Postoperative analgesic effects of an external cooling system and intra-articular bupivacaine/morphine after arthroscopic cruciate ligament surgery

The aim of this study was to evaluate the analgesic effect of an external cooling system with or without the combined effect of intra-articularly administered bupivacaine/morphine after arthroscopic anterior cruciate ligament (ACL) reconstruction. Fifty patients with isolated ACL insufficiency operated on under general anaesthesia were randomized to three different postoperative treatment groups. Group I was treated with the cooling system during the first 24 h after surgery and an intraarticular injection of 20 ml of physiological saline given at the completion of surgery; in group II, the cooling system was combined with an intra-articular injection of 20 ml bupivacaine 3.75 mg/ml and 1 mg of morphine at the end of the operation; while group III (placebo group) received an intra-articular injection of 20 ml of physiological saline at the completion of surgery. Pain was assessed using a visual analogue scale (VAS) at 1, 2, 4, 6, 24 and 48 h postoperatively. Supplementary analgesic requirements were registered. In group I 80% (16/20) and in group II 90% (18/20) of the patients were satisfied with the postoperative pain control regimen (NS). This was significantly better than in group III, where 30% (3/10) were satisfied. The pain scores were significantly lower in the two treatment groups compared with the placebo group during the entire postoperative period. The pain score was significantly lower in group II than in group I at 24 and 48 h after surgery. The supplementary analgesic requirements were also lower in the two treatment groups compared with the placebo group. No complications due to the use of the cooling system or the intra-articular injections of bupivacaine/morphine were observed. The external cooling system used in this study provides an effective method of obtaining pain relief after arthroscopic surgery. The combination with an intra-articular injection of morphine and bupivacaine results in a slightly greater analgesic effect than the cooling system alone.