In-vitro Force Assessments of an Autoclavable Instrumented Sternal Retractor

It is well known that median sternotomy might lead to rib and/or sternum micro/macro-fractures and/or brachial plexus injuries, eventually resulting in chronic pain with significant impact on patient’s quality life.Postoperative chronic pain is recognized as a multifactorial complex issue, it has been assessed that excessive sternum retraction forces can be considered one of these factors. On this basis, the Authors developed a reliable and sterilizable system potentially able to real-time monitor and control the retraction forces along the hemisternums. A Finochietto sternal retractor was instrumented by means of ultra-thin force sensors interfaced with ad hoc electronic circuitry. Two different sets of sensors were adopted, one of which able to support autoclave operating conditions. In vitro tests were performed by means of a made on purpose dummy. The instrumented retractor allows monitoring of the force exerted on both the arms during the opening procedure. Force versus time patterns were real-time acquired and stored, distribution of forces was determined along with the values of mean, maximum and plateau force. Results demonstrate the reliability of the instrumented retractor in measuring forces, up to 400N. Cost-effectiveness and feasibility can be considered further additional values of the proposed instrumented retractor.