Mechanical Analysis and Corrosion Analysis of Zinc Alloys for Bioabsorbable Implants for Osteosynthesis.

Salome Hagelstein,Michael Seidenstuecker,Adalbert Kovacs,Roland Barkhoff,Sergej Zankovic

doi:10.3390/ma15020421

Abstract

Zinc alloys have recently been researched intensely for their great properties as bioabsorbable implants for osteosynthesis. Pure zinc (Zn) itself has relatively poor strength, which makes it insufficient for most clinical use. Research has already proven that the mechanical strength of zinc can be enhanced significantly by alloying it with silver. This study evaluated zinc silver alloys (ZnAg) as well as novel zinc silver titanium alloys (ZnAgTi) regarding their mechanical properties for the use as bioabsorbable implants. Compared to pure zinc the mechanical strength was enhanced significantly for all tested zinc alloys. The elastic properties were only enhanced significantly for the zinc silver alloys ZnAg6 and ZnAg9. Regarding target values for orthopedic implants proposed in literature, the best mechanical properties were measured for the ZnAg3Ti1 alloy with an ultimate tensile strength of 262 MPa and an elongation at fracture of 16%. Besides the mechanical properties, the corrosion rates are important for bioabsorbable implants. This study tested the corrosion rates of zinc alloys in PBS solution (phosphate buffered solution) with electrochemical corrosion measurement. Zinc and its alloys showed favorable corrosion rates, especially in comparison to magnesium, which has a much lower degradation rate and no buildup of hydrogen gas pockets during the process. Altogether, this makes zinc alloys highly favorable for use as material for bioabsorbable implants for osteosynthesis.

Highlights

In the last two decades, research for bioabsorbable implants has been intensified [1,2,3,4] because they offer great advantages in comparison to conventional implants.Conventional implant materials are associated with many adverse effects like stress shielding [5,6,7], chronic inflammation [8,9], soft tissue damage, and stress on the body through metallosis [8,10,11]
Comparison revealed an increase of ultimate tensile strength (UTS) as well as elongation at fracture [A]
With a UTS of above 200 MPa, they met the criteria mentioned in literature for implants for osteosynthesis

Summary

Introduction

In the last two decades, research for bioabsorbable implants has been intensified [1,2,3,4] because they offer great advantages in comparison to conventional implants.Conventional implant materials are associated with many adverse effects like stress shielding [5,6,7], chronic inflammation [8,9], soft tissue damage, and stress on the body through metallosis [8,10,11]. In the last two decades, research for bioabsorbable implants has been intensified [1,2,3,4] because they offer great advantages in comparison to conventional implants. There is an ongoing search for implants, which exhibit mechanical properties that match those of bone and offer the sufficient strength needed. Targets for ultimate tensile strength have been set between 200 and 300 MPa, an elongation at fracture of around 15% to 20% and a Young’s modulus of 10 to 30 GPa [15,16,17,18,19]. Venezuela et al [20], for instance, proposed target values of a yield strength of >230 MPa, a tensile strength of >300 MPa, a Young’s modulus of 10–20 GPa, and an elongation at fracture of 15–18% for orthopedic internal fixation devices

Methods

Discussion

Conclusion