Surgical Tool Failure Analyses
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FEATURE
Surgical Tool Failure Analyses Eric P. Guyer • Brad A. James
Submitted: 7 October 2013 / Published online: 26 November 2013 Ó ASM International 2013
Abstract The tools used during surgical procedures are an important component to clinical success. Innovative surgical tool designs have enabled more intricate and lessinvasive procedures resulting in advanced procedures, reduced patient pain, and recovery time. Examples of surgical tools include drills, catheters, needles, cannulas, scissors, and so on. These tools are often subjected to corrosive environments, high stresses, high loading frequencies, sterilization, and/or cleaning procedures. Given the extreme use conditions to which surgical tools can be exposed, and the potential for misuse, these devices can and do fail. These failures often occur during a surgical procedure and therefore can compromise clinical success. Understanding how and why failures occur is an important first step to prevent their occurrence. Accordingly, this paper provides selected surgical tool failure case studies. Keywords Corrosion Hydrogen embrittlement Medical device Failure analysis Stress corrosion cracking Surgical tool
electrical, and software-driven machines. Surgical tools are used in every surgical procedure and are manufactured from many different types of materials. Engineers vary the physical properties of these materials based on expected service conditions and whether or not the tool is meant to be re-used. As with most medical devices, there are tradeoffs for surgical tools between performance and expected lifetimes. For instance, the intended use condition for a hip implant broach handle involves striking the instrument with a hammer. In this case, the designer desires plastic deformation of the part prior to fracture, and therefore must choose materials and create a design that can accommodate plastic deformation. In the case of scissors, the intended use requires high hardness to enhance cutting edge retention and reduce wear. However, these inherent strength requirements may result in susceptibility to failure modes like stress corrosion cracking, depending on the use conditions. Understanding these tradeoffs allows designers to create tools for a wide variety of applications while minimizing the possibility of failure. Surgical tool failure case studies are now presented with an emphasis on these tradeoffs.
Background Case Study 1: 420 Stainless Steel Scissor Failure Surgical tools are defined as any device or instrument used during a surgical procedure. These tools range from simple knives, needles, and cannulae to sophisticated mechanical,
E. P. Guyer (&) Exponent, Failure Analysis Associates Inc., Atlanta, GA, USA e-mail: [email protected] B. A. James Exponent, Failure Analysis Associates Inc., Menlo Park, CA, USA
A manufacturer discovered that two separate blades from a new surgical scissor design had fractured after only a few weeks in service. The blades were specified to be made with 420 martensitic stainless steel, in the ‘‘full-har
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