[Experimental study on repairing composite defect of mandible and skin by prefabricated musculocutaneous flap including ectopic bone].

Objective: To evaluate the effect on repairing composite defect of mandible and skin by prefabricated musculocutaneous flap including ectopic bone induced by BMP-2 and cdllagen in rabbits' latissimus dorsi muscle.

Methods: Twenty-four rabbits (4-6 weeks old) were randomly divided into 3 groups: experimental, control and blank control group (n = 8 in each group). Composite carriers composed of BMP-2 and collagen I sponge were implanted into latissimus dorsi muscle pouches of rabbits. The bone formation was evaluated with roentgenography, ALP staining, Von Kossa staining, HE staining, toluidine blue staining and CD31 immunohistochemical labelling of microvessels. After 6 weeks, the mandibular defect of 8 mm in diameter with local skin defect of 2 cm x 3 cm was made in experimental group, and a musculocutaneous flap including ectopic-induced bone was prefabricated to transfer and repair the composite defect. The mandibular defect of 8 mm in diameter without local skin defect was made in control and blank control group. Free ectopic-induced bone was used for the repair of mandibular defect in control group, but repairing was not performed in blank control group. All the samples were detected 6 weeks after operation for tetracycline fluorescent staining, X-ray, histological examination and bone quantity analysis to evaluate the effect.

Results: Bone formation induced by BMP-2/collagen composites were found as woven bone between 4 to 6 weeks. It showed that cartilaginous osteogenesis was the mainly type of bone formation. Microvessels could be seen in the bony tissues. The composite defects of mandible and skin were healed well in the experimental group. Major bony tissue were seen in the control group, while it still remained bony defect in the blank control group. The bone quantity analysis in the experimental, control, and blank control group were (1.594 +/- 0.674), (0.801 +/- 0.036), and (0.079 +/- 0.010) mm2, there were significant differences between each groups (P < 0.05).

Conclusion: Prefabrication of musculocutaneous flap including bone induced by the composite of BMP-2 and collagen is feasible and prevalent. It can be regarded as vascularized bone graft and used in repairing composite defect of bone and skin.