Continuous intra-articular infusion of ropivacaine after unilateral total knee arthroplasty

Intra-articular infusion of local anaesthetic after joint arthroplasty is attractive in that it is simple and will not cause motor block. However the efficacy of the technique has yet to be established. We enrolled 66 patients scheduled for unilateral total knee arthroplasty under general anaesthesia and single-shot femoral and sciatic nerve blocks. All patients had an intra-articular Painbuster (R) device sited at the end of the procedure. Patients were then randomised to control or one of two treatment arms - low-dose and high-dose ropivacaine. In the control group the balloon was filled with saline, in the low-dose group with 0.2% ropivacaine and in the high-dose group 0.375% ropivacaine. The catheters were infused continuously for 48 hours and then removed. Patients were followed up daily for three days to determine pain scores, opioid consumption and subjective assessment of the analgesic efficacy of the catheter Data were analysed for 30 controls and 31 in the treatment arms. Both groups were similar There were no significant differences between the control and treatment groups at all time points after adjustment for age. Patients in the high-dose group had higher pain scores and higher opioid consumption than the control groups from 24 to 48 hours. There were two cases of infection, both in the treatment groups. No positive benefit of intra-articular infusion of local anaesthetic after total knee arthroplasty could be identified. On the contrary there may be negative effects in terms of expense, pain and possibly infection risks.