Efficiency of femoral nerve block for recovery after primary total knee arthroplasty

Background
Femoral nerve block (FNB) is a suitable option for pain management and recovery after total knee arthroplasty (TKA). It is usually used along with a multimodal analgesia protocol. The major disadvantage of FNB is the risk of quadriceps muscle strength loss. This study aims to compare the efficiency of the FNB with two different concentrations of bupivacaine for recovery after TKA. We primarily aim to provide adequate analgesia with a lower concentration of bupivacaine (0.125%) rather than the usual concentration (0.25%). Secondarily, we aim to compare the degree of motor block, opioid consumption, and ambulation time between the groups. The study was conducted as randomized, controlled, and double-blind. Sixty three patients were randomized into three groups: G125 (:21) received FNB with 20ml of 0,125% bupivacaine, G25 (n:21) received 10ml of 0,25% bupivacaine and GCont (:21) received no block.
Results
For GCont, pain scores were significantly higher at 2nd, 6th, 12th, and 24th hours postoperatively, total opioid consumption was higher (G125: 75 mg, G25: 0 mg, GCont: 280 mg, < 0.001) and first opioid demand time was earlier (G125: 12th hour, G25:21st hour GCont:2nd hour, : 0.002). First knee flexion time and ambulation time were also delayed for GCont. G25 had lower scores for quadriceps muscle strength (manual test at 6th hour, G25: 3/5, G125: 4/5, GCont:5/5, < 0.001) compared to other groups.
Conclusions
G125 had lower quadriceps muscle strength loss compared to the G25; earlier ambulation and flexion times, low opioid consumption, and low pain scores compared to the control group. In this respect, we believe the femoral nerve block with 0.125% bupivacaine proves to be a suitable option for analgesia with the potential of maintaining enough muscle strength for recovery after TKA.
Trial registration
Protocol Registration and Results System, NCT03623230. Registered 09 August 2018, at