Analysis of osteotomy distance and other predictors of osseous union following mandibular reconstruction with fibula free flap.

[OBJECTIVES] Optimal contouring of fibula free flaps (FFF) for mandibulectomy often requires osteotomies. This study aimed to define criteria for initial gap width by evaluating whether postoperative gap size and other factors influence long-term osseous union on CBCT, and to identify key determinants of bone healing.

[METHODS] This retrospective study included 75 patients who underwent segmental mandibulectomy with FFF reconstruction from 2017 to 2024. Initial osteotomy gaps were measured at four points on postoperative CBCT scans. Osseous union was assessed using a callus scale. Demographic, anatomical, and surgical variables-including 3D-assisted planning, fibula morphology, osteotomy location, systemic comorbidities, and segment number -were analyzed using uni- and multivariate regression models.

[RESULTS] A total of 202 osteotomy sites were evaluated. The mean initial gap was 1.68 ± 0.97 mm, and gap size did not significantly predict long-term union. Complete union occurred in 50.0% of sites, partial union in 36.6%, and nonunion in 13.4%. Fibula-fibula interfaces showed significantly better healing than fibula-mandible interfaces (p < 0.001). Symphyseal osteotomies demonstrated superior union compared with body and angle regions. Systemic vascular comorbidities were strong negative predictors of union, whereas reconstructions using more than two segments showed improved outcomes (p < 0.001). Alcohol consumption negatively affected both initial gap formation and union.

[CONCLUSIONS] Long-term osseous union after FFF reconstruction is influenced mainly by systemic vascular health, osteotomy location, interface type, and fibula morphology rather than initial gap width.