Effect of indomethacin on fracture healing in rats.

The healing of closed, non-immobilized femoral fractures in rats was seriously impaired by indomethacin given orally at a dose of 2 mg/kg daily. The fracture haematomas were larger and disappeared later in the animals receiving indomethacin. Mechanical strength testing of fracture healing showed that maximal tensile strength, elastic stiffness and maximal bending moment between fragments were significantly diminished in the indomethacin-treated animals. Radiological examination showed a smaller amount of mineralized callus and a more pronounced angulation between the fragments in these animals than in the placebo-treated ones. Hsitological examination showed bridging between the fragments by callus tissue 24 days after fracture in placebo-treated animals, whereas indomethacin treatment was followed by histological findings resembling those seen in early pseudarthrosis development.