Solution
Various plastic bearings were used to realise the bone-fixed parallel robot due to the requirements described. The surgical instrument guidance comprises, for example, a
drylin N glide bar with two carriages. The latter are rigidly connected to each other by means of a stainless steel component (interlocking) to minimise clearance, which cannot be completely avoided for guide systems due to their design principle. This tool guide entirely fulfils the stated requirements (in particular: no rolling elements, no need for lubricants) and can be easily dismantled, cleaned and reassembled due to the open design of the rail. In addition, the interchangeability of the carriages offers a wide range of options for carrying out intraoperative tool changes. Two push actuators of the parallel robot were connected by means of a rotary joint. The axis of this rotary joint is formed by an adapter screw, whereby the radial clearance is absorbed by two steam-sterilisable
iglidur X slide bearings. The joint can also be axially pre-loaded by tightening the adapter screw. Thanks to the plastic bearings used, a bone-anchored surgical instrument guide could be developed, constructed and evaluated for the first time, which is characterised by universal applicability and reusability as well as patient-specific adaptability. The fulfilment of the accuracy requirements has been successfully proven experimentally.