Technical Note: Usage of an Ultrasonic Knife to Perform Key Osteotomies in a Cranio-Orbital Zygomatic Approach

Introduction: The Cranio-Orbital Zygomatic (COZ) approach is a commonly used approach for intra- and extradural lesions of the anterior and middle skull base, as well as lesions of the basilar artery. Traditionally, osteotomies of the supraorbital foramen, zygomatic arch, and superior-lateral orbit are made to complete this approach. Tools previously used for these osteotomies include the gigli saw, osteotome, and a B1 bit on a Midas Rex drill without a footplate. Here, we report the first reported experience making osteotomies for a COZ approach using an ultrasonic irrigating knife (Stryker Sonopet sonicontrol knife), which has a single-side seriated-edge blade with a blunt tip. Methods: A standard COZ approach was performed in the same manner as previously described. 1 On exposure of the zygomatic arch, incisions were made at the root of the zygomatic arch and adjacent to the malar eminence using the ultrasonic knife (Fig. 1). The supraorbital nerve, which was in a foramen, was freed by creating an osteotomy with the ultrasonic knife. Finally, cuts in the frontozygomatic process, lateral, and superior orbital walls were performed using the ultrasonic knife. The surgery was free of complications such as damage to cranial nerves, dura, or perirobita. Conclusion: The use of the Sonopet knife was performed safely without the need for osteotome, gigli saw, or high speed drill. Theoretically, these other instruments could cause damage to soft tissue by application of high force, high rotational speeds, or high temperatures. The ultrasonic knife has the advantage of high-frequency and low-amplitude movements which greatly affect boney tissue while avoiding injury to soft tissue. In addition, the ultrasonic knife allows precise narrow cuts measuring 0.8 mm in width, allowing for easy reconstruction during closure (Fig. 2). Finally, the continuous irrigation prevents thermal injury to soft tissues. We propose the use of the ultrasonic irrigating knife as a safe, easy to use, alternative of the conventional methods for COZ osteotomies, and could be further applied to other cranial procedures.