Spinal Palpation Error and Its Impact on Skin Marker-Based Spinal Alignment Measurement in Adult Spinal Deformity

Spinal alignment measurement in spinal deformity research has recently shifted from using mainly two-dimensional static radiography toward skin marker-based motion capture approaches, allowing three-dimensional (3D) assessments during dynamic conditions. The validity and accuracy of such methods is highly depending on correct marker placement. In this study we quantified, for the first time, 3D palpation error adult (ASD) compared it to healthy spines. Secondly, impact incorrect placement was investigated. 3D, mediolateral inferosuperior errors thoracolumbar lumbar vertebral levels were measured biplanar images by extracting positions skin-mounted markers their corresponding anatomical landmarks 20 ASD 10 control subjects. Relationships investigated between radiographic (lordosis scoliosis), as well body morphology [BMI soft tissue (ST) thickness]. Marker-based a previously validated method, which polynomial fit through trial allows radiograph-based position correction. To assess measurement, agreement lordosis scoliosis through, respectively, (1) uncorrected positions, (2) error-corrected (optimal) (3) anatomically corrected (toward body), equivalents expressed Cobb angles (ground truth), Spearman correlations root mean square (RMSE). results showed that, although overall level identification similar across groups, less accurate group (ASD : 6.8 mm; Control 2.5 p = 0.002). Significant with indicated that determining factors misplacement malalignment, particular scoliotic ( r 0.77; < 0.001), [i.e., increased BMI s 0.78; 0.008) ST thickness 0.66; 0.038)] Improved measurements after correction, shows need correction methods, therefore, should be considered when interpreting kinematics.