Predictors of Flexibility of Thoracolumbar and Lumbar Idiopathic Scoliosis

University of California, San Francisco, San Francisco, CA, USA

INTRODUCTION:
Flexibility of scoliosis provides information about curve rigidity and it has always been a part of surgical decision-making. Flexibility of a curve is one predictor of postoperative curve correction. Curve magnitude and age of patients are thought to be predictor of flexibility. However, this has not been quantified. The purpose of this study is to evaluate potential predictors of flexibility in patients with thoracolumbar and lumbar scoliosis.

MATERIAL AND METHOD:
Seventy-five patients with idiopathic thoracolumbar and lumbar scoliosis, average age 41years(13-78) were included in this study. Preoperative standing and side bending radiographs of thoracolumbar and lumbar curves were evaluated. Cobb angles of structural and fractional curves, curve flexibility, presence of lateral listhesis, axial and radicular pain were documented. Predictors of structural, and fractional curve flexibility were evaluated with correlation and regression analysis. Correlation between radiographic findings and clinical presentation of these patients reported. We used Pearson correlation, and linear regression analysis.

RESULTS:
Seventy-five patients had average 56°(34-82) curves with average 55%(20-93) flexibility. Structural curve flexibility (SCF) is highly correlated with curve magnitude (r=0.7; p<0.001) and age (r=0.6; p<0.001). Lumbar fractional curve (L4-S1) flexibility showed high correlation with age (r=0.65;p<0.001), but did not show correlation with Cobb angle. Thoracic compensatory curves showed moderate correlation with Cobb angle (r=0.53). Axial pain showed moderate correlation with flexibility (r=0.45) and high correlation with age (r=0.63) and radicular pain showed moderate correlation with age, slip and percentage of slip (0.41-0.44). (p<0.01).

CONCLUSION:
We have showed that curve magnitude and age of the patients are the main predictors of structural flexibility. Every 10° increase in curve magnitude over 40° causes 10% decrease in flexibility; every 10 year increase in age decreases flexibility of structural curve by 5% and lumbosacral curve by 10%. Curve magnitude, structural curve, and age of the patient are predictors of curve flexibility and also for postoperative curve correction.