Intraoperative Navigation-Assisted Identification of Deep Inferior Epigastric Artery Perforators

Sir:FigureOperative navigation systems, which use cameras to track instruments in the operative field and display their location in real time on preoperatively or intraoperatively obtained images, are routinely used in neurosurgical cases, where much of the anatomy is rigid and not affected by operative manipulation of tissues. We previously showed that navigation systems could be used with preoperatively obtained computed tomographic scans to provide accurate tracking of instruments in regions with far less rigidity, such as the abdomen and pelvis, during cancer resections.1 Based on this work, we hypothesized that this accuracy could be translated to the soft tissues of the lower abdomen. As a result, we have developed a novel method for using the navigation system to provide real-time, intraoperative tracking of a modified Bovie handle to facilitate identification of perforating vessels at the level of the anterior abdominal fascia during deep inferior epigastric perforator (DIEP) flap dissection for breast reconstruction. The procedure and steps involved are outlined in the supplemental video available online. (See Video, Supplemental Digital Content 1, which demonstrates how the patient is prepared for imaging, https://links.lww.com/PRS/A489. It also shows intraoperative footage of the navigation system being used to provide real-time tracking of the modified cautery handle to facilitate perforator identification and dissection during a DIEP flap breast reconstruction case.) Briefly, before undergoing preoperative computed tomographic angiography, adhesive fiducial markers are placed on the lower abdomen. These fiducial points are used at surgery to “register” the preoperative computed tomographic angiography images being displayed by the navigation system to the patient's anatomy (Fig. 1). Based on the accuracy of this registration process, the system calculates a maximum global error that can be expected when an instrument is tracked in the registered volume. In our cases, our global errors have ranged from 2.1 to 2.4 mm. The final step before guidance-directed flap elevation can begin involves modification of the Bovie handle with a tracking frame, which is then used to elevate the flap off the fascia. As dissection proceeds, the navigation system displays the tissues and structures that are at varying distances ahead of the Bovie tip (Fig. 2).Video: Supplemental Digital Content 1 demonstrates how the patient is prepared for imaging, https://links.lww.com/PRS/A489. It also shows intraoperative footage of the navigation system being used to provide real-time tracking of the modified cautery handle to facilitate perforator identification and dissection during a DIEP flap breast reconstruction case.Fig. 1: An Omni-Tract retractor arm (Omni-Tract Surgical, St. Paul, Minn.), mounted to the rail of the table, is used to rigidly fixate the reference frame in close proximity to the operative field. The navigation wand is then sequentially pointed by the surgeon at the fiducial marker spots on the abdominal skin. This registers or aligns the images in the navigation system to the patient's anatomy. A detection frame is then mounted to the Bovie handle. After a brief registration process, this modified Bovie handle can be tracked by the navigation system while it is used for the flap dissection.Fig. 2: (Below) The modified Bovie device is seen as it is being used to elevate the skin and subcutaneous tissue off of the anterior rectus fascia. (Above) Computed tomographic images show look-ahead views taken in the trajectory of the Bovie. They show the tissues and structures that are at varying distances from the Bovie tip. In this frame shot, a perforator can be seen in the lower left computed tomographic image, indicated that a perforating vessel is present 10 mm ahead of the Bovie tip. The real-time display and tracking corresponding to this figure can be seen on the supplementary video footage (see Video, Supplemental Digital Content 1, https://links.lww.com/PRS/A489).We believe this to be the first report of armless navigation of a modified Bovie device to facilitate intraoperative perforator identification for DIEP flap dissection. Although previous studies by Rozen and colleagues have used an armless navigation system to identify and mark perforators at the level of the skin before surgery, our method applies the navigation system intraoperatively to obtain real-time identification of perforators at the level of the fascia.2–4 Surgical deformation of tissues and alteration of the anatomy captured on the preoperative computed tomographic images would be expected to cause a loss of navigation accuracy. This would certainly be true if we were concerned with tracking the course of vessels in the subcutaneous tissue or skin that is being moved. However, we are more interested in where the perforating vessels exit the fascia, a plane that is relatively static if care is exercised when manipulating the superficial tissues, making it possible to accurately locate fascial perforator exit sites. In summary, the armless navigation system has been used to provide intraoperative, real-time tracking of a modified Bovie device to facilitate perforator identification and dissection in the elevation of DIEP flaps. Future work using this technology to validate preoperatively obtained computed tomographic angiography images is underway. Frederick Durden, M.D. Katherine H. Carruthers Oriana Haran, M.D. Ergun Kocak, M.D., M.S. Department of Plastic Surgery, The Ohio State University, Columbus, Ohio DISCLOSURE The authors have no conflicts of interest to report.