A reinforced expansion screw
By adding an inner core rod inside the expansion screw to form a solid structure, the problem of insufficient strength of existing expansion screws is solved, achieving stable mechanical fixation for osteoporosis patients, significantly improving bending and shear strength, and preventing bone cement loosening.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ZHEJIANG CANWELL MEDICAL DEVICES CO LTD
- Filing Date
- 2025-08-14
- Publication Date
- 2026-07-21
Smart Images
Figure CN224523210U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of orthopedic implant technology, specifically relating to a reinforced expansion screw. Background Technology
[0002] Osteoporosis is a common bone disease characterized by decreased bone density and deterioration of bone microstructure, leading to increased bone fragility and a predisposition to vertebral compression fractures, pelvic fractures, and comminuted fractures of the limbs. Clinical treatment of these fractures often requires the implantation of expansion screws into the cancellous bone to provide mechanical support.
[0003] Existing expansion screws come in various structures, one type employing the principle of axial compression driving radial expansion: shortening the length of the expansion portion causes it to deform and expand outward. For example, patent document CN213217554U discloses a vertebral implant and a vertebral implantation system, comprising an outer sleeve and an inner sleeve. The outer sleeve has multiple circumferential openings on its sidewalls; the inner sleeve includes a head, an expansion portion, and a tail connected sequentially, the expansion portion consisting of multiple expansion ribs; the inner sleeve is placed inside the outer sleeve with the head fixedly connected to it, the expansion ribs corresponding to the openings, and the tail can slide axially; in the closed state, the expansion ribs cover the openings, and sliding the tail shortens the distance between the head and tail, allowing the expansion ribs to expand outward through the openings. However, this implant is a hollow structure, lacking internal support components, resulting in insufficient axial bending strength and radial shear strength, making it prone to fracture during surgery and failing to meet the mechanical fixation needs of osteoporosis patients. Summary of the Invention
[0004] This invention addresses the technical problem of insufficient mechanical strength in hollow implants by providing a reinforced expansion screw that significantly improves bending and shear strength by adding an inner core rod to form a solid structure.
[0005] The technical solution provided by this utility model is: The screw body has an axial guide hole inside, and multiple windows communicating with the guide hole are spaced circumferentially on the side wall of the screw body. The inner sleeve includes a head, an expansion portion and a tail connected in sequence. The expansion portion includes a plurality of expansion ribs spaced apart in the circumferential direction. The inner sleeve is disposed in the guide hole. The head is fixedly connected to the screw body. Each expansion rib corresponds to a window. The tail is slidably disposed along the guide hole. In the closed state, the expansion rib covers the window; in the expanded state, the tail slides along the guide hole, and by reducing the distance between the head and the tail, the expansion rib expands from the window toward the outside of the screw body. The inner core rod has one end inserted into the inner sleeve and through the expansion portion of the inner sleeve, and the other end fixedly connected to the screw body.
[0006] The mechanical strengthening principle of this expansion screw lies in the addition of an inner core rod penetrating the expansion portion of the inner sleeve inside the original hollow expansion screw, transforming the hollow structure of the screw body and inner sleeve into a solid structure with inner core support. This structural transformation significantly improves the overall axial bending strength and radial shear strength of the screw. Furthermore, when bone cement is injected into the inner sleeve cavity within the screw body, the bone cement flows into the surrounding cancellous bone through the window. The expansion ribs on the inner sleeve and the penetrating inner core rod can all embed themselves within the bone cement, forming a stable mechanical anchoring structure. This not only effectively maintains the stable distribution of bone cement in the cancellous bone but also significantly inhibits the risk of loosening and displacement of the bone cement. Ultimately, the expansion screw, bone cement, and surrounding cancellous bone are tightly bonded together, forming a stable overall load-bearing system.
[0007] Preferably, the end of the inner core rod that is fixedly connected to the screw body is provided with an external thread, and the guide hole is provided with an internal thread that mates with the external thread, and the inner core rod is threadedly connected to the screw body.
[0008] Preferably, the inner core rod located inside the inner sleeve has threads on its surface.
[0009] Preferably, the guide hole is an open guide hole, and the bottom of the guide hole is provided with a through hole with a size smaller than the guide hole. The inner core rod extends out of the inner sleeve, and the part of the inner core rod extending out of the inner sleeve is set as a cylindrical rod. The cylindrical rod passes through the through hole, and its protruding part forms the nail tip of the screw body.
[0010] Preferably, the guide hole is a closed guide hole, and a blind hole with a smaller size than the guide hole is provided at the bottom of the guide hole. The inner core rod extends out of the inner sleeve, and the part of the inner core rod extending out of the inner sleeve is a cylindrical rod. The cylindrical rod is inserted into the blind hole, and the closed end of the screw body is a screw head with a radius that gradually decreases from the open end to the closed end of the screw body.
[0011] Preferably, a boss is provided on the inner wall of the guide hole along the circumferential direction, and the boss is located between the window and the internal thread of the screw body; The surface of the expansion portion is provided with a limiting groove. When the limiting groove engages with the boss, the expansion portion is kept in an expanded state.
[0012] Preferably, the boss is an annular boss, and the limiting slots are spaced apart along the length direction of the expansion rib. The annular boss engages with any one of the multiple limiting slots to keep the expansion part in different expansion states.
[0013] Preferably, the width of the middle portion of the expansion rib is smaller than the width of both ends of the expansion rib, or the middle portion of the expansion rib has a perforated hole. This design makes this part of the inner sleeve most prone to outward deformation and expansion when under pressure.
[0014] Preferably, the outer surface of the front section of the screw body is provided with a single-threaded thread, and the outer surface of the rear section is provided with a double-threaded thread.
[0015] Preferably, the rear end face of the screw body is provided with multiple grooves along the circumferential direction.
[0016] The beneficial effects of the reinforced expansion screw of this utility model are: by having the inner core rod penetrate the expansion part of the inner sleeve and fix it to the screw body, the hollow structure is transformed into a solid structure with central rigid support. While ensuring the expansion function, the overall bending and shear strength of the screw is significantly improved. When bone cement is injected into the expansion screw, the inner core rod is embedded in the bone cement to maintain the stability of the bone cement and prevent the bone cement from loosening and shifting. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the expanded state structure of the reinforced expansion screw in Example 1; Figure 2 This is a cross-sectional view of the screw body in Example 1; Figure 3 This is a schematic diagram of the inner core rod in Example 1; Figure 4 This is a schematic diagram of the inner sleeve in Example 1; Figure 5 This is a cross-sectional view of the reinforced expansion screw in the closed state according to Example 2; Figure 6 This is a schematic diagram of the screw body in Example 2; Figure 7 This is a schematic diagram of the inner core rod in Example 2; Figure 8 This is a schematic diagram of the inner sleeve in Example 2; Figure 9 This is a cross-sectional view of the expanded state of the reinforced expansion screw in Example 1.
[0018] In the diagram, 1-screw body, 11-guide hole, 111-internal thread, 112-annular boss, 12-through hole, 13-window, 14-single thread, 15-double thread, 16-groove, 17-screw tip, 18-screw head, 19-blind hole, 2-inner sleeve, 21-head, 22-expansion section, 23-tail, 24-hollow hole, 221-expansion rib, 222-limiting slot, 3-inner core rod, 31-external thread, 32-cylindrical rod, 33-thread. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of this utility model clearer, the expansion screw of this utility model will be further described in detail below through embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit this utility model.
[0020] Example 1
[0021] like Figure 1 As shown, the reinforced expansion screw in this embodiment mainly consists of a screw body 1, an inner sleeve 2, and an inner core 3. The screw body 1 and the inner core 3 are made of titanium alloy, while the inner sleeve 2 is made of a titanium-based material, such as titanium alloy, pure titanium, or nickel-titanium alloy. This expansion screw is suitable for the fixation and implantation of osteoporotic bones, and is especially suitable for minimally invasive treatment of vertebral compression fractures.
[0022] like Figure 2 As shown, the screw body 1 is a hollow cylindrical structure. The outer surface of the front section of the screw body is provided with a single-threaded thread 14, and the outer surface of the rear section is provided with a multi-threaded thread 15. The single-threaded thread 14 and the multi-threaded thread 15 can respectively enhance the holding force of the screw in cancellous bone and cortical bone. The screw body 1 has a guide hole 11 along the axial direction. The front section of the guide hole 11 is designed as an open type. Specifically, the bottom of the guide hole 11 is provided with a through hole 12, and the diameter of the through hole 12 is smaller than the diameter of the guide hole. The side wall of the screw body 1 is provided with a plurality of windows 13 evenly spaced along the circumference (4 in this embodiment). The windows 13 are connected to the guide hole 11 and are located on the single-threaded thread 14. An internal thread 111 is provided in the guide hole 11 of the rear section of the screw body 1. An annular boss 112 is provided on the inner wall of the guide hole 11 along the circumferential direction. The annular boss 112 is between the window 13 and the internal thread 111 of the screw body 1. The rear end face of the screw body 1 is provided with a plurality of grooves along the circumferential direction to facilitate the clamping and rotation of surgical tools (in this embodiment, there are two grooves 16 arranged at 180°).
[0023] like Figure 4 and Figure 9As shown, the inner sleeve 2 is placed inside the screw body 1. The inner sleeve 2 includes a head 21, an expansion portion 22, and a tail portion 23 connected in sequence. The expansion portion 22 consists of multiple expansion ribs 221 spaced apart circumferentially (four in this embodiment), with the width of the middle portion of each expansion rib 221 being smaller than the width of its two ends. The inner sleeve 2 is coaxially disposed within the guide hole 11 of the screw body 1. The head 21 is fixedly connected to the front end of the screw body 1 by threads, and threads are provided on the outer wall of the head 21 (not shown in the figure). Threads are also provided at the connection between the guide hole 11 and the head 21 (not shown in the figure). Each expansion rib 221 corresponds to a window 13, and the tail portion 23 can slide axially along the guide hole 11. In the closed state, the expansion rib 221 covers the window 13; in the expanded state, the tail portion 23 slides along the guide hole 11, reducing the distance between the head 21 and the tail portion 23, causing the expansion rib 221 to expand outward from the window 13 into the screw body 1.
[0024] like Figure 4 As shown, a limiting groove 222 (four limiting grooves in this embodiment) is provided on the surface of the expansion portion 22 near the tail portion 23. The limiting grooves 222 are spaced apart along the length direction of the expansion rib 221, and the multiple limiting grooves 222 correspond one-to-one with the annular boss 112 on the inner wall of the guide hole 11. When the expansion rib 221 expands outward, the annular boss 112 engages with a certain limiting groove 222 to form a radial interlock, keeping the expansion portion 22 in an expanded state (e.g., Figure 9 (As shown), to prevent retraction. By adjusting the sliding distance of the tail 23, the annular boss 112 can engage with the limiting slot 222 at different expansion depths to achieve multi-level expansion locking.
[0025] like Figure 3 As shown, the inner core rod 3 is a solid round rod. One end is inserted into the inner sleeve 2 and passes through the expansion portion 22 of the inner sleeve 2. The other end is placed inside the screw body 1 and fixedly connected to the screw body 1. The end of the inner core rod 3 connected to the screw body 1 has an external thread 31, and the end connected to the inner sleeve 2 is a cylindrical rod 32 extending out of the inner sleeve 2. The external thread 31 is threadedly connected to the internal thread 111 in the guide hole 11 to fix the inner core rod 3 to the screw body 1. The cylindrical rod 32 passes through the through hole 12 of the screw body 1, and its protruding part forms the screw tip 17 of the screw body 1. The surface of the inner core rod 3 located inside the inner sleeve 2 has a thread 33, which can enhance the bonding with bone cement. When bone cement is injected into the guide hole 11, the inner core rod 3 can maintain the stable distribution of bone cement and prevent the bone cement from loosening and shifting. At the same time, the addition of the inner core rod can further increase the bending and shear strength of the expansion screw and effectively avoid the risk of screw breakage.
[0026] In addition, to facilitate the threaded connection between the inner core rod 3 and the screw body 1, an internal hexagonal groove for engaging with a screw-in tool is provided on the end face of the inner core rod 3. The annular boss can also be configured as multiple point-shaped bosses along the circumferential direction and on the same radial plane, with the number of bosses being the same as the number of expansion ribs and corresponding to the limiting slot 222.
[0027] Example 2
[0028] like Figure 5 As shown, this embodiment is another implementation of the present invention: the assembly method and materials of the screw body, inner sleeve and inner core rod are the same as those in embodiment 1, the difference is that the structure of the screw body, inner sleeve and inner core rod is different from that in embodiment 1.
[0029] The guide hole 11 of the screw body 1 adopts a closed design (such as...). Figure 6 (As shown). Specifically, the bottom of the guide hole 11 is provided with a blind hole 19, which is smaller than the guide hole 11. The closed end of the screw body 1 is provided with a screw head 18 whose radius gradually decreases from the open end to the closed end of the screw body. The rest is the same as in Embodiment 1.
[0030] like Figure 8 As shown, the inner sleeve 2 includes a head 21, an expansion section 22 and a tail section 23 connected in sequence; the expansion section 22 is composed of four expansion ribs 221 arranged circumferentially, and each expansion rib 221 has a hollow hole 24 in the middle, and the rest is the same as in Embodiment 1.
[0031] like Figure 7 As shown, the inner core rod 3 is a solid round rod. When the inner core rod 3 is assembled with the screw body 1 and the inner sleeve 2, the inner core rod 3 extends out of the inner sleeve 2, and the part of the inner core rod 3 extending out of the inner sleeve 2 is set as a cylindrical rod 32. The cylindrical rod 32 is inserted into the blind hole 19, and the rest is the same as in Embodiment 1. The addition of the inner core rod can increase the mechanical strength of the expansion screw. When bone cement is injected into the expansion screw, the inner core rod is embedded in the bone cement, which can maintain the stability of the bone cement and prevent the bone cement from loosening and shifting.
[0032] It should be noted that the design of the hollow hole 24 in the middle of the expansion rib 221 can also be applied to Embodiment 1, and the design of the width of the middle part of the expansion rib 221 being smaller than the width at both ends can also be applied to Embodiment 2.
[0033] In summary, this invention, through structural optimization, significantly improves the bending and shear strength of the screw and maintains the stability of the bone cement while ensuring the expansion function, thus meeting the special needs of osteoporotic bone implantation.
[0034] The surgical procedure for the expansion screw of this invention is as follows: (1) When closed, the expansion rib 221 covers the window 13, and the screw body 1 with the inner sleeve 2 is in the shape of a slender column. (2) Insert the screw with the inner cannula into the fracture area while it is in a closed state; (3) By pushing the tail 23 of the inner sleeve 2 towards the nail tip using the pushing tool, the distance between the head 21 and the tail 23 is reduced, and the expansion rib 221 expands outward from the window 13 (e.g. Figure 1 As shown), an umbrella-shaped support structure is formed. At this time, the annular boss 112 on the inner wall of the guide hole 11 engages with the limiting groove 222 on the expansion rib 221, keeping the expansion part 22 in an expanded state.
[0035] (4) When bone cement is injected into the inner cavity of the inner sleeve 2 located in the screw body 1, the bone cement flows out through the window 13 and adheres to the surrounding cancellous bone; then the inner core rod 3 is screwed in, and the inner core rod 3 passes through the bone cement and connects to the screw body 1; finally, after the bone cement has solidified, the expansion screw, bone cement and cancellous bone form an integrated load-bearing system.
[0036] In summary, the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.
Claims
1. A reinforced expansion screw, characterized in that, include: The screw body has an axial guide hole inside, and multiple windows communicating with the guide hole are spaced circumferentially on the side wall of the screw body. The inner sleeve includes a head, an expansion portion and a tail connected in sequence. The expansion portion includes a plurality of expansion ribs spaced apart in the circumferential direction. The inner sleeve is disposed in the guide hole. The head is fixedly connected to the screw body. Each expansion rib corresponds to a window. The tail is slidably disposed along the guide hole. In the closed state, the expansion rib covers the window; in the expanded state, the tail slides along the guide hole, and by reducing the distance between the head and the tail, the expansion rib expands from the window toward the outside of the screw body. The inner core rod has one end inserted into the inner sleeve and through the expansion portion of the inner sleeve, and the other end fixedly connected to the screw body.
2. The expansion screw according to claim 1, characterized in that, The inner core rod is fixedly connected to the screw body at one end and has an external thread. The guide hole has an internal thread that mates with the external thread, and the inner core rod is threadedly connected to the screw body.
3. The expansion screw according to claim 2, characterized in that, The inner core rod located inside the inner sleeve has threads on its surface.
4. The expansion screw according to claim 3, characterized in that, The guide hole is an open guide hole, and the bottom of the guide hole is provided with a through hole with a size smaller than the guide hole. The inner core rod extends out of the inner sleeve, and the part of the inner core rod extending out of the inner sleeve is set as a cylindrical rod. The cylindrical rod passes through the through hole, and its protruding part forms the nail tip of the screw body.
5. The expansion screw according to claim 3, characterized in that, The guide hole is a closed guide hole, and a blind hole with a smaller size than the guide hole is provided at the bottom of the guide hole. The inner core rod extends out of the inner sleeve, and the part of the inner core rod extending out of the inner sleeve is a cylindrical rod. The cylindrical rod is inserted into the blind hole. The closed end of the screw body is a screw head with a radius that gradually decreases from the open end to the closed end of the screw body.
6. The expansion screw according to any one of claims 2-5, characterized in that, A boss is provided circumferentially on the inner wall of the guide hole, and the boss is located between the window and the internal thread of the screw body; The surface of the expansion portion is provided with a limiting groove. When the limiting groove engages with the boss, the expansion portion is kept in an expanded state.
7. The expansion screw according to claim 6, characterized in that, The boss is a ring-shaped boss; The limiting slots are spaced apart along the length of the expansion rib, and the annular boss engages with any one of the multiple limiting slots to keep the expansion portion in different expansion states.
8. The expansion screw according to claim 6, characterized in that, The width of the middle part of the expansion rib is smaller than the width of the two ends of the expansion rib, or the middle part of the expansion rib is provided with a hollow hole.
9. The expansion screw according to claim 6, characterized in that, The outer surface of the front section of the screw body is provided with a single-threaded thread, and the outer surface of the rear section is provided with a double-threaded thread.
10. The expansion screw according to claim 6, characterized in that, The rear end face of the screw body has multiple grooves along the circumferential direction.