**4. Cation extraction**

Cation extraction tests were carried out only for Ti6Al7Nb prostheses that have undergone very particular surface treatments. **Table 6** presents the characteristics of the two series of prostheses used.

To minimize the volume/surface ratio, Pyrex glass reactors have been developed and adapted to the prosthesis shape (**Figure 17**). The orthopedic implant has a total area of 115.9 cm2 . An electrolyte solution of HCl 0.07 N (300 ml) prepared from Titrisol® 1.0 N (Merck) was used. For extraction tests the release solution volume (ml)/total sample surface (cm2 ) ratio was equal to 3. The choice of electrolyte extraction was based on thermodynamic considerations [40] (solubility). Standards (EN-71-3) concerning bioavailability [41] and constraints of the analysis technique (simple matrix causes no perturbations) were considered.

For washing the glass reactors, concentrated nitric acid was used for 24 h. Afterwards they were thoroughly rinsed with deionized water (18 MΩ cm), in order to completely eliminate the acid and then, finally, dried. The extraction tests were conducted at 37 ± 2°C. The prosthesis were kept in the extraction solution for 168 h and then removed, rinsed, and dried. 50 ml of the extraction solution was used for the analysis using ICP-OES/MS method (PerkinElmer Elan DRC). A blanc solution was measured as a reference. The release of elements in the diluted solution of hydrochloric acid 0.07 N shows significant differences between the two types of


**215**

**Table 7.**

*Cations released in solution.*

prostheses (**Table 7**). The following elements, which correspond to the detection limit (Be, Mo, Ni, P, S, and V) as well as those that show a released value identically

**Element Blanc Series 1 Series 2**

As <1 <1 1.4 <1 <1 1.7 2.6 Ba 0.24 0.51 0.24 0.48 0.63 0.8 0.77 Be <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 Br 3.54 6.32 4.89 4.72 4.13 5.73 7 Cd <0.02 0.18 0.02 <0.02 0.09 <0.02 <0.02 Co 0.02 0.78 0.76 0.79 0.12 0.22 0.16 Hg 0.81 0.62 0.18 0.13 0.1 0.13 <0.05 Li 0.11 0.16 0.16 0.15 0.17 <0.1 0.15 Mo <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 Nb <0.02 130 110 110 73 55 62 Pb 1.9 0.93 0.46 0.71 0.84 0.95 1.0 Sb 0.06 0.1 0.08 0.08 0.06 0.03 0.07 Sn 0.13 0.13 0.15 0.14 0.12 0.1 0.08 Zr <0.02 0.03 <0.02 0.04 0.16 0.19 0.15 Al 18 193 143 135 194 180 199 Ca 0.0 0.1 0.0 0.1 0.0 <0.02 <0.02 Cr (total) <0.5 0.9 0.9 0.9 2.1 1.8 2.2 Cu <2 <2 <2 <2 <2 6.1 <2 Fe <2 51.5 36 48.4 32.6 30.1 41.7 Ni <2 <2 <2 <2 <2 <2 <2 P <10 <10 <10 <10 <10 <10 <10 S <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 Ti 0.7 1600 1590 1500 1510 1350 1500 V <0.2 <0.02 <0.02 <0.02 <0.02 <0.02 <0.02 Zn <2 15.9 4.2 6.9 5.5 5.9 7.7

**#A #B #C #D #E #F**

to the blanc solution (Br, Hg, Pb and Sn), were not taken into account.

*Multicomponent Alloys for Biomedical Applications DOI: http://dx.doi.org/10.5772/intechopen.88250*

**Figure 17.**

*Glass reactors for cation extraction tests.*

**Table 6.** *Description of Ti6Al7Nb prosthesis used for cation extraction.* *Multicomponent Alloys for Biomedical Applications DOI: http://dx.doi.org/10.5772/intechopen.88250*

#### **Figure 17.** *Glass reactors for cation extraction tests.*

*Engineering Steels and High Entropy-Alloys*

development of modular prostheses.

of the two series of prostheses used.

(ml)/total sample surface (cm2

#B #C

#E #F

*Description of Ti6Al7Nb prosthesis used for cation extraction.*

**4. Cation extraction**

area of 115.9 cm2

distal modules.

dynamic test with crevice corrosion stimulation) shows that the location of the visible spots on the proximal explanted module approximately corresponds to the electrolyte deposits observed during cyclic fatigue dynamic tests with crevice corrosion stimulation. SEM observation does not reveal obvious localized corrosion in the spots area (**Figure 16c**). In exchange, the EDX analysis (**Figure 16d**) reveals the presence of C and Na, which suggests that biological fluids have penetrated and diffused at the proximal/distal module interface. The evaluation of cyclic dynamic corrosion with crevice stimulation on Ti6Al4V modular prostheses shows a similar analogue phenomenon of electrolyte pumping at the interface of the proximal/

The comparison of the explanted proximal parts with modular prostheses of the same type evaluated by cyclic fatigue dynamic tests with crevice corrosion stimulation reveals that there are significant similarities, in particular with regard to the electrolyte diffusion, deposition of products, and corrosion. Thus, these observations justify the use of cyclic fatigue dynamic tests with crevice corrosion stimulation in order to compare and evaluate different types of materials for the

Cation extraction tests were carried out only for Ti6Al7Nb prostheses that have undergone very particular surface treatments. **Table 6** presents the characteristics

To minimize the volume/surface ratio, Pyrex glass reactors have been developed and adapted to the prosthesis shape (**Figure 17**). The orthopedic implant has a total

Titrisol® 1.0 N (Merck) was used. For extraction tests the release solution volume

For washing the glass reactors, concentrated nitric acid was used for 24 h. Afterwards they were thoroughly rinsed with deionized water (18 MΩ cm), in order to completely eliminate the acid and then, finally, dried. The extraction tests were conducted at 37 ± 2°C. The prosthesis were kept in the extraction solution for 168 h and then removed, rinsed, and dried. 50 ml of the extraction solution was used for the analysis using ICP-OES/MS method (PerkinElmer Elan DRC). A blanc solution was measured as a reference. The release of elements in the diluted solution of hydrochloric acid 0.07 N shows significant differences between the two types of

(simple matrix causes no perturbations) were considered.

**Series Code Type Surface treatment**

Series 2 #D SL-Plus r Stem Corundum blasted

extraction was based on thermodynamic considerations [40] (solubility). Standards (EN-71-3) concerning bioavailability [41] and constraints of the analysis technique

Series 1 #A SL-Plus r NT Stem Corundum blasted + mechanical-chemical cleaning

. An electrolyte solution of HCl 0.07 N (300 ml) prepared from

) ratio was equal to 3. The choice of electrolyte

**214**

**Table 6.**


#### **Table 7.**

*Cations released in solution.*

prostheses (**Table 7**). The following elements, which correspond to the detection limit (Be, Mo, Ni, P, S, and V) as well as those that show a released value identically to the blanc solution (Br, Hg, Pb and Sn), were not taken into account.

The presence of the alloying elements, Ti and Al, is comparable for both series of implants and confirms the literature data [42–45]. Spriano et al. [42] also reported an increase of metal ion concentration after a long time exposure, for the Ti6Al7Nb alloy in a SBF solution. On the other hand, the concentration of Nb cations for series 2 is significantly smaller than for series 1 (60–120 μg l<sup>−</sup><sup>1</sup> , respectively). The most important impurity is Fe (between 30 and 50 μg l<sup>−</sup><sup>1</sup> ), almost identical for the two types of prostheses. The samples of series 1 released less chromium than series 2, respectively, 0.9 and 2 μg l<sup>−</sup><sup>1</sup> . The prostheses of sample #E released 6 μg l<sup>−</sup><sup>1</sup> Cu. Samples #B, #E and, #F released 1.4–2.6 μg l<sup>−</sup><sup>1</sup> As. The specimens from series 1 released less Ba than series 2. Series 1 released 0.8 μg l<sup>−</sup><sup>1</sup> Co, 0.03 μg l<sup>−</sup><sup>1</sup> Zr and series 2, 0.2 μg l<sup>−</sup><sup>1</sup> Co and respectively 0.17 μg l<sup>−</sup><sup>1</sup> Zr.

Part of the cations released in solution (Pb and Sn) probably originates from the glass reactor or the HCl composition (according to Merck information). As Cd and Cu are considered to be accidental impurities, their presence is not related to the affiliation of the tested sample to one or the other series of prostheses.

## **5. Conclusions**

Various biomaterials have been used for orthopedic implant manufacturing. Polymeric materials, as a result of their mechanical weakness, have been considered unsuitable for the stress deformation requirements of orthopedic implant components, while ceramics have good biocompatibility but are brittle, and designs should take this into account. Alloys are known for their good mechanical properties, but poorer biocompatibility, due to the systemic release of ions [46]. An orthopedic implant is frequently made of a metallic or ceramic component articulating with a metal, ceramic, or polyethylene surface [19]. Different possible combinations are possible: metal (stainless steel or Co-Cr) on ultrahigh molecular weight polyethylene, metal on metal, ceramic on polyethylene, ceramic on ceramic, or ceramic on metal [47]. Coatings such as bioinert films, which have the main purpose of hindering corrosive processes of the underlying metal and bioactive films, which are capable of improving biological compatibility, avoiding inflammation or implantassociated infection processes, are used more and more often. The ideal coating is a system in which anticorrosion, anti-infection, and osseointegration can be obtained simultaneously [48]. Because of their favorable characteristics, Ti alloys are the first choice material in case of orthopedic implants. Even in case of Co-Cr-Mo alloys, Ti-vacuum-plasma-sprayed (VPS) coatings decrease the release of the substrate elements (Co, Cr, and Mo) considerably, but they do not suppress it completely [49].

Titanium remains the predominant material used for medical implants. Despite its high strength and good resistance to corrosion, multiple studies have demonstrated that degradation products of titanium alloys may be detected in neighboring tissues as well as in distant organs. Titanium particles are released from the implant's surfaces for many reasons, such as mechanical wear, contact with chemical agents, and bacteria embedded in adherent biofilm and inflammatory cells [16].

It is obvious that none of the orthopedic prosthetic materials are "inert". However the question regarding their toxicological behavior "Which are the longterm consequences for humans?" still stands.

The near future of multicomponent alloys for biomedical applications does not only belong to high-quality Co-Cr, Ti, Ta, or Zr alloys but also to customized orthopedic prostheses, manufactured by 3D printing techniques, based on a CT or MRI scan, which fit perfectly. One can also imagine the not-so-distant future, which seems to belong to the bioprinting techniques, in this case, bone-made orthopedic implants.

**217**

**Author details**

Lucien Reclaru1

Craiova, Romania

and Catalin Adrian Miu4

, Lavinia Cosmina Ardelean2

1 Biomaterials and Medical Devices, Marin-Neuchâtel, Switzerland

Medicine and Pharmacy from Timisoara, Timisoara, Romania

\*Address all correspondence to: lavinia\_ardelean@umft.ro

provided the original work is properly cited.

2 Department of Technology of Materials and Devices in Dental Medicine, "Victor Babes" University of Medicine and Pharmacy from Timisoara, Timisoara, Romania

3 Orthopaedics and Traumatology, University of Medicine and Pharmacy Craiova,

4 3rd Department of Orthopaedics-Traumatology, "Victor Babes" University of

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*, Alexandru Florian Grecu3

*Multicomponent Alloys for Biomedical Applications DOI: http://dx.doi.org/10.5772/intechopen.88250*

The authors declare no conflict of interest.

**Conflict of interest**

*Multicomponent Alloys for Biomedical Applications DOI: http://dx.doi.org/10.5772/intechopen.88250*
