Chemokine analysis as a novel diagnostic modality in the early prediction of the outcome of non-union therapy: A matched pair analysis

Abstract

Background: Despite the regenerative capability of skeletal tissue fracture, non-union is common. Treatment of non-unions remains challenging, and early determination of the outcome is impossible. Chemokines play an important role in promoting the formation of new bone and remodeling existing bone. Despite their importance regarding the regulation of bone biology, the potential of chemokines as biological markers reflecting osseous regeneration is unknown. The purpose of this study was to determine (1) if serum chemokine expression levels correlate with the outcome of non-union surgery and (2) if chemokine expression analysis can be used to identify patients at risk for treatment failure. Methods: Non-union patients receiving surgical therapy in our institution between March 2012 and March 2014 were prospectively enrolled in a clinical observer study. Regular clinical and radiological follow-up was conducted for 12months including collection of blood during the first 12weeks. Based on the outcome, patients were declared as responders or non-responders to the therapy. To minimize biases, patients were matched (age, sex, body mass index (BMI)) and two groups of patients could be formed: responders (R, n=10) and non-responders (NR, n=10). Serum chemokine expression (CCL-2, CCL-3, CCL-4, CXCL-10, CCL-11, and interferon gamma (IFN-γ)) was analyzed using Luminex assays. Data was compared and correlated to the outcome. Results: CCL-3 expression in NR was significantly higher during the course of the study compared to R (p=0.002), and the expression pattern of CCL-4 correlated with CCL-3 in both groups (NR: p<0.001 and r=0.63). IFN-γ expression in NR was continuously higher than in R (p<0.001), and utilization of CCL-3 and IFN-γ serum expression levels 2weeks after the treatment resulted in a predictive model that had an AUC of 0.92 (CI 0.74-1.00). Conclusion: Serum chemokine expression analysis over time is a valid and promising diagnostic tool. The chemokine expression pattern correlates with the outcome of the Masquelet therapy of lower limb non-unions. Utilization of the serum analysis of CCL-3 and IFN-γ 2weeks after the treatment resulted in an early predictive value regarding the differentiation between patients that are likely to heal and those that are prone to high risk of treatment failure.