Measurements of lumbopelvic lordosis using the pelvic radius technique as it correlates with sagittal spinal balance and sacral translation

Abstract

Background context: Maintenance of normal lumbar lordosis is important in the treatment of spinal disorders. Many attempts have been made to quantify normal sagittal spinal alignment and lordosis using a C7 plumb line and segmental angulations of the spinal vertebrae. Little attention has been given to pelvic compensation as it correlates to lumbar lordosis and overall sagittal spinal alignment. Better methods of measuring lordosis, which correlate with sagittal spinal balance and pelvic compensation, are needed in treating patients with spinal disorders. Purpose: To determine the correlation between lumbopelvic lordosis, pelvic rotation and sagittal spinal balance and standardize a method for measuring lumbopelvic lordosis, sacral translation, and sagittal spinal alignment. Study design: Sagittal alignments using the C7 plumb line, Cobb angles, sacral plumb line and the pelvic radius (PR) technique were used to measure standing 36-inch lateral radiographs of patients with various spinal disorders. Patient sample: A review of the records identified 62 patients with various spinal pathologies presenting to the (RGW) spine clinic that had standing lateral spine radiographs. Only radiographs that allowed positive identification of the C7 vertebral body, the entire thoracolumbar spine, the sacrum and both femoral heads were studied. These criteria allowed inclusion of 28 subjects in this study. The final population had 12 women and 16 men with an average age of 52 years (SD, 16.6 years; range, 20 to 84 years). Outcome measures: No outcomes measures were used in this study. Methods: Measurements for sagittal spinal balance and lumbopelvic lordosis were made on 36-inch standing lateral radiographs of adult patients. Measurements included the C7 plumb line, segmental angulations of spinal vertebrae (Cobb angles), sacral translation and the PR technique for lumbopelvic lordosis. Data were analyzed for significant correlation between lumbopelvic lordosis, sagittal spinal balance, sacral translation and total segmental lumbar lordosis using the Cobb method. Results: Our population averaged 50 degrees of total segmental lumbar lordosis from L1 to S1 (SD, 14.3; maximum, 89.5; minimum, 17.9). Nearly 75% of total segmental lumbar lordosis measured from L1 to S1 can be accounted for through the L4 to S1 superior end plates and 47% through L5 to S1 superior end plates in our population. Total segmental lumbar lordosis correlated with total thoracic kyphosis (r=0.45, p=.008). Total segmental lumbar lordosis measured by the Cobb method significantly correlated with sagittal spinal balance (r=−0.35, p=.022) and sacral translation (r=0.41, p=.016). Measurements for lumbopelvic lordosis significantly correlated with sagittal spinal balance (r=−0.33, p=.042), sacral translation (r=−0.70, p=.00002) and total segmental lumbar lordosis (r=0.82, p<.000001). Measurements for sacral translation and sagittal spinal balance also correlated significantly (r=0.35, p=.034). Conclusions: Sacral translation, the C7 plumb line and lumbopelvic lordosis are useful measures for sagittal spinal balance. Lumbopelvic lordosis and sacral translation can be correlated to the sagittal spinal balance. Understanding these measurements and the range of lumbopelvic compensation can be extremely helpful in treating patients with spinal pathology and in avoidance of flatback deformity. Application of these measures would be especially helpful in the treatment of patients with spinal fusion, degenerative spondylosis, disc disease, fractures, and in the prevention of sagittal malalignment.