Reliability and validity of angle measurements using radiograph and smartphone applications: experimental research on protractor.
Takenori Awatani, Taisuke Enoki, Ikuhiro Morikita
PMID 29184309WHAT IT FOUND
For photographed protractor angles set between 0° and 180°, a smartphone app and radiograph both stayed within 0.28 degrees of the target angle on average.
The app may help measure angle photos, but this study tested a tool, not patients.
Key findings
01The average absolute difference from the set protractor angle was no more than 0.28 degrees.
02The smallest change that could be counted as real between examiners was 0.99 degrees or less.
03The study measured photographed protractor angles, not human joint angles.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
No patients or body parts were measured; the subject was a digital protractor. The radiograph software could not measure four angles between 0° and 15°, so 26 of 30 angles were analysed. The examiners had no previous experience with radiograph or app angle measurement. The study did not test smartphone distances closer than 50 cm. Radiograph and app used the same captured images, so the study measured digitizing error, not independent clinical capture. The app images were edited and standardized to the 50 cm size, which may not reflect ordinary photo measurement.
Declared interests
The authors state that the research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
The easy way to misread this
Do not conclude that a smartphone app is ready to replace goniometer or radiograph measurements of patient range of motion. The study measured only photographed protractor angles, not human joints, and the authors say human body measurements still need study.