A recent meta-analysis examining the safety and efficacy of single-dose intra-articular (IA) magnesium (Mg) for pain relief following arthroscopic knee surgery was published online in November in Scientific Reports.1

Researchers from Central South University in Hunan Province, China searched the medical literature through January 2016 for all randomized controlled trials related to the use of Mg in arthroscopic knee surgery. They also retrieved records describing relevant in vitro and in vivo experimental studies. Eight randomized controlled trials and 8 experimental studies were ultimately included in their final analysis. The primary outcome measure analyzed were the effects of IA Mg and Mg plus bupivacaine on postoperative pain control. Secondary outcomes were time to first post-operative analgesic consumption and adverse effects.

Single-dose IA injections with analgesic agents represent a common pain management strategy in arthroscopic knee surgery. Bupivacaine is frequently used for this purpose due to its long duration of action.2 Additional agents used in IA injections include other local anesthetics, opioids, nonsteroidal anti-inflammatory drugs, corticosteroids, alpha-2 agonists, and N-methyl D-aspartate (NMDA) receptor antagonists.3 Conflicting results have been found for the efficacy of analgesic IA injections; additionally, their use has been associated with reports of chondrolysis, a condition characterized by the rapid, extensive destruction of articular cartilage.2

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Results of the meta-analysis indicated that single-dose IA injection of Mg following arthroscopic knee surgery provided effective pain relief, with adverse effects no greater than those seen with placebo. Results also showed that patients who received IA Mg waited longer to request supplementary analgesic medication than placebo-receiving patients. 

Adverse reactions including knee effusion, nausea, vomiting, flushing, shivering, hypotension, bradycardia and drowsiness were reported for IA Mg in 4 trials; however, no statistically significant differences were found for adverse effects in patients who received IA Mg vs comparators. The analysis of experimental studies showed that Mg had chondrocyte or cartilage protective effects, suggesting that Mg has potential as a less toxic substitute for local anesthetics. The authors note that more research in this regard is necessary.

Summary and Clinical Applicability

“Single-dose IA Mg at the end of arthroscopic surgery was effective in pain relief without increasing adverse reactions, and it could also enhance the analgesic effect of bupivacaine,” wrote the authors in their conclusion. “In addition, Mg seemed to exhibit the cartilage or chondrocyte protective effect according to the experimental studies. Perhaps IA Mg should be considered as an alternative to local anesthetics after arthroscopic surgery. However, the optimal concentration and dosage of IA Mg still needs to be explored in further fully powered RCTs, to fully address this point.”

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  1. Zeng C, Li Y, Wei J, et al. Analgesic effect and safety of single-dose intra-articular magnesium after arthroscopic surgery: a systematic review and meta-analysis. Sci Rep. 2016;6:38024. doi:10.1038/srep38024.
  2. Webb ST, Ghosh S. Intra-articular bupivacaine: potentially chondrotoxic? Br J Anaesth. 2009;102(4):439-441. doi:10.1093/bja/aep036.
  3. Young A, Buvanendran A. Multimodal systemic and intra-articular analgesics. Int Anesthesiol Clin. 2011;49(4):117–133.