Comparison between Oxford Cobbmeter and digital Cobbmeter for measurement of Cobb angle in adolescent idiopathic scoliosis

The purpose of this study was to compare Cobb angle measurements performed using an Oxford Cobbmeter and digital Cobbmeter in a series of 20 adolescent idiopathic scoliosis (AIS) patients. Four observers measured major Cobb angles on 20 standing postero-anterior radiographs of AIS patients with both Oxford Cobbmeter and digital Cobbmeter (iPhone Cobbmeter Application). The measurements were repeated a week after the original measurements. The mean Cobb angle in this study was 43.6A degrees A A +/- A 23.62A degrees. The mean measurement time for an observer to measure the 20 Cobb angles was 24.9 min for the smart phone compared with 25.6 min for the Oxford Cobbmeter. The 95 % confidence interval for differences between smart phone and Oxford Cobbmeter measurements on the same radiograph was +/- 3.68A degrees. The intra-observer variability of the smart phone is equivalent to the Oxford Cobbmeter. The 95 % confidence intervals for inter-observer error were +/- 5A degrees and +/- 5.8A degrees for the smart phone and Oxford Cobbmeter, respectively. We conclude that the smart phone with integrated Tiltmeter and Cobbmeter application is an equivalent Cobb measurement tool to the Oxford Cobbmeter. The advantages of smart phone are the accuracy of determining the most inclined vertebrae and accordingly more precise Cobb angle measurement. The new smart phones with these integrated applications may be really helpful to the spine surgeons, especially in hospitals where PACS or Oxford Cobbmeter is not available.