CAN THE PRESENT SYSTEMS FOR POSITION RECOGNITION IN SPACE BE IMPROVED: PROBLEMS AND SOLUTIONS

Abstract

Computer Aided Surgery (CAS) systems are soon to become an essential tool in the armamentarium of the orthopaedic surgeon. By generating precise three-dimensional information about patient-specific anatomy, these devices enable the planning of complex procedure, either pre-operatively or intra-operatively, to be performed with a high degree of accuracy. In addition, by communicating imaging data to the surgical field, CAS applications allow the surgeon to reproduce the plan precisely, with a higher degree of repeatability than conventional surgery.

In order for CAS systems to be effective, however, accurate and up-to-date information about the patient’s and instruments’ position needs to be available at all times. Therefore, virtually all CAS systems in orthopaedic surgery utilise some form of tracking device, for initial registration and intra-operative real-time position update. The pioneer, Northern Digital (Northern Digital, Waterloo, Ont., Canada) set precision standards with Optotrak™, a high resolution infrared (IR) optical digitiser. Since then, a number of commercial offerings exploiting this technology have made their appearance in the marketplace. These can be used with active LED based markers, as well as passive reflective localisers, which do not require cabling to connect to the intra-operative console. Magnetic field generators, such as the Aurora System (Northern Digital), mechanical digitisers, such as the Wayfinder™-mounted MicroScribe (Immersion Corporation), and digital camera based trackers, such as the Claron™ System, have also proved to be viable substitutes to IR-based localisation systems.

The quintessence in position recognition can be defined clearly from the user/clinician’s point of view. It should be far-reaching (i.e. with a large working envelope), non-obtrusive, robust, flexible, accurate and compact. Each of the technologies available, however, falls short in at least one of these criteria. The presentation will offer a broad review of promising new technology in the field, which may help to address some of the shortcomings of current instrumentation.