Dolph Houben

44 CHAPTER 2 Flap monitoring Thrombosis of the vascular pedicle results in impaired outcomes since the autograft has to incorporate by means similar to those of conventional non-vascularized allografts. They can result in late stress fractures and eventual resorption of the bone graft. The monitoring of a vascularized bone graft in the immediate post-operative period is therefore desirable [60] . Graft viability can be assessed by a variety of methods. Continuous monitoring of the flap is possible by the use of implantable or surface Doppler ultrasound. Although measuring the blood blow in an embedded free flap is difficult, special implantable probes have been used effectively for at least 48h postoperatively. The use of implantable devices carries the risk of thrombosis, spasm, and dislocation of the mircoanastomosis with subsequent hemorrhage [68, 69] . The most feasible and easily interpreted continuous monitor is a fasciocutaneous “buoy” flap. Direct monitoring of the cutaneous island allows immediate return to the operating room if loosening of the dressing, altering limb position, or anticoagulants do not reverse the observed changes. In lower extremity reconstruction, especially in femoral reconstructions, a buoy flap is often impractical since due to the depth of the fibula placement. Osteocutaneous or osteomuscular flaps can be harvested when additional soft-tissue coverage is needed. Intermittent monitoring methods of the fibula flap are more practical and include; angiography, radiographic monitoring of healing and hypertrophy, bone biopsy, early 99Tc bone scans, Doppler ultrasound or SPECT scans. All of these methods are a single time point assessment of viability and do not allow immediate action in case of impaired vascularity. Intermitted monitoring with bone scans correlates with vascular patency when completed before the end of the first week [71] . Outcomes Union The most common indication for the use of vascularized bone transfers is the need for reconstruction of a skeletal defect after radical resection of malignant bone tumor or metastasis (Fig 4). The primary union rate in this group of patients is 67-84%, after secondary bone grafting the rate of union is 81-92% [23, 72] . After tumor resection, infection is the most common indication for vascularized bone reconstruction. Patients who have segmental bone loss due to infection, have the lowest rate of union (47-77%) and, if unsuccessful, may result in amputation. Patients who do not have an infection have the best chance of healing with a primary union rate of 70- 77% and an overall union rate of 92-95% after secondary procedures to achieve union [23, 73] .