Bionic root type high-holding-force bone screw for osteoporosis patient

Abstract

The invention discloses a bionic root type bone screw with high holding force for an osteoporosis patient. The screw comprises a hollow main screw provided with a guide hole, a flexible branch and an ultrasonic vibration device. The flexible branch is arranged in the main nail guide hole in advance, penetrates out under the assistance of ultrasonic vibration in the implanting process and is bent and expanded to form a multi-point distributed anchoring structure to simulate rooting of a plant root system in cancellous bone, so that the contact area with bone tissue is remarkably increased, and the pulling resistance is improved. The ultrasonic vibration device is driven by a piezoelectric element, high-frequency vibration can be provided in the implanting process, resistance is reduced, and damage to fragile bone tissue is reduced. After implantation is completed, the device can be removed immediately, and the risk of rejection after operation is avoided. The low-density bone screw is reasonable in structural design, stable fixation can be achieved in low-density bones, the occurrence rate of screw loosening and falling is effectively reduced, and the high clinical application value is achieved.

Description

Technical Field

[0001] This invention belongs to the field of medical device technology, and particularly relates to a biomimetic root-type high-holding-force bone screw for osteoporosis patients. Specifically, it relates to a bone screw designed with biomimicry, which effectively improves the stability and pull-out resistance of cancellous bone through ultrasonic vibration and a flexible branching structure, making it particularly suitable for patients with fragile bone due to osteoporosis and other diseases. Background Technology

[0002] Osteoporosis is a common skeletal disease among the elderly, especially women, and often leads to fractures. Patients with osteoporosis have significantly reduced bone density and damaged bone microstructure, particularly in the cancellous bone, which becomes more fragile. These patients are prone to fractures from external trauma or even minor falls. Common fracture types include those in the hip, spine, and wrist, severely impacting patients' quality of life and functional recovery.

[0003] Currently, for fracture treatment in patients with osteoporosis, traditional bone screws such as intramedullary nails and locking plates are commonly used for fixation. Although these devices can provide a certain degree of stability under normal bone conditions, the porous and low-density characteristics of osteoporotic bone make it difficult for traditional bone screws to adapt. This results in a small contact area between the bone screw and bone tissue, weak bonding force, and a high risk of screw loosening, displacement, or even detachment, especially in weight-bearing areas or patients with poor bone quality. In severe cases, this can lead to complications. Furthermore, the rigidity of traditional screw fixation methods can easily cause significant damage and stress concentration to bone tissue, and long-term use may affect bone healing.

[0004] To address the issues of poor pull-out resistance and high fixation failure rate of traditional bone screws due to the cancellous bone structure, there is an urgent need for a novel structure that can improve bone tissue compatibility and pull-out resistance without increasing tissue damage. Especially in patients with osteoporosis, fixation devices must not only possess sufficient mechanical properties but also adapt to the low-density, porous bone environment, providing a larger contact area and a superior force transmission mechanism to improve long-term screw stability and reduce postoperative complications.

[0005] Currently, although some novel bone screws have been applied clinically, their effectiveness in optimizing cancellous bone structure remains limited. For example, the patent with publication number "CN222693505U" mainly improves fixation through material degradation properties and a double-threaded structure, but its stability still relies on traditional thread engagement and lacks adaptability to the complex porous structure inside cancellous bone. It cannot achieve active control of the anchoring path or multi-point distributed fixation in space, and its long-term stability in sparse trabecular environments such as osteoporosis is limited. Another example is the patent with publication number "CN115517752A," which mainly relies on external threaded segments to compress the bone fragment ends, providing guidance and suture convenience, showing good fixation in the cortical bone region. However, its fixation mechanism is still rigid contact, lacking an active interlocking strategy tailored to the porous and loose characteristics of cancellous bone. It cannot effectively penetrate into the trabecular bone, resulting in limited anchoring depth and stress distribution, especially in patients with osteoporosis where stability is insufficient. Existing designs primarily focus on increasing the threaded structure on the surface of the bone screw or improving stability by increasing the number of screws. However, these approaches still fall short in terms of adaptability to cancellous bone and long-term fixation. Therefore, a novel bone screw design is needed that can fully utilize the porous nature of cancellous bone and enhance fixation with bone tissue through optimized structure and materials, thereby addressing the problems of poor stability and insufficient fixation in existing bone screw technologies.

[0006] This invention proposes a novel cancellous bone chimera design that integrates structural and behavioral biomimicry, featuring flexible branches, guide holes, and ultrasonic-driven coordinated deployment. The branches are constructed from a gradually tapering flexible material, capable of actively deforming at a preset angle under the guidance of the guide holes. Under ultrasonic vibration, they unfold along a non-linear path, conforming to the porous structure within the bone, ultimately constructing a root-like multi-point anchoring network deep within the cancellous bone, effectively increasing contact area and pull-out resistance. This structure is particularly suitable for complex bone regions with uneven trabecular density and where traditional screw implantation is difficult. It significantly reduces postoperative loosening while improving fixation performance, exhibiting superior clinical adaptability and sustainable implantation value. It also significantly improves screw stability, overcoming the shortcomings of existing technologies. Attached Figure Description

[0007] Figure 1 This is a side view of the branched piezoelectric ceramic assembly in a bone screw system. Figure 2 This is a schematic diagram of the front structure of the branched piezoelectric ceramic assembly in a bone screw system. Figure 3 A schematic cross-sectional view of the bone screw system; Figure 4 This is a schematic diagram of the exploded structure of the flexible branch in a bone screw system. Figure 5This is a schematic diagram showing the installation position of the piezoelectric ceramic sheet vibration device in the bone screw system; Figure 6 A schematic diagram showing the drilling angle design for flexible branch implantation; Figure 7 This is a schematic diagram of the power connection wire structure for an ultrasonic vibration device.

[0008] 1- Ultrasonic power connection wire, used to connect the flexible branch assembly and transmit vibration; 2- Guide hole main nail, used to bear the main structural load of the bone screw system; 3- First group of flexible branches, located at the distal end of the main nail, responsible for inserting into the cancellous bone and forming a fit; 4- Second group of flexible branches, located in the lower middle part of the main nail; 5- Third group of flexible branches, located at the lower part of the main nail; 6- Fourth group of flexible branches, located at the proximal end of the main nail; 7- Fifth group of flexible branches, located at the upper part of the main nail; 8- Sixth group of flexible branches, located at the top of the main nail; 9- Ultrasonic vibration generator (piezoelectric ceramic drive module), used to generate ultrasonic vibration; 10- Power connection wire, used to connect the ultrasonic vibration generator and the flexible branch assembly; 11- Piezoelectric ceramic drive plate, located in the deep part of the central axis of the main nail, used to convert high-frequency electrical signals into mechanical vibration energy and couple it to the flexible branches along the guide structure; 12- Guide connection structure (vibration transmission rod), used to transmit vibration energy to the flexible branches. Summary of the Invention

[0009] This invention provides a biomimetic root-type high-holding-force bone screw for osteoporosis patients. Existing bone screws, when implanted into cancellous bone, often suffer from insufficient contact area and fixation force due to the porous structure of cancellous bone, leading to loosening, displacement, and even dislodgement, especially in osteoporosis patients. To address these issues, this invention designs an innovative bone screw structure that combines a high-strength main screw, biomimetic flexible branches, and ultrasonic vibration-assisted technology to improve the compatibility, pull-out resistance, and stability of the bone screw with cancellous bone, thereby effectively reducing the risk of screw loosening and improving implantation outcomes and long-term bone healing quality.

[0010] Specifically, the biomimetic flexible branch structure of this invention mimics the anchoring pattern of plant roots in nature, actively adapting to the size and distribution of bone tissue pores, significantly increasing the contact area between the bone screw and bone tissue, and achieving low-damage insertion and efficient deployment through ultrasound assistance. The main screw is made of high-strength metal or reinforced composite material, bearing the main axial load and ensuring the overall mechanical stability of the structure. The above design fully considers the anatomical characteristics and mechanical properties of cancellous bone, significantly improving the fixation reliability and clinical applicability of bone screws in patients with osteoporosis. Master screw design with guide hole The main screw in the bone screw system of this invention features a multi-hole guide design. Its body is made of medical-grade titanium alloy, possessing high axial load-bearing capacity and structural stability. The main screw has multiple guide holes asymmetrically distributed along the axial direction. The exit direction of each guide hole corresponds one-to-one with the advancement direction of the flexible branch, guiding it to extend at a predetermined angle (preferably 16°–18°) into the three-dimensional trabecular network within the cancellous bone during flexible branch implantation. The guide holes are arranged along the axis of the main screw, with axial spacing at a certain angle to construct a stable branch divergence path, avoiding branch path deviation and tissue damage. The diameter of the guide holes is approximately 0.9 mm, and their length is geometrically precisely matched to the shape of the flexible branch, forming a stable guiding channel. This allows the flexible branch to be smoothly released and directionally embedded into the target area of ​​the cancellous bone under ultrasonic vibration, improving the anchoring performance and long-term stability of the porous bone structure. Flexible branch design The flexible branch is made of PDMS (polydimethylsiloxane) material, which has good elasticity, toughness, and biocompatibility. Its end is designed with a tapered shape, allowing the flexible branch to easily penetrate into the pores of cancellous bone, providing a larger contact area and enhancing the stability and fixation force between the bone and the screw. The flexible branch design is inspired by tree roots in nature, and through biomimetic design, it optimizes the stability of the screw in cancellous bone.

[0011] The bone screw of the present invention includes an ultrasonic vibration device, which is connected to a flexible branch via an external wire and uses a piezoelectric ceramic plate as the core component for vibration transmission. The ultrasonic vibration device can activate the piezoelectric ceramic plate through a power supply wire, converting electrical energy into high-frequency mechanical vibration, and transmitting the vibration energy to the cancellous bone through the flexible branch.

[0012] The flexible branch design of this invention draws inspiration from the principle of tree roots penetrating the soil, employing a conical design for deep insertion into cancellous bone. This design maximizes the contact area between the root and cancellous bone through the gradual expansion of the flexible branches, thereby significantly improving the stability of the implant. Specifically, the flexible branches, through their conical design, gradually adapt to the porous structure of the cancellous bone during insertion, forming a good contact interface in different density areas of the cancellous bone, ensuring the implant is firmly fixed within the bone tissue.

[0013] This invention significantly improves the effectiveness of bone implants in osteoporosis patients by combining a flexible branch design with an optimal insertion angle range. Experimental results show that an insertion angle of 16°–18° is the key angle for achieving optimal fixation of the flexible branch. This angle significantly improves implant stability while minimizing damage to cancellous bone. Compared to the traditional vertical insertion method, the 16°–18° insertion angle not only avoids excessive pressure on cancellous bone but also better adapts to the three-dimensional structure of the trabeculae, reducing stress concentration in the bone during insertion and thus lowering the risk of fracture and implant loosening. In experiments, after the implant penetrates the bone tissue at an angle of 16°–18°, it forms a natural anchoring structure similar to tree roots between the trabeculae, providing more uniform fixation force, especially demonstrating higher stability and adaptability in osteoporosis patients. Compared to traditional linear fixation methods, the 16°–18° angle reduces implant displacement and loosening, effectively improving initial fixation force and long-term stability.

[0014] The ultrasonic vibration device of this invention has adjustable vibration frequency and amplitude. The vibration frequency and amplitude can be individually adjusted according to the patient's bone condition, particularly the severity of osteoporosis. For patients with severe osteoporosis, the ultrasonic vibration device can provide higher vibration intensity to help the flexible branch effectively penetrate cancellous bone, while for patients with better bone quality, the vibration intensity can be reduced to avoid excessive stimulation of the bone.

[0015] To reduce the risk of biological rejection in patients, this invention incorporates a postoperative removal mechanism for the ultrasonic vibration device. Once the screws are stable, the ultrasonic vibration device is removed, preventing potential adverse effects on the patient from continuous postoperative mechanical vibration.

[0016] The bone screws of this invention are suitable for patients with osteoporosis and other fractures, especially in fragile cancellous bone environments where they offer significant advantages. Through ultrasonic vibration technology and biomimetic design, this invention provides a highly efficient, safe, and customizable treatment option suitable for patients with different bone conditions.

[0017] Compared with existing inventions, the present invention has the following beneficial effects.

[0018] Integration of embedding and anchoring. Compared to traditional rigid implants, the flexible branch of this invention adopts a gradually tapering conical structure design based on biomimetic principles. It can automatically adjust its shape along the pores of bone tissue during implantation, achieving a higher degree of fit and adaptation. This structure allows the flexible branch to gradually contract from proximal to distal, unfolding layer by layer as it enters the cancellous bone, forming a distributed contact surface with the porous trabeculae. This effectively disperses stress, significantly improving the embedding depth and stability of the implant, and avoiding structural loosening and displacement problems caused by insufficient local contact area.

[0019] Significantly enhances pull-out stability. The conical structure significantly reduces frictional resistance and the risk of bone compression during branch advancement, effectively minimizing damage to fragile bone tissue while ensuring smooth insertion of the flexible branch to the predetermined depth. This structure is particularly suitable for areas with sparse trabeculae and reduced bone density in osteoporotic patients, enabling the construction of multi-point anchorage paths similar to plant roots, thereby enhancing initial intraoperative stability and long-term postoperative fixation.

[0020] Reduced implant tissue damage. Traditional bone implants often lack in fixation and stability, especially in patients with osteoporosis, where the high stress during insertion can lead to fractures or injury due to fragile bone tissue. In contrast, this invention utilizes a flexible branch design combined with ultrasound-assisted vibration technology, allowing the implant to be inserted under lower mechanical loads. Ultrasonic vibration not only improves the penetration of the flexible branch but also reduces the risk of bone tissue compression and damage during insertion. This low-damage, high-efficiency bone repair method effectively avoids the problems associated with traditional rigid implants in fragile bone, while also improving postoperative recovery speed and patient comfort.

[0021] Excellent rejection resistance significantly improves postoperative safety and comfort. The ultrasonic vibration device of this invention is briefly activated during implantation, using high-frequency vibration to assist the flexible branch in successfully penetrating bone tissue and forming an anchoring structure. After implantation, the vibration device is immediately removed. The ultrasonic vibration device and the main screw utilize a pluggable connection structure, allowing for rapid and non-destructive disassembly after ultrasonic vibration implantation. As an external temporary auxiliary tool, the vibration device is designed for short-term operation and controllable removal during surgery, ensuring it does not remain in the patient's body for extended periods. This eliminates the risk of immune reactions and biological rejection that may arise from continuous contact with tissue, reducing the probability of postoperative complications. Simultaneously, the removal operation is simple and quick, without affecting the fusion of the implanted structure with bone tissue, thus improving surgical safety and postoperative recovery comfort.

[0022] In summary, the bone screw of this invention, through the combination of optimized structural design, the introduction of ultrasonic vibration technology, and a biomimetic root-like design, provides a highly stable bone screw suitable for patients with osteoporosis and fragile bone. These innovative designs ensure that the screw can be stably rooted in the cancellous bone, avoiding the loosening and displacement problems common in traditional techniques, greatly improving the success rate of surgery and shortening the recovery period. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention are clearly and completely described below through specific examples. These described examples represent not only a portion of the embodiments of the present invention, but all of them. Different embodiments can lead to different improvements in the specific application of the invention. Based on different embodiments of the present invention, those skilled in the art can achieve better application by adjusting some details of the implementation method.

[0024] Example 1: A biomimetic root-type high-holding-force bone screw for spinal fixation in osteoporosis patients, comprising a main screw with a guide hole, a flexible branch, and an ultrasonic vibration device. Specifically, it includes: The main screw, featuring guide holes, is a hollow cylindrical structure made of biocompatible metallic materials (such as titanium alloy). Its outer surface has a bidirectional threaded structure to enhance the contact area between the screw and bone tissue and improve pull-out resistance. The main screw has an insertion end and a tail end at its axial ends, with a connector at the tail end for connecting to an ultrasonic vibration device. Multiple axial guide holes are evenly arranged along the circumference of the main screw. These guide holes are through-hole structures used to accommodate the lateral arrangement of multiple flexible branches, constraining their initial orientation and providing insertion direction guidance. The flexible branches are used to anchor the cancellous bone in patients with osteoporosis, enhancing the pull-out stability after screw implantation. Each flexible branch has a conical structure and is made of medical-grade polydimethylsiloxane (PDMS) material with excellent flexibility and biocompatibility. The diameter of the flexible branch can be 0.5mm to 0.8mm, with a conical tip angle of 20° to 30°, a tip length controlled at approximately 2.0mm, and a vertex diameter not exceeding 0.3mm. The specific size can be selected according to the bone thickness. The flexible branches are pre-placed in the main screw cavity in a transverse arrangement, corresponding one-to-one with the asymmetrically arranged guide holes on the main screw during insertion. During implantation, under the combined action of axial force and ultrasonic vibration, the flexible branches are released sequentially along the axis of the guide holes and pass through the cancellous bone trabecular channel, ultimately completing bending expansion to form a three-dimensional multi-point anchorage. This structure can form a reasonably distributed anchoring mechanical support in the cancellous bone without relying on cortical bone, thereby improving the overall stability and load-bearing capacity of the screw. An ultrasonic vibration device is mounted on the upper end of a flexible branch. The device contains a piezoelectric ceramic actuator module that generates axial high-frequency vibrations at a frequency of 26–30 kHz. Activation and deactivation are controlled by the surgeon during the procedure. To adapt to different patients' bone conditions, the system has a built-in vibration frequency adjustment unit, which can adjust the vibration mode based on preoperative imaging or intraoperative feedback. A high-frequency, low-amplitude vibration mode is used in patients with fragile bones, while a low-frequency, high-amplitude mode is used in areas of dense bone to reduce bone irritation.

[0025] This example involves intraoperative path control of a flexible branch. The surgeon can use a guide to initially position the flexible branch at the predetermined insertion location. An ultrasonic vibration device assists the flexible branch in smoothly penetrating the porous structure of cancellous bone and gradually reaching the desired depth. During implantation, an image-guided navigation system can be used to monitor the branch's advancement path in real time, assisting the surgeon in adjusting the direction and reducing the risk of damage to important tissues such as nerves and blood vessels. Experiments have verified that the optimal insertion angle for the flexible branch is 16°–18°. Under the control of the guide, the flexible branch is inserted at the set unfolding angle, and the overall path approaches the predetermined direction, achieving good spatial embedding adaptability under intraoperative dynamic control.

[0026] This embodiment relates to the application of an ultrasonic vibration device in the implantation of a flexible branch. The ultrasonic vibration device is connected to the flexible branch and is used to provide stable and continuous axial vibration during implantation, effectively reducing the resistance of cancellous bone tissue, avoiding excessive tissue compression or damage, and ensuring that the flexible branch smoothly penetrates the trabecular bone structure along the guide hole and is positioned in the target area. Once the flexible branch has fully expanded and reached the predetermined interlocking depth, the ultrasonic vibration device can be immediately removed during the same procedure. The operation requires no additional incisions or tissue intervention; only the connecting components need to be disconnected and the device itself removed. After removal, the tail end of the main screw can be sealed, without affecting the stability of the screw implant or bone healing, while also reducing the risk of biological rejection and promoting postoperative recovery.

[0027] This implementation structure is particularly suitable for bone areas with low bone density where traditional rigid screws are difficult to anchor securely, such as vertebral cancellous bone, femoral shaft, and calcaneus. It can significantly improve implantation stability and long-term fixation, and has good surgical adaptability and clinical application value.

Claims

1. A high-holding-force bone screw with a biomimetic root design for osteoporosis patients, characterized in that, include: The guide hole main nail (2) is made of medical grade titanium alloy and has a hollow cylindrical structure. The outer wall is provided with multiple guide holes to accommodate and guide the flexible branch (6) to unfold. The main nail serves as a load-bearing structure to bear axial load and ensure stability. The flexible branch (6) is pre-placed in the guide hole. Its tip is a conical structure. During the implantation process, it can bend and pass through the trabeculae of cancellous bone under the action of external force and ultrasonic vibration to form a three-dimensional anchoring network similar to plant roots. An ultrasonic vibration device is used to provide high-frequency vibration assistance to the flexible branch (6) during implantation.

2. The guide hole master nail (2) according to claim 1, characterized in that, The guide holes are arranged along the axis of the main nail and are asymmetrically distributed in the circumferential direction. The outlet direction of each guide hole corresponds one-to-one with the insertion direction of the corresponding flexible branch (6), which is used to limit the unfolding path of the flexible branch (6) and guide it through the trabeculae of cancellous bone.

3. The flexible branch (6) according to claim 1, characterized in that, The flexible branch (6) is made of polydimethylsiloxane (PDMS) medical material, which is tough and biocompatible. During implantation, it can adapt its shape according to the porosity distribution of the cancellous bone of osteoporotic patients. Its conical tip gradually expands when entering the trabecular bone network to form a multi-point anchoring contact surface, thereby improving the pull-out strength.

4. The ultrasonic vibration device according to claim 1, characterized in that, It includes a piezoelectric ceramic sheet (11) and a connecting wire (10). The piezoelectric ceramic sheet (11) is provided with electrodes and is connected to an external driving power supply. During the implantation process, it generates high-frequency vibrations and acts on the flexible branch (6).

5. The ultrasonic vibration device according to claim 4, characterized in that, The electrode of the piezoelectric ceramic sheet (11) is connected to an external driving power source through a wire (10). The wire is connected to the electrode once by an electro-adhesive before implantation. The flexible wire is inserted into the flexible branch (6) and fixed to its outer wall. When an ultrasonic signal is applied for a short time, the flexible branch (6) unfolds and reaches a preset depth. After the anchoring effect is obtained, the drive stops and the flexible branch (6) remains embedded. At this time, the wire (10) is pulled out and no conductive component is retained inside the system.

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