JP6041045B2 - Zirconium alloy for living body and bone fixing device using the same - Google Patents

Description

  The present invention relates to a biological zirconium alloy and a biological medical instrument using the same.

  Metal materials are used in many medical devices mainly because of their mechanical reliability. Among them, implant materials such as artificial hip joints, artificial knee joints, bone plates, and artificial tooth roots are pure materials with excellent hard tissue compatibility. Ti and Ti alloys are used. However, these metal materials are considered to have the following problems at the time of image diagnosis using a magnetic resonance diagnosis (MRI) apparatus.

  When MRI is performed in a state where a metal material is placed in the body, an image defect called an artifact occurs around the member, making it difficult to evaluate and confirm the bone fusion of the member. The cause of the artifact is a mismatch between the magnetic susceptibility of the implant material and the negative magnetic susceptibility of the living tissue. As a solution to this problem, the use of a metal material having a low magnetic susceptibility or a negative magnetic susceptibility has been proposed. Can be mentioned. Since a diamagnetic metal material (eg, a gold alloy) having a negative magnetic susceptibility has difficulty in strength, the present inventors have attempted to lower the magnetic susceptibility with a paramagnetic metal material.

  Zirconium (Zr) is inferior in mechanical strength to Ti, but has lower cytotoxicity and magnetic susceptibility than Ti, and has led to the proposal of a low-magnetic-susceptibility alloy for living organisms mainly composed of Zr. In recent years, when a Ti alloy is applied as a material for a bone anchor, a problem has been reported in which the bone anchor adheres to the bone and is difficult to remove after bone fusion. Since the Zr-based alloy of the present invention has the property of not forming calcium phosphate, which is the main component of bone, on the surface of the material, the above problem is solved.

  Ti-based alloys have a modulus of elasticity (approximately 100-200 GPa) that is much greater than that of cortical bone (approximately 20 GPa). This elastic modulus gap causes overload shielding (stress shielding) to the bone, resulting in bone atrophy. Therefore, if a low-elasticity Zr alloy that is as close to cortical bone as possible can be developed, it can be provided as a material for a bone anchor that can be easily removed and stress shielding is less likely to occur.

There is a possibility that the magnetic susceptibility and elastic modulus of the Zr-based alloy may change greatly by controlling the alloying elements and the constituent phases. In this regard, several proposals have been made in the past.
For example, in Patent Document 1, among the main transition metals of Groups 4 to 6 in the periodic element periodic table, Zr is a main component, and the main component other than Zr is used as a subcomponent having a lower content than the main component. A biomedical metal material containing 0.5 to 15% by mass of at least one transition metal (Ti, V, Cr, Nb, Mo, Hf, Ta, W) is described.
For example, Patent Document 2 describes a biological zirconium alloy containing Zr as a main component and containing Nb in a range of more than 15 mass% and 25 mass% or less.

JP 2010-75413 A JP 2012-66017 A

  In the medical field, the magnetic field of MRI is increasing for high-resolution imaging, and a further low magnetic susceptibility alloy is required in the future. Conventional biomedical zirconium alloys represented by those described in Patent Document 1 or 2 have room for improvement in magnetic susceptibility and strength.

The present invention aims to solve the above problems.
That is, an object of the present invention is to provide a biomedical zirconium alloy having a low magnetic susceptibility and high strength and a biomedical device using the same.

The inventor has intensively studied to solve the above-mentioned problems, and has completed the present invention.
The present invention includes the following (1) to (15).
(1) A biological zirconium alloy containing Zr as a main component and containing Ta in a range exceeding 15 mass%.
(2) The biomedical zirconium alloy according to (1), wherein Zr is a main component and Ta is contained in an amount of 16 to 35% by mass.
(3) The biomedical zirconium alloy according to (2), wherein Zr is a main component and Ta is contained in an amount of 16 to 24% by mass.
(4) The biomedical zirconium alloy according to (3), wherein Zr is a main component and Ta is contained in an amount of 16 to 19% by mass.
(5) The biomedical zirconium alloy according to (2) above, containing Zr as a main component and containing 25 to 35% by mass of Ta.
(6) The biomedical zirconium alloy according to (1), wherein Zr is a main component and Ta is contained in an amount of 40 to 50% by mass.
(7) Ta is contained in an amount of more than 15% by mass and 50% by mass or less, the balance is made of Zr and inevitable impurities, and the constituent phases are either ω phase or β-Ta phase, α ′ phase, The biomedical zirconium alloy according to (1), comprising:
(8) The biomedical zirconium alloy according to (7), wherein Ta is contained in an amount of 16 to 19% by mass, and the constituent phase includes an ω phase and an α ′ phase, and is used for a bone anchor.
(9) The biomedical zirconium alloy according to (7), containing 25 to 35% by mass of Ta, wherein the constituent phase includes a β-Ta phase and an α ′ phase, and is used for a bone anchor.
(10) The biomedical zirconium alloy according to (7), containing 16 to 35% by mass of Ta.
(11) The biomedical zirconium alloy according to (10), containing 16 to 24% by mass of Ta.
(12) The biomedical zirconium alloy according to (11), wherein Ta is contained in an amount of 20 to 22% by mass, and the constituent phases include an ω phase and an α ′ phase.
(13) The biomedical zirconium alloy according to (9), containing 25 to 28% by mass of Ta.
(14) The biological zirconium alloy according to (7), wherein Ta is contained in an amount of 40 to 50% by mass, and the constituent phase includes a β-Ta phase and an α ′ phase.
(15) A biomedical device using the biomedical zirconium alloy according to any one of (1) to (14).

  ADVANTAGE OF THE INVENTION According to this invention, the magnetic zirconia alloy with low magnetic susceptibility and high intensity | strength and the biomedical device using the same can be provided.

It is a graph which shows the measurement result of the relationship between Ta content rate and magnetic susceptibility. It is a graph which shows the measurement result of the relationship between Ta content rate and hardness. It is a graph which shows the measurement result of the relationship between Ta content rate and an elasticity modulus. 10 is a graph showing the XRD result of Comparative Example 3. It is a graph which shows the XRD result of Example 2. 10 is a graph showing the XRD result of Example 5. 10 is a graph showing the XRD result of Example 7. It is a graph which shows the XRD result of Example 8. 2 is a photograph of a metal structure by a scanning electron microscope of Comparative Example 1. 4 is a photograph of a metal structure obtained by a scanning electron microscope of Comparative Example 2. 6 is a photograph of a metal structure obtained by a scanning electron microscope of Comparative Example 3. 2 is a photograph of a metal structure by a scanning electron microscope of Example 1. FIG. 3 is a photograph of a metal structure by a scanning electron microscope of Example 2. 3 is a photograph of a metal structure obtained by a scanning electron microscope in Example 3. 6 is a photograph of a metal structure by a scanning electron microscope of Example 5. 7 is a photograph of a metal structure obtained by a scanning electron microscope in Example 7. It is a figure which shows the structure of a bone fixing tool.

The present invention will be described.
The present invention is a biological zirconium alloy containing Zr as a main component and containing Ta in a range exceeding 15 mass%.
Such a biomedical zirconium alloy is hereinafter also referred to as “the alloy of the present invention”.

Each component of the alloy of the present invention will be described.
In addition, C content rate and S content rate in the alloy of the present invention are values obtained by measurement by high frequency combustion-infrared absorption method, Si content rate is a value obtained by measurement by silicon dioxide weight method, and O content rate. Is a value obtained by measurement by an infrared absorption method, N content is a value obtained by measurement by a thermal conductivity method, and the content of other components is a value obtained by measurement by an ICP-AES method. .

<Zr>
The alloy of the present invention contains Zr as a main component. “Main component” means a content of 30% by mass or more. The alloy of the present invention preferably contains 40 mass% or more of Zr, more preferably contains 50 mass% or more, more preferably contains 60 mass% or more, and more preferably contains 65 mass% or more. In such a case, the alloy of the present invention having a low magnetic susceptibility and higher strength can be obtained.
Hereinafter, unless otherwise specified, the “main component” is used in the meaning as described above.

  In addition, the alloy of the present invention preferably contains Zr as a main component, Ta in a specific range, and the other consists of inevitable impurities. Inevitable impurities mean components that may be mixed from raw materials, manufacturing processes, etc. without intentional addition.

<Ta>
The alloy of the present invention contains Ta in a range exceeding 15% by mass.
The present inventor has found that when Zr is a main component and Ta is contained in a range exceeding 15 mass%, a biomedical zirconium alloy having a low magnetic susceptibility and a high strength can be obtained. The Ta content in the alloy of the present invention is preferably more than 15% by mass and 50% by mass or less.
The Ta content in the alloy of the present invention is more preferably 16 to 35% by mass. This is because a biomedical zirconium alloy having a lower magnetic susceptibility and higher strength can be obtained.

  The alloy of the present invention preferably contains 16 to 24% by mass of Ta. In such a case, the present inventors have found that the alloy of the present invention has a lower magnetic susceptibility. The lower the magnetic susceptibility, the smaller the artifact in MRI diagnosis, which is preferable. Moreover, the alloy with high X-ray contrast property is obtained by containing 16-24 mass% of Ta. In addition, intensity | strength can be improved more by containing 20-22 mass% of Ta.

  The alloy of the present invention preferably contains 16 to 19% by mass of Ta. In such a case, the present inventors have found that the alloy of the present invention has a low elastic modulus in addition to a low magnetic susceptibility and high strength. When the elastic modulus is low, for example, when the alloy of the present invention is used as a bone fixing device, a load is easily transmitted to the bone tissue, and bone resorption is suppressed and bone contraction is suppressed.

  Moreover, it is preferable that the alloy of this invention contains 25-35 mass% of Ta. In such a case, the present inventors have found that the alloy of the present invention has a low elastic modulus in addition to a low magnetic susceptibility and high strength. In addition, an elastic modulus can be reduced more by containing 25-28 mass% of Ta.

  Moreover, it is preferable that the alloy of this invention contains 40-50 mass% of Ta. In such a case, the present inventors have found that the alloy of the present invention has a lower magnetic susceptibility. The lower the magnetic susceptibility, the smaller the artifact in MRI diagnosis, which is preferable. Moreover, the alloy with high X-ray contrast property is obtained by containing 40-50 mass% of Ta.

Next, the impurity component in the alloy of the present invention will be described.
In the alloy of the present invention, B, C, N, O, Na, Mg, Si, P, S, K, Ca, Mn, and the like are impurity components. The lower the content, the better.

<Organization>
Zr alone has an α phase (close-packed hexagonal crystal) at normal temperature and a β phase (body-centered cubic) at a temperature higher than 862 ° C.
In an alloy containing Zr as a main component and containing Ta, the crystal phase thereof is a phase called α ′ phase formed by Zr and Ta at room temperature, and is a β phase at higher temperature.
When rapidly cooling from the high temperature region where the β phase appears to room temperature, the α ′ phase does not appear and the β phase may be frozen (quenched). Further, when the temperature is raised and tempered, a phase called hexagonal phase (hexagonal crystal) formed by Zr and Ta may appear in the β phase. The ω phase may be appeared without being tempered only by quenching from the β phase in the high temperature range. In addition, when the alloy in the high temperature region where the β phase appears is allowed to cool at room temperature, the ω phase may appear in the β phase even without rapid cooling. The ease of appearance of the ω phase in the alloy is related to the Ta content.
The alloy of the present invention may have a structure of α ′ phase, β-Ta phase and ω phase. These tissues can be confirmed using XRD.
When the alloy of the present invention contains Ta in excess of 15% by mass and 50% by mass or less, and the balance is composed of Zr and inevitable impurities, the constituent phase is either ω phase or β-Ta phase. , Α ′ phase.
When the alloy of the present invention contains 16 to 19% by mass of Ta and the balance is composed of Zr and inevitable impurities, the constituent phases include an ω phase and an α ′ phase.
When the alloy of the present invention contains 25 to 35% by mass of Ta and the balance is composed of Zr and inevitable impurities, the constituent phases include a β-Ta phase and an α ′ phase.
When the alloy of the present invention contains 16 to 35% by mass of Ta and the balance is composed of Zr and inevitable impurities, the constituent phases are either ω phase or β-Ta phase, and α ′ phase. ,including.
When the alloy of the present invention contains 16 to 24% by mass of Ta and the balance is composed of Zr and inevitable impurities, the constituent phases are either ω phase or β-Ta phase, α ′ phase, ,including.
When the alloy of the present invention contains 20 to 22% by mass of Ta and the balance is made of Zr and inevitable impurities, the constituent phases include an ω phase and an α ′ phase.
When the alloy of the present invention contains 25 to 28% by mass of Ta and the balance is made of Zr and inevitable impurities, the constituent phases include a β-Ta phase and an α ′ phase.
When the alloy of the present invention contains 40 to 50% by mass of Ta and the balance is made of Zr and inevitable impurities, the constituent phases include a β-Ta phase and an α ′ phase.
The inventor has intensively studied and found that the existence ratio of these structures affects the magnetic susceptibility, strength (hardness) and elastic modulus of the alloy of the present invention. Further, it has been found that an alloy having mainly an α ′ phase and a β-Ta phase and having a low magnetic susceptibility and a high elastic modulus can be obtained when the volume fraction of the β-Ta phase is increased with respect to the α ′ phase.

<Manufacturing method>
The method for producing the alloy of the present invention is not particularly limited.
For example, an alloy was melted by a non-consumable electrode type arc melting method in an Ar atmosphere using melting raw materials of Zr 99.5 mass% and Ta 99.5 mass%. The alloy of the present invention can be obtained only in a cast state.

<Medical medical device>
A biomedical device can be obtained using the alloy of the present invention.
Such a biomedical device is also referred to as “the device of the present invention”.

  The device of the present invention can be manufactured by, for example, dissolving a raw material containing Zr and Ta and then solidifying the raw material into a predetermined shape. After solidification, machining such as cutting and grinding, surface treatment such as various blast treatments, and the like may be performed as necessary.

  Specific examples of biomedical devices include aneurysm treatment devices (clips, embolization coils, stent grafts, etc.), stents (blood vessels, bile ducts, pancreatic ducts, tracheas, esophagus, intestinal tracts, etc.), indwelling in the body Devices (hemostatic clips, prosthetic valves, etc.), medical instruments (MRI compatible surgical instruments, devices (endoscopes, etc.), etc.), bone fixation instruments (eg osteosynthesis plates, osteosynthesis nails, osteosynthesis screws, bone fixation) Plate, intramedullary nail, etc.).

Next, examples and comparative examples of the present invention will be described.
<Melting of Zr-Ta alloy>
An alloy was melted by a non-consumable electrode type arc melting method in an Ar atmosphere using melting raw materials of Zr 99.5 mass% and Ta 99.5 mass%. In order to prevent segregation of the alloy, melting was performed three times, and the ingot was inverted each time.
Thereby, an ingot of 9 compositions of Zr-Ta alloy (each 350 g, about 500 mm × 400 mm × 15 mm) was obtained. The target composition of Ta in 9 alloys is 10 mass%, 13 mass%, 15 mass%, 18 mass%, 20 mass%, 22 mass%, 25 mass%, 30 mass%, 35 mass%, 40 mass%. , And 50% by mass, and the remainder is Zr.

  And about each alloy, the identification of the constituent phase, the hardness measurement, the elastic modulus measurement, and the magnetic susceptibility measurement were performed only in the cast state.

<Identification of constituent phases>
Each alloy was phase-identified by X-ray diffraction (XRD). The surface mechanically polished with water-resistant abrasive paper is used as the measurement surface, and measurement is performed under the conditions of an acceleration voltage of 40 kV, a current of 30 mA (in the atmosphere, room temperature), a measurement range (2θ) of 20 to 120 °, and a scanning speed of 1.2 ° / min. Went.
The measurement results are shown in Table 1.

<Magnetic susceptibility measurement>
Using a magnetic balance MSB-MKI (manufactured by Sherwood Scientific LTD), the magnetic susceptibility of each alloy was measured by the Evans method in the atmosphere and at room temperature. A sample obtained by cutting a round bar of φ3 mm × 25 mm from an ingot was used. Moreover, it measured twice about the sample of the same composition, and those average values were made into the magnetic susceptibility in the alloy of each composition.
The measurement results are shown in Table 1 and FIG. In addition, the literature value was used for the value of 0 mass% Ta in FIG.

<Hardness measurement>
In accordance with JIS Z 2244, the hardness was measured using a Vickers hardness tester under the conditions of 30 kgf and 15 s. The sample used was a resin-filled material cut into 10 mm × 10 mm × 5 mm from the ingot. Moreover, it measured 5 times about the sample of the same composition, and let those average values be the hardness in the alloy of each composition.
The measurement results are shown in Table 1 and FIG. The plot of 0 mass% Ta in FIG. 2 is obtained by arc melting casting of pure Zr as a melting raw material.

<Elastic modulus measurement>
The elastic modulus of each alloy was measured by the free resonance method in the atmosphere and at room temperature using JE-RT (manufactured by Nippon Techno Plus). A sample obtained by cutting a round bar of φ3 mm × 25 mm from an ingot was used. Moreover, it measured twice about the sample of the same composition, and made those average values into the elasticity modulus in the alloy of each composition.
The measurement results are shown in Table 1 and FIG. In addition, the literature value was used for the value of 0 mass% Ta in FIG.

As shown in FIG. 1, the magnetic susceptibility is greatly reduced by the addition of 10% by mass Ta, and after being almost constant in the 10% by mass to 15% by mass Ta alloy, then the 1.00 × in the 20% by mass Ta alloy. It decreased to 10 ⁻⁶ cm ³ / g. The increase started with the 25 mass% Ta alloy, but then gradually decreased with an increase in the amount of Ta added. The magnetic susceptibility reached 0.94 × 10 ⁻⁶ cm ³ / g with 40 mass% Ta and 50 mass% Ta alloy.

  As shown in FIG. 2, the Vickers hardness increased with an increase in the amount of Ta, reached a maximum with a 20 mass% Ta alloy, and then monotonously decreased.

  As shown in FIG. 3, the elastic modulus decreased with an increase in the amount of Ta, reached a minimum with an 18% by mass Ta alloy, then started to increase, and reached a maximum with a 20% by mass Ta alloy. After the 20% by mass Ta alloy, it decreased again, and after the 25% by mass Ta alloy showed the minimum value, the elastic modulus started to increase. Among the measured samples, 50 mass% Ta alloy was the largest, and the value was larger than the elastic modulus of pure Zr.

As shown in Table 1, an α ′ phase was observed throughout the entire composition. A ω phase appeared in a 20 mass% Ta alloy, and a β-Ta phase newly appeared in an alloy of 25 mass% or more. On the other hand, no peak derived from the β-Zr phase was detected by XRD throughout the entire composition. 4A to 4E are graphs showing the XRD results of Comparative Example 3, Examples 2, 5, 7, and 8. FIG. FIG. 5A to FIG. 5H are photographs of metal structures obtained by a scanning electron microscope in Comparative Examples 1, 2, 3, and Examples 1, 2, 3, 5, and 7.
The hardness and modulus of elasticity show maximum values with a 20 mass% Ta alloy in which the ω phase is only found. Further, since the magnetic susceptibility shows a minimum value, the ω phase is expected to contribute to higher hardness, higher elastic modulus, and lower magnetic susceptibility.

  After the 30% by mass Ta alloy in which the β-Ta phase was observed, the proportion of β-Ta increased as the amount of Ta added increased. As a result, the hardness and magnetic susceptibility decreased, and the elastic modulus increased. Therefore, although the β-Ta phase is the same as the ω phase in terms of the effects of increasing the elastic modulus and decreasing the magnetic susceptibility, the hardness tends to decrease.

  The magnetic susceptibility of the alloys of Examples 1 to 8 is a value at which MRI imaging can be performed without any problem in the entire composition region, and is equivalent to or compared with Zr—Mo alloys and Zr—Nb alloys that are being developed in the same manner. Low value. In addition, the alloys of Examples 1 to 8 can be applied to biological medical devices such as bone anchors. FIG. 6 is a diagram showing a configuration of the bone anchor 10. The bone anchor 10 includes an osteosynthesis plate 10a for fixing the bone 12 and an osteosynthesis screw 10b.

  The biomedical zirconium alloy of the present invention has a low magnetic susceptibility and high strength, and thus is useful for biomedical devices such as bone anchors.

Claims (4)

16 to 19% by mass of Ta, with the balance consisting of Zr and inevitable impurities,
Structure Narusho is, and a ω phase and the α 'phase,
Used in the bone anchor, the raw-body zirconium alloy. Containing 25 to 35% by mass of Ta, with the balance consisting of Zr and inevitable impurities,
Structure Narusho is, and a β-Ta phase and the α 'phase,
Used in the bone anchor, the raw-body zirconium alloy. The biomedical zirconium alloy according to claim 2, comprising 25 to 28% by mass of Ta. The bone fixing tool using the biomedical zirconium alloy as described in any one of Claims 1-3 .