The effect of indomethacin on Achilles tendon healing in rabbits

In a randomized, blind study, percutaneous tenotomy was performed on the right Achilles tendon complex of 32 male, New Zealand rabbits. The rabbits were placed in long-leg casts to approximate the tendon. Sixteen rabbits received oral therapeutic doses (1.5 mg/kg/day) of indomethacin elixir; the remaining 16 rabbits received no medication and comprised the control group. At two and six weeks following tenotomy, eight rabbits in each group were sacrificed and the Achilles tendon complexes were resected. Each tendon was evaluated for tensile force-to-failure by uniaxial tensile loading using an Instron Materials Testing Machine at a velocity of 0.85 cm/second. Histologic evaluation assigned the specimens to categories of either "relatively mature" or "relatively immature," based on the degree of cellularity, neovascularity, and collagen orientation that had occurred in the healing process. The mean force-to-failure two weeks post-tenotomy for the experimental group was 75.7 +/- 42.3 Newtons (N), and 96.6 +/- 35.2 N for the control group; at six weeks post-tenotomy, the mean force-to-failure for the experimental group was 165.5 +/- 34.3 N and 160.2 +/- 31.6 N for the control group. Statistical analysis revealed no significant differences in tensile force-to-failure or histologic appearance between the experimental and control groups at either time interval. These results suggest that indomethacin, and potentially other nonsteroidal antiinflammatory drugs, may be used in conjunction with a tendon injury without significantly affecting the early healing process.