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.