Greetings Colleagues,

Andrew T. Huang, M.D.

Reconstruction of segmental bony defects of the maxilla and mandible following traumatic injury or oncologic resection has been revolutionized by the introduction of microvascular free tissue transfer.  Specifically, since its first description by Hidalgo et al¹, the osteocutaneous fibula free flap (OFFF) in reconstruction of maxillary and mandibular deficits has been demonstrated to result in superior functional and aesthetic outcomes compared to pedicled flap and prosthetic reconstructions^2,3.  The OFFF is ideal as a donor site for these reconstructions due to its provision of an ample length of thick bicortical bone, well-vascularized fasciocutaneous tissue for intraoral resurfacing, and the ability to harvest muscular tissue from the flexor hallucis longus or soleus for more extensive cavitary defects.

Figure 1. Preoperative planning of a total palatectomy defect secondary to osteonecrosis and osteomyelitis. A. 3-D model of the total palatectomy defect. B. Frontal view of the patient pre-operatively. Note loss of upper lip projection. C. Intraoperative view of the total palatectomy deformity (NS=nasal septum, IT=inferior turbinate, MS=maxillary sinus).

As OFFF reconstruction for complex defects of the maxilla and mandible becomes standard practice, limitations and pitfalls in its use have been encountered.  Standard OFFF procedures involve intraoperative conformation of titanium reconstruction plates to the native mandible or maxilla prior to resection in order to construct patient-specific anatomic templates for freehand shaping of the fibula. No matter the skill of the surgeon, this intraoperative freehand technique can result in shaping inaccuracies that not only translate to increased operative time needed for correction of these errors, but can also ultimately lead to poor bony apposition, malunion, fracture, and negative cosmetic appearance.  In addition, in cases of large tumors or trauma that distort or destroy a patient's normal bony anatomy, the ability to construct intraoperative templates that accurately restore native anatomic relationships can be difficult to impossible.

Figure 2. CAD/CAM plan and intraoperative technique. A. Virtual cutting guide on the left fibula bone.  Slots allow easy placement of an oscillating saw to create precise shaping osteotomies. B. Virtual model showing the shaped fibula in place. C. Left leg donor site marked for flap harvest. D. OFFF harvested, contoured, and ready for inset. E. Microvascular anatomosis between the peroneal and facial vessels (A=Artery, V=Vein). F. OFFF inset with skin paddle exposed for monitoring.

To remedy these issues, new surgical protocols involving computer-aided design and computer-aided manufacturing (CAD/CAM) for OFFF reconstruction have been devised and are now available commercially.  This technique utilizes high-resolution computed tomography (CT) scan imaging of both the surgical resection site and fibula donor site to pre-operatively plan and develop patient-specific models, cutting guides, and reconstruction plates used in OFFF reconstruction.  CAD/CAM protocols consist of three stages: 1.) Virtual surgical planning (VSP); 2.) Rapid manufacture of the customized surgical devices; and 3.) The surgery itself.   VSP requires the cooperation of the ablative surgeon, reconstructive microsurgeon, and a biomedical engineer to precisely map and detail the extent of surgical resection based on CT imaging which, in turn, allows the planning and development of specific fibular cutting guides and reconstruction plates used to exactly contour a straight fibula bone into a 3-D neomandible or neomaxilla.  In cases where there is loss of native bony anatomical references needed for planning a reconstruction, a major benefit of VSP is the ability to develop fibular constructs that mirror contralateral bony landmarks, or, when all reference points are absent, develop constructs that adhere to ideal facial measurements and geometry.  Rapid manufacture of the customized models and guides can take eight business days, and although this may seem negative, it should be noted that the reconstruction plates created are milled, bent, heat-treated, and can be specifically engineered with increased individual bar widths, ultimately conferring an up to 40% improved fatigue strength compared to standard reconstruction bars ⁴.  Surgical harvest of the OFFF is unchanged compared to standard techniques.  Once harvested, however, utilization of the customized cutting guides allows precise shaping of osteotomies and expedient bony inset which has been demonstrated to significantly decrease flap ischemia operative time ^5,6.

Figure 3. 6 week post-operative result. A. Left lateral view. B. Right lateral view. C. Frontal view. D. Intraoral view of skin paddle healed in place.

Indications for CAD/CAM use are not universal yet, but at our institution it is reserved for complex bony reconstructions of the head and neck where normal anatomic landmarks are abnormal or absent, and in cases where extended length of fibula bone is required, necessitating minimization of error and discarded bone during shaping.  Pre-operatively planning complex surgical defects of the maxilla and mandible allows the surgeon, with the integral assistance of a biomedical engineer, to develop patient-specific reconstructive plans, maximizing both functional and aesthetic outcomes while minimizing flap ischemia operative time.  Although not yet proven, the utilization of stronger, milled reconstruction plates may reduce post-operative plate fracture, reducing re-operation rates.

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