The effects of common anti-inflammatory drugs on the healing rat patellar tendon

Background: Tendon injuries that occur at the osteotendinous junction are commonly seen in clinical practice and range from acute strain to rupture. Nonsteroidal anti-inflammatory drugs are often prescribed in the treatment of these conditions, but the effect that these agents may have on the healing response at the bone-tendon junction is unclear. Hypothesis: In response to an acute injury at the osteotendinous junction, the healing patellar tendon will have inferior biomechanical properties with administration of anti-inflammatory drugs as compared with acetaminophen and control. Study Design: Controlled laboratory study. Methods: A total of 215 Sprague-Dawley rats underwent transection of the patellar tendon at the inferior pole of the patella, which was subsequently stabilized with a cerclage suture. The animals were then randomized into 7 groups and administered 1 of the following analgesics for 14 days: ibuprofen, acetaminophen, naproxen, piroxicam, celecoxib, valdecoxib, or control. At 14 days, all animals were sacrificed, and the extensor mechanism was isolated and loaded to failure. Biochemical analysis of the repair site tissue was performed. Animal activity throughout the study was monitored using a photoelectric sensor system. Results: The control group demonstrated greater maximum load compared with the celecoxib, valdecoxib, and piroxicam groups (P <.05). The acetaminophen and ibuprofen groups were also significantly stronger than the celecoxib group (P <.05) but not statistically different than the control group. A total of 23 specimens had failure of the cerclage suture with the following distribution: control (0/23), ibuprofen (0/23), acetaminophen (0/24), naproxen (3/24), piroxicam (4/24), celecoxib (6/22), and valdecoxib (10/24). The difference in distribution of the failures was significant (P <.001). Conclusions: Anti-inflammatory drugs, with the exception of ibuprofen, had a detrimental effect on healing strength at the bone-tendon junction as demonstrated by decreased failure loads and increased failures of the cerclage suture. Acetaminophen had no effect on healing strength. The biomechanical properties paralleled closely with the total collagen content at the injury site, suggesting that these agents may alter healing strength by decreasing collagen content. Clinical Relevance: Selective and nonselective cyclooxygenase (COX) inhibitors should be used judiciously in the acute period after injury or surgical repair at the bone-tendon junction.