Absorbable interface screw

Abstract

The invention relates to the technical field of medical instruments, in particular to an absorbable interface screw which comprises a screw body and threads arranged on the screw body, and the threads comprise high-thread-type threads and low-thread-type threads. The high-thread-form threads and the low-thread-form threads are of an integrated structure and are arranged on the surface of the screw body in the length direction of the screw body. Compared with a traditional absorbable interface screw of a single thread structure, the axial pull-out force of the absorbable interface screw is improved by 20%-35%, and the total bone loss amount in the implanting and screwing-out process is reduced by 70% or above.

Description

Technical Field

[0001] The present application relates to the technical field of medical devices, and in particular to an absorbable interface screw. Background Art

[0002] In the field of medical devices, absorbable interference screws play an important role in tissue or implant fixation. With the development of medical technology and the improvement of patients' requirements for postoperative recovery experience, absorbable interference screws have gradually become an important choice for clinical applications due to their advantage of not requiring secondary surgery for removal. However, existing absorbable interference screws still have many shortcomings in practical applications.

[0003] From the perspective of fixation effect, the thread design of existing absorbable interference screws is relatively conventional (see Figure 1 ), the contact area between the thread and the tissue is limited. In practical applications, it is impossible to form sufficient friction to ensure stable fixation. Taking the common fracture internal fixation surgery as an example, during the postoperative recovery stage, due to the poor screw fixation effect, the implanted screws are prone to loosening and displacement, resulting in the fracture site not being able to heal as expected. In severe cases, reoperation is even required for adjustment, which greatly affects the patient's recovery process and treatment effect.

[0004] In terms of mechanical properties, the existing absorbable interface screws are not as good as metal and PEEK interface screws because of their material properties, and the single tooth type and thread structure. When facing the complex biomechanical environment of the human body, it is difficult to provide sufficient anchoring force for tissues or implants in all directions. When patients are engaged in normal activities, especially when subjected to large tensile or shear forces, the screws are not able to resist pull-out, resulting in loosening of implants (such as ligaments), which greatly reduces the long-term effect of the surgery and cannot provide reliable support and fixation for patients.

[0005] In addition, during the screw implantation process, the design of existing absorbable interface screws is unreasonable, which will cause great damage to the surrounding tissues. On the one hand, when the screw is screwed in, the thread will over-exert the bones and soft tissues, causing bone splitting, soft tissue tearing, etc., affecting the normal healing of the tissues. On the other hand, because the design cannot accurately disperse stress, it will cause more bone debris, destroy the integrity of the bones, and then delay the healing process of the bones, increasing the patient's pain and recovery time.

[0006] In summary, the existing absorbable interface screws have obvious technical defects in fixation effect, mechanical properties and impact on bone quality. It is urgent to develop a new type of absorbable interface screw to effectively solve the above problems and improve the clinical treatment effect and patient rehabilitation quality. Summary of the invention

[0007] The purpose of the present application is to provide an absorbable interface screw through a unique structural design to solve the problems of the existing absorbable interface screws mentioned in the above background technology, such as unstable fixation effect, unsatisfactory mechanical properties, easy bone splitting or excessive bone debris during implantation, etc., to provide more reliable protection for tissue repair and implant fixation.

[0008] To achieve the above purpose, this application adopts the following technical solutions: An absorbable interface screw comprises a screw body and a thread arranged on the screw body, wherein the thread comprises a high-profile thread and a low-profile thread, and the high-profile thread and the low-profile thread form an integrated structure and are arranged on the surface of the screw body along the length direction of the screw body.

[0009] The unique integrated high and low tooth thread design allows the high tooth thread to quickly penetrate into the tissue at the initial stage of implantation, providing strong gripping force to resist shear and tension, ensuring immediate stability during fixation, while the low tooth thread increases the contact area and friction between the thread and the tissue, dispersing stress distribution and avoiding tissue damage or screw loosening caused by stress concentration. The synergistic effect of high and low teeth significantly improves the pull-out resistance of the screw, ensuring that the screw can stably play a fixing role throughout the entire process of tissue healing, providing solid protection for tissue repair.

[0010] In addition, the thread structure design allows the screw to better adapt to tissues of different densities and textures. For harder bone tissue, the high-profile thread can penetrate deep into it to provide a firm fixation; for softer soft tissue or more brittle bone such as osteoporosis patients, the low-profile thread can increase friction and reduce damage to tissues, thereby expanding the application range of the screw.

[0011] The low-profile thread is a multi-thread thread, preferably a double-thread thread. The double-thread thread includes a first low-profile thread and a second low-profile thread, and the high-profile thread is located between the first low-profile thread and the second low-profile thread.

[0012] Low-profile threads use multi-threads, such as a double-thread structure. When the screw is screwed into the tissue, it can not only apply anchoring force from two directions, forming a stable triangular support with the high-profile thread, and enhancing the screw's anti-rotation and anti-pullout capabilities in all directions, but also greatly reduce the torque required for screw insertion, thereby reducing damage to the bone during the implantation process, reducing the risk of bone splitting, and effectively controlling bone loss, providing a more reliable guarantee for the patient's postoperative recovery.

[0013] The high-profile thread may be a pointed thread, a flat-top thread with rounded corners, or a dome thread, preferably a pointed thread. The sharp tooth profile of the high-profile thread can accurately penetrate the bone when quickly cutting into the tissue, reducing excessive squeezing and damage to the surrounding bone; the flat-top thread and dome thread with rounded corners can provide a certain gripping force while being more gentle in contact with the tissue, reducing damage to the tissue, and are suitable for situations where the requirements for tissue damage are low.

[0014] The tooth profile of the low-profile thread is different from the tooth profile of the high-profile thread.

[0015] Preferably, one side corner of the low-profile thread is rounded.

[0016] Preferably, the first low-profile thread and the second low-profile thread in the low-profile thread are both asymmetric threads with relatively smooth side surfaces connected to the high-profile thread.

[0017] The asymmetric design of the low-profile thread and the rounded transition allow the screw to contact the bone more gently during the screwing process, avoiding bone splitting or excessive bone debris due to stress concentration, thereby protecting the integrity of the bone to the greatest extent.

[0018] Preferably, the connection between the first low-profile thread and the second low-profile thread and the high-profile thread is rounded. The rounded transition can not only reduce stress concentration points and improve the fatigue strength of the screw, but also optimize the contact interface between the screw and the tissue, promote tissue growth and healing, and provide strong support for the long-term stability of the screw.

[0019] When the high-profile thread is a pointed top thread, the tooth angle of the pointed top thread is α≤45°, preferably α≤42°, and more preferably 38°≤α≤40°. A smaller tooth angle makes the tip more sharp, further enhancing the ability of the thread to quickly cut into tissue and accurately penetrate bone. This helps to more easily enter the bone during implantation, reducing damage to surrounding bone, and also improves the grip and fixation effect of the screw.

[0020] The height difference between the high-profile thread and the low-profile thread is 0.1 mm to 0.6 mm. When the interface screw is used to fix soft tissue, the height difference between the high-profile thread and the low-profile thread is preferably 0.1 mm to 0.3 mm.

[0021] Furthermore, the screw body includes a screw head, a screw middle part and a screw tail part, and the thread heights of the first low-profile thread and the second low-profile thread arranged in the thread at the screw head and / or the screw middle part are not equal.

[0022] Preferably, the thread height of the first low-profile thread near the tail of the screw is lower than the thread height of the second low-profile thread near the head of the screw. This structure enables the screw to play different roles in different parts. The higher thread height at the head can provide stronger initial fixing force and gripping force to ensure the stability of the screw at the initial stage of implantation; the lower thread height at the tail can reduce the squeeze on the surrounding tissues and reduce the damage to the bone, and is also conducive to the smooth screwing of the screw.

[0023] Compared with the prior art, this application has the following beneficial effects: (1) The absorbable interface screw of the present application adopts a unique integrated high and low thread type design, breaking the limitation of the single thread of traditional screws. The synergistic effect of high and low threads significantly improves the axial pull-out force of the screw. According to experimental tests, the axial pull-out force of the absorbable interface screw of the present application is improved by 20% to 35% compared with the traditional absorbable interface screw.

[0024] (2) The low-profile thread adopts a multi-thread structure design, which can significantly reduce the torque required for screw insertion, reduce the damage to the bone during the implantation process, and thus significantly reduce the risk of bone splitting and effectively control bone loss. According to experimental tests, the total bone loss during the implantation and removal of the absorbable interface screw of this application is reduced by more than 74% compared with the traditional absorbable interface screw. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 It is a schematic diagram of the overall structure of the existing absorbable interference screw; Figure 2 This is a schematic diagram of the overall structure of the interface screw of Example 1; Figure 3 is a cross-sectional schematic diagram of the interface screw of Example 1; Figure 4 for Figure 2 Enlarged view of the interface screw A; Figure 5 This is a schematic diagram of the overall structure of the interface screw of Example 2; Figure 6 is a schematic cross-sectional view of the interface screw of Example 2; Figure 7 This is a schematic diagram of the overall structure of the interface screw of Example 3; Figure 8 This is a schematic cross-sectional view of the interface screw of Example 3.

[0027] Figure numerals: 1, screw body; 11, screw head; 12, middle part of the screw; 13, tail part of the screw; 2, thread; 21, high-profile thread; 22, low-profile thread; 221, first low-profile thread; 222, second low-profile thread. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0029] It should be noted that when a component is referred to as being "fixed on" or "set on" or "disposed on" another component, it may be directly on the other component or there may also be a central component. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may be a central component at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in the specification of this application are for illustrative purposes only and do not represent the only implementation method.

[0030] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0031] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first feature is directly in contact with the second feature, or the first feature and the second feature are indirectly in contact through an intermediate medium. Moreover, a first feature being “above”, “above” or “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below” or “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0032] Unless otherwise defined, all technical and scientific terms used in the specification of this application have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in the specification of this application includes any and all combinations of one or more related listed items.

[0033] Example 1 Screw material selection: by weight, an absorbable composite material containing 10 parts of polylactic acid PLLA, 60 parts of PLGA (85:15), 5 parts of PEG-400, 25 parts of hydroxyapatite powder with an average particle size of 750 mm and 2 parts of maleic anhydride.

[0034] After the above materials were mixed evenly, an absorbable interface screw (screw size was φ7×25) was prepared by injection molding process. The injection temperature was set at 210°C, the injection pressure was 240 bar, the holding time was 40 s, and the mold temperature was 35°C.

[0035] like Figure 1~Figure 3 As shown, the absorbable interface screw of this embodiment includes a screw body 1 and a thread 2 arranged on the screw body 1, the screw body 1 includes a screw head 11, a screw middle part 12 and a screw tail 13, the thread 2 includes a high-profile thread 21 and a low-profile thread 22, the high-profile thread 21 and the low-profile thread 22 are an integrated structure and are arranged on the surface of the screw body 1 along the length direction of the screw body 1; the high-profile thread 21 is a pointed top thread with a tooth top angle α value of 45°, the low-profile thread 22 includes a first low-profile thread 221 and a second low-profile thread 222, and the low-profile threads 22 are all asymmetric Thread, the high-profile thread 21 is arranged between the first low-profile thread 221 and the second low-profile thread 222, and the high-profile thread 21 is respectively rounded with the first low-profile thread 221 and the second low-profile thread 222, and the other side corners of the first low-profile thread 221 and the second low-profile thread 222 are rounded; the thread height of the first low-profile thread 221 near the screw tail 13 is lower than the thread height of the second low-profile thread 222 near the screw head 11, and the thread height difference between the high-profile thread 21 and the second low-profile thread 222 is 0.15~0.2mm.

[0036] Example 2 Compared with the embodiment 1, the only difference is that the high-tooth type thread 21 of the embodiment 2 is a flat-top thread with a rounded corner, and the fillet radius is 0.3 mm. Figure 4~Figure 5 shown.

[0037] Example 3 Compared with the embodiment 1, the only difference is that the other side corners of the first low-profile thread 221 and the second low-profile thread 222 of the embodiment 3 are transitioned at a right angle, such as Figure 6~Figure 7 shown.

[0038] Example 4 Compared with the embodiment 1, the only difference is that the high-profile thread 21 of the embodiment 4 is a pointed-top thread with a tooth top angle α value of 42°.

[0039] Example 5 Compared with the embodiment 1, the only difference is that the high-profile thread 21 of the embodiment 5 is a pointed-top thread with a tooth top angle α value of 40°.

[0040] Example 6 Compared with the embodiment 1, the only difference is that the high-profile thread 21 of the embodiment 5 is a pointed-top thread with a tooth top angle α value of 38°.

[0041] Example 7 Compared with the embodiment 1, the only difference is that the high-profile thread 21 of the embodiment 5 is a pointed-top thread with a tooth top angle α value of 35°.

[0042] Comparative Example 1 Compared with Example 1, the only difference is that the thread structure of Comparative Example 1 is a traditional single thread structure, such as Figure 8 shown.

[0043] Comparative Example 2 Compared with Example 1, the only difference is that the high-profile threads 21 and the low-profile threads 22 of Example 2 are arranged at intervals rather than being an integrated structure.

[0044] Performance Test: Axial pull-out force: Tested according to the method specified in YY / T1504, and the test data are recorded in Table 1.

[0045] The bone loss test is as follows: (1) Use an electronic balance to weigh the mass of the 20-pcf simulated bone block with the bone marrow tunnel drilled (the inner diameter of the bone tunnel is 1 mm smaller than the outer diameter of the screw), recorded as M0; (2) Use a dedicated screw implantation tool to slowly screw the interference screw into the preset position of the medullary canal along the center line of the medullary canal, check the stability of the screw, and adjust or fix it as needed to ensure that the screw has sufficient holding force; (3) Use a dedicated screw removal tool to align the screw head and remove the screw gently and slowly to avoid causing pressure or damage to the surrounding bone tissue; (4) After the screw is unscrewed, clean the bone debris remaining in the bone marrow canal of the bone sample and put it back on the electronic balance to reweigh the mass of the bone sample, which is recorded as M1.

[0046] (5) According to the formula: bone loss = (M0-M1) / M×100%, where M is the mass of the absorbable interference screw, the bone loss caused by screw implantation and screw removal is calculated. Five absorbable interference screws of each embodiment and comparative example were tested five times in parallel according to the above test method, and the average value was taken. The test results are shown in Table 1.

[0047] Table 1

[0048] After conversion, the amount of bone loss of the absorbable interface screw obtained by the technical solution of the present application during the implantation and unscrewing process is significantly improved compared with the bone loss of the absorbable interface screw of Example 1 with conventional thread design in the prior art, as shown in Table 2 for details.

[0049] Table 2

[0050] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0051] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the scope of patent protection of the present application shall be subject to the attached claims.

Claims

1. An absorbable interference screw, characterized in that: The invention comprises a screw body (1) and a thread (2) arranged on the screw body (1), wherein the thread (2) comprises a high-profile thread (21) and a low-profile thread (22), and the high-profile thread (21) and the low-profile thread (22) form an integrated structure and are arranged on the surface of the screw body (1) along the length direction of the screw body (1).

2. The absorbable interference screw according to claim 1, characterized in that: The low-profile thread (22) is a multi-thread thread.

3. The absorbable interference screw according to claim 2, characterized in that: The low-profile thread (22) is a double-thread thread, comprising a first low-profile thread (221) and a second low-profile thread (222), and the high-profile thread is located between the first low-profile thread (221) and the second low-profile thread (222).

4. The absorbable interference screw according to claim 3, characterized in that: The high-tooth type thread (21) is a pointed top thread, a flat top thread with rounded corners, or a round top thread.

5. The absorbable interference screw according to claim 4, characterized in that: The tooth profile of the low-profile thread (22) is different from the tooth profile of the high-profile thread (21), and a corner on one side of the low-profile thread (22) is rounded.

6. The absorbable interference screw according to claim 5, characterized in that: The first low-profile thread (221) and the second low-profile thread (222) are both asymmetric threads with relatively flat side surfaces connected to the high-profile thread (21); the connection between the first low-profile thread (221) and the second low-profile thread (222) and the high-profile thread (21) is a rounded transition.

7. The absorbable interference screw according to claim 6, characterized in that: The high-profile thread (21) is a pointed thread, and the pointed thread has a profile angle α≤45°.

8. The absorbable interference screw according to claim 7, characterized in that: The height difference between the high-profile thread (21) and the low-profile thread (22) is 0.1 mm to 0.6 mm.

9. The absorbable interference screw according to claim 3, characterized in that: The screw body (1) comprises a screw head (11), a screw middle part (12) and a screw tail part (13), and the thread heights of the first low-profile thread (221) and the second low-profile thread (222) in the thread (2) arranged at the screw head (11) and / or the screw middle part (12) are unequal.

10. The absorbable interference screw according to claim 9, characterized in that: The thread height of the first low-profile thread (221) close to the screw tail (13) is lower than the thread height of the second low-profile thread (222) close to the screw head (11).

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