Validity of a smartphone protractor to measure sagittal parameters in adult spinal deformity

Publication date: Available online 14 August 2017
Source:The Spine Journal
Author(s): William Aaron Kunkle, Michael Madden, Shannon Potts, Jeremy Fogelson, Stuart Hershman
Background ContextSmartphones have become an integral tool in the daily life of healthcare professionals (Franko 2011). Their ease of use and wide availability often make smartphones the first tool surgeons use to perform measurements. This technique has been validated for certain orthopaedic pathologies (Shaw 2012, Quek 2014, Milanese 2014, Milani 2014), but never to assess sagittal parameters in adult spinal deformity. This study was designed to assess the validity, reproducibility, precision and efficiency of using a smartphone protractor application to measure sagittal parameters commonly measured in adult spinal deformity assessment and surgical planning.Purpose1) determine the validity of smartphone protractor applications, 2) determine the intra- and inter-observer reliability of smartphone protractor applications when used to measure sagittal parameters in adult spinal deformity, 3) determine the efficiency of using a smartphone protractor application to measure sagittal parameters, 4) elucidate whether a physician's level of experience impacts the reliability or validity of using a smartphone protractor application to measure sagittal parameters in adult spinal deformity.Study Design/SettingExperimental Validation StudyMethodsThirty standard 36" standing lateral radiographs were examined. Three separate measurements were performed using a marker and protractor; then at a separate time point, three separate measurements were performed using a smartphone protractor application for all thirty radiographs. The first ten radiographs were then remeasured two more times, for a total of three measurements from both the smartphone protractor and marker and protractor. The parameters included lumbar lordosis, pelvic incidence, and pelvic tilt. Three raters performed all measurements - a junior level orthopaedic resident, a senior level orthopaedic resident, and a fellowship trained spinal deformity surgeon. All data, including the time to perform the measurements, was recorded and statistical analysis was performed to determine intra- and inter-observer reliability, as well as accuracy, efficiency and precision. Statistical analysis utilizing the intra- and inter-class correlation coefficient (ICC) was calculated using R (version 3.3.2, 2016) to determine the degree of intra- and inter-observer reliability. The study required no outside funding and there were no financial conflicts of interest associated with any part of the study.ResultsHigh rates of intra- and inter-observer reliability were observed between the junior resident, senior resident and attending surgeon when using the smartphone protractor application as demonstrated by a high ICC - 0.881-0.976. High rates of inter- and intra- observer reliability were also seen between the junior resident, senior resident and attending surgeon when a marker and protractor were used as demonstrated by ICC values between 0.903-0.954. The lumbar lordosis, pelvic incidence, and pelvic tilt values were accurately measured by all three raters with ICC values above 0.87. When the first ten radiographs were remeasured at different time points, a high degree of precision was noted. Measurements performed using the smartphone application were consistently faster than using a marker and protractor - this difference reached statistical significance -p <0.05.ConclusionsAdult spinal deformity radiographic parameters can be measured accurately, precisely, reliably, and more efficiently using a smartphone protractor application than with a standard protractor and wax pencil. A high degree of intra and inter observer reliability was seen between the residents and attending, indicating measurements made with a smartphone protractor are unaffected by an observers level of experience. As a result, smartphone protractors may be used when planning adult spinal deformity surgery.



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