Inertial Measurement Unit-based Evaluation of Global and Regional Lumbar Spine and Pelvis Alignment in Standing Individuals With a Flat Lumbar Posture

Objective: The purpose of this study was to investigate the global and regional lumbar spine and pelvis postural alignment in standing individuals with a flat lumbar posture using an inertial measurement unit (IMU) system. Methods: A total of 80 symptomatic young volunteers (25 men and 55 women in their early 20s) were recruited at Inje University in Gimhae, South Korea for this study. Participants stood in a comfortable posture for 5 seconds with IMUs on the T10, L3, and S2 level. Participants were then categorized into 3 groups according to the global lumbar lordosis (GLL) angle (T10-S2): <20 degrees, 20 degrees <= GLL angle < 30 degrees, and 30 degrees <= GLL angle < 40 degrees. We compared the GLL and regional lumbar lordosis (RLL) angles among the 3 groups. Results: As GLL increased, RLL angles (upper, P = .001; lower, P <.001) tended to increase, whereas the sacrum angle decreased (P < .001). A stepwise regression model showed that the sacrum angle was the single best predictor of GLL in standing participants. Based on IMU measurements, participants with GLL <20 degrees are considered representative of participants with a flat lumbar posture. Conclusion: Posture measurements in a standing position conducted to assess lordosis should consider the relationship between GLL and RLL rather than GLL or RLL alone. We found that S2 was the best predictor of GLL.