Background:The effect of selective and non-selective cyclooxygenase (COX) inhibitors on tendon healing was variable.The purpose of the study was to evaluate the influence of non-selective COX inhibitor,ibuprofen and flurbiprofen axetil and selective COX-2 inhibitor,celecoxib on the tendon healing process in a rabbit model.Methods:Ninety-six New Zealand rabbits were used as rotator cuff repair models.After surgery,they were divided randomly into four groups:Ibuprofen (10 mg·kg-1·d-1),celecoxib (8 mg·kg 1·d 1),flurbiprofen axetil (2 mg·kg 1·d-1),and control group (blank group).All drugs were provided for 7 days.Rabbits in each group were sacrificed at 3,6,and 12 weeks after tendon repair.Tendon biomechanical load failure tests were performed.The percentage of type Ⅰ collagen on the bone tendon insertion was calculated by Picric acid Sirius red staining and image analysis.All data were compared among the four groups at the same time point.All data in each group were also compared across the different time points.Qualitative histological evaluation of the bone tendon insertion was also performed among groups.Results:The load to failure increased significantly with time in each group.There were significantly lower failure loads in the celecoxib group than in the control group at 3 weeks (0.533 vs.0.700,P =0.002),6 weeks (0.607 vs.0.763,P =0.01),and 12 weeks (0.660 vs.0.803,P =0.002),and significantly lower percentage of type Ⅰ collagen at 3 weeks (l 1.5％ vs.27.6％,P =0.001),6 weeks (40.5％ vs.66.3％,P =0.005),and 12 weeks (59.5％ vs.86.3％,P =0.001).Flurbiprofen axetil showed significant differences at 3 weeks (failure load:0.600 vs.0.700,P =0.024;percentage of type Ⅰ collagen:15.6％ vs.27.6％,P =0.001),but no significant differences at 6 and 12 weeks comparing with control group,whereas the ibuprofen groups did not show any significant difference at each time point.Conclusions:Nonsteroidal anti-inflammatory drugs can delay tendon healing in the early stage after rotator cuff repair.Compared with nonselective COX inhibitors,selective COX-2 inhibitors significantly impact tendon healing.