| Objective To explore the improved method of measuring foot force line X-ray and analyze changes in plantar contact area, as well as its evaluation value for patients with flat feet. Methods A retrospective analysis was conducted on the clinical data of 200 patients with suspected flat feet admitted to our hospital between January 2023 and December 2024. Based on diagnoses from a 3D foot scanner, the patients were classified into 117 cases of flat feet(166 feet; study group) and 83 cases of normal feet(166 feet; control group). The differences in modified hindfoot alignment X-ray measurements and plantar contact area were compared between the two groups at different projection angles. Additionally, receiver operating characteristic(ROC) curve analysis was used to evaluate the diagnostic value of modified hindfoot alignment X-ray measurements and plantar contact area for flatfoot diagnosis at different projection angles. Results The X-ray measurements of the improved foot force line in the research group were higher than those in the control group at projection angles of 10°, 15°, and 20°(P<0.05). There was no statistically significant difference in the contact area of the forefoot between the two groups(P>0.05). The contact area of the forefoot in the study group was higher than that in the control group, while the contact area of the hind foot was lower than that in the control group(P<0.05). Binary logistic multiple regression analysis showed that the improved foot force line X-ray measurement at a projection angle of 10°, the improved foot force line X-ray measurement at a projection angle of 15°, the improved foot force line X-ray measurement at a projection angle of 20°, the contact area of the midfoot, and the contact area of the hind foot were all factors affecting a flat foot(P<0.05). ROC curve analysis showed that the area under the curve(AUC) for diagnosing flatfoot using the modified hindfoot alignment X-ray measurements at projection angles of 10°, 15°, and 20°, as well as the midfoot and hindfoot contact areas, was 0.870, 0.828, 0.800, 0.750, and 0.594, respectively, with sensitivities of 57.2%, 51.8%, 100.0%, 100.0%, and 89.8%, respectively, and specificities of 100.0%, 100.0%, 50.0%, 50.0%, and 38.0%, respectively. The AUC for diagnosing flatfoot using the five combined variables was 0.992, with sensitivity and specificity of 97.6% and 94.6%, respectively. Conclusion The improved foot force line X-ray measurement, midfoot contact area, and hindfoot contact area have certain value in diagnosing flat feet at projection angles of 10 °, 15 °, and 20 °, and the combined diagnostic value is more effective. |
