Comparison of adductor canal block with femoral nerve block for post-operative pain relief after bilateral total knee arthroplasty: A non-randomised controlled trial

BACKGROUND AND AIMS: Pain perception and pain threshold vary from one individual to another and also differ in the right and left limbs leading to an inter-cerebral pain variability bias and inter-patient pain variability bias. To date, data comparing adductor canal block (ACB) with femoral nerve block (FNB) in the same patient who underwent bilateral total knee arthroplasty (TKA) remain limited. METHODS: We performed a prospective, non-randomised, controlled study. Patients scheduled for bilateral TKA with central neuraxial anaesthesia received every 12-hourly intermittent boluses of 15 mL of ropivacaine 0.5% in two different peripheral nerve blocks (ACB and FNB) in either of the lower limbs postoperatively. The primary outcome was to assess postoperative VAS score, and the secondary outcomes were muscle strength of the quadriceps muscle and degree of flexion at the knee joint. RESULTS: Among the 80 patients assessed for eligibility, 72 patients were enroled, and 69 were included in the final analysis. VAS scores after the two blocks during rest at 30 minutes, 6 hours, 12 hours and 48 hours post-operatively had no significant difference. VAS scores during rest at 24 hours and on doing exercise at 24 hours and 48 hours showed a significant difference. Quadriceps muscle strength and degree of flexion of knee at 24 hours and 48 hours post-operatively did show a significant difference in favour of the ACB over FNB. CONCLUSION: ACB provides equivalent analgesia in comparison with FNB at rest and during passive exercise up to 48 hours post-operatively. ACB significantly preserved motor power of quadriceps muscles when compared with FNB with no added complications.