BACKGROUND: Electromagnetic (EM) navigation has been reported to be a noninvasive and easy-to-use technique. However, the use of metal neurosurgical instruments (e.g., skin hooks, head frames, brain retractors systems) can interfere with the magnetic fields of such systems. We present the freehand technique, a new technique involving the manual manipulation of the emitter of an EM navigation system, which helps to prevent interference caused by metal instruments during surgery. METHODS: The AxiEM Electromagnetic StealthStation Navigation System (Medtronic) was used in this study. The emitter was placed in the sterilized surgical field, which allowed it to be moved freely during surgery. When navigation was necessary during the procedure, the assistant held the emitter at an appropriate angle to the sterile surgical field to avoid interference caused by the metal neurosurgical instruments. RESULTS: During surgery involving metal surgical instruments, all of the functions of the EM navigation system were available throughout the procedure. The accuracy of the navigation system was sufficient to allow craniotomy and intradural manipulation to be conducted. CONCLUSIONS: During the use of EM navigation systems, the freehand technique with the emitter can prevent interference caused by metal instruments.
BACKGROUND: Electromagnetic (EM) navigation has been reported to be a noninvasive and easy-to-use technique. However, the use of metal neurosurgical instruments (e.g., skin hooks, head frames, brain retractors systems) can interfere with the magnetic fields of such systems. We present the freehand technique, a new technique involving the manual manipulation of the emitter of an EM navigation system, which helps to prevent interference caused by metal instruments during surgery. METHODS: The AxiEM Electromagnetic StealthStation Navigation System (Medtronic) was used in this study. The emitter was placed in the sterilized surgical field, which allowed it to be moved freely during surgery. When navigation was necessary during the procedure, the assistant held the emitter at an appropriate angle to the sterile surgical field to avoid interference caused by the metal neurosurgical instruments. RESULTS: During surgery involving metal surgical instruments, all of the functions of the EM navigation system were available throughout the procedure. The accuracy of the navigation system was sufficient to allow craniotomy and intradural manipulation to be conducted. CONCLUSIONS: During the use of EM navigation systems, the freehand technique with the emitter can prevent interference caused by metal instruments.