Feasibility of Specific Anesthesia of the Forefoot Preserving the Sensitivity of the Heel for Foot Surgery

Overview

Foot surgery is a painful surgery that is usually scheduled in outpatients. A good management of analgesia is the crucial point. Regional anesthesia (RA) is the gold standard, that provides good anesthesia and a long duration of analgesia. The sciatic nerve block (or its branches) is the most adapted analgesic technique. Limitation of proximal sciatic block is the motor block of the ankle and results in the impossibility, for the patient, to walk during the early post-operative period. Distal block of the sciatic nerve (tibial and fibular nerve blocks), at the level of the ankle, has been proposed to maintain the mobility of the ankle, to make deambulation with crutches easier. Nevertheless, the lack of sensibility of the heel remains a limitation for early walking, even with adapted shoes (ie : Barouk). A specific anesthesia of the distal part of the foot, respecting the heel, could be the best option to provide an early deambulation and a suitable analgesia. Ultrasound identification and specific anesthesia of the branches supplying the distal part of the foot (medial and lateral plantar nerves) could meet this dual objective : good anesthesia and suitable analgesia for early deambulation. This study is a feasibility study of a specific block of the plantar branches of the tibial nerve, to preserve the sensibility of the heel, in case of foot surgery. The safety of the procedure will be assessed according to the rate of postoperative dysesthesia.

Block of the medial and lateral plantar branches of the tibial nerve will be performed under the medial malleolar-calcaneal axis (MMCA) in order to preserve the calcaneal nerves. Blocks of the deep peroneal nerve (DPN) and the superficial peroneal nerve (SPN) will be added to provide an adequate anesthesia. Every block will be performed under Ultrasound using a 27-gauge, 5-cm, short bevel needle. 5 mL of 0.375% Ropivacaine will be injected for each block. The sensory blocks will be assessed by pinprick test and cold test every 10 minutes for 40 minutes in the following locations: Calcaneal nerves, Lateral plantar nerve and Medial plantar nerve. The extent of sensory block will be graded as follows: 2: normal sensation; 1: decreased sensation; and 0: no sensation (complete block).