Effect of tadalafil and COMB-4 on inducible nitric oxide synthase (iNOS) expression at day 14 and day 42 after femoral osteotomy determined by immunohistochemistry. Microphotographs of iNOS expression taken at the osteotomy site: a) and b) are control; c) and d) are tadalafil; e) and f) are COMB-4. Panels (a), (c) and (e) depict 14-day results and panels (b), (d) and (f) depict 42-day results.