[Intraoperative volumetry in ENT surgery. Objectivation of surgical success by the volume control system].

PROBLEM At present no procedure exists to measure distances or volumes in endoscopic or otherwise limited surgical approaches directly and with high accuracy. Here a laser measuring system is evaluated for the first time as a clinical application in ENT surgery. MATERIAL AND METHODS The volume control system (VCS) measures with the help of automatic recognition of laser measuring points in the surgical situs. A lab test examines the accuracy and the precision at anatomically accurate paranasal sinus and tympanic cavity models under flexible endoscopic visualization. The true values are known in each case as calibrated distances. Thus 90 values were available for evaluation. The clinical trial serves as proof of the intraoperative applicability and includes 32 patients. RESULTS The measurements in the lab test resulted in an average deviation from the true value at a maximum of 7.1%. The precision was between 0.2 and 0.5 mm. In the clinical setting the system could be used in all 32 patients. Altogether 97 measured values could be included. The VCS functioned without system failures. The additional time required for setting up amounted to less than 2 min. The manageability of the flexible endoscope was reduced because of the length and the difficulty in controlling the adjustment. The additional intraoperative time required for collection of the measured values was less than 4 min in each case. Many results led to clinically relevant interpretations with intraoperative consequences. DISCUSSION The VCS shows for the first time an intraoperatively applicable measuring function for distances, surfaces and volumes. There is a multiplicity of meaningful applications in ENT and in other surgical disciplines. The available study has proved the concept.