Kerrison rongeur redesign

Abstract

This report outlines the redesign of a Kerrison surgical instrument used by surgical staff at the Winnipeg Health Sciences Center (HSC). The primary goal of the redesign was to strengthen the current instruments while maintaining the vitally important ease of sterilization. Our team was also requested to determine any notable causes of failure in the current instruments. It was determined through physical testing and computer analysis that a significant weakness was evident in the cutting tip of the Kerrison. The center of the crossbar was noted to experience relatively high tensile strain along the top portion causing a bowing effect that was noticeable by the technical staff at HSC. Our redesign of the Kerrison comprises several new elements. These include multiple stages of sharpening to improve the service life of the instrument, a set of handles with varying geometries to accommodate the stage sharpening, and a redesigned hand rest for improved comfort. The material of the Kerrison was also altered to 420 martensitic stainless steel containing Molybdenum along with Titanium Nitride and Zirconium Nitride coatings to improve durability and corrosion resistance. Finite element analysis (FEA) was performed on a computer model of our redesigned Kerrison showing that the stresses experienced in various locations were reduced due to the stronger material that was chosen. During the FEA it was determined that a reduction in the height of the blade did not contribute significantly enough to a reduction in stress to warrant altering the geometry. Our design has been determined to fulfill the objectives set by our client. Consideration of the various elements in our design would lengthen the service life of the Kerrison while still being able to be easily accommodated in the current sterilization techniques at HSC [1-2].