Clopidogrel Influences Fracture Healing Under Ischemic Conditions

Background/Objectives: Patients suffering from fractures are often treated with clopidogrel during the phase of bone healing due to multiple comorbidities. Studies indicate that clopidogrel suppresses osteoblast proliferation and the formation of trabecular bone. However, it is unknown whether clopidogrel also affects fracture healing under ischemic conditions, as they may occur in multimorbid patients. Methods: To test this in the present study, a murine ischemia model was performed in CD-1 mice by ligating the right deep femoral artery to induce mild ischemia of the right lower limb. A closed fracture of the femur was then stabilized by inserting an intramedullary lag screw. The animals received either 3 mg/kg body weight clopidogrel daily per os or vehicle (control). Bone healing was assessed by biomechanical, radiological, histomorphometrical and Western blot analyses 2 and 5 weeks postoperatively. Results: The fractured femurs in the clopidogrel group exhibited no increase in biomechanical stiffness throughout the observation period in contrast to controls. While the radiological analysis showed no differences between both groups, histomorphometric analyses demonstrated a significantly reduced bridging score, less bone and more connective tissue within the callus of clopidogrel-treated animals. Western blot analyses revealed a significantly reduced expression of the osteogenic marker bone morphogenetic protein (BMP)-4 and an increased expression of the blood vessel marker CD31. Conclusions: These results show that clopidogrel may impair fracture healing under challenging ischemic conditions, which is associated with a shift in angiogenic and osteogenic expression markers in the callus tissue. Therefore, clopidogrel treatment may not be recommended in fracture patients with tissue ischemia.