The chimeric descending genicular artery flap: expanding the applications of the medial femoral condyle pedicle to composite free flap reconstruction

Background The descending genicular artery (DGA) axis can provide a versatile reconstruction that includes several tissue components including bone, skin, muscle, tendon and nerve. We present a novel CT angiography study to define the branches of the DGA axis as they relate to flap design for composite bone and soft tissue defect reconstruction. Methods Lower limb CT angiography studies performed at a major microsurgery unit between 2019-2021 were evaluated by two independent clinicians. Vascular anatomy of the DGA, saphenous artery (SA) and branches to regional structures were evaluated and measured. Results An initial 98 studies were identified with 64 studies included for final analysis. The DGA was seen in 56 (87.5%) cases. Cutaneous supply via the DGA axis was possible in 40 cases (70%). Cutaneous supply was seen via direct perforators in 18 (32.1%) cases and the SA in 34 (53.1%) cases. Branches to the vastus medialis were frequent (51.6%). A novel four-tier classification system of the cutaneous supply was developed to assist in chimeric flap design based on these findings. Based on this classification, cutaneous paddle design was possible via the SA in 60% of cases and a further 10% of cases via a direct DGA perforator (skin perforator arising from the DGA proper). Conclusion The DGA axis provides separate and consistent soft tissue and bone pedicles, enabling reliable chimeric flap design. Preoperative CT angiographic imaging ensures a simple, versatile flap with long pedicle and minimal donor morbidity.