3d-printed augmenting sleeve for post-hip arthroplasty bone defects

Abstract

The present application relates to the technical field of medical devices, and especially relates to a 3D printing enhanced sleeve for bone defect after hip arthroplasty, which comprises a sleeve assembly, the sleeve assembly comprises an inner sleeve and an outer sleeve, the inner sleeve is in a hollow sleeve shape and is provided with a receiving porous area on the outer wall, the outer sleeve comprises a plurality of arc-shaped outer segments, a sliding micro-gap is arranged between the inner sleeve and the outer sleeve and is connected through an integrated elastic suspension reset piece, and the outer wall surface of the outer segment is provided with a porous channel which penetrates through the wall thickness and extends towards the receiving porous area. A degradable elastic damping medium is filled in the sliding micro-gap, and the porous channel, the sliding micro-gap and the receiving area are sequentially connected. In the early stage after the operation, the reset piece and the damping medium are used to realize multidirectional micro-elastic buffering and energy dissipation, so as to ensure the safety of fragile bone. In the later stage, the damping medium is degraded, the new bone crosses the micro-gap through the channel, and a high-rigidity biological bone bridge which locks the inner and outer layers is formed, so that the transition from early shock avoidance to later self-locking is realized.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, and in particular to a 3D-printed reinforcing sleeve for bone defects after hip replacement surgery. Background Technology

[0002] In total hip arthroplasty, periprosthetic bone defects (especially large-area bone loss in the proximal femur) are a common cause of prosthesis loosening, subsidence, and replacement failure. In recent years, the use of 3D-printed porous reinforcing sleeves to fill medullary cavity defects and promote host bone ingrowth has become a common clinical approach for reconstructing joint stability. Especially for patients with osteoporosis, the sleeve design must not only fill the anatomical space but also consider biocompatibility and interfacial adaptation during bone ingrowth.

[0003] However, existing periprosthetic reinforcement sleeves still face the following shortcomings in practical applications. First, they lack an early postoperative stress buffering and energy dissipation mechanism. Most existing reinforcement sleeves are one-piece rigid structures. In the early postoperative period, especially when patients put weight on themselves or move excessively, the rigid sleeve directly transmits localized peak stress to the fragile osteoporotic cortical bone, easily inducing periprosthetic microfractures or severing newly formed capillaries and bone buds that have not yet ingrained into the channel due to excessive micromovement at the interface. Second, they cannot cope with late-stage periprosthetic bone resorption. In the mid-to-late postoperative period, due to mechanical shielding or physiological mechanisms, bone remodeling and resorption often occur around the prosthesis. Because the outer contour dimensions of traditional sleeves are fixed, once bone resorption causes a small gap between the sleeve and the host bone, traditional sleeves cannot adaptively deform and fine-tune, easily leading to aseptic loosening due to interface relaxation. Furthermore, if flexible or slippery structures are used to buffer early stress, the long-term rigid load-bearing capacity required under heavy loads cannot be provided after bone healing is complete, resulting in a lack of dynamic adaptive transition of stiffness from early flexible buffering to later rigid self-locking of the sleeve. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a 3D-printed reinforcing sleeve for bone defects after hip replacement surgery.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A 3D-printed reinforcing sleeve for bone defects after hip replacement surgery includes a sleeve assembly for fitting around the periphery of the femoral stem and adapting to the proximal medullary cavity of the femur. The sleeve assembly is connected to the femoral head via the femoral stem that is locked thereon. The sleeve assembly includes an inner sleeve and an outer sleeve. The inner sleeve has a hollow sleeve structure and a receiving porous area is provided on the outer wall of the inner sleeve. The outer sleeve includes a plurality of arc-shaped outer segments arranged around the inner sleeve. A sliding microgap is provided between the outer wall of the inner sleeve and the inner wall of each arc-shaped outer segment. The inner sleeve and each of the arc-shaped outer segments are integrally connected by a plurality of elastic suspension and repositioning plates. The elastic suspension and repositioning plates are suspended in the sliding microgap, so that the arc-shaped outer segments and the inner sleeve are elastically suspended. Each arc-shaped outer segment has a plurality of through-hole channels on its outer wall surface. Each of the porous channels penetrates the wall thickness of the arc-shaped outer segment and extends toward the receiving porous area on the surface of the inner sleeve. The sliding microgap is filled with a biodegradable elastic damping medium. The porous channels, the sliding microgap and the receiving porous area are sequentially connected to allow new bone tissue to grow in.

[0006] Furthermore, each of the porous channels extends obliquely from the outer surface of the arc-shaped outer flap inward toward the proximal end of the inner sleeve, with the angle between the central axis of each porous channel and the longitudinal axis of the inner sleeve being 30°–60°. When a person stands and walks, the load on the hip joint is transmitted obliquely downward along the femoral head. The oblique angle formed by the porous channels thus promotes the directional growth of new bone tissue along this physiological force line, bridging the inner sleeve and the arc-shaped outer flap. When the patient later bears weight while walking, and the femoral stem generates a small downward axial thrust, this force is converted into a pure compressive load along the axial direction of the oblique bone column. This force mechanism allows the mineralized living bone bridge to resist axial loads with extremely high load-bearing capacity, thereby reducing the risk of prosthesis subsidence in the later stages and playing a role in anti-subsidence and anti-rotation locking.

[0007] Furthermore, the receiving porous region has a three-dimensional ingrowth mesh structure with a pore size of 150μm to 300μm, and the porous channel has a pore size of 500μm to 800μm. The outer arc-shaped, segmented porous channel has a large pore size, providing ample space, which not only facilitates the rapid ingrowth of new bone tissue and microvessels but also avoids the problem of ingrowth interruption caused by premature blockage of the porous channel by local amorphous blood clots. The inner receiving porous region adopts a microporous mesh structure. When bone progenitor tissue passes through the channel to reach this point, the microporous mesh provides a large active surface area, which is conducive to the adsorption and adhesion of osteoblasts and bone matrix mineralization, achieving high-density micro-interlocking of new bone trabeculae on the surface of the inner sleeve.

[0008] Furthermore, each porous channel has a drug-loaded porous micro / nano coating on its inner wall surface, wherein the drug-loaded porous micro / nano coating is loaded with bone morphogenetic protein or basic fibroblast growth factor. The drug-loaded porous micro / nano coating is a micro / nano bilevel titanium dioxide layer or a chitosan-gelatin drug-loaded composite coating prepared on the inner surface of the porous channel by electrochemical deposition. Osteoporosis patients have low bone remodeling activity and slow bone ingrowth rate. By loading active primers into the porous channels, local slow release can be achieved in the early postoperative period, directionally activating osteogenic progenitor cells in the bone defect area. This helps guide the new bone tissue to accelerate its ingrowth along the porous channels, thereby ensuring that bone tissue can pass through the sliding microgap and eventually grow into the receiving porous area at a predetermined time point, even in an environment with poor cancellous bone quality.

[0009] Furthermore, the elastic suspension reset plate is an elastically bent sheet structure with an Ω-shaped, S-shaped, or C-shaped cross-section, and the elastic suspension reset plate is integrally formed with the inner sleeve and each of the arc-shaped outer segments by 3D printing from titanium alloy or PEEK material. Utilizing selective laser melting (SLM) technology or 3D printing technology for PEEK material, the elastic suspension reset plate, inner sleeve, and arc-shaped outer segments are integrally formed without interface welding, thereby eliminating the interface stress concentration and fretting wear problems common in split assembly structures. The Ω-shaped, S-shaped, or C-shaped elastic curved sheet structure has undergone topological mechanics optimization, allowing the bent sheet to undergo elastic buckling deformation under combined axial and radial loads transmitted from the femoral stem. The isotropic elastic yielding characteristic can filter instantaneous peak shear force, while providing self-resetting elastic force for the arc-shaped outer segments after unloading, ensuring that the entire sleeve assembly maintains dynamic balance throughout the early gait cycle.

[0010] Furthermore, the biodegradable elastic damping medium includes at least one of cross-linked sodium hyaluronate hydrogel, collagen-gelatin copolymer, or polylactic acid-caprolactone elastomer. The biodegradable elastic damping medium fills the sliding micro-gap between the inner sleeve and the arc-shaped outer flap, wrapping around the periphery of the elastic suspension reduction plate. During early postoperative limb movement, the inner sleeve and the arc-shaped outer flap undergo slight sliding, causing shear rheology in the biodegradable elastic damping medium. The internal shear resistance of the viscoelastic fluid combines with the elastic restoring force of the elastic suspension reduction plate to form a composite damping system, converting the instantaneous mechanical impact energy that could easily lead to fracture into shear energy dissipation within the medium, thus avoiding the impact of high-peak stress on brittle bone. As hydrolysis or enzymatic reactions proceed, the medium gradually degrades and is safely absorbed by body fluids, creating sufficient space for subsequent interstitial ingrowth of new bone tissue.

[0011] Furthermore, the width of the sliding microgap along the radial direction of the inner sleeve is 0.3mm to 0.8mm. Within the range of 0.3mm to 0.8mm, the sliding microgap ensures both the thickness of the damping shear layer and the ability for the bone bridge to traverse the microgap within 12 cycles.

[0012] Furthermore, when the elastic suspension repositioning piece undergoes elastic deformation, the maximum relative axial displacement between the inner sleeve and each of the arc-shaped outer flaps is 100μm~150μm, and the maximum relative radial displacement is 50μm~80μm. The mechanical micro-strain generated when the micro-movement at the prosthesis-bone interface is less than 150μm will generate mechanobiological strain stimulation through the cytoskeleton, promoting osteoblast differentiation and the growth of new cancellous bone. However, when the micro-movement exceeds 150μm, the multi-directional high-intensity shear force will destroy the early cartilage callus tissue, leading to the ingrowth of fibrous connective tissue and the formation of fibrous healing. By controlling the extreme displacement values ​​of the arc-shaped outer flaps within an extremely narrow range of 100μm~150μm axially and 50μm~80μm radially, the shear slip at the bone interface is precisely locked within the bone-promoting micro-strain window, allowing the micro-movements during the patient's daily walking to be converted into bone-promoting forces.

[0013] Furthermore, the outer wall of the inner sleeve is provided with an integrally formed limiting protrusion, and the inner wall of each of the arc-shaped outer segments is provided with a matching limiting groove. The limiting protrusion extends into the limiting groove to limit the maximum relative displacement between the inner sleeve and the arc-shaped outer segments. During normal gait, the elastic suspension reset plate undergoes elastic deformation, and the limiting protrusion floats freely within the limiting groove without touching the side wall of the groove. If the patient falls or experiences a severe impact, causing the input load to exceed the safe bearing limit of the elastic suspension reset plate, the limiting protrusion will instantly impact the side wall of the limiting groove, causing the inner sleeve and the arc-shaped outer segments to become rigidly locked. The destructive force of the overload will bypass the elastic suspension reset plate and be distributed and transmitted to the distal end by the entire sleeve assembly.

[0014] Furthermore, an elastic buffer layer is fixed to the inner wall of the limiting groove. The elastic buffer layer is made of medical-grade silicone rubber or medical-grade polyurethane. The elastic buffer layer is fixed to all impact boundaries inside the limiting groove by ultrasonic welding or bonding. When the limiting protrusion touches the side wall of the limiting groove under extreme overload conditions, it first compresses the elastic buffer layer. The compression process of the polymer elastic pad has a significant stress damping effect, making the deceleration curve during extreme impact tend to be gentle and suppressing the impact stress wave, thereby reducing the instantaneous local bone pressure transmitted to the brittle greater trochanter or metaphysis cancellous bone, and avoiding fractures.

[0015] Furthermore, the sleeve assembly is connected to the femoral stem via the inner wall surface of the inner sleeve. The inner wall surface is provided with a micron-level anti-slip crystalline layer, allowing the inner sleeve and the outer mating surface of the femoral stem to be connected via a Morse taper fit. The Morse taper angle on the inner surface of the inner sleeve corresponds to the proximal taper of the matching femoral stem. The 3D-printed micron-level anti-slip crystalline layer consists of multi-faceted micro-titanium crystals with a height of 50μm to 150μm. Postoperatively, when the surgeon inserts the femoral stem into the inner sleeve using a hammer, the micron-level anti-slip crystalline layer undergoes microscopic plastic deformation under the axial impact wedging force, forming multi-point physical interlocking with the outer mating surface of the femoral stem, thus providing high-strength Morse taper interlocking.

[0016] Furthermore, a sealing groove is provided between each of the two adjacent arc-shaped outer segments, and an elastic sealing strip is embedded between the two adjacent sealing grooves to seal the gap between the arc-shaped outer segments and prevent the loss of the biodegradable elastic damping medium in the sliding microgap. The elastic sealing strip is tightly embedded in the relative sealing groove of the adjacent arc-shaped outer segments through an interference fit, completely blocking the circumferential physical gap of the sleeve assembly. In the early postoperative period after implantation, if the biodegradable elastic damping medium leaks outward under the high-frequency shear compression of the gait cycle, it will not only cause the damping energy dissipation mechanism in the sliding microgap to fail prematurely, but the free hydrogel may also cause local sterile fluid accumulation around the prosthesis. The elastic sealing strip provides a physical barrier to firmly lock the damping medium in the microgap. At the same time, its highly elastic material can conform to the circumferential expansion and contraction of the arc-shaped outer segments, maintaining a sealed state when the outer segments are relatively displaced.

[0017] Furthermore, the elastic sealing strip is made of a biodegradable polymer, and its degradation rate in the human body is greater than that of the biodegradable elastic damping medium. The elastic sealing strip is made of fast-degrading materials such as low-molecular-weight polylactic-co-glycolic acid copolymer. Its biodegradation cycle is controlled within 2-4 weeks post-surgery, shorter than the degradation cycle of the damping medium. The 2-4 weeks post-surgery period is critical for the initiation of local new capillary networks and connective tissue fiber networks into the outer flap. By allowing the elastic sealing strip to degrade and dissipate at an early stage, the circumferential seal between the outer flaps naturally dissipates and transforms into a physical window. The surrounding living microcirculation system can then promptly penetrate the outer flap gap and laterally invade towards the inner sleeve, promoting the reconstruction of multi-directional blood supply to the bone tissue, thereby improving the speed and quality of bone integration.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention, by setting an elastic suspension repositioning plate and cooperating with a biodegradable elastic damping medium filled in the sliding micro-gap, can provide a small amount of axial and radial elastic buffer displacement when the patient bears weight or experiences movement deviation in the early postoperative period, thereby achieving fluid shear energy dissipation buffer. This not only helps to disperse and mitigate the peak stress transmitted to the fragile cortical bone, but also reduces the risk of early fracture and shearing of new bone tissue. 2. The arc-shaped outer flap of the present invention maintains a small degree of mobility, and the porous channel extends inclinedly from the outside to the inside towards the proximal end. When micro-movement or slight subsidence occurs due to bone resorption in the later stage, the inclined porous channel can guide the ingrained bone tissue to mainly bear compressive stress during daily weight-bearing, thereby effectively utilizing the good compressive resistance of bone tissue and forming a bio-locking effect to resist subsidence, so as to compensate for the interface gap and reduce the probability of aseptic loosening in the later stage. 3. In this invention, the porous channel, sliding microgap, and receiving porous area are sequentially connected. In the early postoperative period, the degradable damping medium provides a flexible elastic defense. As the damping medium gradually and safely degrades, new bone tissue crosses the sliding microgap through the through channel and grows directly and adheres to the receiving porous area of ​​the inner sleeve, forming a living bone bridge connecting the inner and outer sleeves. This enables the sleeve to adaptively transition from an early elastic shock-absorbing state to a later high-rigidity biological locking state. Attached Figure Description

[0019] Figure 1 This is a cross-sectional structural diagram of the present invention; Figure 2 This is an exploded view of the present invention; Figure 3 This is a partially enlarged schematic diagram of the connection between the inner sleeve and the outer sleeve; Attached diagram labels: 1-Inner sleeve, 101-Receiving porous area, 102-Limiting protrusion, 2-Arc-shaped outer segment, 201-Porous channel, 3-Elastic suspension reset piece, 4-Degradable elastic damping medium, 5-Limiting groove, 6-Elastic buffer pad, 7-Elastic sealing strip, 8-Femoral stem. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0021] Example 1, as Figures 1-3As shown, the present invention discloses a 3D-printed reinforcing sleeve for bone defects after hip replacement surgery, comprising a sleeve assembly for fitting around the femoral stem 8 and adapting to the proximal medullary cavity of the femur. The sleeve assembly is connected to the femoral head through the femoral stem 8 locked thereon. The sleeve assembly includes an inner sleeve 1 and an outer sleeve. The inner sleeve 1 has a hollow sleeve structure. The outer wall of the inner sleeve 1 is provided with a receiving porous area 101. The outer sleeve includes a plurality of arc-shaped outer segments 2 arranged around the inner sleeve 1. A sliding microgap is provided between the outer wall of the inner sleeve 1 and the inner wall of each arc-shaped outer segment 2. The inner sleeve 1 and each of the arc-shaped outer segments 2 are integrally connected by a plurality of elastic suspension repositioning plates 3. The elastic suspension repositioning plates 3 are suspended in the sliding microgap, so that the arc-shaped outer segments 2 and the inner sleeve 1 are elastically suspended. Each arc-shaped outer segment 2 has a plurality of through porous channels 201 on its outer wall surface. Each porous channel 201 penetrates the wall thickness of the arc-shaped outer segment 2 and extends toward the receiving porous area 101 on the surface of the inner sleeve 1. The sliding microgap is filled with a biodegradable elastic damping medium 4. The porous channels 201, the sliding microgap and the receiving porous area 101 are sequentially connected to allow new bone tissue to grow in.

[0022] Each porous channel 201 has a drug-loaded porous micro / nano coating on its inner wall surface, wherein the drug-loaded porous micro / nano coating is loaded with bone morphogenetic protein-2 or basic fibroblast growth factor. Specifically, the drug-loaded porous micro / nano coating is a micro / nano bilevel titanium dioxide layer or a chitosan-gelatin drug-loaded composite coating prepared on the inner surface of the porous channel 201 by electrochemical deposition. Osteoporosis patients have low bone remodeling activity and slow bone ingrowth. By loading bone morphogenetic protein-2 (BMP-2) or basic fibroblast growth factor (bFGF) into the porous channel 201, these active promoters can be slowly released locally in the early postoperative period (4-8 weeks), and directionally activate osteogenic progenitor cells in the bone defect area. This helps guide newly formed bone tissue to grow into the porous channel 201 at an accelerated pace, thereby ensuring that bone tissue can pass through the sliding microgap and eventually grow into the receiving porous region 101 at predetermined time points in an environment with poor cancellous bone quality, providing a bone mass basis for the mid-to-late stage of biological bridging and self-locking.

[0023] The elastic suspension repositioning plate 3 is an elastically bent sheet structure with an Ω-shaped, S-shaped, or C-shaped cross-section. The elastic suspension repositioning plate 3 is integrally formed from titanium alloy or PEEK material with the inner sleeve 1 and each of the arc-shaped outer segments 2 via 3D printing. Specifically, using selective laser melting (SLM) technology or 3D printing technology with PEEK material, the elastic suspension repositioning plate 3 is integrally formed with the inner sleeve 1 and the arc-shaped outer segments 2 through interface-free welding, thereby eliminating the interface stress concentration and fretting wear problems common in split assembly structures. The Ω-shaped, S-shaped, or C-shaped elastic curved sheet structure has undergone topological mechanics optimization, allowing the bent sheet to undergo elastic buckling deformation under the combined axial and radial loads transmitted by the femoral stem 8. The isotropic elastic yielding feature can filter instantaneous peak shear force and provide self-resetting elastic force for the arc-shaped outer flap 2 after unloading, so that the entire sleeve assembly can maintain dynamic balance in the gait cycle in the early postoperative period (especially within 12 weeks after surgery when the degradable elastic damping medium 4 has not been fully degraded).

[0024] The biodegradable elastic damping medium 4 comprises at least one of cross-linked sodium hyaluronate hydrogel, collagen-gelatin copolymer, or polylactic acid-caprolactone elastomer. Specifically, the biodegradable elastic damping medium 4 fills the sliding micro-gap between the inner sleeve 1 and the arc-shaped outer flap 2, wrapping around the periphery of the elastic suspension reduction plate 3. During early postoperative limb movement, the inner sleeve 1 and the outer sleeve undergo slight sliding, causing shear rheology of the biodegradable elastic damping medium 4. The internal shear resistance of the viscoelastic fluid combines with the elastic restoring force of the elastic suspension reduction plate 3 to form a composite shock absorption system, converting the instantaneous mechanical impact energy that could easily lead to fracture into shear energy dissipation within the medium, thus avoiding the impact of high peak stress on brittle bone. Its degradation kinetics are controlled within 8 to 12 weeks. As hydrolysis or enzymatic reactions proceed, the medium gradually degrades and is safely absorbed by body fluids, creating sufficient space for subsequent interstitial ingrowth of new bone tissue.

[0025] The inner sleeve 1 has an integrally formed limiting protrusion 102 on its outer wall surface, and each of the arc-shaped outer segments 2 has a corresponding limiting groove 5 on its inner wall surface. The limiting protrusion 102 extends into the limiting groove 5 to limit the maximum relative displacement between the inner sleeve 1 and the arc-shaped outer segments 2. Specifically, during normal gait, the elastic suspension repositioning plate 3 undergoes elastic deformation, and the limiting protrusion 102 floats freely within the limiting groove 5 without touching the side wall of the groove 5. If the patient falls or experiences a severe impact, causing the input load to exceed the safe bearing limit of the elastic suspension repositioning plate 3, the limiting protrusion 102 will instantly impact the side wall of the limiting groove 5, causing the inner sleeve 1 and the arc-shaped outer segments 2 to become rigidly locked. The destructive force of the overload will bypass the elastic suspension repositioning plate 3 and be distributed and transmitted to the distal end by the entire sleeve assembly. This protects the integrally printed elastic suspension repositioning plate 3 from plastic deformation or fatigue fracture, thereby maintaining the mechanical safety of the overall implant structure.

[0026] An elastic buffer layer 6 is fixed to the inner wall of the limiting groove 5. The elastic buffer layer 6 is made of medical-grade silicone rubber or medical-grade polyurethane. Specifically, the elastic buffer layer 6 is fixed to all impact boundaries inside the limiting groove 5 by ultrasonic welding or bonding. When the limiting protrusion 102 touches the side wall of the limiting groove 5 under extreme overload conditions, it first compresses the elastic buffer layer 6. The compression process of the polymer elastic layer has a significant stress damping effect, making the deceleration curve during extreme impact tend to be flat and suppressing the impact stress wave, thereby reducing the instantaneous local bone pressure transmitted to the brittle greater trochanter or metaphysis cancellous bone, avoiding catastrophic fractures, and also avoiding the risk of micro-particle abrasion debris generated by direct metal impact.

[0027] The sleeve assembly is connected to the femoral stem 8 via the inner wall surface of the inner sleeve 1. The inner wall surface is provided with a micron-level anti-slip crystalline layer, which allows the inner sleeve 1 and the outer mating surface of the femoral stem 8 to be connected via a Morse taper fit. Specifically, the Morse taper angle on the inner surface of the inner sleeve 1 corresponds to the proximal taper of the femoral stem 8. The 3D-printed micron-level anti-slip crystalline layer consists of multi-faceted micro-titanium crystals with a height of 50μm to 150μm. Postoperatively, when the surgeon inserts the femoral stem 8 into the inner sleeve 1 using a hammer, the micron-level anti-slip crystalline layer undergoes microscopic plastic deformation under the axial impact wedging force, forming multi-point physical interlocking with the outer mating surface of the femoral stem 8, thus providing high-strength Morse taper interlocking.

[0028] A sealing groove is provided between each of the two adjacent arc-shaped outer segments 2, and an elastic sealing strip 7 is embedded between the two adjacent sealing grooves to seal the gap between the arc-shaped outer segments 2 and prevent the loss of the biodegradable elastic damping medium 4 in the sliding microgap. Specifically, the elastic sealing strip 7 is tightly embedded in the corresponding sealing groove of the adjacent arc-shaped outer segments 2 through an interference fit, completely blocking the circumferential physical gap of the sleeve assembly. In the early postoperative period after implantation, if the biodegradable elastic damping medium 4 (such as hydrogel fluid) leaks outward under the high-frequency shear compression of the gait cycle, it will not only cause the damping energy dissipation mechanism in the sliding microgap to fail prematurely, but the free hydrogel may also cause local sterile fluid accumulation around the implant. The elastic sealing strip 7 provides a physical barrier to firmly lock the damping medium 4 in the microgap. At the same time, its highly elastic material can adapt to the circumferential expansion and contraction of the arc-shaped outer segments 2, maintaining a sealed state when the outer segments are relatively displaced.

[0029] The elastic sealing strip 7 is made of a biodegradable polymer, and its degradation rate in the human body is greater than that of the biodegradable elastic damping medium 4. Specifically, the elastic sealing strip 7 is made of fast-degrading materials such as low molecular weight polylactic-glycolic acid copolymer (PLGA). Its biodegradation cycle is controlled within 2-4 weeks postoperatively, significantly shorter than the degradation cycle of the damping medium 4 (8-12 weeks). The 2-4 weeks postoperative period is a critical period for the local newly formed capillary network and connective tissue fiber network to begin ingrowth into the outer flap. By allowing the elastic sealing strip 7 to degrade and dissipate at an early stage, the circumferential seal between the outer flaps naturally dissipates and transforms into a physical window. The surrounding living microcirculation system can then promptly penetrate the outer flap gap and laterally invade towards the inner sleeve 1, promoting the reconstruction of multi-directional blood supply to the bone tissue, thereby improving the speed and quality of bone integration.

[0030] Example 2: Based on Example 1, this example proposes a through-type inclined porous channel based on a sleeve assembly.

[0031] Each of the porous channels 201 extends obliquely from the outer surface of the arc-shaped outer flap 2 inward toward the proximal end of the inner sleeve 1, with the angle between the central axis of each porous channel 201 and the longitudinal axis of the inner sleeve 1 being 30° to 60°. Specifically, based on the physiological orientation of the natural heavy-duty trabecular meshwork of the proximal femur, the optimal angle is 45°. When a person stands and walks, the load borne by the hip joint is transmitted obliquely downward along the femoral head. The oblique angle formed by each porous channel 201 thus promotes the directional growth of new bone tissue along this physiological force line and bridges the inner sleeve 1 and the arc-shaped outer flap 2. When the patient later bears weight and walks, when the femoral stem 8 generates a small downward axial thrust, this force is converted into a pure compressive load along the axial direction of the oblique bone column. Based on the characteristic that bone tissue is resistant to compression but not to shear or tension, this force mechanism allows the mineralized living bone bridge to resist axial load with extremely high load-bearing capacity, thereby reducing the risk of prosthesis subsidence in the later stages and playing a role in anti-subsidence and anti-rotation locking.

[0032] The receiving porous region 101 has a three-dimensional ingrowth mesh structure with a pore size of 150μm to 300μm, and the porous channel 201 has a pore size of 500μm to 800μm. Specifically, the porous channel 201 of the outer arc-shaped outer flap 2 has a large pore size, providing ample space, which not only facilitates the rapid ingrowth of new bone tissue and microvessels, but also avoids the problem of ingrowth interruption caused by premature blockage of the porous channel 201 by local amorphous blood clots. The inner receiving porous region 101 adopts a microporous mesh structure. When bone progenitor tissue passes through the channel to reach this location, the microporous mesh provides a large active surface area, which is conducive to the adsorption and adhesion of osteoblasts and the mineralization of bone matrix, achieving high-density micro-interlocking of new bone trabeculae on the surface of the inner sleeve 1.

[0033] Example 3: Based on Example 2, this example proposes a suspension fit structure based on the extreme range of sliding micro-gap and micro-displacement control.

[0034] The sliding microgap has a radial width of 0.3mm to 0.8mm along the inner sleeve 1. Specifically, if the sliding microgap width is less than 0.3mm, when the inner sleeve 1 and the arc-shaped outer segment 2 slide relative to each other under load, the degradable elastic damping medium 4 is easily over-compressed and sheared and prematurely emptied, resulting in dry friction between metals and failing to achieve early low-hardness buffering. Conversely, if the gap width is greater than 0.8mm, due to the limited bridging ability of bone growth in an unsupported space, an extremely long span microgap will significantly prolong the time for later osteogenic bridging or even cause bridging fracture. Therefore, within the range of 0.3mm to 0.8mm, the sliding microgap ensures both the thickness of the damping shear layer and that the bone bridge can traverse the microgap within 12 weeks.

[0035] When the elastic suspension repositioning piece 3 undergoes elastic deformation, the maximum relative axial displacement between the inner sleeve 1 and each of the arc-shaped outer segments 2 is 100μm~150μm, and the maximum relative radial displacement is 50μm~80μm. Specifically, according to Wolff's law of bone remodeling and the theory of osteogenic micromotion barrier, the mechanical microstrain generated when the relative micromotion between the sleeve assembly and the bone interface is less than 150μm will generate mechanobiological strain stimulation through the cytoskeleton, promoting osteoblast differentiation and the growth of new cancellous bone. However, when the micromotion exceeds 150μm, the multi-directional high-intensity shear force will destroy the early cartilage callus tissue, leading to the ingrowth of fibrous connective tissue and the formation of fibrous healing. In this embodiment, the relative axial displacement between the inner sleeve 1 and each of the arc-shaped outer segments 2 is controlled within an extremely narrow range of 100μm~150μm, and the relative radial displacement is controlled within a range of 50μm~80μm. The shear slip at the bone interface is precisely locked within the micro-strain window that promotes bone growth, so that the slight micro-movements during the patient's daily walking are transformed into bone growth-promoting forces.

[0036] Example 4, based on Example 3, proposes a specific implantation procedure for a 3D-printed reinforcing sleeve for bone defects after hip replacement surgery.

[0037] S1: High-resolution CT scans were performed on the pelvis and affected femur of osteoporosis patients to obtain three-dimensional DICOM data of bone defects. Using computer-aided design, personalized three-dimensional models were created for the medial cortex, greater trochanter, and medullary canal bone defects in the proximal femur caused by bone resorption or prosthesis loosening. A combined solid model of an inner sleeve 1 and an arc-shaped outer flap 2 was designed, with the outer contour conforming to the anatomical deformation of the residual cortical and cancellous bone, and the inner surface adapted to the Mohs taper of the standard femoral stem.

[0038] S2: Using selective metal melting (SLM) 3D printing technology, the designed sleeve assembly is integrally formed using medical-grade titanium alloy (Ti6Al4V). After printing, a biodegradable elastic damping medium 4, such as cross-linked sodium hyaluronate hydrogel, is uniformly and pressurized into the sliding microgap through the gap between the inner sleeve 1 and the arc-shaped outer segment 2. A rapidly degradable PLGA elastic sealing strip 7 is then pressed into the lateral sealing groove between adjacent arc-shaped outer segments 2. Finally, an electrochemical deposition layer of BMP-2 osteogenic drug solution is loaded onto the inner wall of the porous channel 201, completing the pre-assembly of the implant.

[0039] S3: During the operation, the hip joint is routinely exposed, and any loosened prosthesis is removed or the diseased joint is cleaned. A special medullary canal file and a trimming curette are used to mechanically trim the remaining medullary canal and bone defect surface of the proximal femur, removing local sclerotic bone and inflammatory granulation tissue to expose the active, punctately bleeding cancellous bone base.

[0040] S4: Based on the spatial anatomical landmarks of the bone defect, the pre-assembled 3D-printed reinforcing sleeve assembly is slowly pushed in along the axis of the proximal femoral medullary canal. This allows the porous layer of the outer wall of the arc-shaped outer flap 2 of the outer sleeve to form an interference fit with the cleaned and leveled host bone defect surface.

[0041] S5: The selected standard medical femoral stem 8 prosthesis is driven into the hollow vertebral foramen of the inner sleeve 1. Under the action of axial hammer force, the proximal cone of the femoral stem 8 compresses the micron-level anti-slip crystalline layer on the inner surface of the inner sleeve 1, forming a high torsional Mohs taper lock, thus completing the implantation.

[0042] Example 5, based on Example 4, proposes a principle for the implementation of a 3D-printed reinforcing sleeve for bone defects after hip replacement surgery.

[0043] Phase 1: In the early postoperative period, the patient begins to bear partial weight or engage in sudden movements. When the axial load borne by the femoral stem 8 is transferred to the inner sleeve 1, the fluid pressure within the sliding micro-gap is sealed off because the elastic sealing strip 7 is intact and the elastic damping medium 4 is sufficient. When the inner sleeve 1 undergoes a slight downward displacement relative to each of the aforementioned arc-shaped outer flaps 2, the damping medium 4 undergoes restricted shear rheology, which, in conjunction with the elastic suspension reduction plate 3, absorbs energy elastically. The relative axial displacement between the two is controlled at 100μm~150μm, and the peak shear stress is diluted and filtered by the damping medium. The bone cortex does not bear shear mutation loads, ensuring the safety of brittle bone and avoiding early fractures.

[0044] Phase Two: Approximately 4 weeks post-surgery, the elastic sealing strip 7 degrades and is absorbed, releasing the circumferential constraint. Healthy surrounding microvascular networks and osteogenic progenitor cells grow inward through the released gaps and porous channels 201. Due to the degradation and loss of the elastic sealing strip 7, the circumferential seal of the sliding microgap is released. Under the reciprocating shear pressure of the gait cycle, the incompletely degraded biodegradable elastic damping medium 4 is gradually squeezed outward along the gap and physically lost. As time progresses to 8-12 weeks post-surgery, the remaining biodegradable elastic damping medium 4 undergoes further hydrolysis and biodegradation, resulting in a gradual decrease in damping stiffness within the sliding microgap from 4 weeks post-surgery. The relative micromotion between the inner sleeve 1 and each arc-shaped outer flap 2 becomes more active. The relative axial and radial micromotions during the gait cycle provide periodic mechanical strain stimulation to the porous channels 201 and the newly formed bone tissue within the sliding microgap, promoting local osteogenic response and trabecular bone calcification, and preventing stress-shielded resorption of bone cells due to lack of stress stimulation.

[0045] Phase 3: Twelve weeks post-surgery, the elastic damping medium 4 has completely degraded within the microgap, transforming the sliding microgap into a hollow connecting channel. Induced by BMP-2, new bone tissue passing through the porous channel 201 crosses the drained sliding microgap and grows directly into the receiving porous area 101 on the outer wall of the inner sleeve 1. As the trabeculae densely intersect and calcify, a living bone bridge structure is eventually formed between the inner sleeve 1 and the arc-shaped outer flap 2. This living bone bridge connects and rigidly fuses the previously relatively mobile inner sleeve 1 and outer sleeve into a composite whole.

[0046] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A 3D-printed reinforcing sleeve for bone defects after hip replacement surgery, comprising a sleeve assembly for fitting around the periphery of the femoral stem (8) and adapting to the proximal medullary canal of the femur, the sleeve assembly being connected to the femoral head via the femoral stem (8) locking thereon, characterized in that: The sleeve assembly includes an inner sleeve (1) and an outer sleeve. The inner sleeve (1) has a hollow sleeve structure. The outer wall of the inner sleeve (1) is provided with a receiving porous area (101). The outer sleeve includes a plurality of arc-shaped outer segments (2) arranged around the inner sleeve (1). A sliding micro-gap is provided between the outer wall of the inner sleeve (1) and the inner wall of each arc-shaped outer segment (2). The inner sleeve (1) and each of the arc-shaped outer segments (2) are integrally connected by a plurality of elastic suspension repositioning plates (3). The elastic suspension repositioning plates (3) are suspended in the sliding microgap, so that the arc-shaped outer segments (2) and the inner sleeve (1) are elastically suspended. Each arc-shaped outer segment (2) has a plurality of through-type porous channels (201) on its outer wall surface. Each porous channel penetrates the wall thickness of the arc-shaped outer segment (2) and extends toward the receiving porous area (101) on the surface of the inner sleeve (1). The sliding microgap is filled with a biodegradable elastic damping medium (4). The porous channels, the sliding microgap and the receiving porous area (101) are sequentially connected to allow new bone tissue to grow in.

2. The 3D-printed reinforcing sleeve for bone defects after hip replacement surgery according to claim 1, characterized in that: Each of the porous channels extends obliquely from the outer surface of the arc-shaped outer segment (2) toward the proximal end of the inner sleeve (1), and the angle between the central axis of each porous channel and the longitudinal axis of the inner sleeve (1) is 30°~60°.

3. The 3D-printed reinforcing sleeve for bone defects after hip replacement surgery according to claim 2, characterized in that: The receiving porous region (101) is a three-dimensional elongated mesh structure with a pore size of 150μm~300μm, and the porous channel has a pore size of 500μm~800μm.

4. The 3D-printed reinforcing sleeve for bone defects after hip replacement surgery according to claim 1, characterized in that: Each of the porous channels has a drug-loaded porous micro / nano coating on its inner wall surface, and the drug-loaded porous micro / nano coating is loaded with bone morphogenetic protein or basic fibroblast growth factor.

5. A 3D-printed reinforcing sleeve for bone defects after hip replacement surgery according to claim 1, characterized in that: The elastic suspension reset piece (3) is an elastically bent sheet structure with an Ω-shaped, S-shaped or C-shaped cross-section, and the elastic suspension reset piece (3) is integrally formed with the inner sleeve (1) and each of the arc-shaped outer segments (2) by 3D printing of titanium alloy or PEEK material.

6. A 3D-printed reinforcing sleeve for bone defects after hip replacement surgery according to claim 1, characterized in that: The biodegradable elastic damping medium (4) includes at least one of cross-linked sodium hyaluronate hydrogel, collagen-gelatin copolymer or polylactic acid-caprolactone elastomer.

7. A 3D-printed reinforcing sleeve for bone defects after hip replacement surgery according to claim 1, characterized in that: The width of the sliding micro-gap along the radial direction of the inner sleeve (1) is 0.3mm~0.8mm.

8. A 3D-printed reinforcing sleeve for bone defects after hip replacement surgery according to claim 1, characterized in that: When the elastic suspension reset piece (3) undergoes elastic deformation, the maximum relative axial displacement between the inner sleeve (1) and each of the arc-shaped outer segments (2) is 100μm~150μm, and the maximum relative radial displacement is 50μm~80μm.

9. A 3D-printed reinforcing sleeve for bone defects after hip replacement surgery according to claim 1, characterized in that: The inner sleeve (1) has an integrally formed limiting protrusion (102) on its outer wall surface, and each of the arc-shaped outer segments (2) has a matching limiting groove (5) on its inner wall surface. The limiting protrusion (102) extends into the limiting groove (5) to limit the maximum relative displacement between the inner sleeve (1) and the arc-shaped outer segments (2).

10. A 3D-printed reinforcing sleeve for bone defects after hip replacement surgery according to claim 9, characterized in that: An elastic buffer layer (6) is fixed on the inner wall of the limiting groove (5), and the elastic buffer layer (6) is made of medical silicone rubber or medical polyurethane material.

11. A 3D-printed reinforcing sleeve for bone defects after hip replacement surgery according to claim 1, characterized in that: The sleeve assembly is connected to the femoral stem (8) through the inner wall surface of the inner sleeve (1). The inner wall surface is provided with a micron-level anti-slip crystalline layer so that the inner sleeve (1) and the outer mating surface of the femoral stem (8) are connected by a Morse taper fit.

12. A 3D-printed reinforcing sleeve for bone defects after hip replacement surgery according to claim 1, characterized in that: A sealing groove is provided between each of the two adjacent arc-shaped outer segments (2), and an elastic sealing strip (7) is embedded between the two adjacent sealing grooves to seal the gap between the arc-shaped outer segments (2) and prevent the loss of the degradable elastic damping medium (4) in the sliding microgap.

13. A 3D-printed reinforcing sleeve for bone defects after hip replacement surgery according to claim 12, characterized in that: The elastic sealing strip (7) is made of a biodegradable polymer, and the degradation rate of the elastic sealing strip (7) in the human body is greater than the degradation rate of the biodegradable elastic damping medium (4).

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