335 Motor Sparing Peripheral Nerve Block: A Modern Approach to Total Knee Arthroplasty

Abstract

Aim To maximise postoperative analgesia, whilst minimising opioid use, motor sparing peripheral nerve blocks have been described as an alternative to local infiltration analgesia (LIA) with adductor canal block (ACB) in total knee arthroplasty (TKA). At The Robert Jones and Agnes Hunt Orthopaedic Hospital, we have developed a new technique, involving ten separate injections to the four genicular nerves, saphenous nerve, nerve to the vastus medialis, the popliteal plexus and to the medial, intermediate, and lateral cutaneous nerves of the thigh. The aim was to compare the analgesic effect of this type of motor sparing nerve block against LIA with ACB in TKA. Method Two groups were identified retrospectively. The test group included fifty patients who received 5ml each of 0.75% Levobupivacaine to the saphenous nerve and nerve to the vastus medialis, and 40ml of 0.25% Levobupivacaine to the four genicular nerves, the popliteal plexus, and to the cutaneous nerves. A matched control group received standard treatment with ACB and LIA. The primary outcome was the consumption of opioid analgesics, measured as a total morphine equivalent. Results For patients in the test group, the mean amount of IV morphine equivalent administered in the first 48-hours postoperatively was 34mg vs 108mg. This equates to a 68% reduction in opioid consumption compared to the control group. Conclusions Motor sparing nerve blocks provide a significant reduction in opioid consumption compared to LIA with ACB in TKA. The results have implications in terms of pain management, reduced opioid-induced side effects and overall, enhanced patient recovery.