The vascularized pig fibula bone flap model: effect of segmental osteotomies and internal fixation on blood flow.

The free fibular flap is the flap of choice for reconstruction of complex mandibular defects, although two or more osteotomies may be required to recreate the normal mandibular contour. The effect of these surgical manipulations on the fibula has not been adequately investigated. This study was designed to study the effect of multiple segmental osteotomies and internal fixation techniques on blood flow in the vascularized pig fibula bone flap model. The hindlimbs of 15 Yorkshire pigs were randomized into 1 of 5 groups (n = 6 fibulae per group) consisting of: (1) a nonoperated, in situ fibula; (2) an elevated fibula flap; (3) an elevated fibula flap with two segmental osteotomies; (4) an elevated fibula with two segmental closing osteotomies rigidly fixed with 2-mm miniplates; (5) an elevated fibula with two segmental closing osteotomies rigidly fixed with 2-mm lag screws. Total and gradient blood flow was measured in the bone and soft-tissue components of these flaps using the 15-microm radioactive microsphere technique. The creation of two segmental osteotomies in the vascularized pig fibula bone flap model resulted in a significant decrease (p<0.05) in the gradient blood flow in the segment of bone distal to the second osteotomy. Application of miniplates or lag screws across closing osteotomies resulted in a significant decrease (p<0.05) in total and gradient blood flow to the bone component of the fibulae, as compared with the elevated and osteotomized fibulae groups. An increase in blood flow suggesting a hyperemic response was noted in the bone and soft tissue in the elevated and osteotomized flap groups as compared with the in situ, nonoperated controls. This study established the validity of the pig fibula as a suitable model for investigating the pathophysiology of blood flow changes in the face of standard surgical maneuvers necessary for the restoration of mandibular form and function. The results demonstrated that the creation of multiple segmental osteotomies and the application of internal fixation significantly decreases (p<0.05) blood flow to the distal portion of the flap. The effects of segmental osteotomies and internal fixation on healing and growth of the pig fibula bone flap model are investigated in a separate study.