Evaluation of Pelvic Sacral Angle as an indicator for spinopelvic balance: A radiographic review of 56 individuals in standing and supine positions

Abstract Background Over the past decade, the sagittal balance of the spine has garnered significant attention from surgeons. The compensatory mechanism of the pelvis plays a crucial role in maintaining the sagittal balance of the whole body. Several methods have been reported for reconstructing spinal sagittal balance based on pelvic parameters. However, controversy persists over restoring appropriate lumbar lordosis in spinal surgery. The purpose of this study is to investigate the role of PSA and APPA in assessing pelvic position and their correlation with spinopelvic parameters. Methods All patients underwent EOS and CT scans in both standing and supine positions to evaluate alterations in spinal sagittal balance parameters between the two postures. Measurements were taken for lumbar lordosis, thoracic kyphosis, sacral slope, pelvic incidence, pelvic tilt, pelvic sacral angle, and anterior pelvis plane angle. Changes and correlations in sagittal balance parameters in the spinal-pelvic region between the two postures were compared and analyzed. Results Statistically significant differences were found between the two groups for pelvic tilt (PT) (p < 0.05). The supine position showed a significantly higher mean value for pelvic sacral angle (PSA) (p = 0.005) compared to the standing position. Similarly, the supine position exhibited a significantly lower mean value for anterior pelvis plane angle (APPA) (p = 0.001) compared to the standing position. Strong correlations were observed between PSA and other spinopelvic parameters, particularly PT, pelvic inclination (PI), sacral slope (SS), thoracic kyphosis (TK), lumbar lordosis (LL), and APPA in both the supine and standing groups. Additionally, a strong correlation was found between APPA and pelvic parameters, especially PI. Conclusion The PSA and spinopelvic parameters showed a significant correlation. Our findings suggest that the PSA and APPA can be valuable parameters for assessing spinopelvic balance, particularly in cases involving pelvic rotation. Additionally, the spinal and pelvic parameters obtained in the supine position may offer greater reliability.