The five-in-two (FIT) ankle block for outpatient foot surgery: a proof-of-concept anatomical and observational study

Regional anesthesia for foot surgery commonly relies on a five-injection ankle block, a technique associated with technical complexity and patient discomfort. We developed an ultrasound-guided five-in-two (FIT) ankle block based on an anatomical rationale, to provide complete foot anesthesia with only two punctures.

A dual-injection ankle block technique was defined through an anatomical study, consisting of a mid-calf injection targeting the superficial and deep fibular nerves and a distal transverse injection 5 cm above the medial malleolus targeting the tibial, saphenous, and sural nerves. The technique was assessed in a bicentric prospective observational study of adult patients undergoing outpatient foot surgery, with surgical anesthesia as the primary outcome. Secondary outcomes assessed block performance, perioperative pain intensity, 24-hour rescue analgesic consumption, patient-reported experience, and block-related safety.

80 patients received a FIT ankle block, with successful surgical anesthesia achieved in 77 cases (96%). Median sensory and motor block durations were 554 (420-758) and 600 (444-882) minutes, respectively. Pain was minimal, with median Visual Analogue Scale scores of 0 (0-7) during block placement and 0 (0-4) on arrival in the post-anesthesia care unit. Intravenous rescue analgesia was required in 5% of patients. The median Echelle du Vécu de l'Anesthésie LocoRégionale global score was 88 (80-97), and the complication rate was 0% (95% CI 0 to 3.75%).

The anatomically guided FIT ankle block is an effective proximal motor-sparing regional anesthesia technique for outpatient foot surgery, providing reliable anesthesia, excellent analgesia, and well-tolerated perioperative outcomes.