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Objective-To investigate the mode of failure of transcondylar screws retrieved from dogs previously treated for incomplete ossification of the humeral condyle (IOHC). Study Design-Metallurgical study. Sample Population-Broken screws (n ¼ 5) from dogs with IOHC. Methods-Broken transcondylar bone screws were retrieved from dogs that had apparently successful surgery for IOHC. Screws were measured and examined using scanning electron microscopy (SEM) and energy-dispersive analysis by X-rays (EDX). Results-EDX confirmed that screws were made from 316L stainless steel and there was no evidence of significant corrosion or manufacturing faults that might have contributed to implant failure. SEM of the fractured surface of screws revealed a similar and complex pattern of fatigue failure characterized by multidirectional fatigue cracks and the presence of several initiation sites. All screws had signs of fatigue failure because of multidirectional forces of variable magnitude. Conclusions-Intercondylar instability is a feature of IOHC that persists despite placement of a transcondylar screw. Clinical Relevance-The pathogenesis of IOHC involves chronic intercondylar instability and its treatment using even relatively large transcondylar screws has a risk of late implant failure. r

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This work analysed the effect of chloride deposition on the susceptibility to atmospherically induced stress corrosion cracking (AISCC) of stainless steel type AISI 316L used to manufacture containers for radioactive intermediate level waste in the UK. Using U-bend specimens contaminated with MgCl 2 , a threshold deposition for AISCC occurrence has been found above chloride contamination levels of 10 and 25 mg cm 22 at 50 and 30uC respectively at the equilibrium relative humidity (RH) of the contaminant salt (,30%RH). Higher contamination levels were required to produce cracking at 60%RH. Based on crack depth data and contaminated area characterisation, it was found that susceptibility to AISCC is affected by the liquid film volume, thickness and continuity.

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