Modified Ankle-Hindfoot Alignment Radiological Evaluation Method and Application in the Flatfeet

CATEGORY: Hindfoot INTRODUCTION/PURPOSE: Based on a prospective study, a new method of photographing and measuring of hindfoot alignment based on X-ray was proposed, and its reliability is verified, as well as its application in flatfeet. METHODS: This study included 28 patients (40 feet) with flatfeet and 20 volunteers (40 feet) from January to December in 2018. The shooting frame, designed by our team, has been used to take the hindfoot alignment view at 10°, 15°, 20°, 25°, 30° respectively. Our modified tibio-hindfoot angles (THA) at standard Saltzman position (shooting at 20°) were evaluated, and the consistency were compared with the van Dijk method and the modified van Dijk method, and compared with weight-bearing CT. The visibility of tibiotalar space were evaluated in all shooting angles. The consistency of the modified THA method at different projection angles were evaluated. The angle of hindfoot valgus of flatfoot patients was measured with use of the modified THA method, and compared in different shooting angles. RESULTS: The mean THA in standard Saltzman view in normal people were significantly differences between the three evaluation methods (P < 0.001). The results of modified THA method were significantly larger than those of Van Dijk method (P < 0.001) and modified Van Dijk method (P < 0.001). There was no significant difference between the results of modified THA method and the weight-bearing CT (P=0.605), and the intra- and inter-group consistency was the best in modified THA group. The tibiotalar space in the normal group were visible in all cases at 10°, 15°, 20°; and visible in some cases at 25°; and invisible in all cases at 30°. In the flatfoot group, the tibiotalar space were visible in all cases at 10°; and in some cases at 15° and 20°; and invisible in all cases at 25° and 30°. In the normal group, the modified THA was 4.84±1.81° at 10°, 4.96±1.77° at 15°, 4.94±2.04° at 20°. No significant difference was found between the three groups (P=0.616). In the flat foot group, the modified THA of 18 feet, which was visible at 10°, 15° and 20°, was 13.58±3.57° at 10°, 13.62±3.83° at 15° and 13.38±4.06° at 20°. There was no significant difference between the three groups (P=0.425). CONCLUSION: The modified THA evaluation method is simple to use and has high intra- and inter-group consistency. It can be used to evaluate hindfoot alignment. For patients with flatfeet, the 10° position view and modified THA measurement can be used to evaluate the hindfoot valgus conditions.