Mid-Calf Block for Foot and Ankle Surgery: A Pilot Study

Research Type: Level 4 – Case series Introduction/Purpose: The mid-calf block is a series of ultrasound-guided nerve blocks performed at a similar branch level as the Ultrasound Guided Ankle Block, but with the probe placed higher on the calf. This technique provides prolonged analgesia while preserving ankle joint motor function. Administration of the mid-calf block targets the posterior tibial nerve, superficial and deep peroneal nerves, sural, and saphenous nerves. The current standard anesthesia technique for foot and ankle surgeries is ultrasound-guided popliteal block, which has the disadvantage of causing muscle weakness at the ankle joint. The pilot study aims to evaluate the feasibility and efficacy of the mid-calf block as a potential alternative for foot and ankle surgeries, which could facilitate early rehabilitation and recovery for these patients. Methods: This nonrandomized, single-intervention clinical pilot study aims to assess the efficacy of the mid-calf block and inform subsequent randomized clinical trials. Twenty patients scheduled to undergo foot and ankle surgery at the Hospital for Special Surgery were recruited. Smaller surgeries used the mid-calf block as the sole anesthetic. Other surgeries used intraoperative spinal anesthesia and a mid-calf block for postoperative analgesia. The operations examined included total ankle replacement, ankle arthroscopy, bunionectomy, cheilectomy, and Achilles tendon repair. Three participants who received additional surgery in surgical areas not covered by the mid-calf block were excluded from sensitivity analysis. Participants were assessed in the PACU and before discharge to record the time of mid-calf block resolution, presence of paresthesia, and any additional side effects. On postoperative day 1 (POD), POD2 and POD7, participants were contacted to report their pain on a numerical rating score (NRS), medication use, and other symptoms. Results: The analysis group (n=17) had a mean age of 55.9 years and mean BMI of 26.3 kg/m². The mean time taken to administer the block in the operating room was 22.5 ± 7.4 minutes. The median duration of analgesia from the mid-calf block was 18.7 [IQR: 13.1-24.8] hours. Patient-reported NRS pain scores in the PACU were 0.8 ± 2.1 at rest and 1.1 ± 2.3 with movement. From pre-op to POD2, patients’ NRS pain scores at rest ranged from 1.8 ± 2.5 to 2.6 ± 1.6 (Table 2). Using the oral morphine equivalent (OME) to compare opioid consumption, the cumulative median OME from PACU to POD2 was 22.5. Conclusion: By considering factors like time required for block administration, duration of analgesia, and patients’ ability to perform foot movement, our findings suggest that the mid-calf block is a viable option for foot and ankle surgeries. Postoperatively, the mid-calf block demonstrated prolonged pain relief. Compared to the ankle block, the mid-calf block allows for extended analgesia. Additionally, all patients were able to move their foot and ankle in the PACU. Unlike the commonly used popliteal block, the mid-calf block allows patients to bear weight immediately, when allowed by the surgeon, which shows promise in achieving earlier rehabilitation and recovery for patients.