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Assessment of mechanical and biological properties of Ti–31Nb–7.7Zr alloy for spinal surgery implant

  • Dong Hwan Kim , Si Joon Lee , Byung Kwan Choi , In Ho Han , Chan Hee Park and Kyoung Hyup Nam EMAIL logo
Published/Copyright: October 17, 2024
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Science and Engineering of Composite Materials
From the journal Science and Engineering of Composite Materials Volume 31 Issue 1

Abstract

In the development of spinal implants, the properties of materials play a very important role in the function of the implant. This study evaluates the mechanical properties and biocompatibility of Ti–31Nb–7.7Zr alloy compared to the widely used Ti–6Al–4V alloy for spinal implants. Mechanical properties and biocompatibility were tested by manufacturing commercially available screws and rods using Ti–31Nb–7.7Zr alloy. Static compression bending test, static torsion test, and static four-point bending test were performed using a mechanical testing machine in accordance with ASTM F1717-18 standard and ASTM F382-17 standard. Additionally, screw insertion torque analysis was measured through a cadaver experiment, and histologic analysis was performed through animal experiments using a rabbit. It demonstrates that Ti–31Nb–7.7Zr, with its high yield strength and low Young’s modulus, closely matches human bone’s elasticity, potentially reducing stress shielding effects. Mechanical testing shows Ti–31Nb–7.7Zr’s superior performance in static compression, torsion, and bending tests. Biocompatibility assessments in vivo reveal no significant difference between the two materials, suggesting Ti–31Nb–7.7Zr’s suitability for spinal surgery applications. This research supports Ti–31Nb–7.7Zr alloy as a promising candidate for spinal implants, offering improved mechanical compatibility with bone and excellent biocompatibility.

Keywords: titanium alloy; mechanical properties; biocompatibility, Young’s modulus, spine, implant

1 Introduction

With the aging of the population, the incidence of degenerative diseases of the spine is increasing. As a treatment for degenerative spine conditions, spinal fusion is an effective method. The spinal instrumentation used in spinal fusion must maintain its mechanical properties until osseointegration is achieved to promote postoperative stability and surgical success [1,2].

The most common materials used commercially for spinal surgery implants are metals are pure titanium, titanium alloys, cobalt–chromium alloys, and stainless steel [2,3]. Among these, titanium alloys are the most commonly utilized material for spinal surgical instruments due to their excellent mechanical properties with high biocompatibility and corrosion resistance [4,5,6,7,8]. Metallic materials used in biomedical applications can have excellent mechanical properties if they exhibit high yield strength and low Young’s modulus [6]. High yield strength reduces the volume of the material to accommodate complex stress states and improves resistance to fatigue fracture, increasing the versatility of surgical implants [6,9,10]. Low Young’s modulus reduces the difference with human bone, which can inhibit bone resorption due to the stress shielding effect [6,11].

The yield strength and Young’s modulus of Ti–6Al–4V alloy, the most commonly used material for spinal implants, are 860 MPa and 114 GPa, respectively [6]. Considering that human bone has a Young’s modulus of 15 to 30 GPa, the relatively high Young’s modulus of the Ti–6Al–4V alloy has a risk of bone resorption due to its stress shielding effect [2,12,13]. It has also been reported that aluminum and vanadium used in the alloy can cause toxic and allergic reactions [2,14,15]. The material for spinal surgical implants must have a modulus of elasticity similar to the surrounding bone tissue while maintaining strength, and at the same time be biocompatible without cytotoxic effects [16,17,18].

As previously reported, our laboratory has developed a new Ti–31Nb–7.7Zr alloy through an efficient processing method [6]. This material received a United States Patent Application Publication in 2017 (Pub. No.: US 2017/0233851 A1). The Ti–31Nb–7.7Zr alloy has the properties of yield strength and Young’s modulus of 55 GPa and 1,000 MPa, respectively. These values are the relatively high yield strength and low Young’s modulus compared to the Ti–6Al–4V alloy.

The aim of this study is to compare the biomechanical properties and biocompatibility of instruments made of both materials using spinal surgical implants fabricated using Ti–6Al–4V alloy and Ti–31Nb–7.7Zr alloy. In this study, the mechanical and biological properties of Ti–31Nb–7.7Zr alloy were evaluated in order to develop a superior spinal surgical implant material.

2 Experimental

2.1 Experimental materials

The experiment was conducted using Ti–6Al–4V alloy and Ti–31Nb–7.7Zr alloy as materials to manufacture screws and rods which are most commonly used for spinal implants. A commercially available spinal implant using Ti–6Al–4V alloy was purchased from Medyssey (Seoul, Republic of Korea). The Ti–31Nb–7.7Zr ingots were prepared by melting high-purity raw materials using plasma arc melting equipment (AF-102-133, Nippon Tokushu Kikai Co., Japan). After forging the ingots and annealing at 800°C for 1 h, the alloy was cold-worked to 90% using a groove rolling machine (CMT, Republic of Korea) to improve load-bearing properties while maintaining a low modulus of elasticity. The cold-worked Ti–31Nb–7.7Zr alloy was then commissioned Medyssey (Seoul, Republic of Korea) to process and fabricate the same shape and size as the spinal implants of Ti-6Al-4V alloy. Spinal implants made of both materials were prototyped in the same manufacturing plant, using the same process (Figure 1). For microstructure analysis, X-ray diffraction (XRD) was performed using a BRUKER D8 instrument equipped with a Cu target (wavelength: 0.154 nm) at a scanning speed of 3 s/step with a step increment of 0.01°. Electron-backscatter diffraction (EBSD) analysis (NordlysNano, Oxford Instruments, United Kingdom) was conducted at an accelerating voltage of 15 kV. Transmission electron microscopy (TEM) was performed at an accelerating voltage of 200 kV (JEM-2100F FE-TEM, JEOL Ltd., Tokyo, Japan) to obtain a selected area diffraction (SAD) pattern.

Figure 1 Prototype of commercialized spinal implant using Ti–31Nb–7.7Zr alloy.
Figure 1

Prototype of commercialized spinal implant using Ti–31Nb–7.7Zr alloy.

2.2 Mechanical properties analyses of screw and rod

The screws were made with a diameter of 6.5 mm and a length of 45 mm, and the rods were machined to a diameter of 6 mm and a length of 100 mm. Mechanical properties analyses were performed by the Osong Medical Innovation Foundation (KBIO Health, Osong, Republic of Korea). ASTM F1717-18 standard and ASTM F382-17 standard were applied as test standards. ASTM F1717-18 standard is for analyzing spinal implant construct in a vertebrectomy model, and ASTM F382-17 standard is for metallic bone plates. Static compression bending test and static torsion test were performed using specimens inserted into the vertebral body model to analyze ASTM F1717-18 standard, and four-point bending test using steel rod was performed to analyze ASTM F382-17 standard. The tests were performed using a mechanical testing machine (MTS, Bionix servohydraulic tester, USA) on five spinal implant models made of Ti–6Al–4V alloy and Ti–31Nb–7.7Zr alloy, respectively (Figure 2).

Figure 2 Specimen for mechanical properties test: (a) Ti–6Al–4V alloy, (b) Ti–31Nb–7.7Zr alloy.
Figure 2

Specimen for mechanical properties test: (a) Ti–6Al–4V alloy, (b) Ti–31Nb–7.7Zr alloy.

2.2.1 Static compression bending test

After mounting the specimen in the jig of MTS, the load–displacement curve was measured by applying compressive force at a test rate of 25 mm/min (Figure 3). The load–displacement curve was measured to establish the displacement at 2% offset yield displacement (mm), compression bending yield load (N), and compression bending stiffness (N/mm).

Figure 3 Photograph of static compression bending test: (a) before testing, (b) after testing.
Figure 3

Photograph of static compression bending test: (a) before testing, (b) after testing.

2.2.2 Static torsion test

The specimen was mounted in the jig of MTS and tested in torsion at a test rate of 60°/min to measure the torque-angular displacement curve (Figure 4). The torque-angular displacement curve was measured to establish the displacement at 2% offset yield angular displacement (°), yield torque (N m), and torsional stiffness (N m/°).

Figure 4 Photograph of static torsion test: (a) before testing, (b) after testing.
Figure 4

Photograph of static torsion test: (a) before testing, (b) after testing.

2.2.3 Static 4-point bending test

The specimen was mounted on the jig of MTS and compressed at the tested rate of 5 mm/min to measure the load–displacement curve (Figure 5). The load–displacement curve was measured to determine the displacement at 0.2% offset yield displacement (mm), yield load (N), bending stiffness (N/mm), bending structural stiffness (N mm2), and bending strength (N mm) were established.

Figure 5 Photograph of static 4-point bending test: (a) before testing, and (b) after testing.
Figure 5

Photograph of static 4-point bending test: (a) before testing, and (b) after testing.

2.3 Screw insertion torque analysis

Experiments on screw insertion torque were performed by measuring the torque displayed on a digital screwdriver’s readout (Model DID-4; Imada, USA) as reported in previous studies [19]. Before the cadaver study, screw insertion torque was measured using a bone model to confirm the reliability of the values measured by DID-4. The experiment was conducted using six cadavers (Figure 6).

Figure 6 Photograph of screw insertion torque analysis using DID-4: (a) test with saw bone, and (b) test with a cadaver.
Figure 6

Photograph of screw insertion torque analysis using DID-4: (a) test with saw bone, and (b) test with a cadaver.

2.4 In vivo biocompatibility study

The animal experiments were reviewed and approved based on ethical procedures for scientific care by the Institutional Animal Care and Use Committee of the Preclinical Research Center of the NDIC [Hwaseong, Republic of Korea (Approval Number P233050)]. Ten male New Zealand white rabbits (18–20 weeks old, 3.0–3.5 kg) were used to create a cortical bone defect model in the tibia. Rabbits were anesthetized by intravascular injection of zoletil (35 mg/kg) and rompun (10 mg/kg). The leg of each rabbit was topically anesthetized by injection of lidocaine 0.5% solution and disinfected using povidone–iodine. After creating cortical bone defect with high-speed drill (Bobust.Co.Ltd, Hongkong, 0803), a 10 mm × 6 mm rod made of Ti–6Al–4V alloy and Ti–Nb–Zr alloy was inserted in each of five rabbits (Figure 7a). The muscle and skin were sutured layer by layer and sterilized to complete the procedure. After five weeks, the rabbits were euthanized and tibia bones were collected (Figure 7b). Tissues were fixed in 10% neutral buffered formalin (BBC Biochemical, Mount Vernon, WA, USA) after collection. Tissues were sent to the Daegu-Gyeongbuk Medical Innovation Foundation (Daegu City, Republic of Korea) for histologic analysis. Hematoxylin and eosin (H&E) and Masson’s trichrome staining were used to analyze the results.

Figure 7 Rabbit experiment for biocompatibility: (a) Titanium alloy insertion into rabbit tibial defect model, and (b) collected tissue after 5 weeks.
Figure 7

Rabbit experiment for biocompatibility: (a) Titanium alloy insertion into rabbit tibial defect model, and (b) collected tissue after 5 weeks.

3 Results and discussions

3.1 Microstructure analyses

Figure 8(a) shows the microstructure of the annealed Ti–31Nb–7.7Zr alloy. It has an equiaxed structure, and the grain size is about 47 μm, which is similar to the grain size of typical titanium alloys. More importantly, the alloy consists of a β phase with no α or ω phases, as seen in the EBSD phase map. Cross-checking with XRD confirms that the annealed Ti–31Nb–7.7Zr alloy is composed of only β phase (Figure 8(b)).

Figure 8 (a) EBSD phase map and (b) XRD result for annealed Ti–31Nb–7.7Zr alloy.
Figure 8

(a) EBSD phase map and (b) XRD result for annealed Ti–31Nb–7.7Zr alloy.

Figure 9(a) shows the microstructure of a cold-worked Ti–31Nb–7.7Zr alloy. The matrix phase is still the β phase, but α or ω phases were formed during cold working. XRD analysis shows a new peak next to the (200)β and (211)β peaks, which is presumed to be the ω phase, suggesting that the ω phase was formed during cold working rather than the α phase. Figure 9(c) shows the result of analyzing the SAD pattern using TEM. It can be seen that the ω phase (spots in solid circles) exists within the β matrix phase. Therefore, the cold-worked Ti–31Nb–7.7Zr alloy has a microstructure with a nanosized omega phase distributed within the β matrix.

Figure 9 (a) EBSD phase map, (b) XRD result, and (c) SAD pattern for cold-worked Ti–31Nb–7.7Zr alloy.
Figure 9

(a) EBSD phase map, (b) XRD result, and (c) SAD pattern for cold-worked Ti–31Nb–7.7Zr alloy.

3.2 Mechanical properties analyses of screw and rod

3.2.1 Static compression bending test

The results of the static compression bending test are summarized in Table 1 and Figure 10. The yield displacement and yield load of the static compression bending test showed that the Ti–31Nb–7.7Zr alloy was measured to be 22.31 mm and 640.76 N, respectively. Compared to the measurements of Ti–6Al–4V alloy, it shows a high yield displacement. Ti–6Al–4V alloy has a linear elastic section, so the yield strength can be obtained with a 2% offset. However, the elastic section of Ti–31Nb–7.7Zr alloy is non-linear (curved), so if the yield strength is calculated with a 2% offset, the yield strength is only about 60% of the actual value. Therefore, the measured yield load in this experiment is 640 N, but the actual yield load is expected to be about 1,100 N. Stiffness is the slope of the elastic portion of the load-displacement curve, and a lower stiffness indicates a lower modulus of elasticity. Taken together, the results of this test show that the Ti–31Nb–7.7Zr alloy has a significantly lower modulus of elasticity than the Ti–6Al–4V alloy.

Table 1

Results of static compression bending test

Yield displacement (mm) Yield load (N) Stiffness (N/mm)
Ti–6Al–4V alloy 17.75 1011.87 62.93
Ti–31Nb–7.7Zr alloy 22.31 640.76 30.23
Figure 10 Load–displacement curve of the static compression bending test: (a) Ti–6Al–4V alloy, (b) Ti–31Nb–7.7Zr alloy.
Figure 10

Load–displacement curve of the static compression bending test: (a) Ti–6Al–4V alloy, (b) Ti–31Nb–7.7Zr alloy.

3.2.2 Static torsion test

The results of the static torsion test are summarized in Table 2 and Figure 11. The results of the yield torque and yield angle of the static torsion test show that the Ti–31Nb–7.7Zr alloy measures 30.86 N m and 15.76°, respectively. The yield angle was the angle at which permanent deformation occurs, indicating the ability of the material to twist within this angle and return to its original state when the load is removed. Yield torque is the torque at which permanent deformation occurs. Compared to the measured values of Ti–6Al–4V alloy, the measured values of Ti–31Nb–7.7Zr alloy are relatively higher, but the torsional stiffness shows that the two materials have similar properties.

Table 2

Results of static torsion test

Yield torque (N m) Yield angle (°) Stiffness (N m/°)
Ti–6Al–4V alloy 25.10 14.10 2.07
Ti–31Nb–7.7Zr alloy 30.86 15.76 2.27
Figure 11 Torque angle of the static torsion test: (a) Ti–6Al–4V alloy, and (b) Ti–31Nb–7.7Zr alloy.
Figure 11

Torque angle of the static torsion test: (a) Ti–6Al–4V alloy, and (b) Ti–31Nb–7.7Zr alloy.

3.2.3 Static 4-point bending test

The results of the Static 4-point bending test are summarized in Table 3 and Figure 12. The results of the yield displacement, yield load, bending structural stiffness, and bending strength of the static 4-point bending test showed that the Ti–31Nb–7.7Zr alloy measured 2.81 mm, 1,397 N, 3,020,460 N mm2, and 17,468 N mm, respectively. As described previously, the elastic section of Ti–31Nb–7.7Zr alloy is non-linear (curved), so when the yield load and bending strength are calculated with a 2% offset, they are measured lower than the actual values. The results of this test show a similar trend to the static compression bending test. Stiffness and bending structure stiffness are lower for the Ti–31Nb–7.7Zr alloy, which means that Young’s modulus is significantly lower.

Table 3

Results of static 4-point bending test

Stiffness (N/mm) Yield displacement (mm) Yield load (N) Bending structural stiffness (N mm2) Bending strength (N mm)
Ti–6Al–4V alloy 1,032 2.38 2,211 5,913,359 27,638
Ti–31Nb–7.7Zr alloy 527 2.81 1,397 3,020,460 17,468
Figure 12 Load displacement curve of the static 4-point bending test: (a) Ti–6Al–4V alloy, and (b) Ti–31Nb–7.7Zr alloy.
Figure 12

Load displacement curve of the static 4-point bending test: (a) Ti–6Al–4V alloy, and (b) Ti–31Nb–7.7Zr alloy.

3.3 Screw insertion torque analysis

The results of the Screw insertion torque analysis are summarized in Tables 4 and 5. Screws of the same shape and size did not show any difference in insertion torque based on the alloy of the pedicle screw inserted into the lumbar spine, regardless of the material properties. This showed the same results in both the saw bone experiment conducted as a preliminary experiment and the actual cadaver experiment (Tables 4 and 5). Statistically, it was analyzed by one-way ANOVA and there was no statistical significance (p > 0.05). In general, the insertion torque and pull-out strength of the screws were not affected by the diameter or shape of the screws, indicating that there is no difference in the insertion torque of the screws based on the material.

Table 4

Results of screw insertion torque in saw bone

Insertion torque in Saw bone (kgf cm)
Ti–6Al–4V alloy Ti–31Nb–7.7Zr alloy
28.45 30.22
30.24 32.71
25.65 30.62
29.27 29.47
31.82 28.54
28.64 27.31
29.44 28.63
31.20 30.88
27.64 28.61
29.11 27.32
Table 5

Results of screw insertion torque in cadaver bone

Insertion torque in Cadaver bone (kgf cm)
Ti–6Al–4V alloy Ti–31Nb–7.7Zr alloy
26.13 20.80
18.90 18.90
13.29 14.50
19.93 19.95
16.08 30.90
16.50 17.82
23.96 16.37
31.32 19.83
6.41 8.6
8.11 12.21
13.58 11.80
6.64 6.99
13.76 11.50
18.25 19.10

3.4 In vivo biocompatibility study

Thin bone tissue was observed to have formed around the tibial bone where the Ti–6Al–4V alloy and Ti–31Nb–7.7Zr alloy were inserted. Periosteum consisting of a small amount of fibrous tissue was observed around the formed bone tissue. No changes in the bone marrow composition due to the titanium alloy were observed in the two groups. Furthermore, there were no remarkable changes or inflammatory cell infiltration, tissue necrosis, and degenerative changes (Figure 13). Both Ti–6Al–4V alloy and Ti–31Nb–7.7Zr alloy showed no significant difference in vivo efficacy and safety evaluation, and it can be concluded that both materials have biocompatibility.

Figure 13 Histologic findings of titanium alloy in rabbit tibial defect model: (a) Ti–6Al–4V alloy with H&E stain, (b) Ti–31Nb–7.7Zr alloy with H&E stain, (c) Ti–6Al–4V alloy with Masson’s trichrome stain, and (d) Ti–31Nb–7.7Zr alloy with Masson’s trichrome stain.
Figure 13

Histologic findings of titanium alloy in rabbit tibial defect model: (a) Ti–6Al–4V alloy with H&E stain, (b) Ti–31Nb–7.7Zr alloy with H&E stain, (c) Ti–6Al–4V alloy with Masson’s trichrome stain, and (d) Ti–31Nb–7.7Zr alloy with Masson’s trichrome stain.

4 Discussion

In the development of spinal implants, the properties of materials play a very important role in the function of the implant. In order to have excellent strength and biocompatibility, it must have high strength and low Young’s modulus while being non-cytotoxic. Ti–6Al–4V alloy, which is currently the most widely used material for spinal implants, has proven its effectiveness, but has the limitation of Young’s modulus, which is relatively high compared to human bone [2,3,12,13,20,21,22]. Additionally, there is a risk of toxicity and allergic reactions due to aluminum and vanadium, which are alloy elements [2,14,15].

In past research, we have proven that the Ti–31Nb–7.7Zr alloy we developed has the properties of a material with Young’s modulus of 55–85 GPa, similar to surrounding bone tissue, while maintaining high strength [2,4,6]. Based on the research results, this study analyzed the mechanical properties and biocompatibility of commercially available spinal implant types.

The Ti–Nb–Zr system was developed based on the excellent properties of the two-component Ti–Zr system introduced in the early 1990s [23,24,25]. In past studies, alloys produced based on the Ti–Nb–Zr system were reported to have high utility as orthopedic implants [2,26]. Second-generation titanium alloys, such as Ti–31Nb–7.7Zr alloy, which was the subject of this study, have higher ß phase content in the microstructure and more biocompatible alloying elements [27,28]. Ti–6Al–4V alloy has been developed by replacing aluminum (Al) with tantalum (Ta), hafnium (Ha), and zirconium (Zr), and vanadium (V) with niobium (Nb), ferrum (Fe), and molybdenum (Mo). Nb, used as a β-stabilizing element in Ti–Nb–Zr alloy, can maintain a stable β phase by affecting microstructure and phase composition [2,29]. For this reason, new β-titanium alloys such as Ti–31Nb–7.7Zr alloy can have high biocompatibility while providing a lower Young’s modulus than Ti–6Al–4V alloy through the use of Nb and Zr [11,30,31].

In particular, it is noteworthy that this work identifies a microstructural mechanism that can increase the strength of Ti–Nb–Zr alloys while maintaining their low Young’s modulus. The physical properties of metals are known to be affected by the concentration of valence electrons, and Young’s modulus of titanium alloys is also affected by the electron-to-atom ratio as shown by the solid curve in Figure 14 [32]. There are two important regions that exhibit low Young’s modulus, one dominated by the α˝ phase and the other dominated by the β phase. Of these two regions, the region dominated by the α˝ phase has the disadvantage of being difficult to manufacture due to its narrow compositional tolerance and very low strength, while the region dominated by the β phase has the advantage of being relatively easy to manufacture and has moderately high strength. Ti–31Nb–7.7Zr alloy has an electron-to-atom ratio of 4.2, and it is positioned in the region with the lowest Young’s modulus even in the domain where the beta phase predominates.

Figure 14 Relationship between Young’s modulus and electron-to-atom ratio of Ti alloys [32]. Ti–6Al–4V alloy and Ti–31Nb–7.7Zr alloys are located around dotted circles and solid circles, respectively.
Figure 14

Relationship between Young’s modulus and electron-to-atom ratio of Ti alloys [32]. Ti–6Al–4V alloy and Ti–31Nb–7.7Zr alloys are located around dotted circles and solid circles, respectively.

One important point to note is that in the annealed condition, Young’s modulus of the Ti–31Nb–7.7Zr alloy is approximately 55 GPa, which is very low, and the yield strength is also not high, at about 550 MPa. Therefore, cold working is essential to increase the yield strength to 1,000 MPa while maintaining the low Young’s modulus. As shown in Figure 8, the microstructure before cold working consists of a single β phase, but as indicated in Figure 9, during cold working, some β phases transform into deformation-induced ω phases of nanosize. In other words, to increase strength while maintaining a low Young’s modulus, it can be advantageous to have a microstructure where nano-sized ω phases are distributed in the β matrix.

Not only the low Young’s modulus of the alloy but also the corrosion resistance and cytotoxicity of the metal are important. If spinal implant fracture easily occurs before the bone union is achieved, the success of the surgery cannot be guaranteed. The corrosion resistance of metals depends on the location of chemical bonds in the oxide layer, with Nb and Zr oxides having lower solubility than Al and V oxides [2,33]. Even in the values measured in this study, Ti–31Nb–7.7Zr alloy shows equal or higher strength compared to Ti–6Al–4V alloy. In addition, no inflammation or necrosis was observed in the histological examination, confirming that there is no cytotoxic effect of titanium as shown in past studies [2,34]. The results of this study confirmed that the combination of Nb and Zr alloy elements used in Ti–31Nb–7.7Zr alloy has high strength, low Young’s modulus, and in vivo stability.

5 Conclusion

In the development of spinal implants, not only device design but also mechanical properties and biological stability are important. This study was conducted to develop a suitable material for the development of excellent spinal implants, and the mechanical strength, Young’s modulus, and biocompatibility of Ti–31Nb–7.7Zr alloy were analyzed. When the properties of Ti–31Nb–7.7Zr alloy material are manufactured in the form of commercialized spinal implants and compared with Ti–6Al–4V alloy, Ti–31Nb–7.7Zr alloy can be a promising candidate as a material for spinal implants.

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Acknowledgements

The authors thank Medyssey (Seoul, Republic of Korea), Osong Medical Innovation Foundation (KBIO Health, Osong, Republic of Korea), NDIC (Hwaseong, Republic of Korea), and Daegu-Gyeongbuk Medical Innovation Foundation (Daegu City, Republic of Korea).

  1. Funding information: This work was supported by the National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MSIT; No. NRF-2021R1F1A1061178).

  2. Author contributions: All authors have accepted responsibility for the entire content of this manuscript and consented to its submission to the journal, reviewed all the results and approved the final version of the manuscript. DHK: conceptualization, methodology, resources, writing – original draft. SJL: animal experiment and histologic analysis. BKC: investigation and visualization. IHH: validation, investigation, and visualization. CHP: conceptualization, methodology, and data analysis. KHN: conceptualization, methodology, formal analysis, writing – original draft, writing – review & editing, supervision.

  3. Conflict of interest: Authors state no conflict of interest.

  4. Ethics approval: The animal experiments were reviewed and approved based on ethical procedures for scientific care by the Institutional Animal Care and Use Committee of the Preclinical Research Center of the NDIC (Hwaseong, Republic of Korea; Approval Number, P233050).

  5. Data availability statement: The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

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Received: 2024-02-26
Revised: 2024-08-22
Accepted: 2024-08-23
Published Online: 2024-10-17

© 2024 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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https://doi.org/10.1515/secm-2024-0037
Keywords for this article
titanium alloy; mechanical properties; biocompatibility, Young’s modulus, spine, implant
Creative Commons
BY 4.0

Articles in the same Issue

  1. Regular Articles
  2. Research on damage evolution mechanisms under compressive and tensile tests of plain weave SiCf/SiC composites using in situ X-ray CT
  3. Structural optimization of trays in bolt support systems
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