Bone fixation system and preoperative planning method for revision surgery

Abstract

The application provides a bone fixation system and a preoperative planning method for revision surgery. The system comprises a bone screw for locking a bone plate to a bone, which comprises a screw head and a screw rod connected with the screw head; the screw head is part of a sphere and is provided with external threads, and the screw rod is provided with external threads; the bone plate is provided with a screw hole; the screw hole is a through hole for the screw rod to pass through and lock the screw head, and comprises a locking portion for locking the screw head, which is part of a spherical hole; when the bone screw locks the bone to the bone, the bone screw is in a selected direction relative to the bone plate; wherein a diameter D1 of a projection C1 of the spherical hole is less than a diameter D2 of a projection C2 of the sphere; the diameter D1 is the diameter of the projection C1 of the spherical hole; and the diameter D2 is the diameter of the projection C2 of the sphere. In the swing angle range, the bone screw can be screwed into the bone at any angle, the depth is limited and the screw is prevented from being reversed, and the postoperative revision is convenient.

Description

Technical Field

[0001] This invention belongs to the field of orthopedic application technology, and particularly relates to a bone fixation system and a preoperative planning method for revision surgery. Background Technology

[0002] In orthopedic fixation devices (including internal and external fixation devices), they are usually connected to the bone by fasteners such as screws, threaded bolts, or fixation pins.

[0003] Currently, common metal fixation plates are made of titanium alloy. After implantation, the large difference in elastic modulus between titanium alloy and bone leads to stress shielding effect, which in turn exacerbates bone resorption and causes postoperative complications such as delayed healing.

[0004] Currently, the locking mechanism of non-metallic implants on the market mainly relies on expansion locking, snap locking, or the use of a portion of metal material for locking. However, these products are complex to manufacture, increasing costs and the financial burden on patients. Moreover, they are cumbersome to operate, prolonging surgical time and increasing the risk of various surgical complications.

[0005] In addition to securing the screws to the fixation device, it is usually necessary to ensure that the screws can be inserted into the fixation device at an angle selected by the surgeon.

[0006] However, existing bone screw devices cannot simultaneously achieve the functions of screwing fasteners into the bone at any angle, preventing fasteners from retracting, and limiting the screwing depth of fasteners. Summary of the Invention

[0007] The purpose of this invention is to provide a bone fixation system and a preoperative planning method for revision surgery. Within a certain swing angle range, bone screws can be inserted into the bone at any angle, simultaneously achieving depth limitation and preventing regression, and facilitating postoperative revision. The technical solution adopted is as follows: A bone fixation system, comprising: Bone screw 2, used to lock bone plate 1 to bone, includes screw head 21 and screw shank 22 connected to screw head 21; the screw head 21 is part of a sphere and has external threads, and the screw shank 22 has external threads; The bone plate 1 has nail holes 11 thereon; The nail hole 11 is for the nail rod 22 to pass through and lock the nail head 21. It is a through hole and includes a locking part 111 for locking the nail head 21. The locking part 111 is part of a spherical hole. When the bone screw 2 locks the bone plate 1 to the bone, the bone screw 2 is in a selected orientation relative to the bone plate 1; Wherein, diameter D1 < diameter D2; diameter D1 is the diameter of the projection C1 of the spherical hole; diameter D2 is the diameter of the projection C2 of the sphere.

[0008] Preferably, the diameter D2 ranges from 4.7mm to 5.3mm, and the diameter D1 ranges from 4.3mm to 5mm.

[0009] Preferably, the diameter D2 is 5 mm and the diameter D1 is 4.6 mm.

[0010] Preferably, the nail hole 11 further includes: The guide portion 110 and the tail portion 112 are connected by the locking portion 111; The guide portion 110 is disposed away from the bone, and the tail portion 112 is disposed close to the bone; The tail portion 112 is a cylindrical hole with a diameter D3 greater than the diameter D4 of the nail rod 22.

[0011] Preferably, the guide portion 110 includes a curve Q1 and a curve Q2 connected to both ends of the curve Q1; both the curve Q1 and the curve Q2 are formed on the bone plate 1; Wherein, curve Q1 is set away from the bone; curve Q2 is set close to the bone; The curve Q2 is connected to a section of the outer end face W of the locking part 111; The curve Q2 lies between the central axis of the spherical hole and the projection of the curve Q1 onto the bone plate 1.

[0012] Preferably, provided that the nail rod 22 can pass through the tail 112, the included angle between the central axis of the nail rod 22 and the central axis of the locking part 111 is in the range of -36.42° to 36.42°.

[0013] The thickness of the central region of the bone plate 1 ranges from 1.5 to 3.2 mm, and the thickness of the edge region of the bone plate 1 ranges from 1.3 to 2.7 mm.

[0014] Preferably, the bone plate 1 is made of non-metallic materials, including non-absorbable biomaterials such as PEEK, PEEK+carbon fiber, PEEK+calcium silicate, PEEK+HA, PEKK, PEKK+carbon fiber, PEKK+calcium silicate, and high molecular weight polyethylene.

[0015] Preferably, the external threads on the nail head 21 and the nail shank 22 have the same pitch; The external thread on the nail head 21 is a three-thread thread, and the external thread on the nail shank 22 is a single-thread thread.

[0016] A preoperative planning method for revision surgery, based on a bone fixation system, includes the following steps: Step 1: Remove the bone screw 2 that has been locked onto the bone; Step 2: Compare the screw head 21 of the removed bone screw 2 and select the bone screw to be used in the revision surgery; The selection rules are as follows: The diameter of the head of the bone screw to be used in the revision surgery is equal to the diameter of the head 21 of the removed bone screw 2. Furthermore, the diameter of the shank of the bone screw to be used in the revision surgery is greater than the diameter of the shank 22 of the removed bone screw 2; Furthermore, the pitch of the bone screw used in the revision surgery is equal to the pitch of the screw shank 22 of the removed bone screw 2. Step 3: Install the bone screws selected in Step 2 onto the bone and bone plate 1.

[0017] Compared with the prior art, the advantages of the present invention are: (1) During the operation, the bone screw is inserted into the bone at any angle within the swing angle range.

[0018] (2) Projection C1 and projection C2 partially overlap to achieve depth limitation.

[0019] (3) Locking to prevent backing.

[0020] The diameter of the nail head 21 is greater than the diameter of the locking part 111, and the bone plate 1 and the bone nail 2 are made of different materials. During the process of screwing the bone nail 2 into the bone, the nail head 21 can be interference-fitted to hold the locking part 111 on the bone plate, and locking is achieved by the deformation of the bone plate 1.

[0021] (4) Easy to repair after surgery. If a later surgery is required for repair, the original bone screw can be removed and a bone screw with a larger diameter rod can be implanted to achieve re-locking between the bone screw and the bone plate. Attached Figure Description

[0022] Figure 1 This is a diagram showing the state of the bone screw in the bone and locked to the bone plate in Example 1; Figure 2 This is a partial sectional view of the bone plate in Example 1; Figure 3 This is a dimensional diagram of the nail holes in Example 1; Figure 4 This is a top view of the bone plate in Example 2; Figure 5 This is a structural diagram of the guide section in Example 2; Figure 6 This is a diagram showing the state before the bone screw is screwed into the bone and locked in the bone plate when the swing angle is 0. Figure 7 This is a diagram showing the state of the bone screw before it is screwed into the bone and locked in the bone plate when the swing angle is 36.42°. Figure 8This is a diagram showing the state of the bone screw before it is screwed into the bone and locked in the bone plate when the swing angle is -36.42. Figure 9 A diagram showing the swing angle; Figure 10 This is a diagram showing the state of the bone screw locked in the bone plate when the swing angle is 0. Figures 11-12 This is a schematic diagram showing the dimensions of the bone plate.

[0023] Among them, 1-bone plate, 11-pin hole, 110-guide part, 111-locking part, 112-tail; 2- Bone screw, 21- Screw head, 22- Screw shaft. Detailed Implementation

[0024] The bone fixation system of the present invention and the preoperative planning method for revision surgery will be described in more detail below with reference to the schematic diagrams, which illustrate preferred embodiments of the invention. It should be understood that those skilled in the art can modify the invention described herein while still achieving the advantageous effects of the invention. Therefore, the following description should be understood as being of general knowledge to those skilled in the art and is not intended to limit the invention.

[0025] Example 1

[0026] In this embodiment, the bone plate 1 is a flat plate, and the guide part 110 is a tapered hole.

[0027] like Figures 1-2 As shown, a bone fixation system includes: The bone screw 2 is used to lock the bone plate 1 to the bone. It includes a screw head 21 and a screw shank 22 connected to the screw head 21. The screw head 21 is part of a sphere and has external threads, and the screw shank 22 has external threads.

[0028] Bone nail 2 is made of medical-grade titanium alloy.

[0029] Bone plate 1, with nail holes 11. Bone plate 1 is an anterior cervical artery plate, made of PEEK-CF material.

[0030] In other embodiments, the bone plate 1 may also be made of non-absorbable biomaterials such as PEEK, PEEK+carbon fiber, PEEK+calcium silicate, PEEK+HA, PEKK, PEKK+carbon fiber, PEKK+calcium silicate, and high molecular weight polyethylene, and absorbable biomaterials such as L-lactic acid, meso-lactic acid, glycolic acid, and trimethylene carbonate.

[0031] The nail hole 11 is a through hole for the nail bar 22 to pass through and lock the nail head 21. It includes a locking part 111 for locking the nail head 21, which is part of a spherical hole.

[0032] When the bone screw 2 locks the bone plate 1 to the bone, the projection C1 of the spherical hole partially overlaps with the projection C2 of the sphere, as shown below. Figure 1 As shown; bone screw 2 is in the selected orientation relative to bone plate 1.

[0033] Wherein, the diameter D1 of projection C1 is less than the diameter D2 of projection C2.

[0034] The phrase "the bone screw 2 is in a selected direction relative to the bone plate 1" means that the angle of the bone screw's swing has been selected by the doctor before the bone screw 2 is passed through the screw hole 11 and screwed into the bone.

[0035] like Figure 2 As shown, the nail hole 11 includes: The guide portion 110 and the tail portion 112 are connected by a locking portion 111; The guide section 110 is positioned away from the skeleton, while the tail section 112 is positioned close to the skeleton; The tail portion 112 is used to cooperate with the nail hole guide portion 110 and the nail hole locking portion 111 so that the bone nail 2 can swing in the nail hole 1. It is a cylindrical hole with a diameter D3 greater than the diameter D4 of the nail rod 22.

[0036] The guide part 110 is used for guidance; the locking part 111 is used to lock the head 21 of the bone screw 2, rather than for universal adjustment; the tail part 112 is for the nail rod 22 to pass through, and has a diameter of 4.1 mm, which is larger than the diameter of the nail rod 22. For example, the diameter of the nail rod 22 can be 4 mm.

[0037] The guide portion 110 includes curves Q1 and Q2; both curves Q1 and Q2 are formed on the bone plate 1.

[0038] The surface area ratio between the guide part 110, the locking part 111 and the tail part 112 is 8:21:10.

[0039] The external threads on the nail head 21 and the nail shank 22 have the same pitch, with a pitch P = 1.75. The external thread on the nail head 21 is a three-start thread, and the external thread on the nail shank 22 is a single-start thread.

[0040] The diameter D2 ranges from 4.7mm to 5.3mm, and the diameter D1 ranges from 4.3mm to 5mm.

[0041] In this embodiment, the diameter D2 is 5 mm and the diameter D1 is 4.6 mm.

[0042] like Figure 3 As shown, the height (thickness) of the locking part 111 along the Y-axis is 1.8 mm. The height (thickness) of the bone plate 1 along the Y-direction is 2.8 mm.

[0043] like Figure 3 As shown, the angle of the bevel cut of the locking part 111 is 45°.

[0044] Regardless of the thickness of the bone plate 1, the height of the locking part 111 is always 1.8, and the other two dimensions (the height of the guide part 110 and the tail part 112) are equally divided.

[0045] During the machining of nail hole 11, the machining is always perpendicular to the nail hole. The direction perpendicular to nail hole 11 is the Y-axis.

[0046] Example 2 In this embodiment, the bone plate 1 is a curved plate.

[0047] like Figures 4-12 As shown, a bone fixation system includes: The bone screw 2 is used to lock the bone plate 1 to the bone. It includes a screw head 21 and a screw shank 22 connected to the screw head 21. The screw head 21 is part of a sphere and has external threads, and the screw shank 22 has external threads.

[0048] Bone nail 2 is made of medical-grade titanium alloy.

[0049] Bone plate 1, with nail holes 11. Bone plate 1 is an anterior cervical artery plate, made of PEEK-CF material.

[0050] In other embodiments, the bone plate 1 may also be made of non-absorbable biomaterials such as PEEK, PEEK+carbon fiber, PEEK+calcium silicate, PEEK+HA, PEKK, PEKK+carbon fiber, PEKK+calcium silicate, and high molecular weight polyethylene, and absorbable biomaterials such as L-lactic acid, meso-lactic acid, glycolic acid, and trimethylene carbonate.

[0051] The nail hole 11 is a through hole for the nail bar 22 to pass through and lock the nail head 21. It includes a locking part 111 for locking the nail head 21, which is part of a spherical hole.

[0052] When the bone screw 2 locks the bone plate 1 to the bone, the projection C1 of the spherical hole partially overlaps with the projection C2 of the sphere; the bone screw 2 is in the selected orientation relative to the bone plate 1.

[0053] Wherein, the diameter D1 of projection C1 is less than the diameter D2 of projection C2.

[0054] The phrase "the bone screw 2 is in a selected direction relative to the bone plate 1" means that the angle of the bone screw's swing has been selected by the doctor before the bone screw 2 is passed through the screw hole 11 and screwed into the bone.

[0055] like Figure 6 As shown, the nail hole 11 includes: The guide portion 110 and the tail portion 112 are connected by a locking portion 111; The guide section 110 is positioned away from the skeleton, while the tail section 112 is positioned close to the skeleton; The tail portion 112 is used to cooperate with the nail hole guide portion 110 and the nail hole locking portion 111 so that the bone nail 2 can swing in the nail hole 1. It is a cylindrical hole with a diameter D3 greater than the diameter D4 of the nail rod 22.

[0056] like Figure 5 As shown, the guide portion 110 includes a curve Q1 and a curve Q2 connected to both ends of the curve Q1; both curve Q1 and curve Q2 are formed on the bone plate 1; Among them, curve Q1 is set away from the skeleton; curve Q2 is set close to the skeleton. A section of the curve Q2 is connected to the outer end face W of the locking part 111; Curve Q2 lies between the central axis of the spherical hole and the projection of curve Q1 onto bone plate 1.

[0057] That is, Figure 5 As shown, the guide section 110 is higher on one side and lower on the other side to ensure a large swing angle.

[0058] The guide part 110 is used for guidance; the locking part 111 is used to lock the head 21 of the bone screw 2 instead of playing a universal adjustment role; the tail part 112 is used to allow the nail rod 22 to pass through, and has a diameter of 4.1 mm, which is larger than the diameter of the nail rod 22.

[0059] The external threads on the nail head 21 and the nail shank 22 have the same pitch, with a pitch P = 1.75. The external thread on the nail head 21 is a three-start thread, and the external thread on the nail shank 22 is a single-start thread.

[0060] The diameter D2 ranges from 4.7mm to 5.3mm, and the diameter D1 ranges from 4.3mm to 5mm.

[0061] In this embodiment, the diameter D2 is 5 mm and the diameter D1 is 4.6 mm.

[0062] Provided that the nail rod 22 can pass through the tail 112, the angle (swing angle) between the central axis of the nail rod 22 and the central axis of the locking part 111 ranges from -36.42° to 36.42°.

[0063] In this embodiment, similarly, regardless of the thickness of the bone plate 1, the height of the locking part 111 is 1.8, and the other two dimensions (the height of the guide part 110 and the tail part 112) are equally divided.

[0064] During the machining of nail hole 11, the machining is always perpendicular to the nail hole. The direction perpendicular to nail hole 11 is the Y-axis.

[0065] like Figure 6 As shown: At this point, the swing angle of the bone screw is 0, meaning that the center line of the bone screw coincides with the center line of the screw hole.

[0066] The depth limit is achieved by partially overlapping projections C1 and C2.

[0067] "Depth limit" refers to: the locking part 111 locks the head 21 of the nail to limit the length of the nail rod 22 that is screwed into the bone.

[0068] In existing technologies, during surgery, the screw rod completely penetrates the bone plate, meaning the screw rod is twisted through the bone plate.

[0069] like Figures 6-7 As shown, the swing angles are 36.42° and -36.42°, respectively.

[0070] like Figure 9 As shown, this illustrates the range of swing angles.

[0071] Depend on Figures 7-9 Within the swing angle range of the nail rod 22, the swing angle of the bone nail 2 can be arbitrarily selected.

[0072] like Figure 11 As shown, the radius of the circle containing the curved surface of the bone plate away from the bone is 22 mm; the radius of the circle containing the curved surface of the bone plate close to the bone is 25 mm.

[0073] The thickness of the center of bone plate 1 is 2.8 mm, and the thickness of the edge of bone plate 1 is 2.6 mm.

[0074] like Figure 12 As shown, the radius of the circle containing the curved surface of the bone plate away from the bone is 182.8 mm; the radius of the circle containing the curved surface of the bone plate close to the bone is 180 mm.

[0075] A preoperative planning method for revision surgery includes the following steps: Step 1: Remove the bone screw 2 that has been locked onto the bone; Step 2: Compare the screw head 21 of the removed bone screw 2 and select the bone screw to be used in the revision surgery; The selection rules are as follows: The diameter of the head of the bone screw to be used in the revision surgery is equal to the diameter of the head 21 of the removed bone screw 2. Furthermore, the diameter of the shank of the bone screw to be used in the revision surgery is greater than the diameter of the shank 22 of the removed bone screw 2; Furthermore, the pitch of the bone screw used in the revision surgery is equal to the pitch of the screw shank 22 of the removed bone screw 2. Step 3: Pass the bone screw selected in Step 2 through the screw hole 11 and screw it into the bone, and finally lock the bone screw into the locking part 111 on the bone plate 1.

[0076] If the first surgery fails, a second bone screw with a larger outer diameter can be used as a replacement. The revision screw has the same pitch as the screw used in the first surgery, but the screw shank is thicker and the head size is the same. This ensures that during revision surgery, the revision screw can continue the operation along the thread channel formed by the original screw in the bone, without affecting its use and maintaining good compatibility.

[0077] In summary, the advantages of this invention are: (1) During the operation, within the swing angle range, no matter from which angle the doctor screws the bone screw 2 into the bone, the head of the bone screw 2 will always be embedded (interference fit) into the screw hole 11. That is, the doctor can choose the angle of the bone screw relative to the bone plate.

[0078] (2) The depth limit is achieved by the partial overlap of projection C1 and projection C2.

[0079] During the tightening process of bone screw 2 and bone plate 1, due to the tightening positioning part (locking part 111), after bone screw 2 is tightened to the position, it cannot be further tightened (screwed in), thus achieving depth limitation.

[0080] In existing technologies, during surgery, the screw rod completely penetrates the bone plate, meaning the screw rod is twisted through the bone plate.

[0081] (3) Locking to prevent backing.

[0082] The diameter of the nail head 21 is greater than the diameter of the locking part 111, and the bone plate 1 and the bone nail 2 are made of different materials. During the process of screwing the bone nail 2 into the bone, the nail head 21 can be interference-fitted to hold the locking part 111 (spherical hole) on the bone plate. Locking is achieved by the deformation of the bone plate 1, without the need for complex screw anti-retraction devices on the market.

[0083] (4) The guide part 110 makes the swing angle as large as possible.

[0084] The screw rod is screwed into the vertebral bone. Because a larger swing angle can be formed between the axis of the screw hole and the axis of the bone screw, the length of the bone plate can be shorter than that of a traditional plate if the intended purpose is achieved (a shorter plate is better during surgery).

[0085] In addition, the swing angle and the size and depth of the nail hole tail 112 are also related.

[0086] The larger the inner diameter of hole 112 at the tail of the nail hole, the greater the swing angle. However, the larger the inner diameter of hole 112 at the tail of the nail hole, the easier it is to screw the nail through.

[0087] (5) Postoperative revision is convenient.

[0088] If revision surgery is needed later, simply remove the original bone screw 2 and implant a bone screw with a larger diameter shaft to re-lock the bone screw to the bone plate. This method is simpler, more convenient, and safer than other revision surgeries on the market.

[0089] (6) Plastic plates (PEEK-CF material) can achieve better fit with the vertebral bones than metal plates.

[0090] The bone screws and bone plates are made of different materials. During the operation, the screws can compress the plastic plate, allowing the plastic plate to better fit the vertebral bone.

[0091] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A bone fixation system for revision surgery, characterized in that, include: A bone screw (2) is used to lock the bone plate (1) to the bone. It includes a screw head (21) and a screw shank (22) connected to the screw head (21). The screw head (21) is part of a sphere and has external threads, and the screw shank (22) has external threads. The bone plate (1) has nail holes (11) thereon. The nail hole (11), for the nail rod (22) to pass through and lock the nail head (21), is a through hole and includes a locking part (111) for locking the nail head (21), the locking part (111) being part of a spherical hole; the locking part (111) is a continuous spherical concave surface without threads; When the bone screw (2) locks the bone plate (1) to the bone, the bone screw (2) is in a selected direction relative to the bone plate (1); the bone plate (1) and the bone screw (2) are made of different materials. During the process of screwing the bone screw (2) into the bone, the screw head (21) is pressurized to hold the locking part (111) on the bone plate. Locking is achieved by deforming the bone plate (1). Where diameter D1 < diameter D2; Diameter D1 is the diameter of the projection C1 of the spherical hole; diameter D2 is the diameter of the projection C2 of the sphere. The diameter of the head of the bone screw to be used in the revision surgery is equal to the diameter of the head (21) of the bone screw (2) that has been removed; and the diameter of the shaft of the bone screw to be used in the revision surgery is greater than the diameter of the shaft (22) of the bone screw (2) that has been removed.

2. The bone fixation system according to claim 1, characterized in that, The diameter D2 ranges from 4.7mm to 5.3mm, and the diameter D1 ranges from 4.3mm to 5mm.

3. The bone fixation system according to claim 2, characterized in that, The diameter D2 is 5 mm, and the diameter D1 is 4.6 mm.

4. The bone fixation system according to claim 1, characterized in that, The nail hole (11) further includes: The guide portion (110) and the tail portion (112) are connected by the locking portion (111); The guide portion (110) is disposed away from the bone, and the tail portion (112) is disposed close to the bone; The tail (112) is a cylindrical hole with a diameter D3 greater than the diameter D4 of the nail rod (22).

5. The bone fixation system according to claim 4, characterized in that, The guide portion (110) includes a curve Q1 and a curve Q2 connected to both ends of the curve Q1; both the curve Q1 and the curve Q2 are formed on the bone plate (1). Wherein, curve Q1 is set away from the bone; curve Q2 is set close to the bone; The curve Q2 is connected to a section of the outer end face W of the locking part (111); The curve Q2 is located between the central axis of the spherical hole and the projection of the curve Q1 onto the bone plate (1).

6. The bone fixation system according to claim 1, characterized in that, The thickness of the central region of the bone plate (1) ranges from 1.5 to 3.2 mm, and the thickness of the edge region of the bone plate (1) ranges from 1.3 to 2.7 mm.

7. The bone fixation system according to claim 1, characterized in that, The bone plate (1) is made of non-metallic materials, which are non-absorbable biological materials, including PEEK, PEEK+carbon fiber, PEEK+calcium silicate, PEEK+HA, PEKK, PEKK+carbon fiber, PEKK+calcium silicate, and high molecular weight polyethylene.

8. The bone fixation system according to claim 1, characterized in that, The external threads on the nail head (21) and the nail shank (22) have the same pitch; The external thread of the nail head (21) is a three-thread thread, and the external thread on the nail shank (22) is a single-thread thread.

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