Lumbopelvic lordosis and pelvic balance on repeated standing lateral radiographs of adult volunteers and untreated patients with constant low back pain.

STUDY
DESIGN: Twenty volunteers and 20 patients with no prior spine surgery had two standing lateral radiographs taken, on the average, 66 months apart and 2 weeks apart, respectively.
OBJECTIVES: To first determine the reliability of the measurement techniques used, and then the longitudinal variation between radiographs for the sagittal spinopelvic alignments measured in two stable populations, the one manifesting no back symptoms (volunteers) and the other showing no changes in symptoms (patients). Pelvic morphology also was assessed quantitatively, and significant correlations for the measurements were studied. SUMMARY OF BACKGROUND DATA: There are no published studies on longitudinal variation for measurements of sagittal spinal alignments in asymptomatic control subjects or untreated patients with stable back problems. It may be helpful to know not only how much variation in alignments can be expected between radiographs of the same individual, but also which measurements and measurement techniques offer the greatest clinical reliability and application.
METHODS: Each patient in this study reported mechanical type low back pain that was constant in location and character as well as clinically consistent with symptomatic degenerative lumbar disc disease. Each patient and volunteer had 36-inch-long lateral radiographs taken of the entire thoracic and lumbar spine, which included the pelvis. After intervening periods of 1 to 4 weeks (patients) and 5 to 6 years (volunteers), a second radiograph was taken for comparison. Two observers made 24 different measurements on the radiographs including determinations for lumbopelvic lordosis, pelvic balance, and pelvic morphology using the pelvic radius technique. Reliabilities, longitudinal variations, and correlations for the measurements were compared.
RESULTS: The most reliable measurements were for pelvic morphology, pelvic balance, and regional lumbopelvic lordosis by the pelvic radius technique. Pelvic morphology was the most constant measurement between individual radiographs. Pelvic morphology and total lumbosacral lordosis were dependent measurements that were complementary in determining total lumbopelvic lordosis. Lumbopelvic lordosis and pelvic balance also had strong correlation, whereas lumbosacral lordosis and pelvic balance were independent measurements.
CONCLUSIONS: The pelvic radius technique is recommended for evaluating lordosis to the pelvis because this approach provided not only good measurement reliability on standing radiographs for lumbopelvic lordosis, but also determination of pelvic balance over the hips and the option to assess pelvic morphology quantitatively. Lumbopelvic lordosis and pelvic balance were strongly correlative. This finding, along with higher reliability and lower longitudinal variation on repeated radiographs, indicated greater clinical application for these specific measurements.