Vitamin D Binding Protein and Postsurgical Outcomes and Tissue Injury Markers After Hip Fracture: A Prospective Study

Context: Hip fracture is a serious injury that can lead to increased morbidity and mortality. Vitamin D binding protein (DBP) is a potential prognostic indicator of outcomes since it is important for actin scavenging and inflammation after tissue injury. Objective: To determine whether circulating DBP is associated with mobility or mortality after hip fracture and its association with acute tissue injury markers. Methods: Post hoc analysis of a multisite North American prospective study of 260 patients with hip fracture; mobility assessed at 30 and 60 days and mortality at 60 days after repair surgery. Biochemical markers were measured before, and 2 to 4 days after surgery. Tissue injury markers were measured in 100 randomly selected patients and controls. The primary outcome was mobility and mortality by DBP tertiles. Secondary outcomes were assessment of pre- and postoperative biomarkers. Results: Among all patients (81 +/- 9 years, BMI 25 +/- 4 kg/m(2); 72% female), the highest DBP tertile had greater mobility at 30 (OR: 2.66; 95% CI: 1.43, 4.92; P =.002) and 60 days (OR: 2.31; 95% CI: 1.17, 4.54; P =.014) and reduced mortality (OR: 0.18; 95% CI: 0.04, 0.86; P =.032) compared with the lowest DBP tertile (<28.0 mg/dL). Total 25-hydroxyvitamin-D did not differ between tertiles (22.0 +/- 9.5 ng/mL). Circulating DBP and gelsolin were lower and interleukin-6, C-reactive protein, and F-actin were higher (P <.01) in patients vs controls, and worsened (P <.01) after surgery. Conclusion: High circulating DBP concentrations are associated with better mobility and reduced mortality after hip fracture surgery. The role of DBP as an acute phase reactant to tissue injury and clinical outcomes should be addressed in future study.