Abstract
BACKGROUND CONTEXT Sagittal balance appraisal and surgical planning rely on the interpretation of spinopelvic parameters. An increased PT reflects pelvic retroversion as a compensatory mechanism to limit sagittal imbalance and correlates with increased pain and disability. However, poor imaging techniques and incorrect patient positioning frequently hamper landmark identification in lateral x-rays; and with no measurable angles in anteroposterior radiographs, is often impossible to determine PT and pelvic retroversion. PURPOSE The purpose of this study was to develop a novel spinopelvic parameter (BSA) measurable in anteroposterior radiographs that indirectly estimates pelvic retroversion and correlates with traditional measurements like pelvic tilt (PT). METHODS Whole-spine radiographs from 105 consecutive patients were used to retrospectively measure conventional spinopelvic parameters and the BSA (angle formed at the intersection of a line that connects the inferior margin of the sacroiliac joint to the midpoint of a horizontal line joining both femoral heads). Intraclass correlation coefficient was used to assess a quantitative correlation between the PT and BSA as indirect measures of pelvic retroversion. RESULTS Average values for PI, LL, SS, PT and BSA were 46.5° (±10.23), 48.56° (±12.30), 29.97° (±9.77), 16.94° (±8.03) and 54.47° (±4.05) respectively. We encountered a moderately strong correlation (r=−0.66) between PT and BSA. ROC plot analysis revealed that a BSA threshold of 46° has a sensitivity of 90% to identify pathologic PT values (>20°), while a BSA ≥60° has a specificity of 90% to rule out pelvic retroversion using anteroposterior radiographs. CONCLUSIONS There is a moderately strong correlation between the BSA, an innovative spinopelvic parameter measurable in anteroposterior radiographs, and PT. BSA seems to show great promise in simplifying spinopelvic appraisal by easily estimating pelvic retroversion associated with sagittal imbalance, while avoiding image-quality issues often encountered in lateral x-rays. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.
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