Non-Radiographic Measurement of Hallux Valgus Angle Using Self-Photography.

Background The reference standard of hallux valgus angle measurement is to use radiographs of the feet. However, its availability is constrained due to cost and radiation exposure. Less invasive non-radiographic assessments have been proposed. However, a measurement using self-photography has not been reported. Objectives To determine 1) the reliability of hallux valgus angle measurement using the same photographs of the feet (pHVA), 2) the reliability of repeated self-photography trials, and 3) the measurement error when the radiographic hallux valgus ankle (rHVA) was estimated using pHVA. Methods Participants took photographs of their own feet using a digital camera. The intra- and interrater reliability of pHVA measurements was assessed using intraclass correlation coefficient (ICC) and 95% minimum detectable change (MDC). The participants took photographs twice, and the reliability of repeated self-photography trials was examined. Participants also received radiographs of their feet from which the rHVA was measured. The measurement error was assessed using the mean difference and 95% limits of agreement. Results The intra- and interrater ICC of pHVA measurement was 0.98, with the MDCs less than 2°. The ICC of pHVA measurement for repeated self-photography was 0.96, and the MDC was 6.9°. pHVA was systematically lower than the rHVA by 5.3°. Conclusion Measurement of pHVA using self-photography was reproducible, although pHVA underestimated rHVA. pHVA can be a useful non-radiographic method to quantify hallux valgus deformity. J Orthop Sports Phys Ther, Epub 12 Sep 2018. doi:10.2519/jospt.2019.8280.