Posterior tibial nerve block. A new approach using the bony landmark of the sustentaculum tali.

A local analgesic block of the posterior tibial nerve, using a new subcalcaneal approach, is described. The point of insertion of the needle is defined in relation to a bony prominence below the medial malleolus, the sustentaculum tali, to which the posterior tibial nerve bears a constant relationship. Twenty patients given a posterior tibial block using the subcalcaneal approach were compared with 20 patients in whom a traditional retrotibial approach was used. In this technique the major landmark for needle insertion is the posterior tibial artery. In all patients the techniques formed part of an ankle block for foot surgery. Eighty-five to 90% of patients had peripheral vascular disease and in 60-65% the posterior tibial artery was not palpable. In the group of patients without palpable pulses, the subcalcaneal approach had a success rate of 100%, whereas all those having the retrotibial approach required additional local analgesic supplements (p less than 0.001). The subcalcaneal approach is simple and is particularly recommended for patients with peripheral vascular disease.