Increasing bony contact and overlap with computer-designed offset cuts in free fibula mandible reconstruction.

BACKGROUND: The free fibula flap is the standard of care in mandibular reconstruction; however, procedural nuances continue to optimize results. More accurate and efficient osteotomies for graft insetting can be envisioned, which address the difficulty in obtaining a perfect match between the cut ends of the fibula and the mandible and the subsequent giving up of maximal bone contact. We propose a method of complementary offset osteotomies. The angled cuts were virtually planned using three-dimensional computed tomographic images. Optimal offset cuts maximized surface area contact and facilitated intraoperative repositioning in the setting of additional native bone margin requirement. METHODS: Using previously described protocols, three-dimensional virtual reconstructions of the facial skeleton and the fibula (average, series of five) were used to simulate osteotomies at 25, 30, 45, 60, 75, and 90 degrees to the long axis of the fibula. Complementary osteotomies were then simulated at the mandibular body just distal to the first molar in simulated free fibula reconstructions. Total area of apposing surfaces was calculated using computer-aided design. The results from the 25-, 30-, 45-, 60-, and 75-degree cuts were compared with the conventional 90-degree cut. Resin-based mandibular osteotomy guides and a complementary fibula jig were manufactured using computer-aided design. Two representative clinical cases were presented to illustrate proof of principle and benefits. RESULTS: The total surface area of apposing fibula and mandible surfaces in a conventional 90-degree cut was 103.8 ± 2.05 mm. Decreasing this angle to 75, 60, 45, 30, and 25 degrees yielded increased surface areas of 0.86%, 10.3%, 35.3%, 136.7%, and 194.3%, respectively. Cuts of 25 degrees also allowed for adequate bony contact in the setting of additional margin requirements up to 2.77 cm. Complementary 45-degree cuts provided excellent bone-to-bone contact in a free fibula reconstruction using resin guides and a jig. This angle also facilitated access of the saw to the distal mandible. CONCLUSIONS: Virtual surgical planning is an increasingly recognized technology for optimizing surgical outcomes and minimizing operative time. We present a technique that takes advantage of the precision complementary osteotomies that this technology affords. By creating offset cuts, we can maximize bony contact and ensure adequate contact should additional margins or intraoperative adjustments be required. This flexibility maximizes the precision of premanufactured cutting guides, mitigates the constraints of sometimes unpredictable intraoperative environments, and maximizes bony contact.

Use of virtual surgery and stereolithography-guided osteotomy for mandibular reconstruction with the free fibula.

UNLABELLED: Fibular osteotomy remains a challenging aspect of mandibular microsurgical reconstruction, dependent largely on surgeon experience, intraoperative judgment, and technical speed. Virtual surgical planning and stereolithographic modeling is a relatively new technique that can allow for reduction in the learning curve associated with neomandible contouring, enhanced levels of accuracy, and acceleration of a time-consuming intraoperative step. The authors present a video (narrated and edited from planning sessions and intraoperative use of technique to illustrate the technology) and describe their favorable results. Five patients underwent composite resection of the mandible and free fibula osteocutaneous reconstruction over a 6-month period (December of 2009 to June of 2010) at a single institution using a virtual planning session and stereolithographic modeling. Outcomes assessed included technical accuracy, aesthetic contour, and functional outcomes. All patients achieved negative margins with cutting guide-directed resection. Use of this technique eliminated the need for intraoperative measurement and yielded fibular segments with excellent apposition and faithful duplication of the preoperative plan. Minimal adjustments were needed for inset. Flap survival was 100 percent. All patients have maintained preoperative occlusion and a symmetric mandibular contour on Panorex study, three-dimensional computed tomography, and clinical examination. Accuracy of the reconstructed contour was confirmed using computed tomographic image overlay. This virtual surgical planning technique combined with stereolithographic model-guided osteotomy is the mainstay of the authors' approach to fibular osteotomy when dealing with patients requiring mandibular reconstruction. The authors feel this technology facilitates realization of technical accuracy, aesthetic contour, and functional outcomes and may be particularly useful if free fibular mandibular reconstruction is performed less frequently. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

The accuracy of virtual surgical planning in free fibula mandibular reconstruction: comparison of planned and final results.

PURPOSE: The concept of virtual surgery uses surgical simulation rather than relying exclusively on intraoperative manual approximation of facial reconstruction. The purpose of this study was to evaluate the degree to which surgical outcomes in free fibula mandibular reconstructions planned with virtual surgery and carried out with prefabricated surgical plate templates and cutting guides correlated to the virtual surgical plan in a series of 11 patients. MATERIALS AND METHODS: This retrospective study evaluated 11 consecutive patients (6 males and 5 females) with an average age of 50.73 years (range, 23-72 years) who required mandibular reconstruction for aggressive benign or malignant disease with a free fibula osseomyocutaneous flap at Emory University Hospital (Atlanta, GA) between January 1, 2009 and December 31, 2009. In each case, a high-resolution helical computed tomography (CT) scan of the maxillofacial region and mandible was obtained prior to surgery. The CT data was sent on a CD to a modeling company (Medical Modeling Inc, Golden, CO). The scans were then converted into 3-dimensional models of the maxillofacial skeleton utilizing both automatic and manual segmentation techniques in the SurgiCase CMF software (Materialise NV, Leuven, Belgium). A virtual surgery planning session was held via a Web meeting between the surgeons and the modeling company, at which the resection planes of the mandible, positioning of the plate, and fibula lengths/osteotomy angles were established. The surgery was then carried out using prefabricated cutting guides and manual bending of a reconstruction plate using a prefabricated plate template. A postoperative CT scan of each patient was obtained within the first 7 postoperative days on the same scanner. Three-dimensional computer models of the final reconstruction were obtained for comparison with the preoperative virtual plan. To make the desired comparisons, the 3-dimensional objects representing the postoperative surgical outcome were superimposed onto the preoperative virtual plan using manual alignment techniques. These objects were then compared by 1-to-1 magnification for measurements of fibular bone volume, location of mandibular osteotomies, location of fibular osteotomies, plate contour, plate position on fibula, and plate position on mandible. Comparison was made between the virtual and final plates with regard to contour and position through superimposition overlays of the 3-dimensional models that are registered in the same coordinate system. RESULTS: A total of 19 mandibular osteotomies were carried out. The mean distance of the actual mandibular osteotomy when compared to the virtual mandibular osteotomy was 2.00 ± 1.12 mm. The mean volume determined by the software program of the 11 virtual fibulas was 13,669.45 ± 3,874.15 mm(3) (range, 9,568 to 22,860 mm(3)), and the mean volume of the 11 actual postoperative fibulas was 12,361.09 ± 4,161.80 mm(3) (range, 7,142 to 22,294 mm(3)). The mean percentage volumes of the actual postoperative fibula compared to the planned fibula were 90.93 ± 18.03%. A total of 22 fibular segments were involved in the study created by 44 separate fibula osteotomies. The mean distance of the actual fibula osteotomy when compared to the virtual fibula osteotomy was 1.30 ± 0.59 mm. The mean percentage overlap of the actual plate to the virtual plate was 58.73% ± 8.96%. CONCLUSIONS: Virtual surgical planning appears to have a positive impact on the reconstruction of major mandibular defects through the provision of accuracy difficult to achieve through manual placement of the graft, even in the hands of experienced surgeons. Although a reasonably high level of accuracy was achieved in the mandibular and fibula osteotomies through use of the surgical cutting guides, the limited ability to correctly contour the plate by hand to replicate the plate template is reflected in our findings.