Single-Dose Intra-Articular Morphine After Arthroscopic Knee Surgery: A Meta-Analysis of Randomized Placebo-Controlled Studies

Purpose: The purpose of this quantitative meta-analysis is to appraise the efficacy and side effects of intra-articular morphine in patients undergoing arthroscopic knee surgery. Methods: The comprehensive literature search, using Medline (1966 to 2013), the Cochrane Central Register of Controlled Trials, and EMBASE databases, was conducted to identify randomized placebo-controlled trials that used single-dose intra-articular morphine for postoperative pain. The relative risk (RR), standardized mean difference (SMD), and their corresponding 95% confidence intervals (CIs) were calculated using statistical software. Results: Twenty-six articles were included in the meta-analysis. The acute postoperative visual analog scale (VAS) pain scores of the morphine group compared with the control group were significantly lower (SMD, - 1.16; 95% CI, -1.79 to -0.53; P = .0003). The number of patients requiring supplementary analgesia was also significantly reduced (RR, 0.80; 95% CI, 0.70 to 0.93; P = .008), and there was a significant difference in the time to first analgesic request (SMD, 1.47; 95% CI, 0.49 to 2.44; P = .003) when the morphine group was compared with the placebo group. However, there was no significant difference in side effects between the morphine group and the control group (RR, 0.93; 95% CI, 0.67 to 1.28; P = .65). Conclusions: The key findings of the present study were that the administration of single-dose intra-articular morphine at the end of arthroscopic knee surgery provided better pain relief, reduced the need for supplementary analgesics, and lengthened the time interval before the first request for additional analgesic medication, all with short-term side effects similar to those of the saline placebo. Level of Evidence: Level II, meta-analysis of Level I-II studies.