Fretting corrosion tests on orthopedic plates and screws made of ASTM F138 stainless steel

Abstract

Introduction: Although there has been significant progress in the design of implants for osteosynthesis, the occurrence of failures in these medical devices are still frequent. These implants are prone to suffer from fretting corrosion due to micromotion that takes place between the screw heads and plate holes. Consequently, fretting corrosion has been the subject of research in order to understand its influence on the structural integrity of osteosynthesis implants. The aim of this paper is to correlate the surface finish characteristics of bone plate-screw systems with fretting corrosion. Methods: The surface finish (machined and polished) of five specimens taken from three commercial dynamic compression plates (DCP) were evaluated. For testing, the specimens were fixed with bone screws, immersed in a solution of 0.90% NaCl and subjected to a rocking motion with an amplitude of 1.70 mm and frequency of 1.0 Hz for 1.0 × 10 6 cycles, according to the ASTM F897 standard. Both, plate and screws were manufactured in Brazil with ASTM F138 stainless steel. Results: Flaws on the hole countersink area and on the screw thread of some specimens were identified stereoscopically. At the end of the test all the specimens showed evidence of fretting corrosion with an average metal loss of 4.80 mg/million cycles. Conclusion: An inadequate surface finish in some areas of the plates and screws may have favored the incidence of damage to the passive film, accelerating the fretting corrosion at the interfaces between the plate hole countersink and the screw head.

Materials for Orthopedic Bioimplants: Modulating Degradation and Surface Modification Using Integrated Nanomaterials

“…In addition, the physical imperfections and long-term wear and tear are also responsible for the corrosion of metal implants. Santos et al have reported the initiation of degradation in metallic screws and plates at the site of wear/tear that have undergone specific corrosion at the load bearing areas [106]. In the implants such as screws and plates that bear regular load, there is a greater tendency to accumulate maximum precipitate at the grain boundaries of these metal/metal alloys implants (Figure 2c).…”

“…In the implants such as screws and plates that bear regular load, there is a greater tendency to accumulate maximum precipitate at the grain boundaries of these metal/metal alloys implants (Figure 2c). Deposition of a larger precipitate at the grain boundary in combination with the regular abrasive motion on the surfaces deems them much susceptible to corrosion [106,107]. Furthermore, physical imperfections have also been known to contribute towards the localized corrosion, precipitation, and aggregation of a large quantity of metal-protein complexes at the specific site, thereby weakening the load-bearing structures.…”

“…Mechanism of metallic bioimplant degradation (a,b)[15,16] and fretting corrosion tests on orthopedic plates and screws made of ASTM F138 stainless steel (c,d)[106]. Adapted with permission from[15]; 2008 John Wiley & Sons; Adapted with permission from[16]; 2003 Springer.…”