Abstract
Background:
Chondrolysis initiated by postoperative, intra-articular pain pumps has recently been described by multiple institutions.
Purpose:
To evaluate the in vitro chondrotoxicity of anesthetic formulations commonly used in pain pumps.
Study Design:
Controlled laboratory study.
Methods:
Freshly isolated human articular chondrocytes were cultured for 24-, 48-, and 72-hour trials in a custom bioreactor that mimics the metabolism of synovial fluid. Chondrocytes were perfused in Dulbecco's Modified Eagle's Medium 10% fetal bovine serum and one of the following medications: 1 % lidocaine, 1 % lidocaine with epinephrine, 0.25% bupivacaine, 0.25% bupivacaine with epinephrine, 0.5% bupivacaine, or 0.5% bupivacaine with epinephrine. Static and perfusion cultures with growth media were used as controls. All experiments were run in duplicate. Live/dead staining was performed, and the ratio of dead: Live cells was assessed by fluorescent microscopy and histomorphometry.
Results:
Significantly more chondrocyte necrosis was found in all cultures with medications containing epinephrine (P < .05) at all time points. Similar necrosis rates were exhibited in 0.25% and 0.5% bupivacaine compared with controls at 24 and 48 hours. However, 0.5% bupivacaine produced significantly more cell death at 72 hours. Similar necrosis rates were exhibited with 1 % lidocaine compared to controls at 24 hours.
Conclusion:
In this in vitro model, 0.25% and 0.5% bupivacaine caused minimal chondrocyte necrosis when used in pain pumps for a maximum of 48 hours. All anesthetics containing epinephrine (pH ⩽ 4) were chondrotoxic and cannot be advocated for pain pump use. The use of 0.5% bupivacaine for greater than 48 hours is not recommended.
Clinical Relevance:
The results of this study may help improve the safety of intra-articular pain pump use by examining the effects of local anesthetics on chondrocyte viability.
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