Comparison of Angle Measurements on Hallux Valgus with Two Different Methods Using Digital Images

Purpose: To study inter- and intra-observer reliabilities of computerized measurements of the angular parameters of hallux valgus deformity, using two different kinds of software tools for angle measurement on the digital radiography. Materials and Methods: On 35 digital radiographies of standing foot anteroposterior view of hallux valgus, two observers (A, B) independently measured hallux valgus angle (HVA) and 1-2 intermetatarsal angle ($IMA_{1-2}$) twice, using two methods. In method I, an angle was determined from duplicated lines to longitudinal axes made for bisecting line on the target bones with software tool. In method II, an angle was calculated automatically and directly from bisecting lines (longitudinal axes) made on the target bones. We compared two methods using paired t-test to determine significance of differences. Inter- and intraobserver reliabilities were evaluated using the intraclass correlation coefficients (ICC). Results: There were no significant differences between measurements of method I and II for each observer (p>0.05) and intraobserver reliability were good. (ICC>0.9) Inter-observer reliability for method I and II was good of the HVA (ICCs, 0.912 and 0.905) and moderate of the $IMA_{1-2}$ (ICCs, 0.505 and 0.537). There were interobserver differences in HVA of method I and II. Conclusion: No significant difference was found statistically between measurements of method I and II. Both methods I and II would be acceptable to measure angular parameters of hallux valgus deformity.

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