Reliability of Intrinsic and Pose-dependent Spinal Deformity Measurements using Full-body Topographic Scans
2Department of Mechanical Engineering, Technion-Israel Institute of Technology, Israel
3Department of Orthopaedic Surgery, Boston Children's Hospital, USA
Introduction:
Adolescent Idiopathic scoliosis (AIS) often presents with several externally visible characteristics including waist crease asymmetry, uneven shoulder height, and chest wall asymmetry. Surface topography enables the measurement of these external characteristics without exposure to radiation. In this study, we investigate the reliability of the 3dMD system and automated topographic measurements on spinal deformity patients and controls.
Methods:
Individuals with spinal deformity and healthy controls were recruited. Subjects were scanned repeatedly by two investigators in several dynamic poses using 3dMD. Clinically relevant poses were selected for analysis. An automated pipeline computed several 3D measurements which were categorized as intrinsic or pose-dependent. Intrinsic measurements are constant after rigid transformations, while pose-dependent measurements are sensitive to orientation or postural changes. Intrinsic measurements computed were spine length, back area, cross-sectional area, and section volume. Pose-dependent measurements computed were angle of trunk rotation, centroid deviation, trunk axis, and Qangle. Intraclass correlation coefficients were computed for each pose and measurement.
Results:
Forty-six subjects participated in this study. Demographics are shown in Table 1. Intra-rater reliability and inter-rater reliability of all surface topographic measurements were highly reliable with 80% of all ICC values ≥ 0.90. Table 2 shows mean ICC values for intra-rater and inter-rater reliability of intrinsic and pose-dependent measurements across all poses and measurements.
Discussion and Conclusion:
High reliability of intrinsic measurements demonstrates that this system can reliably measure well defined surface parameters. The moderate reliability of pose-dependent measurements shows that these measurements must be taken in well-defined poses to be useful. Clinical spine deformity surface measurements can be reliably measured in a fully automated system, enabling objective analysis of symmetry and body shape over the course of treatments without exposure to ionizing radiation.