Combined internal fixator for cross-micro-motion joint fixation and fixation method

Abstract

This invention belongs to the field of medical devices, specifically a combined internal fixator and fixation method for fixing joints with micro-motion. The combined internal fixator includes a first bone screw and a second bone screw. A movable connecting structure is provided between the connecting ends of the first and second bone screws. The movable connecting structure includes a groove and a shaft. The groove includes an insertion port and a mounting groove communicating with the insertion port. The mounting groove has a semi-circular cross-section. The shaft includes a semi-circular shaft adapted to the mounting groove, which is rotatably accommodated within the mounting groove, allowing the first and second bone screws to rotate relative to each other around a first radial axis. This invention, through a hook-groove sliding self-locking structure, achieves controllable micro-motion and integrated implantation for fixing joints with micro-motion. It has achieved significant technological advancements in preserving joint physiological function, simplifying surgical procedures, avoiding secondary surgeries, and reducing the incidence of complications. It has important clinical application value and is suitable for fixing joints with micro-motion.

Description

Technical Field

[0001] This invention belongs to the field of medical devices, specifically a combined internal fixator and fixation method for fixing joints with micro-motion. Background Technology

[0002] The human body contains several micro-movement joints. These joints allow for a certain range and direction of movement under physiological conditions to meet the biomechanical needs of daily activities and weight-bearing. Typical micro-movement joints include the distal tibiofibular syndesmosis (ankle), the distal radius and ulna joint (wrist), the acromioclavicular joint (shoulder), and some micro-movement segments of the spine. Taking the distal tibiofibular syndesmosis as an example, it is a micro-movement joint formed by the distal tibia and distal fibula. During ankle dorsiflexion and weight-bearing, it undergoes physiological rotation and translation, which is crucial for maintaining the biomechanical stability and normal function of the ankle joint.

[0003] Distal tibiofibular syndesmosis injury is a common ankle injury. If not treated properly, it can easily lead to ankle instability and traumatic arthritis. Currently, the mainstream techniques for internal fixation of distal tibiofibular syndesmosis injuries in clinical practice mainly include cortical screw fixation and loop plate elastic fixation.

[0004] Cortical screw fixation is a classic method for treating distal tibiofibular syndesmosis injuries. Its working principle involves inserting one or more cortical screws from the fibular side towards the tibial side, typically penetrating four layers of cortex (two layers of fibula and two layers of tibia), rigidly fixing the tibia and fibula in their normal anatomical position, providing a stable mechanical environment for the healing of the damaged distal tibiofibular ligament. However, this rigid fixation method has the following inherent drawbacks: First, screw fixation completely restricts the physiological micro-movements of the distal tibiofibular syndesmosis. This fixation mode leads to joint stress shielding, which may cause joint stiffness and limited range of motion in the long term, affecting the recovery of ankle joint function. Second, during postoperative weight-bearing or activity, the restricted micro-movements are converted into stress on the screws, easily leading to screw loosening or breakage. Once internal fixation failure occurs, a second surgery is often required to remove the screws, increasing patient suffering and medical costs. Finally, to avoid complications such as screw breakage and limited joint function caused by long-term screw retention, clinical practice usually recommends a second surgery to remove the screws 8–12 weeks postoperatively, after ligament healing. This not only increases the patient's financial burden and surgical risks, but also prolongs the overall recovery period.

[0005] To overcome the drawbacks of rigid fixation restricting micromovement, elastic fixation techniques, represented by loop plates (or button plates), have emerged and are widely used. These devices typically consist of plates or buttons located on the medial side of the tibia and the lateral side of the fibula, along with high-strength cables that pass through bone tunnels and connect the two. Their working principle is to provide continuous and flexible restraint through the elastic deformation of the cables, maintaining the reduction of the distal tibiofibular syndesmosis while allowing a certain degree of physiological micromovement in the joint. Although loop plate technology is an improvement over traditional screws in preserving joint function, it still has several shortcomings in clinical application: First, the implantation of loop plate systems requires precise preparation of bone tunnels, cable passage, and precise knotting on the lateral side of the fibula. The surgical procedure is cumbersome and requires a high level of surgeon experience. Improper operation can easily lead to tunnel position deviation, uneven cable tension, or loosening of knots, affecting the quality of fixation. Second, the cost of loop plates and related instruments is high, increasing the patient's medical expenses compared to traditional screw fixation. Secondly, prolonged postoperative stress poses a risk of loosening or breakage of buttons or cables, potentially leading to loss of repositioning. Buttons located on the skin surface may also cause soft tissue complications such as skin irritation and infection. Long-term micromovement of cables within the bone tunnel may cause bone abrasion and damage, affecting long-term stability. Finally, while loop plates provide some elastic fixation, their mechanical properties do not perfectly match complex physiological needs. In certain high-intensity activities or specific mechanical environments, their fixation strength may be insufficient, raising concerns about limited ability to control displacement. Furthermore, their fixation effectiveness is significantly affected by individual patient differences (such as osteoporosis or poor soft tissue conditions), limiting their applicability.

[0006] In summary, the rigid fixation of existing cortical screws cannot meet the physiological micromotion requirements of the distal tibiofibular syndesmosis; while the elastic fixation of loop plates can preserve micromotion, it has limitations. Summary of the Invention

[0007] To address the aforementioned shortcomings in the existing technology, this invention aims to provide a combined internal fixator for bridging micro-movement joints, so as to reliably maintain reduction, allow physiological micro-movement, simplify operation, and avoid secondary surgery.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a combined internal fixator for stabilizing trans-articular joints, comprising...

[0009] A first bone screw and a second bone screw, both of which have external threads;

[0010] The first bone screw has a first connecting end, and the second bone screw has a second connecting end; a movable connecting structure is provided between the first connecting end and the second connecting end; the movable connecting structure includes:

[0011] A groove is provided on one of the first connecting end and the second connecting end. The groove includes an insertion port opened on the side wall of the bone screw end and a mounting groove communicating with the insertion port. The cross-section of the mounting groove is semi-circular.

[0012] A shaft portion is disposed on the other of the first connecting end and the second connecting end, the shaft portion including a semi-circular shaft adapted to the mounting groove;

[0013] The semi-circular shaft is rotatably accommodated in the mounting groove, allowing the first bone screw and the second bone screw to rotate relative to each other about the first radial axis.

[0014] As a limitation of the present invention: one edge of the insertion port is flush with the edge of the mounting groove, and the dimension of the insertion port along the axial direction of the bone screw is adapted to the radius of the semi-circular cross section of the mounting groove.

[0015] As a limitation of the present invention: the shaft portion is also provided with a hook hole, which is formed between the semi-circular shaft and the bone nail body; the end of the groove portion can be inserted into the hook hole with a gap to form a hook engagement.

[0016] As a limitation of the present invention: the size of the hook hole in the first radial direction of the bone nail is greater than the size of the end of the groove in the first radial direction of the bone nail, so that the first bone nail can swing relative to the second bone nail around the second radial axis by a predetermined angle.

[0017] As a limitation of the present invention, the preset angle is 8°.

[0018] As a limitation of the present invention: the diameter of the mounting groove is larger than the diameter of the semi-circular shaft, so that the first bone screw can move relative to the second bone screw in the axial direction.

[0019] As a limitation of the present invention, the diameter of the mounting groove is 1.5 mm larger than the diameter of the semi-circular shaft.

[0020] As a limitation of the present invention: the first bone nail has a driving part, and the driving part is provided with a direction mark, the direction of which is the same as or opposite to the plane direction of the semi-circular axis.

[0021] As a limitation of the present invention: the nominal diameters of the first bone nail and the second bone nail are the same.

[0022] This invention also discloses a fixation method for stabilizing a transarticular joint, implemented using the aforementioned combined internal fixator, comprising the following steps:

[0023] Step 1: Using the movable connection structure, the first connecting end of the first bone screw and the second connecting end of the second bone screw are movably connected, so that the first bone screw and the second bone screw are coaxial;

[0024] Step 2: The first and second bone screws that have been connected are implanted as a whole into the pre-set bone tunnels of the first and second bones that constitute the micro-movement joint;

[0025] Step 3: Adjust the relative position and angle of the first and second bone screws to restore the micro-movement joint to its anatomical position, while preserving the relative axial movement and radial oscillation between the first and second bone screws.

[0026] By adopting the above technical solution, the beneficial effects achieved by the present invention compared with the prior art are as follows:

[0027] (1) This invention provides a movable connection structure between the first and second bone screws. Specifically, the first and second bone screws are rotatably accommodated in a semi-circular mounting groove via a semi-circular shaft, allowing them to rotate relative to each other around a first radial axis. Simultaneously, the design gap between the hook hole and the end of the groove allows the first and second bone screws to swing around a predetermined angle around a second radial axis. Furthermore, the design of the mounting groove diameter being larger than the semi-circular shaft diameter allows the first and second bone screws to move relative to each other along the bone screw axis. This structural design enables the combined internal fixator to retain physiological micro-movements in multiple directions while simultaneously fixing the micro-movement joint. Compared to the rigid fixation of traditional cortical bone screws, it avoids complications such as joint stiffness, limited range of motion, stress shielding, stress concentration, and screw breakage caused by completely restricting micro-movements. Compared to the elastic fixation of loop plates, the combination of rigid bone screws and the movable connection structure achieves more precise and controllable micro-movement retention, conforming to the biomechanical characteristics of micro-movement joints while avoiding risks such as wire cutting of bone and laxity.

[0028] (2) Traditional cortical screws are prone to complications such as screw breakage and limited joint function due to long-term retention, and usually require a second surgery to remove them 8-12 weeks after surgery. This invention releases the shear force and stress borne by the cross-joint fixation through a movable connection structure, making the internal fixator less prone to metal fatigue fracture, and its micro-movement characteristic will not have a long-term adverse effect on joint function, so there is no need for a second surgery to remove it. This not only avoids the surgical risks such as infection and bleeding caused by a second surgery, but also reduces the patient's pain, psychological burden and economic cost, which is in line with the surgical concept of rapid recovery.

[0029] (3) This invention achieves an integrated operation method of connection followed by implantation through a unique hook-groove sliding self-locking structure design. Specifically, before implantation, the operator only needs to connect the first and second bone screws at a specific angle through the insertion port, and then rotate them to align their axes, allowing them to be implanted as a whole through the drive unit in one go. This operation process is no different from the implantation of a single screw, eliminating the need for complex bone tunnel preparation, cable passage, and precise knotting operations as with loop plate fixation. Therefore, the surgical operation of this invention is simple and requires low technical skills, allowing even junior physicians to quickly master it, significantly shortening the operation time and reducing the risk of operational errors.

[0030] (4) The present invention ensures the reliability and stability of fixation through the following multiple structural designs: First, both the first and second bone screws are provided with external threads, which can be firmly anchored in the bone; second, the cooperation between the semi-circular shaft and the mounting groove provides a stable rotation center; third, the hook hole and the hook at the end of the groove form a self-locking structure, which maintains effective connection except at specific assembly angles, preventing disengagement; fourth, the movable connection structure is located in the micro-movement joint space, which maximizes the approximation of the natural movement characteristics of the joint and reduces the irritation of the internal fixation device to the surrounding soft tissues. Compared with the loop plate, the present invention avoids complications such as loosening or breakage of buttons or cables, skin irritation, and bone cutting and wear; compared with traditional screws, the present invention avoids the risk of screw breakage caused by stress concentration.

[0031] (5) The combined internal fixation device provided by the present invention does not depend on the anatomical morphology of a specific joint. Its core structure consists of two bone nails connected by a movable connection structure, which can be applied to the fixation of a variety of micro-movement joints throughout the body. Specifically, the present invention can be used for the repair of injuries to micro-movement joints such as the distal tibiofibular syndesmosis (ankle joint), distal radius and ulna joint (wrist joint), acromioclavicular joint, coracoclavicular joint, sternoclavicular joint, sacroiliac joint, and pubic symphysis.

[0032] (6) For simple micro-movement joint dislocation injuries without fractures, this invention can be implanted via percutaneous puncture or a small incision, without the need for extensive incision and exposure. This minimally invasive implantation method reduces surgical trauma, scar formation, and the risk of infection. At the same time, because this invention preserves the physiological micro-movement function of the joint, patients can begin functional exercises and early ambulation rehabilitation training earlier after surgery, shortening the overall recovery time and conforming to the treatment concept of modern orthopedic accelerated rehabilitation surgery.

[0033] (7) When this invention is used in open reduction and internal fixation surgery for distal fibular fractures, the combined internal fixator of this invention can be directly inserted into the compression screw holes of the plate after the distal fibular plate is placed, without the need for additional screws outside the plate. This good compatibility allows this invention to be used in conjunction with existing internal fixation systems, providing a flexible and convenient solution for the treatment of complex fractures combined with joint injuries.

[0034] In summary, this invention, through its hook-groove sliding self-locking structure, achieves controllable micro-motion and integrated implantation for micro-motion joint fixation. It has made significant technological progress in preserving joint physiological function, simplifying surgical procedures, avoiding secondary surgeries, and reducing the incidence of complications, and has important clinical application value. Attached Figure Description

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0036] Figure 1 This is a three-dimensional structural diagram of an embodiment of the present invention;

[0037] Figure 2 This is a cross-sectional view of an embodiment of the present invention;

[0038] Figure 3 This is a three-dimensional structural diagram of the first bone nail;

[0039] Figure 4 This is a three-dimensional structural diagram of the second bone nail;

[0040] Figure 5 This is a schematic diagram of the installation process according to an embodiment of the present invention;

[0041] Figure 6 This is an installation diagram of an embodiment of the present invention.

[0042] In the figure: 10-first bone nail, 11-first connecting end, 12-self-tapping tip, 20-second bone nail, 21-second connecting end, 22-driving part, 23-direction mark, 30-movable connecting structure, 31-groove, 311-insertion port, 312-mounting groove, 313-end, 32-shaft, 321-semi-circular shaft, 322-hooking hole, 40-tibia, 50-fibula. Detailed Implementation

[0043] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the combined internal fixator and fixation method for stabilizing transarticular joints described herein are preferred embodiments and are used only for illustration and explanation of the present invention, and do not constitute a limitation thereof.

[0044] To facilitate the description of the technical solution of the present invention, the following coordinate system is defined: the axial direction of the first or second bone screw is taken as the X-axis, and the plane perpendicular to the X-axis is taken as the radial plane. A first radial and a second radial axis, perpendicular to each other, are defined within the radial plane. The direction of the first radial axis is parallel to the first radial direction, and the direction of the second radial axis is parallel to the second radial direction.

[0045] This embodiment uses the combined internal fixation device provided by the present invention for internal fixation of distal tibiofibular syndesmosis injury as an example. The distal tibiofibular syndesmosis is a micro-movement joint formed by the distal end of the tibia 40 and the distal end of the fibula 50. During ankle dorsiflexion and weight-bearing, it is accompanied by physiological rotation around the first radial direction, physiological internal or external rotation around the second radial direction, and transverse translational micro-movement along the X-axis.

[0046] like Figure 1 As shown, the combined internal fixator for bridging micro-movement joints provided in this embodiment includes a first bone screw 10 and a second bone screw 20. Both the first bone screw 10 and the second bone screw 20 have external threads for forming a threaded connection with the bone. In this embodiment, the nominal diameters of the first bone screw 10 and the second bone screw 20 are the same, both 4.0 mm, to facilitate the use of the same specification tools for bone tunnel preparation. The first bone screw 10 has a first connecting end 11, and the second bone screw 20 has a second connecting end 21. A movable connecting structure 30 is provided between the first connecting end 11 and the second connecting end 21.

[0047] The movable connection structure 30 includes a groove 31 and a shaft 32. In this embodiment, the groove 31 is disposed at the first connecting end 11 of the first bone screw 10, and the shaft 32 is disposed at the second connecting end 21 of the second bone screw 20. It can be understood that in other embodiments, the groove 31 may also be disposed at the second bone screw 20, and the shaft 32 may be disposed at the first bone screw 10.

[0048] like Figure 3 As shown, the groove 31 includes an insertion port 311 formed on the side wall of the end of the bone screw and a mounting groove 312 communicating with the insertion port 311. The mounting groove 312 has a semi-circular cross-section, with its arc surface located at the bottom of the groove, i.e., on the side away from the insertion port 311. One edge of the insertion port 311 is flush with the edge of the mounting groove 312. The dimension of the insertion port 311 along the axial direction of the bone screw is adapted to the radius of the semi-circular cross-section of the mounting groove 312, so that when the first bone screw 10 is perpendicular to the second bone screw 20, the shaft portion 32 can enter the mounting groove 312 through the insertion port 311.

[0049] like Figure 4As shown, the shaft portion 32 includes a semi-circular shaft 321 adapted to the mounting groove 312, and a hook hole 322 formed between the semi-circular shaft 321 and the bone screw body, the hook hole being formed along a second radial direction. The arcuate surface of the semi-circular shaft 321 mates with the arcuate surface of the mounting groove 312, allowing them to rotate relative to each other. The semi-circular shaft 321 is rotatably accommodated within the mounting groove 312, allowing the first bone screw 10 and the second bone screw 20 to rotate relative to each other around a first radial axis, thereby accommodating the physiological rotation of the distal tibiofibular syndesmosis around the first radial direction. Simultaneously, the diameter of the mounting groove 312 is slightly larger than the diameter of the semi-circular shaft 321, allowing the first bone screw 10 and the second bone screw 20 to move relative to each other along the X-axis. In this embodiment, the diameter of the mounting groove 312 is 1.5 mm larger than the diameter of the semi-circular shaft 321, this gap corresponding to a lateral translational micro-movement of approximately 1.5 mm for the distal tibiofibular syndesmosis under load. In other embodiments, the amount of this lateral translational micro-movement gap can be designed as needed.

[0050] like Figure 2 As shown, the end 313 of the groove 31 can be inserted into the hook hole 322 with a gap, forming a hook engagement. Specifically, the hook hole 322 is formed on the second bone screw 20, located at the transition position between the semi-circular shaft 321 and the bone screw body. Since the radial dimension of the hook hole 322 is smaller than the nominal diameter of the second bone screw 20, in order to allow the end 313 of the groove 31 to be inserted into the hook hole 322 with a gap, the end of the first bone screw 10 has been structurally optimized in this embodiment. Specifically, as shown... Figure 3 As shown, the first connecting end 11 of the first bone screw 10 is partially removed on both sides along the first radial direction, forming a gradually narrowing tapered structure (in other embodiments, it can also be a stepped structure). In other words, the end 313 of the groove 31 maintains its original size in the second radial direction, while its size in the first radial direction is reduced so that its projected size in the first radial plane matches the opening size of the hook hole 322. This structural design allows the end 313 to be inserted into the hook hole 322 with a certain gap, ensuring smooth insertion and providing reliable limiting for subsequent hook engagement. With the above structure, when the first bone screw 10 and the second bone screw 20 are coaxially arranged, the end 313 is inserted into the hook hole 322, and the two form a gap fit. This gap fit allows the first bone screw 10 and the second bone screw 20 to swing relative to the first bone screw 10 around the second radial axis by a preset angle while maintaining the hook connection. In this embodiment, the preset angle is 8°, which satisfies the physiological internal and external rotation requirements of the tibiofibular syndesmosis while preventing excessive axial separation. In other embodiments, a suitable gap can be calculated as needed to design a preset angle that satisfies other internal and external rotation activities.

[0051] like Figure 2 As shown, when the first bone screw 10 and the second bone screw 20 are aligned axially, the semi-circular shaft 321 is fully accommodated in the mounting groove 312, and the end 313 of the groove 31 is inserted into the hook hole 322, forming a stable hook-locked state. At this time, the combined internal fixation device can be screwed in as a whole.

[0052] The end of the second bone screw 20 furthest from the first bone screw 10 has a driving part 22, on which a direction mark 23 is provided. The direction mark 23 points in the same direction as or opposite to the plane direction of the semi-circular shaft 321. In this embodiment, the driving part 22 is an internal hexagonal cap, and the direction mark 23 is a groove formed on the end face of the internal hexagonal cap. By observing the direction mark 23, the operator can determine the orientation of the internal semi-circular shaft 321, thereby accurately adjusting the connection angle before implantation. The end of the first bone screw 10 furthest from the second bone screw 20 has a self-tapping tip 12, which facilitates penetration into the bone during implantation and simplifies the surgical procedure.

[0053] The first bone screw 10 and the second bone screw 20 can be made of biocompatible metallic materials, including but not limited to titanium alloys, stainless steel, or cobalt-chromium-molybdenum alloys. Their external threads can be designed as cortical bone threads or cancellous bone threads according to clinical needs. The drive part 22 is not limited to an internal hexagonal form; it can also adopt standard drive forms such as external hexagonal, cross-shaped, or Torx-shaped grooves. The direction marking 23 is not limited to a groove form; it can also be a raised or planar marking formed by laser marking, embossing, etc.

[0054] After implantation, such as Figure 6 As shown, the movable connecting structure 30 of the combined internal fixation device is located in the gap between the fibula 50 and the tibia 40. During daily ankle activities, the combined internal fixation device can achieve relative movements of several degrees of freedom to simulate the physiological micro-movements of the distal tibiofibular syndesmosis:

[0055] Rotation about the first radial axis: The engagement of the semi-circular shaft 321 with the mounting groove 312 allows the first bone screw 10 and the second bone screw 20 to rotate relative to each other about the first radial axis. This movement corresponds to the physiological rotational micro-movement of the fibula 50 relative to the tibia 40.

[0056] Swinging around the second radial axis: The engagement of the hook hole 322 and the end of the groove 313 allows the first bone screw 10 and the second bone screw 20 to swing around the second radial axis at a preset angle. This movement corresponds to the physiological internal and external rotation of the fibula 50 relative to the tibia 40.

[0057] Relative movement along the X-axis: The diameter of the mounting groove 312 is larger than the diameter of the semi-circular shaft 321, allowing the first bone screw 10 and the second bone screw 20 to move relative to each other along the X-axis. This movement corresponds to the physiological lateral displacement of the fibula 50 relative to the tibia 40.

[0058] The three degrees of freedom of movement mentioned above are independent yet synergistic, enabling the combined internal fixation device to precisely simulate the physiological micro-motion characteristics of the tibiofibular syndesmosis while firmly fixing it. Compared to the rigid fixation of traditional cortical screws, it avoids joint stiffness, stress concentration, and screw breakage caused by completely restricting micro-motion; compared to the elastic fixation of loop plates, the combination of rigid bone screws and movable connecting structures achieves more precise and controllable micro-motion preservation, avoiding risks such as wire cutting of bone and laxity.

[0059] This embodiment also provides a fixation method for stabilizing a transarticular joint, achieved using the aforementioned combined internal fixator for stabilizing a transarticular joint. The method will be described in detail below in conjunction with a surgical procedure for repairing distal tibiofibular syndesmosis injuries.

[0060] (I) Preoperative preparation and bone tunnel preparation

[0061] The patient was placed in a supine position, and routine disinfection and draping were performed. Spinal or epidural anesthesia was administered. After successful anesthesia, the affected limb was routinely drained and a tourniquet was applied.

[0062] About 4 cm above the lateral malleolus, make a longitudinal incision about 1 cm long along the long axis of the fibula, and then cut through the skin, subcutaneous tissue and deep fascia in sequence. Bluntly dissect to the bone to expose the lateral cortical bone of the distal fibula.

[0063] C-arm fluoroscopy was used to confirm the separation of the tibiofibular syndesmosis. After dorsiflexing the ankle joint to approximately 5°, point reduction forceps or bone hooks were used to assist in reduction, anatomically aligning the fibula and tibia, and maintaining the reduced state.

[0064] Along the reduced tibiofibular syndesmosis, parallel to the tibiotalar joint surface, a guide pin is drilled horizontally 3 cm from the posterolateral aspect of the fibula towards the anteromedial aspect of the tibia at approximately 25°–30°. After confirming the appropriate position, direction, and depth of the guide pin with fluoroscopy, a hollow drill is used to drill through four layers of cortical bone (two layers of fibula and two layers of tibia) along the guide pin, forming a bone tunnel penetrating the fibula and tibia. The depth of the bone tunnel in the fibular segment and the total depth of the bone tunnel in the tibia and fibula are measured using a depth gauge, and a first bone screw of appropriate length (10 mm) and a second bone screw of appropriate length (20 mm) are selected.

[0065] (II) Assembly and implantation of internal fixation devices

[0066] The operator holds the second bone nail 20 and brings the first connecting end 11 of the first bone nail 10 and the second connecting end 21 of the second bone nail 20 close together at a mutually perpendicular angle. Figure 5 As shown, the insertion port 311 of the groove 31 of the first bone nail 10 is aligned with the semi-circular shaft 321 of the shaft 32 of the second bone nail 20, so that the semi-circular shaft 321 enters the mounting groove 312 through the insertion port 311.

[0067] Then, rotate the first bone screw 10 to align its axis with that of the second bone screw 20 (coaxial state). At this time, as... Figure 2 As shown, the semi-circular shaft 321 is completely accommodated in the mounting groove 312, and the end 313 of the groove 31 is inserted into the hook hole 322 to form a hook engagement, thus completing the assembly of the movable connection structure 30.

[0068] The first bone screw 10 and the second bone screw 20, already connected, are used as a whole. An internal hex screwdriver is connected to the drive part 22 of the first bone screw 10, and the entire combined internal fixation device is screwed into the pre-prepared bone tunnel. During screwing, the first bone screw 10 and the second bone screw 20 enter the bone tunnels of the fibula and tibia, respectively, and their external threads form a firm threaded connection with the bone. Because the first bone screw 10 and the second bone screw 20 are connected and coaxially positioned before implantation, the entire implantation process is no different from the implantation of a single screw, making it simple and quick.

[0069] (III) Reset Adjustment and Micromotion Retention

[0070] After implantation, the reduction of the inferior tibiofibular syndesmosis is observed using C-arm fluoroscopy. If the reduction is not ideal, the relative position and angle of the first bone nail 10 and the second bone nail 20 can be finely adjusted by slightly rotating or swinging the drive part 22 of the first bone nail 10 and utilizing the multi-degree-of-freedom adjustment capability provided by the movable connection structure 30 until the inferior tibiofibular syndesmosis is restored to its anatomical position and the inferior tibiofibular gap is measured to be less than 6 mm.

[0071] After adjustment, the movable connection structure 30 brings the combined internal fixation device into a dynamically stable state: on the one hand, the first bone screw 10 and the second bone screw 20 are firmly anchored in the bone through a threaded connection, providing reliable axial tension and maintaining a basically constant tibiofibular syndesmosis gap; on the other hand, the engagement of the semi-circular shaft 321 and the mounting groove 312 allows them to rotate relative to each other around the first radial axis, the engagement of the hook hole 322 and the end of the groove 313 allows them to swing relative to each other around the second radial axis, and the diameter difference between the mounting groove 312 and the semi-circular shaft 321 allows them to move relative to each other along the X-axis. Thus, the combined internal fixation device maintains anatomical reduction while precisely preserving the relative axial movement and radial swing of the first bone screw 10 and the second bone screw 20, thereby simulating the physiological micro-motion characteristics of the tibiofibular syndesmosis.

[0072] (iv) Examination and suturing

[0073] After implantation, check the ankle joint range of motion to confirm there is no significant restriction or abnormality. Irrigate the incision and suture layer by layer.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can make various improvements and modifications without departing from the spirit and 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 combined internal fixation device for stabilizing trans-articular joints, characterized in that, include A first bone screw and a second bone screw, both of which have external threads; The first bone screw has a first connecting end, and the second bone screw has a second connecting end; a movable connecting structure is provided between the first connecting end and the second connecting end; the movable connecting structure includes: A groove is provided on one of the first connecting end and the second connecting end. The groove includes an insertion port opened on the side wall of the bone screw end and a mounting groove communicating with the insertion port. The cross-section of the mounting groove is semi-circular. A shaft portion is disposed on the other of the first connecting end and the second connecting end, the shaft portion including a semi-circular shaft adapted to the mounting groove; The semi-circular shaft is rotatably accommodated in the mounting groove, allowing the first bone screw and the second bone screw to rotate relative to each other about the first radial axis.

2. The combined internal fixation device for stabilizing trans-articular joints according to claim 1, characterized in that, One edge of the insertion port is flush with the edge of the mounting groove, and the dimension of the insertion port along the axial direction of the bone screw is adapted to the radius of the semi-circular cross section of the mounting groove.

3. The combined internal fixation device for stabilizing trans-articular joints according to claim 2, characterized in that, The shaft portion is also provided with a hook hole, which is opened between the semi-circular shaft and the bone nail body; the end of the groove portion can be inserted into the hook hole with a gap to form a hook engagement.

4. The combined internal fixator for stabilizing trans-articular joints according to claim 3, characterized in that, The size of the hook hole in the first radial direction of the bone nail is larger than the size of the end of the groove in the first radial direction of the bone nail, so that the first bone nail can swing relative to the second bone nail around the second radial axis by a preset angle.

5. The combined internal fixator for stabilizing a trans-micro-motion joint according to claim 4, characterized in that, The preset angle is 8°.

6. The combined internal fixation device for stabilizing trans-micro-motion joints according to claim 1, characterized in that, The diameter of the mounting groove is larger than the diameter of the semi-circular shaft, allowing the first bone screw to move relative to the second bone screw axially.

7. The combined internal fixator for stabilizing a trans-micro-motion joint according to claim 6, characterized in that, The diameter of the mounting groove is 1.5 mm larger than the diameter of the semi-circular shaft.

8. The combined internal fixation device for stabilizing trans-articular joints according to any one of claims 1 to 7, characterized in that, The first bone screw has a driving part, and the driving part is provided with a direction mark. The direction of the direction mark is the same as or opposite to the plane direction of the semi-circular axis.

9. The combined internal fixator for stabilizing trans-articular joints according to claim 8, characterized in that, The first and second bone screws have the same nominal diameter.

10. A fixation method for fixing a trans-micro-motion joint, characterized in that, This is achieved using the combined internal fixation device as described in any one of claims 1 to 9, comprising the following steps. Step 1: Using the movable connection structure, the first connecting end of the first bone screw and the second connecting end of the second bone screw are movably connected, so that the first bone screw and the second bone screw are coaxial; Step 2: The first and second bone screws that have been connected are implanted as a whole into the pre-set bone tunnels of the first and second bones that constitute the micro-movement joint; Step 3: Adjust the relative position and angle of the first and second bone screws to restore the micro-movement joint to its anatomical position, while preserving the relative axial movement and radial oscillation between the first and second bone screws.

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