Safe zones and a technical guide for cerclage wiring of the femur: a computed topographic angiogram (CTA) study

Cerclage wiring for reduction of complex femoral shaft fractures can create iatrogenic vascular injury. To describe the anatomical relation of blood vessels to the femur and develop a technical guide for safe passage of cerclage wire. CT lower-limb angiographs (CTA) of 80 patients were reviewed and analysed to identify the superficial femoral artery (SFA) and the deep femoral artery (DFA) as well as the relation of those arteries to the femoral cortex. The total length of the femur was measured and divided into eight equal segments (seven levels). At each level, the medial half of the femur was divided into eight sectors labelled A through H and the position of the SFA and DFA was recorded. The shortest distance between the femoral cortex and the SFA and DFA at each level was measured. The data was analysed using STATA version 10.0. The average total femoral length from the tip of greater trochanter to lateral joint line was 402.98 +/- 26.16 cm. The average distances from the SFA to the femur (d1) for levels 1 through 7 were 37.20 +/- 5.0, 32.09 +/- 4.74, 27.13 +/- 4.19, 27.71 +/- 5.46, 23.71 +/- 4.40, 13.63 +/- 3.59 and 10.08 +/- 3.09 mm, respectively. The average distances between the DFA and the femur (d2) for levels 1 through 3 were 26.70 +/- 4.13, 14.76 +/- 3.27 and 9.58 +/- 3.79 mm, respectively. The position of the SFA is located in sectors B through E at levels 1-3 and in sectors E through H at levels 4-7 and the position of the DFA located in sectors B through F at levels 1-3. Cerclage wiring should be started from the posterior intermuscular septum at the linea aspera. The safe area is the proximal half (midshaft) of the femur where the SFA and DFA lie at a safe distance from the femur. Between the midshaft and the distal 1/4, insertion of the passer must be done meticulously with the tip kept close to posteromedial cortex. Below the distal 1/4, the tip of the passer should be kept close to the posterior cortex to avoid injury to the SFA and the sciatic nerve.