Abstract
Background
There are several case reports of chondrolysis following joint arthroscopy. Continuous post-operative infusion of local anaesthetic solutions, especially 0.5% Bupivacaine, has been implicated as the causative factor in many of these cases. Recent in vitro studies have shown that even a single exposure of articular cartilage to different local anaesthetic solutions can cause apoptosis and mitochondrial dysfunction in chondrocytes leading to cell death. There is currently no study looking at methods to prevent this toxicity of local anaesthetic solutions to articular cartilage. Glucosamine has a protective and reparative effect on articular cartilage and a Cochrane review in 2007 found that it provides mild benefit in pain and function in patients with arthritis.
Aims
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Oncologic: To compare the effect of a single exposure, in vitro, of different local anaesthetic solutions on human articular cartilage.
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To investigate the protective and reparative effects of Glucosamine on articular cartilage exposed to 0.5% Bupivacaine.
Methods
Chondral explants (n = 354) were obtained from femoral heads of 14 fracture neck of patients undergoing hemiarthroplasty. To compare the effect of local anaesthetics, each specimen was exposed to one of 8 test solutions for one hour.
After this exposure, the specimens were washed and incubated in culture medium containing radio-labelled 35-sulphur for 16 hours. The unbound radioactivity was then washed off and the chondral specimens were digested with proteinase for 24 hours. The uptake of 35-S by each specimen was measured and this gave an estimate of proteoglycan metabolism.
Test solutions: 1. 1% Lidocaine; 2. 2% Lidocaine; 3. 0.25% Bupivacaine; 4. 0.5% Bupivacaine,
5. 0.5% Levo-Bupivacaine; 6. Control solution of M199 culture medium.
7. To investigate its protective effect, 100 micrograms of Glucosamine was added along with 0.5% Bupivacaine; 8. To investigate the reparative effect of Glucosamine, the specimen was exposed to 0.5% Bupivacaine for one hour. After washing, 100 mcg of Glucosamine was added to the culture medium in which the chondral specimen was incubated.
Results
Compared to the control culture medium, the inhibition of proteoglycan metabolism was 54% with 1% Lidocaine (p<0.001), 75% with 2% Lidocaine (p<0.01), 50% with 0.25% Bupivacaine (p = 0.04), 78% with 0.5% Bupivacaine (p<0.001) and 73% with 0.5% Levo-Bupivacaine (p<0.001). Adding Glucosamine for protection reduced the toxicity of 0.5% Bupivacaine to 43%, compared to 78% without. However, Glucosamine was not able to repair the damage caused by 0.5% Bupivacaine, with inhibition of proteoglycan metabolism at 70% even after 16 hours of incubation.
Conclusion
All local anaesthetic solutions tested were toxic to articular cartilage, 0.5% Bupivacaine being the worst offender. Higher concentrations were more harmful. The addition of Glucosamine to 0.5% Bupivacaine protected against its toxicity to articular cartilage but was not able to repair the damage caused.
