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 m andibular defects, although two or more osteotomies may be required to recr eate the normal mandibular contour. The effect of these surgical manipulati ons on the fibula has not been adequately investigated. This study was desi gned to study the effect of multiple segmental osteotomies and internal fix ation techniques on blood flow in the vascularized pig fibula bone flap mod el. 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 ost eotomies; (4) an elevated fibula with two segmental closing osteotomies rig idly 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 fla ps using the 15-mu m radioactive microsphere technique. The creation of two segmental osteotomies in the vascularized pig fibula bo ne 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. Applicat ion of miniplates or lag screws across closing osteotomies resulted in a si gnificant decrease (p < 0.05) in total and gradient blood flow to the bone component of the fibulae, as compared with the elevated and osteotomized fi bulae groups. An increase in blood flow suggesting a hyperemic response was noted in the bone and soft tissue in the elevated and osteotomized flap gr oups as compared with the in situ, nonoperated controls. This study established the validity of the pig fibula as a suitable model f or investigating the pathophysiology of blood now changes in the face of st andard surgical maneuvers necessary for the restoration of mandibular form and function. The results demonstrated that the creation of multiple segmen tal osteotomies and the application of internal fixation significantly decr eases (ib < 0.05) blood flow to the distal portion of the flap. The effects of segmental osteotomies and internal fixation on healing and growth of th e pig fibula bone flap model are investigated in a separate study.