The authors' experiences with intraoperative computer assisted guidance in interventions in oromaxillofacial and craniofacial surgery are reported. The guidance system SPOCS (Surgical Planning and Orientation Computer Systems, Aesculap, Germany) consists of an infrared light emitting system of diodes and camera, an imaging workstation and assorted freehand instruments. The software is an updated version of the well-known Viewing Wand software (ISG Technologies, Canada). In tests on phantoms, the system proved a mean accuracy of less than 1.5 mm. Within the last 15 clinical tests, the system has achieved an accuracy better than 3 mm which, at the moment, the authors estimate to be sufficient to proceed with its clinical evaluation. Using bone screws to register the patient's position, an accuracy in the range of less than 2 mm in relation to bony reference points has been achieved. By visualizing the tip of the instrument in real time, this technique allows surgical interventions, even in anatomically complicated situations, without endangering vital neighbouring structures. The 'offset' function of the software, by which the surgeon can elongate the tip of the instrument virtually, allows the surgeon to analyse structures before they are penetrated by the instrument as in a 'look ahead' operation. The authors expect computer assisted simulation and guidance systems to improve surgical quality and reduce the risks associated with surgical interventions.

A combined self-retaining retractor and hand-rest system for neurosurgery is presented. It was developed from the original Leyla system but has the advantage of an integrated hand-rest.

Minimally invasive surgery (MIS) has become an important field in the health care sector over the last decade. Still, there is the need for improving existing instruments and developing new tools providing increased functionality. This work presents innovative solutions and experimental results for a new generation of innovative polymer-based shaft instruments for minimally invasive surgery. The investigated components comprise a new kind of end-effector mechanism and an improved force transmission for actuating the effector. The new end-effectors consist of few discrete parts. They combine the advantages of compliant joints with those of conventional hinges ("hybrid effector"). The simple configuration will be advantageous during sterilization and, furthermore, is suitable for large-scale production by polymer technology. The effectors show low friction and low backlash properties and therefore high functionality. In addition to that we have developed a new kind of sensitive hydraulic force transmission which may replace the force transmission by push rods of conventional shaft instruments. The hydraulic force transmission is based on leakage-free embedding of the hydraulic fluid in modified polymer tubing. This specific hydraulic transmission component provides high efficiency force transmission and can be entirely fabricated by polymers. Both newly developed solutions reveal an increased functionality and due to their simple configuration can be manufactured by polymer technology, e.g. injection moulding. They show the potential for large-scale production of a new class of polymer-based shaft instruments for minimally invasive surgery.

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