Dolph Houben

35 Vascularized Bone Grafts, a closer look at the free fibula flap 2 Pre-operative patient evaluation A successful free vascularized bone transfer is depending upon careful preoperative planning and complete evaluation of the donor and recipient site. The characteristics of the recipient's site must be evaluated for its bony, soft tissue, and vascular anatomy to ensure appropriate graft selection [42, 57] . Free vascularized transfer of the fibula requires systematic evaluation of the donor site including the bony and vascular anatomy variations that may compromise graft harvest [58] . The evaluation includes a radiograph to rule-out previous fractures, and vascular examination with Doppler ultrasound is vital [42] . Pre-operative angiography should be considered routine in trauma cases, or if a preoperative Doppler exam suggests a vascular abnormality. In both trauma and post-irradiation cases, the extent of soft tissue damage may extend well above and below the defect. In such cases, the anastomosis should be planned away from the zone of injury. For this reason, it is sometimes preferable to perform a distal anastomosis instead of a proximal anastomosis. If osteomyelitis is present, one must make sure extensive debridement of all devitalized bone has been performed and adequate soft tissue coverage is present before vascularized bone grafting is considered [59, 60] . The technique of free fibula harvest Anatomy Like other long bones, the fibula shaft receives its blood supply through a combination of endosteal and periosteal vessels. Approximately 70% of the cortical blood supply derives from the endosteal vasculature. The remaining 30% of the cortex receives its blood supply through a transverse circulation from the periosteum [44, 61, 62] . The endosteal centrifugal blood supply derives from the nutrient artery branch of the peroneal artery entering the fibula in the middle third of the diaphysis through the nutrient foramen. The nutrient artery of the fibula arises 6-14cm from the peroneal artery origin [42, 58] . The periosteal blood supply derives from small branches of the peroneal and anterior tibial arteries in the middle third of the diaphysis [42] . The peroneal artery branches approximately 3 cm distal to the origin of the anterior tibial artery. The artery typically penetrates the soleus muscle close to the lateral intermuscular septum and continues distally in the leg parallel to the fibula, running in between the posterior tibialis and flexor hallucis longus muscle. It is accompanied by two venae comitantes on both sides of the artery. The peroneal pedicle has a length of 6-8 cm with an arterial diameter of 1.5-3.0 mm. The free fibula flap can be harvested with a skin paddle up to 10-20 cm. The skin paddle is vascularized by a series of fasciocutaneous or myocutaneous perforators who arise from the peroneal artery. The perforating vessels in the mid-fibula area are often found coursing through the flexor hallucis longus and peroneus longus muscles. In the distal fibula the perforating vessels are found between the soleus and peroneus brevis muscles. The exact location of the perforators can be determined by the use of Doppler ultrasound, thus skin paddle can be designed around these perforators. Due to the myocutaneous course of the perforating vessels, one could design composite grafts including bone, skin, and muscle. The flexor hallucis longus may be used and provides enough coverage for the distal fibular segment. A larger muscle sufficient to obliterate dead space or provide coverage may be needed. The lateral part of the soleus muscle can be used for this reason without loss of function. This can be accomplished by sparing the soleus muscle branches when visualized during the exposure of the peroneus pedicle [60] .