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Background and Aims Postoperative pain management after primary total knee arthroplasty remains the main challenge for orthopaedic anaesthesiologists. Single shot adductor canal block is widely accepted as part of multimodal analgesia reducing postoperative opiate consumption and promotes early mobilization.

Methods Ethics approval was gained from the study centre. Patients scheduled for primary knee arthroplasty in a tertiary referral centre for elective orthopaedic surgery were identified and randomised into 2 groups. Group A received ultrasound guided(USG) adductor canal block(ACB) with 20mls of 0.25% levobupivacaine. Group B received a periarticular block by surgeon as per protocol plus sham USG ACB. A non-blinded anaesthesiologist, prepared the solution for adductor canal block, performed the spinal anaesthesia and looked after the patient in the operating theatre. A separate, blinded anaesthesiologist performed the USG ACB. Both groups received the same dose of spinal anaesthesia. The same intraoperative and postoperative analgesia and antiemetics were administered, with other medications at the discretion of the non-blinded anaesthesiologist. Primary outcome measures were morphine milligram equivalent(MME) at 24 and 48 hours. Secondary outcomes were time to first opiate(mins) and visual analogue pain score(VAS) at 24 and 48 hours.

Results 22 suitable patients were recruited and randomised into groups A and B. Mean +/- standard error 24-hour MME for test group (A) was 70+/-10.8 and for sham group (B) was 59.6+/-7.64, p=0.47. 48-hour MME for group A 72.23 +/- 22.4 and group B was 84.45+/-15.4, p=0.71.

Conclusions There was no significant difference in primary outcomes between groups. Secondary outcomes similarly had no significant difference between groups.