The use of a vibrotactile sensor as an artificial sense of touch for tissues of the head and neck

Despite unquestionable advantages for the patient, minimally invasive surgery (MIS) brings an almost complete loss of the sensory qualities familiar to the surgeon from classic macroscopic surgery. This handicap of MIS is most dramatically exemplified by the loss of the natural sense of touch. The reimplementation of the sense of touch would clearly reduce the present limitations of MIS and possibly expand its spectrum of indications. We evaluated a vibrotactile sensor as an artificial organ of touch for minimally-invasive otorhinolaryngology and head and neck surgery (ORL-HNS). In general, two technical principles are available to artificially transmit tactile information from inside the patient's body to the surgeon. First, tissue hardness can be measured by static compression and, second, tissue stiffness can be determined by its dynamic resonance. We implemented the latter technique for use in minimally invasive ORL-HNS. As a first approach, normative data were obtained by measuring the impedance of intraoperatively resected soft tissues and bony structures from the skulls of cadavers. Characteristic resonance frequencies were detected for normal soft tissues ranging from 16 Hz for tonsils to 30 Hz for mucosa. In a pathological situation, resonance frequencies even allow the discrimination of healthy tissue from infiltrating carcinoma in hypopharyngeal mucosa. For normal bony structures from cadavers, resonance frequencies increased with thickness, ranging from 240 Hz to 320 Hz for the ethmoid septi, and from 780 Hz to 930 Hz for the frontal skull base. The introduction of this artificial tactile sense to minimally invasive procedures in ORL-HNS would enable the surgeon to differentiate between critical anatomical structures and normal and pathological tissues. Thus, the technology presented here has the potential to reduce complication rates in MIS and to possibly expand its range of indications.