Optimal Lumbar Lordosis Correction for Adult Spinal Deformity with Severe Sagittal Imbalance in Patients over Age 60: Role of Pelvic Tilt and Pelvic Tilt Ratio.

STUDY DESIGN A Retrospective study. OBJECTIVES The purpose of this study was to evaluate optimal and ideal target values of the spine balance correction in elderly patients with adult spinal deformity (ASD) who were over the age of 60 years. SUMMARY OF BACKGROUND DATA The target values of the Scoliosis Research Society (SRS)-Schwab classification to obtain satisfactory alignment and favorable outcomes are used in many spinal reconstruction surgeries. However, uniformly applying the SRS-Schwab classification to all elderly patients aged 60 years or older showing sagittal malalignment may lead to several inconsistencies. METHODS This study included 121 patients (average age 70.5 years and a minimum 2-year follow up) with ASD who underwent long-segment fusion from T10 to sacrum. We used Pearson's correlation coefficient to analyze the relationship between clinical and radiographic parameters, and multilinear regression analysis and multivariate logistic regression model (backward elimination method) were conducted using the correlation factors of postoperative (Post) and last follow-up (Last) sagittal vertical axis (SVA) to find the risk factors of Post sagittal imbalance. RESULTS Logistic regression analysis with the correlation factors of Post and Last SVA led to risk factors of Post sagittal imbalance, and after confirming the significance of each path, it was confirmed that the effects of pelvic incidence (PI) - lumbar lordosis (LL) and Post PT ratio (PTr) were valid (P < 0.05). After using ROC curve, target value of PI-LL was 1.33, and that of PTr was 25.95%. CONCLUSION Through our study, the risk factors of Post sagittal imbalance were the Post value of PI-LL and that of PTr, and target value of PI-LL was <1.33 and that of PTr was <25.95%. Theses target values can be effective guidelines for spine surgeons who perform spine reconstruction surgeries for elderly patients with a pure sagittal imbalance based on Schwab's formula.Level of Evidence: 4.