Ankle block implemented through two skin punctures

Recently, peripheral nerve blocks have increasingly been used in orthopedic surgery. The foot block is an alternative for anesthesia in cases of forefoot and midfoot operations. We propose a modification of the block technique due to potential difficulties concerning the tibial nerve.

The spatial position of the tibial nerve in the neurovascular bundle, proximal to entering the tarsal tunnel and sural nerve behind lateral malleolus was measured on 60 dissected preparations. Modification of the block technique was proposed. A tibial nerve block was administered by inserting a needle, at an area above the upper edge of the heel bone, tangential to the Achilles tendon. The needle was then withdrawn and redirected to the frontal plane and inserted through the tissue, anterior to the Achilles tendon and laterally behind the lateral malleolus to block the sural nerve. A block of the saphenous nerve superficial and deep peroneal nerves was implemented by needle insertion subcutaneously two centimeters proximal to the crest of the ankle joint. The technique was then evaluated in the clinical part of the study in 84 operative procedures.

The tibial nerve is located 21.1 mm +/- 2.1 mm from the medial aspect of the Achilles tendon and 11.6 mm +/- 1.3 mm deep in the neurovascular bundle. The distance from the posterior margin of the lateral malleolus to the sural nerve is 18.3 mm +/- 1.9 mm. We achieved a 93% success rate in implementation of the complete foot block in 84 operations.

The technique, proposed in the anatomical portion of the study and evaluated in the clinical part, had a similar success rate when compared to techniques published in the literature. Though comparable to currently used techniques, this technique provides easier positioning of a patient and a complete block of the foot can be done with two skin injection sites.