A novel rapid measurement of hallux valgus parameters using the built-in photo edit function of smartphones

OBJECTIVE: The objective of this study was to assess the accuracy and reliability of and time taken by a novel method using the built-in photo-edit function of smartphones compared with PACS in measuring hallux valgus parameters. METHODS: Seventy patients (124 ft) admitted to our hospital with a diagnosis of hallux valgus without previous surgical procedures were retrospectively reviewed. The foot radiographs of all the patients were extracted from PACS. The hallux valgus angle (HVA) and the first and second intermetatarsal angles (IMAs) were measured by PACS and by this novel method using the built-in photo-edit function of a smartphone. The results of these two methods were compared, and the accuracy and reliability were assessed between these two methods. RESULTS: The average parameters measured by PACS were as follows: HVA average: 37.43 ± 9.61°; IMA average: 13.37 ± 4.01°. The average parameters measured by smartphones were as follows: HVA average: 37.09 ± 9.52° and IMA average: 13.49 ± 3.91°. When compared by the independent-samples T test, the average parameters between PACS and smartphones were not significantly different (HVA PACS vs HVA smartphones: P = 0.776; IMA PACS vs IMA smartphones: P = 0.816). The variability of the HVA (F = 0.166, P = 0.992) and IMA (F = 0.215, P = 0.982) measurements was similar for the PACS and smartphones. The ICCs of the average parameters of four measurements of HVA and IMA between PACS and smartphones were 0.995 (0.991–0.997) and 0.970 (0.958–0.979), indicating that the two methods were highly correlated. For the smartphone measurement, the interobserver and intraobserver reliability was very good for HVA and IMA. The average measurement time of PACS was 25.41 ± 0.86 s, and the average measurement time of smartphones was 20.29 ± 1.22 s. The smartphone time was significantly faster than that of PACS by approximately 5 s (P<0.001). CONCLUSION: This novel method using the built-in photo-edit function of smartphones is accurate, reliable, convenient and time-saving in measuring the angles of hallux valgus.