COMPUTER-ASSISTED 3-DIMENSIONAL ANATOMIC AND SURGICAL APPROACH OF THEPOSTERIOR AMPULLARY NERVE

Objective To establish a method for resuming the three dimensional sha pe of micro-structures in the inner ear and for designing the surgical approach of the posterior ampullary nerve (PAN) assisted by computer. Methods Four normal temporal bones were harvested within 24 hours aft er death and processed according to the traditional celloidin sectioni ng protocol. With the reference points to determine accurate orientati on, the structural contours of each serial section were entered into a n imaging computer via a digitizer. The data files were generated by a reconstruction software to display 3-D images of the structures on th e computer monitor. The measuring software written by authors was adap ted to obtain 3-D parameters and carry out surgical approach calculati on and simulation of the PAN transection on the imaging computer.Resul ts The lifelike 3-D images of the PAN and its neighboring structures a nd many important 3-D anatomic parameters were obtained. The PAN can h e dissected completely and perfectly without damaging itself and its n eighboring structures. For the exposure of the round window membrane ( RWM), the postero-superior bony edge of the round window niche (RWN) w as partially removed with a diamond bur. The limit in removing bony ti ssue of the RWN which suggested by the measuring results should be 1 m m superiorly and 2 mm posteriorly, otherwise the RWM might be damaged. A mathematical method which has the mid-point of inferior margin of t he round window membrane as the reference point to find the PAN was bu ilt up. The 3-D surgical simulation of the PAN transection can be play ed step by step on the monitor. Conclusions The technique of computer- aided 3-D reconstruction which was introduced into the process of the micro-surgery's study and design, provides abundant anatomic knowledge and useful information for the PAN transection. In the near future, t he technique of the computer-assisted surgery will be developed consum mately and most operations will be performed more effectively and safe ly.