Measuring Cobb's Angle in Scoliosis: Can Smartphones Match Manual Methods and Software Based Analysis? A Three Way Crossover Study

Abstract

Introduction Cobb's angle in scoliosis has been widely accepted to analyze the extent of deformities and can be used as an indicator of the degree of correction obtained following a corrective surgery. Measurement has traditionally been manual using a pencil and protractor on radiographs. Smartphones have changed the way we live in every field of life. Use of apps in smartphones with accelerometers aids to measure the angle quickly. This study analyzes the accuracy and efficiency of the inclinometer app in smartphones to measure cobb's angle in scoliosis. Material and Methods We analyzed cobb's angle in scoliotic patients who underwent robotic guided corrective surgery at our center over the past 2 years. The Cobb angle measure tool in the software used in robotic surgery (Renaissance, Mazor robotics) was used as the gold standard (GS) as it was software based analysis. Clinometer app was used in the smartphone by the primary observer over the computer screen to measure the cobb angle and then manual method was used. Time taken to measure using both the techniques was noted by other observers. Another two observers then independently measured the angle using their smartphones to assess the interobserver variability. Data was tabulated and analyzed by a biostatistician. Results Cobb angle of 25 patients with mean age of 14.1 years were analyzed for primary and secondary curves separately. The mean Cobb angle of all measured X-rays was 48.9 degrees in the manual set and 47.9 degrees in the smartphone set as compared with 48.2 degrees as per GS. The mean time consumed was 13.5 seconds for the smartphone set, significantly shorter than that of the manual set which was 36.2 seconds (statistically significant – p < 0.05). 95% confidence intervals for inter-observer variability using smartphones were ±1.5degrees. Conclusion Cobb angle measurement using the smartphones was more accurate than the manual methods in our study. With significant time difference between the methods indicating the simplicity of the use of apps in our daily use and the minimal interobserver variability, smartphones indeed can replace the manual methods and can be a reliable tool in the hands of spinal deformity surgeons.