Effects of Multiple Intra-articular Injections of 0.5% Bupivacaine on Normal and Osteoarthritic Joints in Rats

Abstract

To determine the invivo effects of multiple local anesthetic injections of 0.5% bupivacaine on normal and osteoarthritic articular cartilage. Rats with normal knee joints received an intra-articular injection of 0.9% saline solution or 0.5% bupivacaine in their right knees joint once a week for 5 consecutive weeks, starting 4weeks after the beginning of the experiment. Rats were humanely killed at 8, 16, and 24weeks. In a parallel experiment, rats underwent anterior cruciate ligament transection to induce osteoarthritic changes. These rats were subjected to the same protocol as those with normal knee joints, starting 4weeks after the procedure. Static weight-bearing tests were performed on both hind limbs to evaluate changes in weight-bearing ability throughout the experiments. Rats were humanely killed at 8 and 16weeks. Cell viability was assessed with confocal microscopy, using samples from the distal femur. Histologic assessment of osteoarthritis was performed using samples from the tibial plateau based on the Osteoarthritis Research Society International (OARSI) cartilage histopathology assessment system (i.e., OARSI score). Static weight-bearing tests showed no significant changes after intra-articular injection of saline solution or bupivacaine, and bupivacaine injection did not increase weight bearing compared with saline solution injection, regardless of whether there were osteoarthritic changes. There were also no significant differences in cell viability, cell density, or OARSI scores between the saline solution and bupivacaine groups at each time point, regardless of whether osteoarthritic changes were induced. This study suggested that single or intermittent intra-articular bupivacaine injections might not have deleterious effects on either osteoarthritic or normal joints. There is no strong evidence that intra-articular bupivacaine injection induces degenerative changes in articular cartilage. Therefore, these results may apply to normal and osteoarthritic joints.