower plate for fixation to the third cervical vertebra, the upper and lower plates being an integral structure. In the sagittal plane, the angle between the upper and lower plates is 100-150 degrees; in the horizontal plane, both the upper and lower plates are curved surfaces, with the upper plate having a radius of curvature of 9-10 mm and the lower plate 11-12 mm; in the coronal plane, the plate is an isosceles trapezoid, narrower at the top and wider at the bottom. Based on the location of the second cervical vertebra, this invention finds a suitable approach that avoids obstruction of the surgery by the mandible while providing maximum holding force and stability. It optimizes the transverse and longitudinal curvature and overall shape of the bone plate, improving its conformity to the morphology of the second cervical vertebra, making the surgery safer and more fitting, and providing reliability and convenience unattainable by traditional bone plates.

Description

Technical Field

[0001] This invention relates to the field of orthopedic implant technology, and in particular to a novel anterior locking bone plate specifically designed for internal fixation of the second and third cervical vertebrae. Background Technology

[0002] For a period of time after its initial description, vertebral avulsion fractures were considered simple avulsion fractures. However, with increased research and a deeper understanding, the impact of second cervical vertebral avulsion fractures on cervical spine stability has received increasing attention and recognition. Some experts believe that the triangular protrusion region anterior and inferior to the axis is the true vertebral body of the axis and the main stress-bearing structure. Teardrop-shaped fractures of the axis differ from teardrop-shaped fractures of the lower cervical vertebrae and often lead to biomechanical instability of the upper cervical spine. Traditional anterior cervical locking plates often fail to fit well with the second and third cervical vertebrae due to physiological changes in the second cervical vertebra.

[0003] For example, Johnson & Johnson's DePuy Synthes has a Skyline anterior cervical titanium plate system. During their research, the inventors of this application discovered that the second cervical vertebra is more anteriorly protruding and narrower than other cervical vertebrae. The Skyline anterior cervical titanium plate system did not take this into account in its design for the anterior cervical approach. The plate often cannot fit well with the second and third cervical vertebrae, especially at the junction of the odontoid process and vertebral body of the second cervical vertebra, where there is often significant narrowing and curvature changes. Due to length and curvature issues, the Skyline anterior cervical titanium plate system is often difficult to place in the appropriate position. Previous studies have not reported any targeted improvements to the surgical characteristics and anatomical morphology of the second cervical vertebra. Furthermore, because the second cervical vertebra is located deep in the neck, the surgical risk is already high. The obstruction of the mandible further narrows the surgical area compared to other cervical vertebrae, increasing the difficulty of the surgery. In the event of a fracture, the traditional plate is difficult to maneuver precisely near the mandible, posing a high risk of irreversible damage to the cervical spinal cord, or even high-level paraplegia. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a novel anterior locking bone plate specifically for internal fixation of the second and third cervical vertebrae, which can fit well with the second and third cervical vertebrae.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] A novel anterior locking bone plate specifically designed for internal fixation of the second and third cervical vertebrae includes a plate body comprising an upper plate for fixation to the second cervical vertebra and a lower plate for fixation to the third cervical vertebra. The upper and lower plate bodies are integrally formed.

[0007] In the sagittal plane, the included angle between the upper plate and the lower plate is 100-150 degrees;

[0008] In the horizontal plane, both the upper plate and the lower plate are curved surfaces, with the upper plate having a radius of curvature of 9-10 mm and the lower plate having a radius of curvature of 11-12 mm.

[0009] Within the coronal plane, the plate is an isosceles trapezoid, narrower at the top and wider at the bottom.

[0010] Furthermore, in the sagittal plane, the included angle between the upper plate and the lower plate is 110-145 degrees.

[0011] Furthermore, in the horizontal plane, the radius of curvature of the upper plate is 9.426 mm, and the radius of curvature of the lower plate is 11.2547 mm.

[0012] Furthermore, the length of the upper base of the isosceles trapezoid is 11.5-13.5 mm, and the length of the lower base is 14-18 mm.

[0013] Furthermore, the height of the isosceles trapezoid is 21-24 mm.

[0014] Furthermore, a pair of upper screw holes are provided on both sides of the upper end of the upper plate in the horizontal direction. In the sagittal plane, the axis of the upper screw holes is inclined upward and the angle between it and the vertical line of the upper plate is 25-35 degrees.

[0015] The lower plate has a pair of screw holes on both sides of its lower end in the horizontal direction, and the axis of the screw holes is perpendicular to the lower plate in the sagittal plane.

[0016] Furthermore, both the upper and lower screw holes are configured such that the screws located therein have 5 degrees of freedom of movement in both the horizontal and vertical directions along their axis.

[0017] Furthermore, the length of the screw in the upper screw hole is 15-25mm, and the length of the screw in the lower screw hole is 13-17mm.

[0018] Furthermore, a cam lock is provided on the lower side of the upper screw hole and the upper side of the lower screw hole.

[0019] Furthermore, a cross-shaped window is provided in the middle of the plate.

[0020] Furthermore, the method for determining the included angle α between the upper and lower plates in the sagittal plane during the design of the anterior locking bone plate includes:

[0021] Step 10: Select 3 points in the midsagittal plane of the vertebral body. The first point is the most convex point M on the anterior surface of the second cervical vertebra, the second point is the most concave point U on the anterior surface of the second cervical vertebra, and the third point is point D at one-third of the anterior surface of the third cervical vertebra.

[0022] Step 11: Construct lines MU and MD to obtain angle ∠UMD, and measure the size of this angle to obtain the size of the included angle α.

[0023] Furthermore, the method for determining the radius of curvature of the lower plate in the horizontal plane during the design of the anterior locking bone plate includes:

[0024] Step 20: Within the horizontal plane of the vertebral body where point D is located, select two nail insertion points D1 and D2 symmetrically on both sides of point D;

[0025] Step 21: Calculate the radius of the circle defined by points D, D1, and D2, which is the radius of curvature of the lower plate.

[0026] The present invention has the following beneficial effects:

[0027] The present invention relates to a novel anterior locking bone plate specifically designed for internal fixation of the second and third cervical vertebrae. Based on the location of the second cervical vertebra, a suitable approach has been found that avoids obstruction of the operation by the mandible while providing maximum holding force and stability. Furthermore, based on the unique "narrow at the top and wide at the bottom" anatomical characteristics of the anterior edge of the second cervical vertebra, the transverse and longitudinal curvature and overall shape of the bone plate have been optimized. The improved plate better conforms to the shape of the second cervical vertebra, making the operation safer and more fitting, and providing a level of reliability and convenience that traditional bone plates cannot achieve. Attached Figure Description

[0028] Figure 1 This is a front structural diagram of the novel anterior locking bone plate of the present invention specifically for internal fixation of the second and third cervical vertebrae;

[0029] Figure 2 for Figure 1 A schematic diagram of the side structure of the novel anterior locking bone plate shown;

[0030] Figure 3 for Figure 1 A three-dimensional structural schematic diagram of the novel anterior locking bone plate is shown.

[0031] Figure 4 This is a side view of the second and third cervical vertebrae.

[0032] Figure 5 for Figure 1 A schematic diagram showing the installation position of the novel anterior locking bone plate on the cervical spine;

[0033] Figure 6 for Figure 1 The diagram shows the structure of the novel anterior locking bone plate installed on the posterior side of the cervical spine.

[0034] Figure 7 This is a schematic diagram showing the measurement of the angle α between the upper and lower plates in the sagittal plane.

[0035] Figure 8 This is a schematic diagram for measuring the radius of curvature of the lower plate in a horizontal plane. Detailed Implementation

[0036] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0037] This invention provides a novel anterior locking plate specifically for internal fixation of the second and third cervical vertebrae, such as... Figure 1-6 As shown, the system includes a plate 1, which comprises an upper plate 11 for fixing to the second cervical vertebra 5 and a lower plate 12 for fixing to the third cervical vertebra 6. The upper plate 11 and the lower plate 12 are integral structures.

[0038] In the sagittal plane, the included angle α between the upper plate 11 and the lower plate 12 is 100-150 degrees (e.g., ...). Figure 2 (as shown), preferably 110-145 degrees;

[0039] In the horizontal plane, both the upper plate 11 and the lower plate 12 are curved surfaces (e.g., ...). Figure 3 As shown), the radius of curvature R1 of the upper plate 11 is 9-10 mm, preferably 9.426 mm, and the radius of curvature R2 of the lower plate 12 is 11-12 mm, preferably 11.2547 mm.

[0040] In the coronal plane, plate 1 is an isosceles trapezoid, narrower at the top and wider at the bottom (e.g., ...). Figure 1 As shown in the figure, considering that the second cervical vertebra has a different anatomical structure than other vertebrae and is narrower at the proximal end, the upper end of the plate is narrower than the lower end to avoid excessive damage to the vertebra.

[0041] During their research, the inventors of this application discovered that the anterior margins of most cervical vertebrae are slightly convex, hillside-like shapes, while the anterior margin of the C2 vertebra (the second cervical vertebra) is... Figure 4 As shown in the diagram, the C2 vertebra, with its unique odontoid process, has a significantly different anterior margin compared to other vertebral bodies. In previous C2 vertebral anterior margin reduction and internal fixation surgeries, postoperative CT scans showed that although the fracture fragments were largely reduced, a large gap remained between the bone plate and the bone surface, indicating a high risk of fracture fragment displacement and poor recovery. Therefore, to design a bone plate that better conforms to the curvature of the C2 vertebra, this application establishes an angle α between the upper and lower plates, with a carefully selected angle α.

[0042] Furthermore, based on 3D imaging and cross-sectional views of the cervical spine, it is evident that due to the unique anatomical characteristics of the C2 vertebral body, its proximal course is narrower and more oblique. Previous bone plates often failed to conform well to the C2 vertebral body, failing to achieve optimal fit at the proximal end (i.e., at the C2 vertebral body). Consequently, the bone plate typically only fits well on one side of the C2 vertebral body in the horizontal direction, leaving a significant gap on the other side. Therefore, to design a bone plate that better conforms to the curvature of the C2 vertebral body, this application ensures that both the upper and lower plates are curved surfaces in the horizontal plane, and the curvature has been rationally selected. (See reference for details.) Figure 5 , where number 7 is the center line of the screw hole.

[0043] As can be seen from the frontal structural diagram of the vertebral body, the anterior edge of the vertebral body becomes narrower towards the proximal end. In the past, bone plates did not have an anatomical design that conformed to the anterior edge of the C2 vertebral body. The width of the proximal end of the bone plate was often the same as that of the distal end. In order to better conform to the anatomy, the front of the plate in this application is an isosceles trapezoid that is narrower at the top and wider at the bottom.

[0044] In summary, the novel anterior locking bone plate of the present invention, specifically for internal fixation of the second and third cervical vertebrae, has found a suitable approach based on the location of the second cervical vertebra. This approach avoids obstruction of the surgery by the mandible while providing maximum holding force and stability. Furthermore, based on the unique "narrow at the top and wide at the bottom" anatomical characteristics of the anterior edge of the second cervical vertebra, the transverse and longitudinal curvature and overall shape of the bone plate have been optimized. The improved plate better conforms to the shape of the second cervical vertebra, making the surgery safer and more fitting. It provides a level of reliability and convenience that traditional bone plates cannot achieve.

[0045] In this application, the length of the upper base L1 of the isosceles trapezoid is preferably 11.5-13.5 mm, the length of the lower base L2 is preferably 14-18 mm, and the height is preferably 21-24 mm. This height selection allows the entry point on the second cervical vertebra to be located at the odontoid process, further improving the stability of the cervical vertebra and the bone plate.

[0046] like Figure 1 and Figure 6 As shown, the upper plate 11 has a pair of upper screw holes 111 on both sides of its upper horizontal direction. In the sagittal plane, the axis of the upper screw holes 111 is inclined upward and the angle γ between it and the perpendicular line of the upper plate 11 is 25-35 degrees. Considering that the anatomical structure of the C2 vertebra is different from other vertebrae and is closer to the head, the surgical field is often narrow during surgery. This angle γ can avoid the influence of the patient's mandible on the surgical operation, which can make the operation more convenient and greatly reduce the surgical risk. In addition, considering that the fracture of the anterior edge of the C2 vertebra is often a fracture of the anteroinferior edge, and the fracture line is often oblique, the setting of this angle γ can make the direction of the proximal screw perpendicular to the fracture line, and the oblique setting of the screw can more fully engage the C2 vertebra, improve the screw holding force, and increase the fixation stability.

[0047] The lower plate 12 has a pair of screw holes 121 on both sides of the lower end in the horizontal direction. In the sagittal plane, the axis of the screw holes 121 is perpendicular to the lower plate 12. Considering that the C3 vertebra is relatively small (compared to the C2 vertebra), the fact that the axis of the screw holes is perpendicular to the lower plate can ensure that the plate and the C3 vertebra are firmly connected after the screws are fixed.

[0048] To facilitate screw insertion, both the upper screw hole 111 and the lower screw hole 121 can be configured such that the screw located therein has 5 degrees of freedom of movement in both the horizontal and vertical directions along its axis (see reference). Figure 6 ).

[0049] The length of the screw in the upper screw hole 111 can be 15-25 mm, allowing the screw to extend from the anterior half of the C2 vertebral body to the posterior edge of the junction between the vertebral body and the odontoid process. The length of the screw in the lower screw hole 121 can be 13-17 mm, allowing the screw to span most of the C3 vertebral body, maximizing the screw's holding force and further improving stability. A cam lock (not shown, a conventional technique in this field, will not be described further here) can also be provided on the lower side of the upper screw hole 111 and the upper side of the lower screw hole 121. Figure 1 (No. 13 is the cam lock mounting hole) to prevent the screw from coming out; a cross-shaped window 14 can also be provided in the middle of the plate 1 to facilitate the use of instruments to clamp the plate or to perform bone grafting through the window.

[0050] In the design of the anterior locking plate of this application, the preferred method for determining the angle α between the upper and lower plates in the sagittal plane (i.e., the method for measuring angle α) is as follows:

[0051] Step 10: As Figure 7 As shown, three points are selected in the midsagittal plane (projection diagram) of the vertebral body. The first point is the most convex point M on the anterior surface of the C2 vertebral body, the second point is the most concave point U on the anterior surface of the C2 vertebral body, and the third point is point D at one-third of the anterior surface of the C3 vertebral body.

[0052] Step 11: Construct lines MU and MD to obtain angle ∠UMD, and measure the size of this angle to obtain the size of the included angle α.

[0053] Furthermore, the preferred method for determining the radius of curvature of the lower plate in the horizontal plane is as follows:

[0054] Step 20: As Figure 8 As shown, within the horizontal plane of the vertebral body where point D is located (projection diagram), two nail entry points D1 and D2 are selected symmetrically on both sides of point D; specifically, the positions of the nail entry points can be selected based on experience, for example, the straight-line distance between the two nail entry points is selected as 9.6mm based on experience;

[0055] Step 21: Calculate the radius of the circle defined by points D, D1, and D2, which is the radius of curvature of the lower plate.

[0056] Similarly, the radius of curvature of the upper plate in the horizontal plane can be determined, which will not be elaborated here.

[0057] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A design method for an anterior locking bone plate specifically used for internal fixation of the second and third cervical vertebrae, wherein the anterior locking bone plate comprises a plate body, characterized in that, The plate includes an upper plate for fixing to the second cervical vertebra and a lower plate for fixing to the third cervical vertebra, wherein the upper plate and the lower plate are an integral structure. In the horizontal plane, both the upper plate and the lower plate are curved surfaces, with the upper plate having a radius of curvature of 9-10 mm and the lower plate having a radius of curvature of 11-12 mm. In the coronal plane, the plate is an isosceles trapezoid that is narrower at the top and wider at the bottom. The length of the upper base of the isosceles trapezoid is 11.5-13.5 mm, the length of the lower base is 14-18 mm, and the height of the isosceles trapezoid is 21-24 mm, so that the entry point on the second cervical vertebra is located at the odontoid process. The method for determining the included angle α between the upper and lower plates in the sagittal plane during the design of the anterior locking bone plate includes: Step A1: Select 3 points in the midsagittal plane of the vertebral body. The first point is the most convex point M on the anterior surface of the second cervical vertebra, the second point is the most concave point U on the anterior surface of the second cervical vertebra, and the third point is point D at one-third of the anterior surface of the third cervical vertebra. Step A2: Construct lines MU and MD to obtain angle ∠UMD, and measure the size of this angle to obtain the size of the included angle α.

2. The design method of the anterior locking bone plate according to claim 1, characterized in that, In the horizontal plane, the radius of curvature of the upper plate is 9.426 mm, and the radius of curvature of the lower plate is 11.2547 mm.

3. The design method of the anterior locking bone plate according to claim 1 or 2, characterized in that, The upper plate has a pair of upper screw holes on both sides of the upper end in the horizontal direction. In the sagittal plane, the axis of the upper screw holes is inclined upward and the angle between it and the vertical line of the upper plate is 25-35 degrees. The lower plate has a pair of screw holes on both sides of its lower end in the horizontal direction, and the axis of the screw holes is perpendicular to the lower plate in the sagittal plane.

4. The design method of the anterior locking bone plate according to claim 3, characterized in that, Both the upper and lower screw holes are configured such that the screws located therein have 5 degrees of freedom of movement in both the horizontal and vertical directions along their axis.

5. The design method of the anterior locking bone plate according to claim 3, characterized in that, The length of the screw in the upper screw hole is 15-25mm, and the length of the screw in the lower screw hole is 13-17mm.

6. The design method of the anterior locking bone plate according to claim 3, characterized in that, Cam locks are provided on the lower side of the upper screw hole and the upper side of the lower screw hole, and / or a cross-shaped window is provided in the middle of the plate.

7. The design method of the anterior locking bone plate according to claim 1, characterized in that, The method for determining the radius of curvature of the lower plate in the horizontal plane during the design of the anterior locking bone plate includes: Step B1: Within the horizontal plane of the vertebral body where point D is located, select two nail entry points D1 and D2 symmetrically on both sides of point D; Step B2: Calculate the radius of the circle defined by points D, D1, and D2, which is the radius of curvature of the lower plate.

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