Study of peri-articular anaesthetic for replacement of the knee (SPAARK): study protocol for a patient-blinded, randomised controlled superiority trial of liposomal bupivacaine

Background: Optimizing the management of peri-operative pain and recovery following knee replacement has been identified as a patient priority. Current pain relief strategies use opiate based analgesia; however, up to 50% of patients experience significant side effects. Local anaesthetic incisional infiltration is one alternative. The length of the duration of action is a major limiting factor of current local anaesthetic techniques. Liposomal bupivacaine has been reported to be effective for up to 72 hours. This randomised controlled trial will evaluate the clinical and cost effectiveness of liposomal bupivacaine. Methods: SPAARK is a patient-blinded, multi-centre, active comparator, superiority, two-arm, parallel-group, randomised controlled trial. Five hundred patients undergoing knee replacement will be recruited and randomised to liposomal bupivacaine plus bupivacaine hydrochloride or bupivacaine hydrochloride alone. The co-primary outcomes are the Quality of Recovery 40 (QoR-40) measured at 72 hours post-surgery, and cumulative pain measured daily using a 0-10 visual analogue scale (VAS) for the first three days following surgery. Secondary outcomes include cumulative opioid consumption, fitness for discharge, functional outcomes, assessed using the Oxford Knee Score and American Knee Society Score, the EQ-5D, and complications. A cost-utility analysis is also planned. Discussion: The clinical and cost effectiveness of liposomal bupivacaine has yet to be evaluated in the National Health Service (NHS), making this trial appropriate and timely.