Effect of irrigation fluids, local anaesthetics, Glucosamine and Corticosteroids on human articular cartilage: an in vitro study

Background: Animal studies have shown that the commonly used arthroscopic irrigation fluid, 0.9% normal saline, can be toxic to articular cartilage. There have been several reports of chondrolysis following arthroscopy especially with the use of local anaesthetic pain pumps post operatively. In vitro studies have shown severe toxicity of local anaesthetics to articular cartilage but there are currently no published studies looking at methods to prevent this toxicity. Aims: To study the effect of different irrigation fluids and local anaesthetics on human articular cartilage and the ability of Glucosamine or Corticosteroids to protect against or recover from any potential toxicity. Materials and Methods: Chondral explants obtained from human femoral heads were exposed to different irrigation fluids, local anaesthetics, Glucosamine, Methylprednisolone or culture medium (control) for one hour. After exposure, explants were incubated with radio-labelled[superscript 35]SO[subscript 4] and uptake was measured after 16 hours as an indicator of proteoglycan synthesis. Results: The inhibition of [superscript 35]SO[subscript 4] uptake was 10% by Ringer's solution, 24% by 1.5% Glycine, 31% by 5% Mannitol (p=0.03)and 35% by Normal saline (p=0.04). Lidocaine 1 and 2%, Bupivacaine 0.25 and 0.5% and Levobupivacaine 0.5% were all toxic causing inhibition ranging from 61% to 85% (p<0.001). The addition of Glucosamine or Methylprednisolone at the same time as 0.5% Bupivacaine protected articular cartilage and reduced the inhibition by approximately 50% (p<0.001). Conclusions: Ringer's solution was the least toxic arthroscopic irrigation fluid and should replace normal saline in clinical practice. Intra-articular local anaesthetic injections should only be used with careful consideration of risks and benefits. Further clinical studies are required to assess the potential damage to cartilage from local anaesthetics or normal saline and to investigate the protective effect of Glucosamine or Corticosteroids.