Purpose: To determine whether continuous infiltration of local anaesthetic can reduce the pain score and morphine use over 48 hours after total knee arthroplasty (TKA).
Methods: 11 men and 43 women aged 50 to 82 years who underwent unilateral TKA for osteoarthritis were recruited. They were randomised into 3 groups. In group 1, 17 patients who acted as controls received patient-controlled analgesia (PCA) with intravenous morphine for 48 hours. In group 2, 16 patients received continuous infiltration of bupivacaine to the subcutaneous tissue and intra-articular space for 48 hours, in addition to PCA. In group 3, 21 patients received an intra-articular injection of local anaesthetic, followed by continuous infiltration of bupivacaine to the subcutaneous tissue and intraarticular space for 48 hours, in addition to PCA. For each patient, a visual analogue score (VAS) for pain was recorded postoperatively at 2, 4, 6, 12, 24, 36, and 48 hours. The total amount of morphine used was recorded at 24 and 48 hours.
Results: Over 48 hours, the VAS for pain and morphine use was significantly higher in controls than patients in groups 2 and 3.
Conclusion: Continuous infiltration of local anaesthetic into the intra-articular space and subcutaneous tissues, in addition to PCA with intravenous morphine, provides significantly more pain relief and reduces morphine use.