Reliability and validity of angle measurements using radiograph and smartphone applications: experimental research on protractor

Abstract

[Purpose] The present study aimed to demonstrate the following by using measurements for the definite angles provided by the digital protractor: inter-rater reliability and validity in radiograph measurements and smartphone application measurements. [Subjects and Methods] The subject angles were 26 angles between 15° and 180° that were selected randomly using a computer. Three examiners measured the angles using the radiograph and smartphone application. The radiograph was obtained at a position 250 cm from the chest shooting cassette holder. The smartphone photograph was obtained at positions 50, 100, 150, 200, and 250 cm from the holder. [Results] Under all conditions, intra-class correlation coefficients showed 0.999. The correlation coefficient was 0.999 for all conditions. The mean absolute difference to the protractor was ≤0.28° for all conditions. [Conclusion] In comparison with the protractor, radiograph measurements and smartphone application measurements, the results of the present study showed high inter-rater reliability, validity, and small error. The results indicated that radiograph and smartphone application measurements could be used as criteria of validity in angle measurements. It supported the legitimacy of high-quality previous studies that used radiograph measurements as a criterion for validity.

Development of a Manual Measurement Device for Measuring Hallux Valgus Angle in Patients with Hallux Valgus

“…The results of statistical analysis show that the intra-class correlation coefficients (ICCs) between X-ray and an average of twice-repeated manual measurements were 0.868, with a 95% CI of 0.649, 0.947 ( p = 0.000), which indicates that there is good correlation between X-ray and the manual measurement method. Based on previous reports by Awatani et al [ 11 ] and Nix et al [ 21 ] with respect to the smartphone or photographic measurement method, we also found that measurement using the newly designed device matched the smartphone measurement method in terms of ICC correlation to X-ray measurement. Therefore, the new measurement device achieved good reliability in measuring HVA.…”

“…HVA is the angle between the longitudinal axes of the first metatarsal and the proximal phalanx of the big toe. IMA is the angle between the longitudinal axes of the first and second metatarsals, whereas DMAA is the angle between the longitudinal axis of the first metatarsal and a line through the distal articular surface of the first metatarsal [ 11 ]. Surgeons consider all angles (HVA, IMA and DMAA) to assess the severity of HV in clinical practice if an X-ray photograph is available.…”

“…In recent years, many measuring devices have developed to measure HVA, including radiological measurement [ 13 , 14 ], smartphone measurement [ 11 , 15 , 16 , 17 ], footprint measurement [ 18 ] and digital photographs [ 19 , 20 , 21 ]. Radiological measurement is regarded as an accurate and commonly used tool in diagnosis and identification of the severity of HV.…”

Accuracy and reliability of a smartphone application for measuring the knee joint angle

“…In addition, it can measure angles without having contact with the patient, which is not only desirable in preventing infection but for remote diagnosis as well. It has been confirmed in the laboratory that angles can be accurately measured using photographs taken with smartphones 24 ) . However, angular measurements of a photo-based smartphone application might be inaccurate if the photo was taken in the wrong orientation 10 ) .…”