Hawkins Sign of the Talus: The Impact of Patient Factors on Prediction Accuracy

Introduction/Purpose: Avascular necrosis (AVN) is a complication of talar neck fractures associated with chronic pain and poor functional outcomes. Hawkins sign, the radiographic presence of subchondral lucency seen in the talar dome 6 to 8 weeks after trauma, is considered to be a strong predictor of preserved talus vascularity. The study sought to assess the accuracy of the Hawkins sign in a large, contemporary cohort and assess factors associated with inaccuracy. Methods: A retrospective review of all talar neck fractures from a single level I trauma center from 2008 to 2016 was performed. The presence of Hawkins sign and AVN were determined based on ankle radiographs 8 weeks after injury and at final follow-up, respectively. Patients with less than 6 months follow-up were excluded. Hawkins sign accuracy was assessed using proportions with 95% confidence intervals (C.I.) and associations were examined with Fisher’s exact testing. Results: In total, 137 talar neck fractures were identified with 105 having adequate follow-up. Hawkins sign was observed in 21 tali, 3 (14%) of which later developed AVN (95% C.I., 3 – 36%). In the remaining 84 tali without Hawkins sign, 32 (38%) developed AVN (95% C.I., 28 – 49%). Of the 3 tali that developed AVN following observation of Hawkins sign, all patients were smokers. There were no cases of AVN in non-smokers with Hawkins sign (P=0.21), and smoking was not associated with AVN in patients without Hawkins sign (41% vs 36%, P=0.82). Conclusion: Hawkins sign may not be a reliable predictor of preserved talus vascularity in all patients. We identified three patients with positive Hawkins signs who developed AVN, all of whom were smokers. Factors impairing microvascular blood supply to the talus may lead to AVN even in the presence of preserved macrovascular blood flow and an observed Hawkins sign. Close monitoring of select patients with Hawkins sign should be considered and further research is needed to understand the factors limiting Hawkins sign accuracy. Prognostic accuracy of the Hawkins sign in predicting talar AVN