Stereolithographic Modeling of the Deep Circumflex Iliac Artery and Its Vascular Branching

Abstract

Sir:FigurePreoperative imaging to plan free flaps for microvascular mandibular reconstruction has been shown to improve clinical outcomes and reduce operative times, particularly for the deep circumflex iliac artery flap.1 Imaging with computed tomographic angiography can guide complex bony design and soft-tissue modifications to the flap. We recently described the use of stereolithographic biomodeling to map bony anatomy to improve operative efficacy; however, the ability to interpret angiographic imaging with these models has been lacking.2 Until now, preoperative computed tomographic angiography scans have been used to predict vascular patterns and trace the vascular pedicle to the bone and soft tissues,3,4 but the interpretation of these scans and direct operative correlation is uniformly difficult. We describe a technique using preoperative imaging with computed tomographic angiography to improve stereolithographic modeling, such that biomodels of both the iliac crest and its vascular supply can be created to a high degree of resolution for operative use. According to our previously described computed tomography–guided biomodeling technique,2 routine computed tomographic angiography is performed and the image data are transferred as raw data for production of image-guided stereolithographic models (BioModels; Anatomics, St. Kilda, Victoria, Australia). These models comprise both bony modeling and angiographic vascular modeling. Using a combination of the differences in contrast levels on imaging, interpretation of the scans, and computer software modeling, the BioModels can effectively differentiate bone from vasculature, and can present the two structures separately within the models (Figs. 1 and 2). Unlike computed tomographic angiography scans alone, these models can be used both preoperatively and intraoperatively to guide operative technique.Fig. 1: Anterior view of a three-dimensional computed tomographic angiogram of the donor iliac crest and deep circumflex iliac artery (left), for production of an image-guided stereolithographic bone and vascular BioModel (right).Fig. 2: Lateral view of a three-dimensional computed tomographic angiogram of the donor iliac crest and deep circumflex iliac artery (left), for production of an image-guided stereolithographic bone and vascular BioModel (right).The use of a single donor-site scan can now achieve accurate mapping for both preoperative and intraoperative analysis of bony anatomy of the donor site, the vascular pedicle, arterial branches from the pedicle to the planned bone flap, and pedicle branches to skin and muscle in composite flaps. This advance in imaging not only supersedes previous modalities, such as plain radiographs (with views superimposed and soft-tissue structures ill-defined) and ultrasound (operator-dependent and low resolution and reproducibility), but also supersedes the previous use of computed tomographic angiography. This technique of combining preoperative computed tomographic angiography with intraoperative vascular biomodeling is potentially able to offer a greater degree of operative guidance and improved accuracy in vascular mapping compared with computed tomographic angiography alone. The finer branches, which can be missed by the interpreting radiologist or surgeon, were clearly demonstrable through computer modeling within the BioModels, and were clearly displayed to the operating surgeon. The benefits of computed tomographic angiography for guiding deep circumflex iliac artery harvest have been described previously, with improved outcomes such as decreased operative time, muscle-sparing osteocutaneous harvest, and improved flap vascularity highlighted in the literature.1,3 The use of this imaging to create computed tomography–guided stereolithographic models has been a useful technological advance, with both donor- and recipient-site models able to demonstrate the anatomy of the defect and aid reconstruction through accurately designed bone harvest, reduced donor-site morbidity, and decreased operative time, with the ability to premold reconstruction plates and premeasure screws for improved fit.2,5 However, the ability to select optimally vascularized bone and guide vascular dissection has until now been achievable only through correlation with preoperative imaging.1,3,4 The current communication has highlighted that biomodeling of the deep circumflex iliac artery in combination with bony models can further aid flap harvest compared with previous techniques. Stereolithographic vascular models further enhance the benefits already associated with bony modeling and preoperative imaging, with high-resolution scans and models able to better highlight three-dimensional vascular anatomy to the operating surgeon. Warren M. Rozen, M.B.B.S., Ph.D. Jeannette W. C. Ting, M.B.B.S. Charles Baillieu, M.B.B.S. James Leong, M.B.B.S. Department of Plastic and Reconstructive Surgery, Dandenong Hospital, Southern Health, Dandenong, Victoria, Australia, and, Department of Surgery, Faculty of Medicine, Monash University, Clayton, Victoria, Australia DISCLOSURE The authors have no financial interest to declare in relation to the content of this article.