Nationwide study on the risk of unprovoked venous thromboembolism in non-traumatic osteonecrosis of femoral head

Purpose: Endothelial dysfunction is a risk factor for osteonecrosis of femoral head (ONFH) and venous thromboembolism (VTE) [defined as deep venous thrombosis (DVT) or pulmonary embolism (PE)]. However, the risk of unprovoked VTE in non-traumatic ONFH patients remains unclear. Methods: We investigated the relationship between ONFH and VTE using Taiwan National Health Insurance Research Database (NHIRD). Between 1997 and 2010, a total of 1514 non-traumatic ONFH patients were identified from 1,000,000 general populations after excluding initially concomitant diagnoses of DVT and PE, and subjects undergoing lower limb surgery within one year since enrollment. The comparison group (n = 15,140) without ONFH was set up by matching study cohort with age, gender, income and urbanization in a 1:10 ratio. Subjects diagnosed with VTE within one year after surgery were also excluded. Results: The patients with non-traumatic ONFH had significantly higher frequency of unprovoked VTE, including DVT, than general population (1.19 vs. 0.5%, p < 0.0007), whereas the frequency of PE was similar between these two groups (p = 0.4922). The cumulative incidence of VTE and DVT was also remarkably higher in the ONFH than non-ONFH group (all p < 0.001). After adjusting for age, gender, medications and comorbidities with multivariate analysis, the ONFH patients had a 2.3-fold increase in risk of DVT compared with non-ONFH counterparts (95% CI 1.28 to 4.13, p = 0.0053). Apart from ONFH, age > 65 years and hypertension were also identified as risk factors for DVT occurrence. Conclusions: The incidence and risk of unprovoked VTE were significantly increased in the non-traumatic ONFH population.