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Failure of Pelvic Compensation in Patients With Severe Positive Sagittal Imbalance: Comparison Between Static Radiographs and Gait Analysis of Spinopelvic Parameters in Adult Spinal Deformity and Lumbar Stenosis.

STUDY DESIGN
Case-control study for motion analysis.


OBJECTIVE
To compare spinopelvic parameters using static radiographs with the values obtained using motion analysis during gait between adult spinal deformity (ASD) or lumbar spinal stenosis (LSS).


SUMMARY OF BACKGROUND DATA
It is still unclear whether measurement of radiological parameters using static radiographs can reflect natural sagittal balance during gait in the patients with severe positive sagittal imbalance.


METHODS
In this age- and sex-matched case control study, a total of 40 patients, each 20 subjects with either ASD or LSS who were scheduled to undergo surgery were included. Both clinical outcomes and sagittal spinopelvic parameters, including sagittal vertical axis (SVA), lumbar lordosis (LL), pelvic tilt (PT), sacral slope (SS), and pelvic incidence (PI) were measured. In motion analysis during walking, the angle of anterior pelvic tilt and the angles of the pelvis, hip, and knee were estimated. The correlation between variables was analyzed.


RESULTS
On standing lateral x-rays, SVA, PT, and PI - LL were significantly higher in the ASD group while SS and LL were significantly lower in the ASD group. However, on motion analysis, the average mean anterior pelvic tilt ± SD values in the ASD group were 8.3 ± 10.7 and 8.5 ± 10.7 on the right and left, respectively, and were not different from matched values in the LSS group. A Bland-Altman plot demonstrated a good agreement between the SS in the x-ray and anterior pelvic tilt in the motion analysis. In the ASD group, SS and SVA showed a significant positive correlation with mean anterior pelvic tilt in motion analysis during gait.


CONCLUSION
The present study showed that the failure of pelvic compensation would likely occur in patients with severe positive sagittal imbalance during walking.


LEVEL OF EVIDENCE
3.