The subthalamic osteotomy-resection of the calcaneous proposed by Pisani in 1979 is designed to correct frontal deformities (varus or valgus). The S shaped external submalleolar incision is prolonged as far as the calcaneo-cuboid joint. The subcutis is cut and the external saphenous nerve is isolated and protected. Using a retroperoneal approach, the lateral wall of the calcaneous is stripped to reveal the posterior tuberosity, the subastragalar area, the tarsal sinus, the anterior process and the calcaneocuboid joint. A scalpel is used to cut two L shaped osteotomic planes: the first under the thalamus is perpendicular to the axis of the leg and avoids the medial cortical; the second is on a frontal plane just behind the calcaneocuboid joint. In subtraction osteotomies (anti-varus) a third plane converging on the subthalamic osteotomy to the medial cortical is cut to create a wedge of bone with an external base. The wedge of bone is removed, the distal osteotomic fragment rotated and the osteotomy surfaces brought together and stabilised with staples. In anti-valgus osteotomies a lever is used to open the subthalamic osteotomy and the wedge required for the correction is stabilised by force. Suturing is in layers. Elastic bandage; mobilisation immediately after surgery; weight bearing after about 45 days.