Dolph Houben

46 CHAPTER 2 Recipient site complications Thrombosis Complications related to thrombosis are compartment syndrome at the recipient site, late stress fracture, and non-union. Due to thrombosis, blood flow, bone formation, and osteocyte counts are reduced. This can ultimately lead to late stress fractures and non-union. If left untreated, thrombosed vascularized bone grafts are significantly less likely to heal compared to conventional non-vascularized grafts [78] . If thrombosis occurs, the surrounding cuff of necrotic soft tissue may likely impede neovascularization. Thus, the process of creeping substitution of necrotic bone is less extensive in these failed vascularized bone grafts. Delayed union The need for secondary bone grafting is necessary for a substantial number of patients with delayed union. Primary healing rates have been reported to be around 68% of the vascularized fibular grafts, with poorer results depending on some recipient site locations and in patients with osteomyelitis [1] . Those patients who do not heal primarily may benefit from a secondary intervention with autogenous corticocancellous bone grafting at the non-united junction. Forty- five percent (45%) of the total reoperations after the vascularized fibular transfer are the result of delayed union treated by supplemental autogenous bone grafting [74] . The total healing rate after secondary intervention reaches 82-88% found in literature [1, 49] . Stress Fracture Stress fractures of vascularized bone graft are not uncommon, they are particularly prevalent in lower extremity reconstructions. In literature, stress fractures occur in the lower extremity in 8-27 percent of the patients [1, 74, 79, 80] . Stress fractures can be divided into two groups: early stress fractures and late stress fractures. Early stress fractures are the result of insufficient fixation or protection from mechanical loads since the fibular graft has had insufficient time to undergo hypertrophy (Fig. 4D). Ridgid internal fixation with spanning plates or intramedullary fixation of fibular grafts may result in a lower incidence of fracture [81] . If the graft has adequate vascularity, the healing of undisplaced stress fractures may occur with immobilization (Fig. 6). Whereas displaced fractures require internal or external fixation with or without bone grafting [1, 79] . Late stress fractures are relatively uncommon and are associated with impaired vascularity. Vascularized fibular grafts should be protected from fatigue fracture during the first year, allowing a gradual increase in mechanical load, which enables remodeling and hypertrophy [48] .