Abstract
Introduction
Previous studies have evaluated the validity and reliability of the Formetric-4D system. They concluded to a good accuracy compared with radiographs and a high intra- and inter-day reliability in healthy volunteer patients. However, to the best of our knowledge, the validity and reliability were not assessed on patients with Adolescent Idiopathic Scoliosis (AIS). Therefore, the aim of this study was to evaluate the validity and reliability of the Formetric 4D system on AIS adolescent patients with Cobb between 10¡ and 40¡ in terms of sagittal, frontal and transverse parameters.
Materials and Methods
This study included 35 AIS adolescents (male=13) aged 13.1 ± 2.0 years. To evaluate the validity of scoliosis angle (SA) provided by the Formetric-4D System, a comparison was performed with the Cobb Angle of major curve (CA) on a 2D EOS¨ radiography (XR). Mean differences of measurements computed by each system were evaluated using paired Student t-test and Pearson correlation coefficient. To evaluate interrater reliability three repeated-measurements were independently performed in a neutral orthostatic position using the Formetric-4D System by two operators the same day. To evaluate the intrarater reliability three more repeated-measurements were performed by the first operator one week later. The parameters measured were vertebra surface rotation, thoracic kyphosis, lumbar lordosis, pelvic obliquity, trunk length and the scoliosis angle. The data analyses used were Intraclasse Correlation Coefficients (ICC).
Results
The 2D radiographic Cobb Angle (CA) and its rasterstereographic equivalent Scoliosis Angle (SA) were strongly correlated (R = 0,70) with a non-significant difference. The ICC for intrarater (same day: ICC (1, 1), n = 35, one week later: ICC (1, 3), n = 29) as interrater reliability coefficients (ICC (3, 3), n = 16) were excellent (ICC > 0.75) for all variables except for pelvic obliquity with the highest for sagittal and rotation parameters and lowest for the pelvis obliquity.
Conclusion
This study showed that the Formetric 4D system allows evaluating AIS patients with a good validity and an overall excellent intra- and interrater reliability. Based on these results, this automatic, fast and non-invasive system will not replace XR clinical analysis but it can reduce the exposure to radiation for the patients and can improve the monitoring of scoliosis evolution with no limits of use, no risks for patients and at lower price than XR.