Degradable intramedullary nail dynamic gasket

Abstract

The invention discloses application of a degradable biological material in preparation of an intramedullary nail dynamic gasket, the degradable biological material is adopted to prepare the intramedullary nail dynamic gasket, the intramedullary nail dynamic gasket can provide excellent mechanical strength at the initial stage of implantation, and the gasket is degraded along with time, provides dynamic space for an intramedullary nail and promotes fracture healing and rehabilitation. The invention further discloses a corresponding nail locking gasket and an intramedullary nail. By means of the degradable lock pin gasket, excellent mechanical strength is provided in the initial stage of implantation, tissue reconstruction at the two ends of a fracture is guaranteed, the gap between the lock pin and the lock hole is expanded along with degradation of the gasket as time goes on, a dynamic space is provided for an intramedullary nail, and fracture healing and rehabilitation are promoted.

Description

Technical Field

[0001] The invention relates to application of degradable biomaterials in preparing a motorized washer for an intramedullary nail, and corresponding motorized washer for an intramedullary nail and an intramedullary nail, belonging to the technical field of medical devices. Background Art

[0002] At present, intramedullary nail fixation technology for fractures has been widely used. Most long bone fractures are fixed with locked intramedullary nails, replacing previous treatment methods such as lag screws and steel plates. The emergence of locked intramedullary nails has greatly expanded the scope of application of intramedullary nails. In the past, comminuted fractures were contraindications for intramedullary nail fixation, but now for locked intramedullary nails, comminuted fractures have become its indication. Fractures of the proximal and distal 1 / 3 of the diaphysis, subtrochanteric fractures involving the lesser trochanter, and ipsilateral femoral neck combined with femoral shaft fractures can all be fixed with locked intramedullary nails. Closed locked intramedullary nail fixation has become the preferred method for treating femoral shaft and diaphyseal fractures, especially for patients with multiple trauma. Studies have shown that the application rate of intramedullary nails in the treatment of long tubular bone fractures in developed countries in Europe and the United States is more than 90%. At the same time, its scope of application is no longer limited to the initial long tubular bone diaphysis fractures. Its current indications mainly include: 1. Fractures of long tubular bones of the limbs; 2. Open fractures; 3. Pathological fractures; 4. Correction after malformation healing of fractures; 5. Nonunion.

[0003] With the widespread use of intramedullary nails, delayed healing or non-union of fractures has become increasingly common due to the effect of static nails on the axial load of the fracture ends. Delayed fracture healing refers to the fact that after the normal fracture healing recovery period, the fracture ends of patients do not show obvious sclerosis and medullary cavity occlusion, nor do they show obvious absorption and gaps, and there is no continuous bone callus growth around the bone ends. Studies have shown that under static fixation, the fracture ends lack compressive stress, and the axial stress of the locking nails on both sides is concentrated, which can easily cause broken nails and delayed fracture healing, and even re-fracture after the intramedullary nail is removed. In recent years, some scholars have proposed the concept of "dynamic" intramedullary nails, that is, planned removal of one side of the static nail of the fracture patient, increasing the micro-motion and pressure of the fracture end, obtaining axial load stress, and facilitating fracture healing.

[0004] In the early stage of fracture healing, the intramedullary nail needs to perform a stop function to limit the relative displacement and torsion of the two ends of the fracture. As healing proceeds, the intramedullary nail needs to gradually move or increase its elasticity, generate compressive stress on the fracture surface, activate the osteogenic potential of interstitial cells, enhance the activity of osteoblasts, and facilitate fracture healing. Therefore, the prerequisite for dynamic treatment is to design materials that can maintain mechanical strength in the early stage of implantation. As time goes by, the strength decreases or the material body collapses, so that the range of motion of the intramedullary nail increases and a certain displacement can be generated. Polylactic acid (PLA) is a high molecular organic polymer formed by ring-opening polymerization of lactide monomers under the catalysis of organic bases or metal anion complexes. Different molecular weights can be obtained by controlling the polymerization conditions. It has the appearance of a white solid powder, is non-toxic, insoluble in water, and easily soluble in a variety of polar organic solvents. PLA has good biocompatibility, good organic polymer compatibility, and good biodegradability. It can be used as a cell growth support material and is compatible with a variety of conventional plastics. It can be completely degraded in 3 to 6 months under physiological conditions. In addition, PLA has good molding and processability, and is widely used in biomedical materials such as controlled-release drug carriers, cell and tissue culture medium frames, and degradable plastic surgical sutures.

[0005] Chinese utility model patent CN217548185U authorizes an elastic pressurized intramedullary nail, the purpose of which is to solve the problem that the existing intramedullary nails in the prior art cannot provide stress stimulation to the fracture site. It includes: a nail body, one end of which is a fixed end and the other end is a movable end, and the end of the movable end is provided with a mounting groove coaxial with the nail body; static and power through holes are respectively arranged on the outer walls of the two ends of the nail body and connected to the mounting groove; a plurality of screws are respectively installed in the static through hole and the power through hole; a spring is arranged in the mounting groove, one end of which is connected to the screw passing through the power through hole; a pressure adjustment screw is installed in the mounting groove and connected to the other end of the spring. The utility model fixes one end of the spring to the pressure adjustment screw and locks the other end in the power through hole by a screw, so that the range of movement of the spring is limited to the power through hole, thereby avoiding the spring from being stuck and unable to reset when stress is generated. This patent provides mobility through the physical elasticity of the material and does not involve material degradation; Chinese invention patent CN111134823A discloses an adjustable intramedullary nail, including an upper nail body, a lower nail body and a sliding rack; the upper nail body is provided with a driving cavity inside, and a driving gear, a reduction device, a driving motor and a battery are provided in the driving cavity; the battery is connected to the driving motor to provide power for it; the driving motor drives the driving gear to rotate through the reduction device; the bottom end of the sliding rack is fixed in the lower nail body, and its upper end is inserted into the driving cavity and meshes with the driving gear; the upper end of the upper nail body and the lower end of the lower nail body are respectively provided with fixing nails that penetrate the nail body. This solution adopts minimally invasive insertion, effectively lengthens the patient's affected limb through in vitro manipulation, and the intramedullary fixation maintains the force line to ensure the linear growth of the extended bone.

[0006] Chinese invention patent CN113509254A discloses an interlocking intramedullary nail kit for improving the mechanical environment, including a first intramedullary nail, a second intramedullary nail and a third intramedullary nail, each of which includes a rod head section and a rod shaft section, a proximal end of the rod head section is provided with a most proximal static locking hole, and a distal end of the rod shaft section is provided with a most distal static locking hole, by changing the distribution position and type of the locking holes of the intramedullary nail, the stress distribution around the fracture site is adjusted, the local mechanical environment is improved, and the anti-rotation ability of the intramedullary nail is enhanced on the basis of maintaining the axial stability of the intramedullary nail; Chinese invention patent CN112294413A discloses a bidirectionally adjustable elastic The intramedullary nail comprises a hollow structure of the intramedullary nail main nail, which comprises an intramedullary nail proximal end and an intramedullary nail main body of an integrated structure, wherein the diameter of the intramedullary nail proximal end is larger than the diameter of the intramedullary nail main body, a through dynamic screw hole is arranged at the proximal end of the intramedullary nail, an adjustment hole is arranged on the intramedullary nail main body away from the proximal end of the intramedullary nail, a dynamic bone screw is installed in the dynamic screw hole, and the dynamic bone screw can move axially along the dynamic screw hole, a tail cap is installed on the proximal side of the intramedullary nail, an elastic body is arranged between the tail cap and the dynamic bone screw, an absorbable washer is arranged below the dynamic bone screw, the absorbable washer supports the dynamic bone screw, and an adjustment device for adjusting the stress of the fracture end is arranged on the intramedullary nail main body. The stress of the fracture end can be adjusted according to the specific situation of the fracture to accelerate the healing of the fracture.

[0007] However, none of these structures can completely solve the problem of dynamic treatment. Summary of the invention

[0008] The purpose of the present invention is to provide an application of a degradable biomaterial in the preparation of a dynamized intramedullary nail gasket. The dynamized intramedullary nail gasket is prepared using a degradable biomaterial, which can provide excellent mechanical strength at the initial stage of implantation and degrade over time to provide a dynamized space for the intramedullary nail and promote fracture healing and rehabilitation.

[0009] Preferably, the degradable biomaterial is polylactic acid or a blend or copolymer of polylactic acid and other polymers.

[0010] Preferably, the blend or copolymer of polylactic acid and other polymers refers to polylactic acid / polycaprolactone (PLA / PCL) blend, polylactic acid / polycaprolactone (PLA-PCL) block copolymer, polylactic acid-glycolic acid copolymer (PLGA).

[0011] Preferably, the number average molecular weight (M n ) is between 5000 and 100,000, and more preferably 5000.

[0012] The invention also discloses a dynamized washer for the intramedullary nail, which is formed by processing of degradable biological materials.

[0013] Preferably, the degradable biomaterial is polylactic acid or a blend or copolymer of polylactic acid and other polymers, and the processing method is mold injection molding, extrusion, solution processing, powder hot melt die casting, additive manufacturing, 3D printing or spinning.

[0014] Preferably, the number average molecular weight (M n ) is between 5000 and 100,000.

[0015] Preferably, the mold injection molding refers to melting the polylactic acid at 170-250°C, injecting it into the mold and cooling it to form the mold, and more preferably at 235°C.

[0016] The present invention also discloses an intramedullary nail, comprising a nail body and a locking nail, wherein the nail body is provided with a locking nail hole for the locking nail to pass through, and also comprises the above-mentioned intramedullary nail motorized washer, wherein the intramedullary nail motorized washer is tightly matched with the locking nail.

[0017] Preferably, the inner diameter of the intramedullary nail motorized washer is 97% to 99.9% of the outer diameter of the locking nail, more preferably 99.3%, and the outer diameter is 100.1% to 103% of the matching locking nail hole, more preferably 101.2%.

[0018] The present invention is based on the design and regulation of the in vivo degradation cycle of degradable biomaterials and their corresponding mechanical properties to construct a degradable gasket for the locking nail of the intramedullary nail. Specifically, by designing the molecular weight and distribution of degradable biomaterials, a degradable gasket matching the locking nail of the intramedullary nail is prepared, and a dynamic intramedullary nail that cooperates with the fracture healing cycle is developed.

[0019] The dynamic locking nail washer after intramedullary nail implantation provides excellent mechanical strength in the early stage of implantation to ensure tissue reconstruction at both ends of the fracture. Over time, the gap between the locking nail and the locking hole expands as the washer degrades, providing a dynamic space for the intramedullary nail and promoting fracture healing and rehabilitation. The intramedullary nail equipped with a dynamic locking nail washer described in the present invention can provide reliable mechanical strength in the early stage of fracture healing, and can also provide gradually enhanced stress stimulation in the middle and late stages of fracture healing, which is conducive to the formation of bone callus in the early stage of fracture, and is also conducive to promoting bone reconstruction and healing in the middle and late stages of fracture, further improving the fracture healing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the locking washer used for dynamization of the intramedullary nail after implantation. Specific implementation methods

[0022] The present invention is further described below in conjunction with embodiments, but the description of the embodiments does not impose any limitation on the protection scope of the present invention.

[0023] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention, and the terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. In addition, although demonstrations of parameters containing specific values ​​may be provided herein, it should be understood that the parameters do not need to be exactly equal to the corresponding values, but can be approximated to the corresponding values ​​within an acceptable error tolerance or design constraint. The directional terms mentioned in the embodiments, such as "up", "down", "front", "back", "left", "right", etc., are only directions with reference to the accompanying drawings. Therefore, the directional terms used are used to illustrate rather than to limit the scope of protection of the present invention.

[0024] Unless otherwise specified, the materials and instruments used in the following examples can be obtained from conventional commercial channels.

[0025] The term "degradable" as used in the present invention means that under physiological conditions, the material will dissolve, the molecular chain will break, and the mechanical properties will decrease. Example 1

[0026] like Figure 1 As shown, an intramedullary nail includes a nail body and a locking nail, wherein the nail body is provided with a locking nail hole for the locking nail to pass through, and further includes a locking nail washer, wherein the locking nail washer is tightly matched with the locking nail, wherein the inner diameter of the locking nail washer is controlled to be 97% to 99.9% of the outer diameter of the locking nail, and the outer diameter is controlled to be 100.1% to 103% of the matching locking nail hole.

[0027] The lock washer adopts the number average molecular weight (M n ) is made by injection molding of polylactic acid with a molecular weight of 5000 to 100,000. It can also be made of a blend or copolymer of degradable polylactic acid and other polymers, such as polylactic acid / polycaprolactone (PLA / PCL) blend, polylactic acid / polycaprolactone (PLA-PCL) block copolymer, polylactic acid-glycolic acid copolymer (PLGA), etc.

[0028] When in use, the locking nail washer is put on the locking nail, and the locking nail passes through the locking nail hole to fix the intramedullary nail in the medullary cavity of the human bone. At this time, the locking nail washer has excellent mechanical strength, which makes the intramedullary nail firmly fixed, thereby ensuring the reconstruction of tissues at both ends of the fracture. Later, as time goes by, the locking nail washer gradually degrades, and the gap between the locking nail and the locking hole expands accordingly, providing a dynamic space for the intramedullary nail and promoting fracture healing and rehabilitation.

[0029] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. Application of degradable biomaterials in the preparation of dynamic washers for intramedullary nails.

2. The use according to claim 1, characterized in that: The degradable biomaterial is polylactic acid or a blend or copolymer of polylactic acid and other polymers.

3. The use according to claim 2, characterized in that: The blend or copolymer of polylactic acid and other polymers refers to a polylactic acid / polycaprolactone blend, a polylactic acid / polycaprolactone block copolymer or a polylactic acid-glycolic acid copolymer.

4. The use according to claim 2, characterized in that: The molecular weight of the polylactic acid is between 5000 and 100,000.

5. A degradable dynamized washer for intramedullary nail, characterized in that: Made of biodegradable biomaterials.

6. The motorized washer for intramedullary nail according to claim 5, characterized in that: The degradable biomaterial is polylactic acid or a blend or copolymer of polylactic acid and other polymers, and the processing method is mold injection molding, extrusion, solution processing, powder hot melt die casting, additive manufacturing, 3D printing or spinning.

7. The motorized washer for intramedullary nail according to claim 6, characterized in that: The molecular weight of the polylactic acid is between 5000 and 100,000.

8. The motorized washer for intramedullary nail according to claim 7, characterized in that: The mold injection molding refers to melting polylactic acid at 170-250° C. and then injecting it into a mold and cooling it to form a mold.

9. An intramedullary nail, comprising a nail body and a locking nail, wherein the nail body is provided with a locking nail hole for the locking nail to pass through, characterized in that: It also comprises the intramedullary nail dynamization washer according to any one of claims 5 to 8, wherein the intramedullary nail dynamization washer is tightly matched with the locking nail.

10. The intramedullary nail according to claim 8, characterized in that: The inner diameter of the intramedullary nail motorized gasket is 97% to 99.9% of the outer diameter of the locking nail, and the outer diameter is 100.1% to 103% of the matching locking nail hole.

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