Validity of sagittal thoracolumbar curvature measurement using a non-radiographic surface topography method

PURPOSE: To estimate the criterion validity of sagittal thoracolumbar spine measurement using a surface topography method in a clinical population against the gold standard and to estimate concurrent validity against two non-radiographic clinical tools. METHODS: In this cross-sectional validity study, thoracolumbar curvature was measured in adults with spinal conditions recruited from a specialist orthopaedic hospital. A surface topography method using a Kinect sensor was compared to three other measurement methods: spinal radiograph (gold standard), flexicurve and digital inclinometer. Correlation coefficients and agreement between the measurement tools were analysed. RESULTS: Twenty-nine participants (79% female) were included in criterion validity analyses and 38 (76% female) in concurrent validity analyses. The surface topography method was moderately correlated with the radiograph (r = .70, p < .001) in the thoracic spine, yet there was no significant correlation with the radiograph in the lumbar spine (r = .32, p = .89). The surface topography method was highly correlated with the flexicurve (r(s) = .91, p < .001) and digital inclinometer (r = .82, p < .001) in the thoracic spine, and highly correlated with the flexicurve (r = .74, p < .001) and digital inclinometer (r = .74, p < .001) in the lumbar spine. CONCLUSIONS: The surface topography method showed moderate correlation and agreement in thoracic spine with the radiograph (criterion validity) and high correlation with the flexicurve and digital inclinometer (concurrent validity). Compared with other non-radiographic tools, this surface topography method displayed similar criterion validity for kyphosis curvature measurement.