Changes in serum levels of TNF-α, IL-6, OPG, RANKL and their correlation with radiographic and clinical assessment in fragility fractures and high energy fractures

Background: Stages of bone turnover during fracture repair can be assessed employing serum markers of osteoblastic and osteoclastic activity, inflammatory cytokines, clinical evaluation and imaging instruments. Our study compares the fracture healing process in fragility fractures and high energy fractures by evaluating serum changes of IL-6, TNF-α, OPG and RANK-L in combination with radiographic (RUST) and clinical (LEM) assessments. Methods: Subjects: femoral or tibial shaft fractures (group A,14), femoral fractures (group B,14), healthy (control A,14) and osteoporotic subjects (control B,14). Serum concentrations of IL-6, TNF-α werequantified by quantikine R&D Systems, RANK-L by BioVendor and OPG by Biomedica Medizinprodukte. Results: Results showed a significant decrease in IL-6 and TNF-α during fracture healing, with their values higher in group A than B and lower in both controls compared to T0 (before surgery). OPG was significantly lower in each control group than that of the respective fractured group. In addition, OPG at T0A was significantly lower than at T0B whereas at T10A (after 10 weeks) OPG was less than at T10B. RANKL was significantly higher at T10 than at T0 only in group B. RANKL/OPG ratio was significantly higher in both controls than in fractured groups and significantly increased at T10. IL-6 and TNF-α correlated with RUST and LEM in fragility fractures and high energy fractures, whereas RANKL/OPG ratio was associated with these parameters only in fragility fractures. Conclusions: Our findings suggest that these serum parameters might be used to assess the stages of fracture healing. Further studies are required to clarify the complex fracture healing process.