An adaptive multi-void femoral head necrosis support rod

Abstract

An adaptive porous femoral head necrosis support rod comprises a head, a body, a temperature-sensitive bone conduction layer and a tail; the head, the body and the tail are coaxially connected in sequence, and the temperature-sensitive bone conduction layer covers the surface of the body; the shape of the head matches the cavity surface left after the removal of dead bone, and the head and the body are both porous structures; the tail is provided with a thread, and the thread groove is provided with a porous structure. The porous personalized adaptive femoral head necrosis support rod has strong personalized adaptation. The shape of the head matches the cavity surface left after the removal of dead bone in the patient's marrow core, can maximize the contact area of the head and the patient's subchondral bone, improve the ability of the support rod to resist pressure and support the subchondral bone, and effectively prevent collapse.

Description

Technical Field

[0001] This invention belongs to the field of medical devices, specifically an adaptive porous femoral head necrosis support rod. Background Technology

[0002] Avascular necrosis of the femoral head (ONFH) refers to a disease caused by interruption or damage to the blood supply to the femoral head, leading to the death of bone cells and bone marrow components, subsequent repair, and ultimately, structural changes, collapse, and joint dysfunction of the femoral head. Data shows that ONFH commonly affects young and middle-aged adults between 20 and 50 years old. If not treated promptly in the early stages of necrosis, it often progresses to femoral head collapse, necessitating total hip replacement. Currently, the lifespan of hip prostheses used clinically is generally 15-20 years, and young and middle-aged adults undergoing total hip replacement often face the issue of prosthesis revision. Therefore, finding minimally invasive, safe, and effective treatments for ONFH has been a hot topic in orthopedic research. For patients with early-stage ONFH, femoral head preservation is the preferred method. One relatively effective treatment for early-stage femoral head necrosis is core decompression surgery combined with implant support. Core decompression removes necrotic bone within the femoral head, reducing excessive pressure. The implant provides effective support to the subchondral bone plate when reconstructing bone defects in the weight-bearing areas of the femoral head after internal decompression.

[0003] Currently, the implants used in large-scale clinical applications are tantalum rods with a regular porous structure. They have good biocompatibility with the human body and an elastic modulus similar to that of bone, providing good support. However, the actual biomechanical properties of the proximal femur vary significantly, especially in the distribution of trabecular bone, elastic modulus, and stress conditions in different regions. Regularly porous tantalum rods have a uniform elastic modulus and do not adequately match the actual stress in the proximal femur of patients, resulting in limited targeted treatment. From a mechanical perspective, this can create local stress shielding, ultimately exacerbating femoral head collapse. Furthermore, pathological studies of femoral head tissue in patients with rod loosening have revealed that the average bone ingrowth of tantalum rods with a regular porous structure is only 1.9%, with dispersed bone ingrowth limited to the periphery of the rod to a depth of less than 2 mm. Poor osteoconductivity makes the support rod prone to loosening. Regarding some design details of the support rod, for example, most existing support rods for femoral head necrosis are designed with a hemispherical head. However, the hemispherical shape cannot be well matched with the curved surface of the cartilage cavity where the necrotic bone is scraped during the core decompression procedure, which weakens its resistance to pressure and its ability to support the subchondral bone. In addition, some support rods have a central through hole for drug injection, but the drug flows too fast in the central through hole, which is not conducive to the targeted dispersion of the drug. Summary of the Invention

[0004] The purpose of this invention is to provide an adaptive porous femoral head necrosis support rod to solve the problems of the support rod not being equivalently matched with the actual biomechanical properties of the proximal femur of the patient, poor osteoconductivity, insufficient fit between the head and the curved surface of the cartilage cavity at the site of scraping away necrotic bone, and the inability of injected drugs to be targeted and dispersed.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] An adaptive porous femoral head necrosis support rod includes a head, a body, a thermosensitive osteoconductive layer, and a tail. The head, body, and tail are coaxially connected in sequence, and the thermosensitive osteoconductive layer covers the surface of the body. The shape of the head matches the curved surface of the cavity left after scraping away the necrotic bone. Both the head and body are porous structures. The tail is provided with threads, and the threaded groove is provided with a porous structure.

[0007] Furthermore, the porous structure of the head and body is segmented according to the actual distribution of the main pressure trabeculae and main force trabeculae in the proximal femur. From the head to the junction of the body and tail, it is divided into the pressure trabeculae area, the pressure-tension trabeculae mixed area, and the tension trabeculae area.

[0008] Furthermore, the porous structure of the head and body adopts a minimal curved surface unit structure; no porous structure is set in the connecting section between the body and the tail.

[0009] Furthermore, the body is cylindrical, with a diameter of 6–12 mm and a length of 80 ± 25 mm; the tail has a larger diameter than the body, with a diameter of 8–14 mm and a length of 10–30 mm.

[0010] Furthermore, the body has a channel along the central axis, and several radial spoke-shaped cavities are arranged along the channel direction. The cross-sectional shape of the spoke-shaped cavities is different in the tension trabecular bone region, the pressure-tension trabecular bone mixed region, and the pressure trabecular bone region.

[0011] Furthermore, in the tension trabecular bone region and the tension-pressure trabecular bone mixed region, the spoke-shaped inner cavity has a V-shaped spoke cross-section, with the number of spokes gradually increasing from the tension trabecular bone region to the tension-pressure trabecular bone mixed region, and the spoke width gradually decreasing; in the pressure trabecular bone region, the cross-section is Y-shaped spoke, with the number of spokes gradually increasing from the pressure trabecular bone region to the head, and the number of spokes near the bottom cross-section of the pressure trabecular bone region is equal to or greater than the number of spokes near the cross-section of the tension-pressure trabecular bone mixed region, with the spoke width gradually decreasing; the spoke-shaped inner cavity in the tail section is a straight through hole.

[0012] Furthermore, the material used in the thermosensitive bone conduction layer is a shape memory polymer SMP, which has a sharp head that can penetrate into the surrounding bone tissue, with a size and length on the order of μm.

[0013] Furthermore, the thermosensitive osteoconductive layer is distributed on the porous outer layer of the head and body, and can conform to the surface of the head and body at room temperature or lower. When implanted in the patient's body and reaching body temperature, the thermosensitive osteoconductive layer stands up and penetrates into the surrounding bone tissue, forming a bio-lock with the patient's bone tissue.

[0014] Furthermore, an internal hexagonal hole is provided at the end of the tail.

[0015] Compared with the prior art, the present invention has the following technical effects:

[0016] The porous, personalized, adaptive femoral head necrosis support rod of this invention has a high degree of personalization. Its head shape matches the curved surface of the cavity at the site of core decompression and scraping of necrotic bone, maximizing the contact area between the head and the patient's subchondral bone. This enhances the support rod's resistance to pressure and its ability to support the subchondral bone, effectively preventing collapse. Furthermore, the porous structure of the head and body is segmented according to the actual distribution of trabeculae in the proximal femur, selecting minimal curved surface unit structures and porosities with equivalent mechanical properties. This closely approximates the morphological characteristics and mechanical properties of the patient's natural bone, effectively avoiding stress shielding and ensuring effective support for the femoral head necrosis area.

[0017] The porous, personalized, adaptive femoral head necrosis support rod of this invention employs minimally curved porous units. These units have a relatively high specific surface area, providing more attachment space for osteoblast proliferation and differentiation. Their uniform, transitional surfaces further facilitate the transport of body fluids and osteoblasts within the structure, effectively promoting bone ingrowth. Furthermore, the minimally curved surfaces are determined by mathematical formulas, allowing for the generation of porous structures with varying porosities by changing parameters, thus providing greater freedom in the personalized design of the support rod.

[0018] The porous personalized adaptive femoral head necrosis support rod of the present invention has a temperature-sensitive osteoconductive layer with shape memory adaptive effect. It can conform to the surface of the head and body at room temperature or lower. When implanted in the patient's body and reaches body temperature, it can stand up and penetrate into the surrounding bone tissue, forming a biological lock with the patient's bone tissue. It has good osteoconductive properties and can prevent the support rod from loosening.

[0019] The gradient spoke-shaped cavity of the porous personalized adaptive femoral head necrosis support rod of the present invention can solve the problem that the injected drug flows too fast and cannot be targeted and dispersed into the patient's body. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the planar structure of the personalized adaptive porous femoral head necrosis support rod of the present invention;

[0021] Figure 2 for Figure 1Left cross-sectional view of AA, BB, CC, DD, EE;

[0022] Figure 3 for Figure 1 An exterior illustration.

[0023] Figure 4 for Figure 1 The left view;

[0024] Figure 5 for Figure 1 A schematic diagram of the implantation status.

[0025] The components and parts indicated by the numbers in the diagram are: 1. Head; 2. Body; 3. Thermosensitive osteoconductive layer; 4. Tail; 5. Spoke-shaped cavity; 6. Internal hexagonal foramen; 7. Proximal femur of the patient; 701. Main pressure trabeculae; 702. Main force trabeculae; 201. Pressure trabeculae region; 202. Mixed pressure and tension trabeculae region; 203. Tension trabeculae region. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the embodiments described herein are only for illustration and explanation of the present invention, but the implementation of the present invention is not limited thereto.

[0027] The embodiments of the present invention are given in detail below.

[0028] An adaptive porous femoral head necrosis support rod includes a head, a cylindrical body, a thermosensitive osteoconductive layer, and a threaded tail. The head has a convex curved surface that matches the cavity surface of the necrotic bone removed during core decompression surgery, improving the support rod's resistance to pressure and its ability to support subchondral bone, and facilitating implantation. The porous structure of the head and body is divided into a pressure trabecular bone zone, a pressure-tension trabecular bone mixed zone, and a tension trabecular bone zone, according to the actual distribution of the main pressure trabeculae and main tension trabeculae in the proximal femur, from the head to the junction of the body and tail. The porous unit uses minimal curved surface units, and is designed according to the different zones. By considering the actual stress conditions of the domain within the patient's body, and selecting a minimal curved surface unit structure and porosity with equivalent mechanical properties, the morphology and mechanical properties of the patient's natural bone can be approximated to the greatest extent, effectively avoiding stress shielding. The support rod has a channel along the central axis, with several radial spoke-shaped cavities along the channel direction, which can solve the problem of injected drugs flowing too fast and failing to be targeted and dispersed within the patient's body. When the thermosensitive osteoconductive layer of the support rod reaches body temperature after implantation, it can stand up and penetrate into the surrounding bone tissue, forming a bio-lock with the patient's bone tissue. It has good osteoconductivity and can prevent the support rod from loosening.

[0029] Please see Figure 1 and Figure 3The head 1 has a convex curved surface that matches the cavity left after the removal of necrotic bone during core decompression surgery. This maximizes the contact area between the head and the patient's subchondral bone, enhancing the support rod's resistance to pressure and its ability to support the subchondral bone, effectively preventing collapse and facilitating implantation. The head 1 and body 2 are connected along the same axis and have a porous structure. A thermosensitive osteoconductive layer 3 covers the surface of the body 2. The body 2 and tail 4 are connected along the same axis. The tail 4 has threads with a porous structure in the threaded groove. The body 2 has a diameter of 6–12 mm and a length of 80 ± 25 mm. The tail 4 has a larger diameter than the body, ranging from 8–14 mm, and a length of 10–30 mm.

[0030] Please see Figure 4 The tail end 4 has an internal hexagonal hole 6 to facilitate the insertion of the support rod.

[0031] Please see Figure 5 The porous structure of the head 1 and body 2 is segmented according to the actual distribution of the main pressure trabeculae 701 and main force trabeculae 702 at the proximal femur 7 of the patient. From the head 1 to the connection between the body 2 and the tail 4, it is divided into pressure trabeculae region 201, pressure-tension trabeculae mixed region 202, and tension trabeculae region 203. The porous units of the head 1 and body 2 adopt minimal curved surface units.

[0032] Minimal curved porous units possess a relatively high specific surface area, providing more attachment space for osteoblast proliferation and differentiation. Their uniform, transitional surfaces facilitate the transport of body fluids and osteoblasts within the structure, effectively promoting bone ingrowth. Furthermore, the minimal curved surfaces are determined by mathematical formulas, allowing for the generation of porous structures with varying porosities by changing parameters, thus providing greater freedom in the personalized design of support rods.

[0033] Based on the actual stress conditions of the pressure trabecular bone region 201, the pressure-tension trabecular bone mixed region 202, and the tension trabecular bone region 203 within the patient's body, a minimally curved surface unit structure and porosity with equivalent mechanical properties are selected. This approach closely approximates the morphological characteristics and mechanical properties of the patient's natural bone, effectively avoiding stress shielding and ensuring effective support for the femoral head necrosis area. No porous structures are incorporated within the length connecting the body and tail sections to ensure the support rod does not break.

[0034] Please see Figure 1 and Figure 2The adaptive porous femoral head necrosis support rod of this invention has a channel along its central axis inside, and several radial spoke-shaped inner cavities 5 are arranged along the channel direction. The diameter of the central channel of the spoke-shaped inner cavity 5 is 2-6 mm. The cross-sectional shape of the spoke-shaped inner cavity is different in the tension trabecular bone region 203, the pressure-tension trabecular bone mixed region 202, and the pressure trabecular bone region 203. In the tension trabecular bone region 203 and the tension-pressure trabecular bone mixed region 202, the cross-section is V-shaped spoke-shaped, and the number of spokes gradually increases from the tail of the tension trabecular bone region 203 to the top of the pressure-tension trabecular bone mixed region 202 at a certain length interval, while the spoke width gradually decreases. In the pressure trabecular bone region 201, the cross-section is Y-shaped spoke-shaped, and the number of spokes gradually increases from the bottom to the top of the pressure trabecular bone region 201 at a certain length interval, and the number of spokes near the bottom cross-section of the pressure trabecular bone region 201 is equal to or greater than the number of spokes near the top cross-section of the pressure-tension trabecular bone mixed region 202, while the spoke width gradually decreases.

[0035] Please see Figure 3 The material used for the thermosensitive osteoconducting layer 3 is a shape memory polymer (SMP) that can deform under temperature stimulation and promote bone cell growth. Its shape is a small spike, triangle, or long rhombus, with a relatively sharp head that can penetrate into the surrounding bone tissue. The size and length are on the order of μm. The thermosensitive osteoconducting layer is distributed on the porous ribs of the outer layer of the porous structure of the head 1 and the body 2. At room temperature or lower, it can conform to the surface of the head 1 and the body 2. When implanted in the patient's body and reaches body temperature, the thermosensitive osteoconducting layer stands up and penetrates into the surrounding bone tissue. It has a shape memory adaptive effect and can form a biological lock with the patient's bone tissue. It has good osteoconductivity and can prevent the support rod from loosening.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An adaptive porous femoral head necrosis support rod, characterized in that, It includes a head (1), a body (2), a thermosensitive bone conduction layer (3), and a tail (4); the head (1), body (2), and tail (4) are coaxially connected in sequence; the shape of the head (1) matches the curved surface of the cavity left after scraping away the dead bone, and both the head (1) and body (2) are porous structures; the tail (4) is provided with threads, and the thread groove is provided with a porous structure; The porous structure of the head (1) and body (2) is divided into segments according to the actual distribution of the main pressure trabeculae (701) and main force trabeculae (702) of the proximal femur (7). From the head (1) to the junction of the body (2) and tail (4), it is divided into pressure trabeculae area (201), pressure-tension trabeculae mixed area (202) and tension trabeculae area (203). The porous structure of the head (1) and body (2) adopts a minimal curved surface unit structure; no porous structure is provided in the connecting section between the body (2) and the tail (4); The thermosensitive bone conduction layer (3) is distributed on the porous structure of the head (1) and body (2) on the outer layer of the porous ribs. It can adhere to the surface of the head (1) and body (2) at room temperature or lower temperature. When implanted in the patient's body and reaches body temperature, the thermosensitive bone conduction layer stands up and penetrates into the surrounding bone tissue, forming a biological lock with the patient's bone tissue. The body (2) has a channel along the central axis inside, and several radial spoke-shaped cavities (5) are arranged along the channel direction. The spoke-shaped cavities (5) have different cross-sectional shapes in the tension trabecular bone region (203), the pressure tension trabecular bone mixed region (202), and the pressure trabecular bone region (201). In the tension trabecular bone region (203) and the pressure tension trabecular bone mixed region (202), the spoke-shaped inner cavity (5) has a V-shaped spoke cross section. The number of spokes gradually increases from the tension trabecular bone region (203) to the pressure tension trabecular bone mixed region (202), and the spoke width gradually decreases. In the pressure trabecular bone region (201), the spoke-shaped inner cavity (5) has a Y-shaped spoke cross section. The number of spokes gradually increases from the pressure trabecular bone region (201) to the head. The number of spokes near the bottom cross section of the pressure trabecular bone region (201) is equal to or greater than the number of spokes near the cross section of the pressure tension trabecular bone mixed region (202), and the spoke width gradually decreases. The spoke-shaped inner cavity (5) is a through hole in the tail section (4).

2. The adaptive porous femoral head necrosis support rod according to claim 1, characterized in that, The body (2) is cylindrical, with a diameter of 6~12mm and a length of 80±25mm; the tail (4) has a larger diameter than the body (2), with a diameter of 8~14mm and a length of 10~30mm.

3. The adaptive porous femoral head necrosis support rod according to claim 1, characterized in that, The material used in the thermosensitive osteoconductive layer (3) is shape memory polymer SMP, which has a sharp head that can penetrate into the surrounding bone tissue and has a size on the order of μm.

4. The adaptive porous femoral head necrosis support rod according to claim 1, characterized in that, The tail (4) has an internal hexagonal hole (6) at the end.

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