Classification of vascularized fibular flap hypertrophy based on X-ray evaluation.

Objective: The aim of this study was to analyze and classify hypertrophy seen in vascularized fibula flaps used for reconstruction of tubular bone defects.

Methods: Thirty-three patients who underwent a vascularized fibula flap for the reconstruction of massive bone defects of the upper or lower extremity long bones were retrospectively reviewed and included in this study. There were 24 lower extremities (21 tibial and 3 femoral) and 9 upper extremities (4 humeral, 2 radial and 3 ulnar) reconstructions in this series. The mean age was 32.7 (range= 10- 59) years. The mean length of bony defect following initial debridement was 10.3 (range= 4-25) cm. The fibula was inserted as a single strut in 29 patients, and as a double barrel construct in 4 patients. The degree of fibular hypertrophy was calculated based on anteroposterior (AP) and lateral X-ray measurements of fibular flaps at an average postoperative period of 52 months. The difference in thickness between the initial and final x- ray measurements were expressed as percentage of hypertrophy. The variances seen in this period were defined and classified.

Results: When bony consolidation of the 33 cases were examined in detail, 4 different modes of flap hypertrophy were defined: type 0- absence of hypertrophy, type 1- limited hypertrophy, type 2- marked hypertrophy triggered by stress fracture, and type 3- massive hypertrophy enhanced by peripheral bone production.

Conclusion: Fibular hypertrophy follows different modes based on vascularity of the flap, amount of stress imparted on the flap, site of reconstruction, and whether the periosteal sleeve is retained at the reconstruction site. Determination of these factors at the initial period may help the surgeons to predict the final hypertrophy that will be seen at the end of flap maturation Level of Evidence: Level IV, Therapeutic Study.