TOXICITY OF NORMAL SALINE AND 0.5% BUPIVACAINE TO HUMAN ARTICULAR CARTILAGE

Abstract

Background: Animal studies have shown that 0.9% NaCl causes inhibition of proteoglycan metabolism in articular cartilage yet it continues to be the most commonly used irrigation fluid for arthroscopic surgery. Ringer’s solution and non ionic fluids have been shown to cause less damage. There is currently no such comparison in human articular cartilage. The aim of this study was to assess the effect of different irrigation fluids on arthritic and non arthritic human articular cartilage.

Materials and Methods: Non arthritic cartilage specimens were obtained from femoral heads of hip fracture patients undergoing hemiarthroplasty where there were no radiological or macroscopic signs of osteoarthritis. Arthritic articular cartilage was obtained from tibial plateau of total knee arthroplasty patients or femoral heads with macroscopic signs of osteoarthritis. Cartilage explants were exposed to either 0.9% normal saline or Ringer’s solution, 1.5% Glycine, 10% Mannitol or a control solution of M199 culture medium. 0.5% bupivacaine, which has been shown to be toxic to chondrocytes, was used as a second control solution. The specimens were then incubated in culture medium containing radiolabelled 35-SO4 for 16 hours and uptake was measured as counts per gram per minute.

Results: In non arthritic cartilage, the inhibition of proteoglycan synthesis was 0% with Ringer’s solution (p> 0.05), 3% with Glycine and Mannitol (p> 0.05), 12% with 0.9% NaCl (p> 0.05) and 75% with 0.5% bupivacaine (p< 0.001).

In arthritic cartilage, the inhibition was 15% with Ringer’s solution (p> 0.05), 20% with Mannitol (p> 0.05), 30% with 0.9% NaCl and Glycine (p=0.04) and 85% with 0.5% bupivacaine (p< 0.001).

Conclusion: Normal saline was most harmful to human articular cartilage. Ringer’s solution was the best solution for joint irrigation. We have provided yet more evidence to suggest that 0.5% bupivacaine is severely toxic to articular cartilage.