Corrosion Fatigue in Surgical Implants

Abstract

Orthopedic appliances of type 316 SMO were examined after removal from human subjects. Fractographic evidence, macroscopic and microscopic, is presented together with the overall incidence of fracture and fatigue for the specimens examined. Bend fatigue tests were conducted in air and in isotonic saline solution (0.9 percent NaCl) and the crack-growth rates determined. Data followed the empirical relationship proposed by Paris [5]: da/dN = C(Δ K)m with m rising from 3.23 in air to 4.16 for isotonic saline. A distinct change in the appearance of the fracture surface was noted on the specimens broken in the saline environment. The specimens broken in air were bright, while the specimens fatigued in 0.9 percent NaCl were darkened with corrosion products.