Sales of stainless steel, Furlong® Modular Hip Replacement Systems, produced by JRI Ltd, have increased significantly in the 12 months following a change from a standard vacuum melted stainless steel to Sandvik Steel’s Bioline® High-N (high nitrogen) stainless steel. Specialists in the manufacture of hip and knee replacement prostheses, JRI chose the new steel for a range of femoral stems. It promoted the new product as offering exceptional value whilst retaining the proven geometry of the Furlong Straight Stem designs. High nitrogen stainless steel is now regarded by the UK medical industry as the material of choice for cemented hip prostheses. It has better corrosion resistance and a much higher yield and fatigue strength than conventional stainless steels. At the same time it meets or exceeds all international specifications for micro-cleanliness. Most hip stems are produced by hot forging, which results in a fully softened microstructure in the metal. In the annealed condition, Bioline High-N exhibits a yield strength more than twice that of standard stainless grade 316LVM. Work hardening, induced by cold working the material, results in an increase in yield strength. It is predominantly this property in combination with improved biocompatibility that makes High-N type steels the material of choice.
