Factors in Surgical Decision Making for Thoracolumbar/Lumbar AIS: It's About More Than Just the Curve Magnitude.

Study Design: A retrospective review of prospective data OBJECTIVE:: The purpose of this study was to compare operative and nonoperative patients with similar curve magnitudes to determine motivating factors associated with surgical correction in "smaller" curves.
Summary of Background Data: Despite traditional treatment recommendations on major curve angle measurements, many patients with thoracolumbar/lumbar (TH/L) curves of smaller magnitudes are unhappy and desire correction.
Methods: A prospectively enrolled multicenter adolescent idiopathic scoliosis database was queried. Patients with major TH/L curves <50 degrees and low risk of progression (Risser 3, 4, and 5) were identified and grouped based on their treatment (operative vs. nonoperative). Preoperative demographic, radiographic, Scoliosis Research Society (SRS) outcome scores, and trunk shape values were compared.
Results: A total of 126 patients undergoing surgical intervention and 17 patients pursuing nonoperative treatment were analyzed. The average lumbar curve of the operative group was 43 degrees (range, 35 to 49 degrees) and for the nonoperative group was 39 degrees (range, 26 to 49 degrees). The operative group was significantly younger, had larger lumbar major curve angles, lower thoracic to lumbar curve ratio, increased TH/L apical translation, and greater trunk shift (P<0.05). Only lumbar curve (P=0.018, OR=1.19) and trunk shift (P=0.01, OR=3.22) remained significant predictors of surgery in a multivariate regression analysis. SRS scores were significantly lower in the operative group for pain, self-image, function, mental health, and total (P<0.05). When SRS total score was entered into the regression, it was the only significant predictor of surgical intervention (P=0.004, OR=0.03).
Conclusions: Many patients with smaller lumbar curves have clinical deformities that are more consistent with larger curves. These smaller curves can produce similar coronal imbalance and trunk shift, with lower SRS domains that may drive patients to seek surgical treatment. What is unclear is the reason for this greater degree of imbalance in this select group of patients and whether the natural history is different for a more balanced TH/L curve.
Level of Evidence: Level II-Prognostic.