PAIN RELIEF FROM INTRAARTICULAR MORPHINE AFTER KNEE SURGERY - A QUALITATIVE SYSTEMATIC REVIEW

Reduction of postoperative pain by injecting opioid into the knee join t is believed to support the hypothesis of peripheral opioid receptor activation in inflammation. The study design consisted of a systematic review of randomised controlled trials (RCTs). Main outcomes were pai n intensity and the use of supplementary analgesics. Efficacy of intra -articular bupivacaine against placebo was used as an index of interna l sensitivity. Evidence of efficacy was sought in both early (0-6 h af ter intra-articular injection) and late (6-24 h) periods. Thirty-six R CTs in knee surgery were found. Six had both a local anaesthetic contr ol and placebo; four showed internal sensitivity. All four sensitive s tudies had at least one outcome showing efficacy of intra-articular mo rphine against placebo. Six studies compared intra-articular morphine with intravenous or intramuscular morphine or with intra-articular sal ine without a bupivacaine control. Four of the six studies showed grea ter efficacy for intra-articular morphine. There was no dose-response evident. No quantitative analysis of pooled data was done. We conclude that intra-articular morphine may have some effect in reducing postop erative pain intensity and consumption of analgesics. These studies ha d significant problems in design, data collection, statistical analysi s and reporting. Trials of better methodological quality are needed fo r a conclusive answer that intra-articular morphine is analgesic, and that any analgesia produced is clinically useful. (C) 1997 internation al Association for the Study of Pain.