Assessing kyphosis with SpineScan: Another attempt to reduce our dependence on radiography

Background context: Kyphosis management is mainly conservative, with annual examinations to assess angular progression. This includes physical examination and usually long spine X-rays, notorious for ionizing radiation. Several nonradiological instruments have been devised for this, but none have become popular. SpineScan, a programmed digital inclinometer, has been proved effective for screening kyphoscoliosis. Purpose: The aim of this study was to assess the accuracy of SpineScan in monitoring kyphosis. Study design/setting: Prospective, observational, diagnostic accuracy study. Patient sample: Twenty-eight subjects examined for kyphosis, with recent full-length lateral spine X-rays. Methods: Each subject was examined by two examiners. The technique involved the subject standing with arms flexed to 90 and then sliding the SpineScan from just below C7 to L2. Maximum X-ray kyphotic Cobb angle was compared with the SpineScan result. The study was institutional review board approved, and all patients signed an informed consent. Results: The mean Cobb angle of the 28 subjects on radiography was 51 ±15. The mean SpineScan angle of all trials of all examiners was 54 ±12. The difference between the two measurements was significantly different from zero (3.2 ±9.4, p<.0001) and not normally distributed. The difference was significantly affected by the Cobb angle, examiner, and interaction between Cobb and examiner (statistical significance for all p<.0001). Ninety-five percent confidence intervals for all examiners ranged between -16 and 22 and for separate examiners between -25 and 32, far above the 5 preplanned error level. Conclusions: The results demonstrated that there is significant error in monitoring kyphosis with SpineScan. Even for a more modest indication including replacing radiography with SpineScan on alternate visits, the measurement was not accurate enough. Future research is necessary to find a nonradiographic method of kyphosis follow-up, possibly using a digitalized modification of one of the described instruments.