Orthopedic Internal Fixation Implant Medical Device

Abstract

The present invention relates to an orthopedic internal fixation implant medical device, which comprises an iron substrate and a filler containing polylactic acid and an alkaline substance, the polylactic acid having a weight-average molecular weight of Mw kDa, the alkaline substance containing a metal element, the mass ratio of the metal element in the alkaline substance to the polylactic acid being p, and p and Mw satisfying the formula 2Mw-^0.8≦p≦30Mw^-0.5. This orthopedic internal fixation implant medical device has excellent mechanical properties, can well control local pH values, and can induce bone healing.

Description

[Technical field]

[0001] The present invention belongs to the field of medical devices, specifically to orthopedic internal fixation implant medical devices. [Background technology]

[0002] Conventional orthopedic internal fixation instruments are generally made of permanent metals such as titanium-based alloys and cobalt-based alloys. Although these materials have excellent mechanical performance and biocompatibility, if these materials remain in the body for a long time, they may cause problems such as corrosion, allergies, and osteoporosis due to stress shielding, which requires secondary surgery to remove them after the patient's fracture has healed, significantly increasing the patient's pain and economic burden. Therefore, in recent years, absorbable orthopedic fixation devices made of degradable biomedical materials have been widely devised in clinical practice. Compared with permanent metal internal fixation devices, absorbable orthopedic internal fixation materials are the most superior in that they do not require secondary surgery and significantly reduce the patient's pain.

[0003] Currently, absorbable orthopedic fixation materials mainly include absorbable polymers, magnesium and its alloys.

[0004] Magnesium alloy orthopedic internal fixation materials have good biocompatibility and can be decomposed in the body, so there is no pain in removing them in secondary surgery, and the released magnesium ions can further promote the differentiation of the proliferation machinery of bone cells, so as to promote bone growth and healing. The elastic modulus of magnesium alloys is close to that of human bones, and can effectively reduce the stress shielding effect. At the same time, its mechanical performance, such as tensile strength, is much higher than that of degradable high molecular polymer materials currently in clinical use, so that it can better meet clinical needs. However, the mechanical performance of magnesium-based alloys does not reach the level of permanent metal implant materials, and the clinical scope is limited, and it is difficult to apply them to load-bearing sites, so that they can only be used in non-load-bearing and low-movement positions at present. Secondly, because the decomposition rate of magnesium-based alloys is fast, implanted medical devices lose their effective support and fixation effect early, and during decomposition, the pH value at the implanted site becomes high, which generates excess hydrogen bubbles, which is unfavorable to healing at the damaged site of the bone.

[0005] Absorbable polymers such as polylactic acid and polycaprolactone have good biocompatibility, and a lot of clinical data has been accumulated. By melting with high molecular weight polylactic acid and then processing and molding, orthopedic internal fixation implant medical devices with a certain mechanical strength can be produced. Compared with traditional permanent metal materials, they have the following disadvantages: (1) poor bone conductivity, slow speed of repairing bone defects, and difficulty in achieving complete bone repair for large bone defects; (2) poor mechanical performance and insufficient mechanical strength, generally cannot be applied to load-bearing sites (such as limbs), and can only be applied to fixation of cancellous bone, articular bone or bone with little activity in various non-load-bearing sites; (3) fast early decomposition rate, cannot guarantee to meet the mechanical performance requirements before new bone tissue grows; and (4) decomposition of polylactic acid becomes acidic, which is prone to cause more severe inflammation at the implant site. All of these disadvantages greatly restrict the application of absorbable polymer-based internal fixation implant medical devices. There is still much room for improvement in terms of the partially acidic and osteoinductive capabilities generated by polylactic acid. Summary of the Invention

[0006] The objective of the present invention is to provide an orthopedic internal fixation implant medical device that has relatively good mechanical performance, can control the local pH value relatively well, can reduce local inflammation, can control the decomposition rate, and can simultaneously induce bone healing.

[0007] A first aspect of the present invention provides an orthopedic internal fixation implant medical device, comprising an iron substrate and a filler comprising polylactic acid and an alkaline substance, wherein the polylactic acid has a weight average molecular weight of MwkDa, the alkaline substance comprises a metal element, and a mass ratio of the metal element to the polylactic acid in the alkaline substance is p, and the p and Mw satisfy the formula 2Mw-^0.8≦p≦30Mw^-0.5.

[0008] The iron base in the orthopedic internal fixation implant medical device can provide sufficient mechanical support, solving the problem of the insufficient mechanical performance of polylactic acid orthopedic internal fixation medical device and magnesium alloy orthopedic internal fixation medical device. The filler includes polylactic acid and alkaline material, the alkaline material can neutralize the acidity of polylactic acid decomposition products in an early stage, and the mass ratio of metal element and polylactic acid in the alkaline material is set to p, the molecular weight of polylactic acid is MwkDa, p and Mw satisfy the formula 2Mw-^0.8≦p≦30Mw^-0.5, when this formula is satisfied, the partial pH value can be kept stable, the pH value can be neutralized, inflammation can be reduced, and bone repair can be promoted, and at the same time, the early decomposition speed of iron base can be slowed down, and good mechanical performance can be maintained during the bone healing period.

[0009] In an embodiment, the weight average molecular weight of the polylactic acid is 5 kDa to 1000 kDa.

[0010] In an embodiment, the alkaline substance is one or more selected from the group consisting of magnesium, magnesium alloys, zinc, zinc alloys, magnesium oxide, magnesium hydroxide, zinc oxide, zinc hydroxide, magnesium carbonate, zinc carbonate, magnesium phosphate, zinc phosphate, sodium carbonate, sodium bicarbonate, calcium oxide, calcium hydroxide, calcium carbonate, calcium phosphate, and hydroxyapatite.

[0011] In an embodiment, the alkaline substance is in one or more of the following forms: powder, particles, block, or bar. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In an embodiment, the alkaline substance is a composition consisting of at least one of magnesium, magnesium alloy, zinc, zinc alloy, magnesium oxide, magnesium hydroxide, zinc oxide, zinc hydroxide, magnesium carbonate, zinc carbonate, magnesium phosphate, zinc phosphate, sodium carbonate, sodium bicarbonate, calcium oxide, calcium hydroxide, calcium carbonate, calcium phosphate, and hydroxyapatite. That is, the alkaline substance contains hydroxyapatite and at least one of magnesium, magnesium alloy, zinc, zinc alloy, magnesium oxide, magnesium hydroxide, zinc oxide, zinc hydroxide, magnesium carbonate, zinc carbonate, magnesium phosphate, zinc phosphate, sodium carbonate, sodium bicarbonate, calcium oxide, calcium hydroxide, calcium carbonate, calcium phosphate.

[0013] In an embodiment, the mass of the hydroxyapatite is 1 to 10% of the mass of the orthopedic internal fixation medical device.

[0014] In an embodiment, the polylactic acid is polyracemic lactic acid or poly-L-lactic acid.

[0015] In an embodiment, the iron base has a hollow structure, and the filler is filled inside the iron base, or the iron base has a net-like skeleton structure, and the filler is filled into the mesh of the net-like skeleton structure, or the iron base has an openwork space skeleton structure, and the filler is filled inside the openwork space of the iron base, or the surface of the iron base is provided with grooves or holes, and the filler is filled into the grooves or holes of the iron base, or the filler is applied to the surface of the iron base.

[0016] In an embodiment, the orthopedic internal fixation implant medical device is a bone screw, a bone plate, a bone rod or a bone cannula.

[0017] In an embodiment, the iron substrate is pure iron, a low alloy steel, or an iron-based alloy having a carbon content of 2.5 wt% or less. [Brief description of the drawings]

[0018] Various advantages and benefits will become apparent to those skilled in the art from the following detailed description of the preferred embodiments. The drawings are merely for the purpose of illustrating the preferred embodiments and are not intended to limit the invention. The same reference numerals are used throughout the drawings to refer to the same elements. [Figure 1] FIG. 1 is a schematic cross-sectional view of an orthopedic internal fixation implant medical device according to embodiment 1. [Diagram 2] FIG. 11 is a schematic cross-sectional view of an orthopedic internal fixation implant medical device according to embodiment 3. [Diagram 3] FIG. 11 is a schematic cross-sectional view of an orthopedic internal fixation implant medical device according to embodiment 5. [Figure 4] FIG. 11 is a schematic cross-sectional view of an orthopedic internal fixation implant medical device according to embodiment 7. [Diagram 5] FIG. 13 is a schematic cross-sectional view of an orthopedic internal fixation implant medical device according to embodiment 9. [Figure 6] FIG. 13 is a schematic cross-sectional view of an orthopedic fixation implant medical device according to embodiment 10. EXAMPLES

[0019] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, exemplary embodiments of the present invention are shown, but it should be understood that the present invention is not limited to the embodiments described herein and can be embodied in various forms. On the contrary, these embodiments can more completely understand the present invention and fully convey the scope of the present invention to those skilled in the art.

[0020] It should be understood that the purpose of the terms herein is to describe specific exemplary embodiments only and is not intended to be limiting. The singular terms "a," "one," and "said" herein also mean to include the plural unless the context clearly dictates otherwise. The terms "comprise," "include," "contain," and "have" are inclusive and thus indicate the presence of a described feature, step, operation, element, and / or component, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The methods and steps, processes, and operations described herein should not be construed as necessarily being in the particular order described or illustrated, unless the order of execution is explicitly indicated. It is also understood that additional or replacement steps may be used.

[0021] The present embodiment provides an orthopedic internal fixation implant medical device, comprising an iron substrate and a filler material comprising polylactic acid and an alkaline substance, the weight average molecular weight of the polylactic acid is Mw kDa, the alkaline substance comprises a metal element, the mass ratio of the metal element to the polylactic acid in the alkaline substance is p, and p and Mw satisfy the formula 2Mw-^0.8≦p≦30Mw^-0.5. The metal element can comprise a metal cation or a metal atom. This formula is expressed in letters as follows: the mass ratio p of the metal element to the polylactic acid in the alkaline substance is equal to or greater than the power of -0.8 of the weight average molecular weight Mw of 2 times the polylactic acid, and the mass ratio p of the metal element to the polylactic acid in the alkaline substance is equal to or less than the power of -0.5 of the weight average molecular weight Mw of 30 times the polylactic acid.

[0022] However, the iron substrate can provide sufficient mechanical support, solving the problem of the insufficient mechanical performance of orthopedic internal fixation medical devices made of polylactic acid and orthopedic internal fixation medical devices made of magnesium alloy. The alkaline substance can neutralize the acidity of the polylactic acid decomposition product early, and p and Mw satisfy the above formula, and can maintain a partial pH value stable, making the pH value neutral and reducing inflammation, which is favorable for bone repair, and can also slow down the early decomposition rate of the iron substrate, allowing it to maintain good mechanical performance during the bone healing period.

[0023] In an embodiment, the weight-average molecular weight of the polylactic acid is 5 kDa to 1000 kDa. Preferably, the weight-average molecular weight of the polylactic acid is 100 kDa or more and 500 kDa or less, so that the initial acidity is weakened and the decomposition period is extended, which is advantageous for accelerating the decomposition of the iron substrate later.

[0024] In an embodiment, the alkaline substance is selected from one or more of magnesium, magnesium alloy, zinc, zinc alloy, magnesium oxide, magnesium hydroxide, zinc oxide, zinc hydroxide, magnesium carbonate, zinc carbonate, magnesium phosphate, zinc phosphate, sodium carbonate, sodium bicarbonate, calcium oxide, calcium hydroxide, calcium carbonate, calcium phosphate, hydroxyapatite. Preferably, the alkaline substance is selected from one or more of magnesium oxide, magnesium hydroxide, zinc oxide, zinc hydroxide, magnesium carbonate, zinc carbonate, magnesium phosphate, zinc phosphate, sodium carbonate, sodium bicarbonate, calcium oxide, calcium hydroxide, calcium carbonate, calcium phosphate, hydroxyapatite, and said oxide or hydroxide or weak acid strong base salt can avoid hydrogen bubbles generated by the reaction of these metals of magnesium, magnesium alloy, zinc, zinc alloy with polylactic acid, which is advantageous for tissue growth repair, and its alkalinity is lower than that of oxide or hydroxide, and its biocompatibility is higher. Preferably, the alkaline substance is a composition of at least one selected from magnesium oxide, magnesium hydroxide, zinc oxide, zinc hydroxide, magnesium carbonate, zinc carbonate, magnesium phosphate, zinc phosphate, sodium carbonate, sodium bicarbonate, calcium oxide, calcium hydroxide, calcium carbonate, calcium phosphate, and hydroxyapatite, with the proviso that hydroxyapatite is used to improve biological activity and promote bone healing.

[0025] In an embodiment, the alkaline substance is in one or more of a powder, particle, block, or rod form, which allows easy addition of the alkaline substance to the filler in various states.

[0026] In an embodiment, the alkaline material comprises hydroxyapatite, the mass of which is 1-10% of the mass of the orthopedic internal fixation medical device.

[0027] In embodiments, the polylactic acid is polyracemic lactic acid or poly-L-lactic acid.

[0028] In an embodiment, the iron substrate is pure iron, low alloy steel or iron-based alloy with a carbon content of 2.5 wt.% or less, where low alloy steel is an alloy steel with a total alloying element content of less than 5%. Preferably, the iron substrate is iron nitride, where the carbon content in iron nitride is <0.25%, belonging to iron-based alloys with a carbon content of 2.5 wt.% or less. Iron nitride has better mechanical performance.

[0029] In the embodiments of the present invention, there are various connection relationships between the iron substrate and the filler: the iron substrate is a hollow structure, and the filler is filled inside the iron substrate, or the iron substrate is a net-like skeleton structure, and the filler is filled into the mesh of the net-like skeleton structure, or the iron substrate is an openwork space skeleton structure, and the filler is filled inside the openwork space of the iron substrate, or the surface of the iron substrate is provided with grooves or holes, and the filler is filled into the grooves or holes of the iron substrate, or the filler is coated on the surface of the iron substrate.

[0030] However, the shape of the iron substrate may be screw-like, net-like, plate-like, rod-like, cylindrical, cubic or conical.

[0031] The orthopedic internal fixation implant medical device in embodiments of the present invention may be a bone screw, a bone plate, a bone rod or a bone cannula.

[0032] The medical device is further described below by specific embodiments.

[0033] The test method according to the following embodiment is as follows.

[0034] 1. Measurement of weight average molecular weight of polylactic acid Detection was performed using a GPC-multiangle laser scattering meter and molecular weight test system manufactured by Wyatt, USA. This test system includes a liquid phase pump and a sample injector manufactured by Agilent, USA, an Agilent PLMIXED-C type GPC column (size: 7.5x300mm, 5 micrometers) manufactured by Agilent, USA, a multiangle laser scattering meter and a differential detector manufactured by Wyatt, USA. The detection conditions are as follows:

[0035] Flow phase: tetrahydrofuran; pump flow rate: 1 mL / min; injection volume: 100 pL; laser wavelength: 663.9 nm; test temperature: 35 °C.

[0036] 2. Mass of polylactic acid The weighed orthopedic internal fixation implant medical device is placed in a solvent capable of dissolving polylactic acid (e.g., ethyl acetate, chloroform, etc.), ultrasonically cleaned for 30 minutes, filtered, and the filtrate is dried and then weighed. The difference of 5 parts by mass before and after cleaning is the mass of polylactic acid.

[0037] 3. Identification of the material phase of alkaline substances XRD detection can be used to detect orthopedic internal fixation implant medical devices, and the material phase of alkaline substances can be determined by comparing with standard spectra such as iron, hydroxyapatite, magnesium, zinc, magnesium oxide, zinc oxide, magnesium hydroxide, zinc hydroxide, magnesium carbonate, zinc carbonate, magnesium phosphate, zinc phosphate, sodium carbonate, sodium bicarbonate, calcium oxide, calcium hydroxide, calcium carbonate, calcium phosphate, etc.

[0038] 4. Mass of metal elements in alkaline substances After the orthopedic internal fixation implant medical device is decomposed with nitric acid, the concentration of magnesium ion, zinc ion, calcium ion, or sodium ion in the decomposition liquid is measured by AAS, and the mass of the metal element in the alkaline substance in the orthopedic internal fixation implant medical device can be obtained by calculation.

[0039] 5、Bending strength

[0040] Using a C43.504 type universal material testing machine manufactured by MTS company, test the three-point bending strength of the sample according to the YBT5349-2006 metal material bending mechanical performance test standard.

[0041] 6. Iron decomposition rate After the absorbable iron-based orthopedic internal fixation implant medical device is implanted in the animal body, the corrosion status of the iron-based substrate is evaluated by the mass loss rate. Specifically, it includes the following steps: after the absorbable iron-based orthopedic internal fixation implant medical device with iron-based substrate mass M0 is implanted in the animal body, at a predetermined observation time such as 3 months, 6 months, and 12 months, the instrument and its surrounding tissue are taken out, and the tissue together with the instrument are immersed in 1 / L sodium hydroxide solution to remove the remaining degradable polyester, and after the tissue is decomposed, the instrument is taken out of the sodium hydroxide solution, and ultrasonically treated in 3% tartaric acid solution, the corrosion products and other alkaline materials attached to the instrument are completely removed or dissolved in a good solvent, and the remaining instrument is taken out, dried and weighed, and the mass is M1. Therefore, the mass loss rate of the iron-based substrate at this observation time is (M0-M1) / M0×100%.

[0042] If the mass loss rate of the iron-based substrate at a given observation time, w<5%, the iron-based substrate is considered not corroded during the time period from the time of implantation to the observation time. If the mass loss rate of the iron-based substrate at a given observation time, w>90%, the iron-based substrate is considered to be completely corroded, and the time period from the time of implantation to this observation time is the corrosion cycle of the iron-based substrate.

[0043] 7. Partial pH value after decomposition Immerse the orthopedic internal fixation implant medical device in PBS solution (pH value = 7.4 ± 0.1) and corrode it at 37 °C for 7 days, then take out the orthopedic internal fixation implant medical device and immediately detect the pH value of the device surface with pH test paper.

[0044] EMBODIMENT 1 Pure iron is cast into a hollow screw-like object with holes on the surface to obtain an iron substrate 11. Pure magnesium powder and hydroxyapatite powder are dispersed in molten poly-L-lactic acid, and the mixture 12 is filled into the hollow iron substrate 11 to produce an absorbable iron-based bone screw, the cross section of which is shown in FIG. 1. However, the weight average molecular weight of the poly-L-lactic acid is 1000 kDa, and the mass ratio of magnesium, magnesium and poly-L-lactic acid is 0.94. The mass of hydroxyapatite is 1% of the total mass of the orthopedic internal fixation implant medical device.

[0045] The initial bending strength of this bone screw is 350 MPa. When this bone screw is implanted in an animal body and removed after 6 months, 10% of the iron is decomposed.

[0046] Immerse this orthopedic internal fixation implant medical device in PBS solution and bathe in water at 37 °C for 7 days. Then, take out the orthopedic internal fixation implant medical device and immediately measure the pH value of the instrument surface to 7 to 8 with pH test paper.

[0047] EMBODIMENT 2 Pure iron is cast into a hollow screw-like object with holes on the surface to obtain an iron substrate. Magnesium oxide particles and hydroxyapatite powder are dispersed in molten poly-L-lactic acid, and the mixture is filled into a hollow iron substrate to produce an absorbable iron-based bone screw. The weight-average molecular weight of the poly-L-lactic acid is 1000 kDa, and the mass ratio of magnesium to poly-L-lactic acid is 0.008. The mass of hydroxyapatite is 1% of the total mass of the orthopedic internal fixation implant medical device.

[0048] The initial bending strength of this bone screw is 350 MPa. When this bone screw was implanted in an animal body and removed after 6 months, 17% of the iron was decomposed.

[0049] Immerse this orthopedic internal fixation implant medical device in PBS solution and bathe in water at 37 °C for 7 days. Then, take out the orthopedic internal fixation implant medical device and immediately measure the pH value of the instrument surface to 6 to 7 with pH test paper.

[0050] EMBODIMENT 3 Pure iron is cast into a screw shape, and its strength is reinforced by ion nitriding to obtain a screw-shaped iron substrate 21. Block-shaped zinc alloy and hydroxyapatite powder are dispersed in molten polyracemic lactic acid, and this mixture 22 is applied to the surface of the screw-shaped iron substrate 21 to produce an absorbable iron-based bone screw, the cross section of which is shown in Figure 2. However, the weight-average molecular weight of the polyracemic lactic acid is 500 kDa, and the mass ratio of zinc to polylactide is 1.3. The mass of the hydroxyapatite is 3% of the total mass of the orthopedic internal fixation implant medical device.

[0051] The bone screw has an initial bending strength of 450 MPa. When the bone screw is implanted in an animal and removed after 6 months, 15% of the iron is decomposed.

[0052] Immerse this orthopedic internal fixation implant medical device in PBS solution and bathe in water at 37 °C for 7 days. Then, take out the orthopedic internal fixation implant medical device and immediately measure the pH value of the surface of the device to 7 to 8 with pH test paper.

[0053] EMBODIMENT 4 Pure iron is cast into a threaded shape with grooves on the surface, and its strength is reinforced by ion nitriding to obtain a threaded iron substrate. Magnesium hydroxide powder and hydroxyapatite powder are dispersed in molten poly-L-lactic acid, and the mixture is applied to the surface of the threaded iron substrate to produce an absorbable iron-based bone screw. The weight-average molecular weight of the poly-L-lactic acid is 500 kDa, and the mass ratio of magnesium to poly-L-lactic acid is 0.014. The mass of hydroxyapatite is 3% of the total mass of the orthopedic internal fixation implant medical device.

[0054] The bone screw has an initial bending strength of 420 MPa. When the bone screw is implanted in an animal and removed after 6 months, 18% of the iron is decomposed. Immerse this orthopedic internal fixation implant medical device in PBS solution and bathe in water at 37 °C for 7 days. Then, take out the orthopedic internal fixation implant medical device and immediately measure the pH value of the surface of the device to 6 to 7 with pH test paper.

[0055] EMBODIMENT 5 Low alloy steel is cast into a hollow screw 31, the inside of which further contains an iron support rod 32 parallel to the iron screw, the cross section of which is shown in FIG. 3. The iron screw is cut into a hollow tube cavity structure by a laser cutting machine. Magnesium oxide powder and hydroxyapatite powder are dispersed in molten polyracemic lactic acid, and the mixture 33 is filled into the inside of an iron substrate to obtain an absorbable iron-based bone screw. The weight average molecular weight of the polyracemic lactic acid is 100 kDa, and the mass ratio of magnesium to polyracemic lactic acid is 0.05. The mass of hydroxyapatite is 10% of the total mass of the orthopedic internal fixation implant medical device.

[0056] The initial bending strength of this bone screw is 380 MPa. When this bone screw is implanted in an animal body and removed after 6 months, 25% of the iron is decomposed.

[0057] Immerse this orthopedic internal fixation implant medical device in PBS solution and bathe in water at 37 °C for 7 days. Then, take out the orthopedic internal fixation implant medical device and immediately measure the pH value of the surface of the device to 6 to 7 with pH test paper.

[0058] EMBODIMENT 6 Low alloy steel was cast into a hollow rod with holes drilled on the surface to obtain a rod-shaped iron substrate. A small zinc rod and hydroxyapatite powder were dispersed in molten polyracemic lactic acid, and the mixture was filled into the iron rod to obtain an absorbable iron-based bone rod. However, the weight-average molecular weight of the polyracemic lactic acid was 100 kDa, and the mass ratio of zinc to polyracemic lactic acid was 3. The mass of hydroxyapatite was 10% of the total mass of the orthopedic internal fixation implant medical device.

[0059] The bone rod has an initial bending strength of 480 MPa. When the bone screw was implanted in an animal and removed after 6 months, 18% of the iron was degraded.

[0060] Immerse this orthopedic internal fixation implant medical device in PBS solution and bathe in water at 37 °C for 7 days. Then, take out the orthopedic internal fixation implant medical device and immediately measure the pH value of the surface of the device to 7 to 8 with pH test paper.

[0061] EMBODIMENT 7 A sheet of pure iron was taken and cut into a mesh shape using a laser cutter to obtain a mesh-like iron substrate 41. Zinc oxide powder and hydroxyapatite powder were dispersed in molten polyracemic lactic acid, and the mixture 42 was applied to the surface and mesh of the iron net to obtain an iron-based absorbable bone net, as shown in Figure 4. However, the weight-average molecular weight of the polyracemic lactic acid was 5 kDa, and the mass ratio of zinc to polyracemic lactic acid was 0.55. The mass of hydroxyapatite was 6% of the entire orthopedic internal fixation implant medical device.

[0062] The initial bending strength of the bone network is 350 MPa. When this bone screw was implanted in an animal and removed after 6 months, 20% of the iron was decomposed.

[0063] Immerse this orthopedic internal fixation implant medical device in PBS solution and bathe in water at 37 °C for 7 days. Then, take out the orthopedic internal fixation implant medical device and immediately measure the pH value of the surface of the device to 6 to 7 with pH test paper.

[0064] EMBODIMENT 8 A piece of pure iron was taken and cut into a mesh shape using a laser cutter to obtain a mesh-shaped iron substrate. Zinc powder and hydroxyapatite powder were dispersed in molten polyracemic lactic acid, and the mixture was applied to the surface and mesh of the iron mesh to obtain an iron-based resorbable bone mesh. However, the weight-average molecular weight of the polyracemic lactic acid was 5 kDa, and the mass ratio of zinc to polyracemic lactic acid was 13.4. The mass of hydroxyapatite was 6% of the total mass of the orthopedic internal fixation implant medical device.

[0065] The initial bending strength of the bone network is 500 MPa. When this bone screw was implanted in an animal and removed after 6 months, 14% of the iron was decomposed.

[0066] Immerse this orthopedic internal fixation implant medical device in PBS solution and bathe in water at 37 °C for 7 days. Then, take out the orthopedic internal fixation implant medical device and immediately measure the pH value of the surface of the device to 7 to 8 with pH test paper.

[0067] EMBODIMENT 9 A wire having a zinc layer on its hollow surface is taken and woven to obtain an iron net, thus obtaining a netted iron substrate 51. Zinc oxide powder and hydroxyapatite powder are dispersed in molten polyracemic lactic acid, and the mixture 52 is applied to the surface and mesh of the iron net to obtain an absorbable iron-based bone net, as shown in FIG. 5. However, the weight-average molecular weight of the polyracemic lactic acid is 200 kDa, and the mass ratio of zinc to polyracemic lactic acid is 0.03. The mass of hydroxyapatite is 7% of the total mass of the orthopedic internal fixation implant medical device.

[0068] The bone matrix has an initial bending strength of 420 MPa. When the bone screw was implanted in an animal and removed after 6 months, 27% of the iron was degraded.

[0069] Immerse this orthopedic internal fixation implant medical device in PBS solution and bathe in water at 37 °C for 7 days. Then, take out the orthopedic internal fixation implant medical device and immediately measure the pH value of the surface of the device to 6 to 7 with pH test paper.

[0070] EMBODIMENT 10 Pure iron is cast into a hollow iron plate 61 with holes drilled on the surface, magnesium oxide powder and hydroxyapatite powder are dispersed in molten polyracemic lactic acid, and this mixture 62 is filled into the center of the iron plate 61 to obtain an absorbable iron-based bone plate, as shown in Figure 6. However, the weight-average molecular weight of the polyracemic lactic acid is 200 kDa, and the mass ratio of magnesium to polyracemic lactic acid is 2.1. The mass of hydroxyapatite is 7% of the total mass of the orthopedic internal fixation implant medical device.

[0071] The initial bending strength of the bone network is 600 MPa. When this bone screw was implanted in an animal and removed after 6 months, 20% of the iron was decomposed.

[0072] Immerse this orthopedic internal fixation implant medical device in PBS solution and bathe in water at 37 °C for 7 days. Then, take out the orthopedic internal fixation implant medical device and immediately measure the pH value of the surface of the device to 7 to 8 with pH test paper.

[0073] Comparative Example 1 The poly-L-lactic acid bone screws are absorbable and have a molecular weight of 500 kDa.

[0074] The bone screw has an initial bending strength of 150 MPa.

[0075] Immerse the absorbable bone screw in PBS solution and water bath at 37 °C for 7 days. After that, take out the orthopedic internal fixation implant medical device and immediately measure the pH value of the surface of the instrument to 4-5 with pH test paper.

[0076] The above are merely preferred specific embodiments of the present invention, and the technical scope of the present invention is not limited thereto, and any modifications or replacements that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention are included in the technical scope of the present invention. Therefore, the technical scope of the present invention should be determined based on the technical scope of the claims.

Claims

1. An orthopedic internal fixation implant medical device comprising an iron substrate and a filler containing polylactic acid and an alkaline substance, wherein the weight average molecular weight (unit: kDa) of the polylactic acid is Mw, the alkaline substance contains a metal element, and a mass ratio p of the metal element contained in the alkaline substance to the polylactic acid satisfies the formula 2 x (Mw^(-0.8)) ≦ p ≦ 30 x (Mw^(-0.5)), The weight average molecular weight Mw of the polylactic acid is 5 to 1000 kDa; the alkaline substance is a composition of at least one of magnesium, magnesium alloy, zinc, zinc alloy, magnesium oxide, magnesium hydroxide, zinc oxide, zinc hydroxide, magnesium carbonate, zinc carbonate, magnesium phosphate, zinc phosphate, sodium carbonate, sodium bicarbonate, calcium oxide, calcium hydroxide, calcium carbonate, and calcium phosphate, and hydroxyapatite; The mass of the hydroxyapatite is 1 to 10% of the mass of the orthopedic internal fixation implant medical device, The orthopedic internal fixation implant medical device is a bone screw, a bone plate, a bone rod, or a bone cannula; The iron substrate is pure iron, low alloy steel, or an iron-based alloy having a carbon content of 2.5 wt.% or less. An orthopedic internal fixation implant medical device characterized by:

2. The orthopedic internal fixation implant medical device of claim 1, wherein the alkaline substance is in one or more of the following forms: powder, granule, block, or rod.

3. The orthopedic internal fixation implant medical device according to claim 1, characterized in that the polylactic acid is polyracemic lactic acid or poly-L-lactic acid.

4. The orthopedic internal fixation implant medical device of claim 1, characterized in that: the iron base has a hollow structure, and the filler is filled inside the iron base; or the iron base has a net-like skeleton structure, and the filler is filled into the mesh of the net-like skeleton structure; or the iron base has an openwork space skeleton structure, and the filler is filled inside the openwork space of the iron base; or the surface of the iron base is provided with grooves or holes, and the filler is filled into the grooves or holes of the iron base; or the filler is applied to the surface of the iron base.

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