Providence Bracing: Predicting the Progression to Surgery in Patients With Braced Idiopathic Scoliosis.

Background: Idiopathic scoliosis (IS) is a common spinal abnormality, in which orthotic management can reduce progression to surgery. However, predictors of bracing success are still not fully understood. We studied a large patient population treated with the nighttime Providence orthosis, utilizing multivariable logistic regression to assess results and predict future spine surgery.

Methods: We retrospectively reviewed patients with IS meeting Scoliosis Research Society inclusion and assessment criteria presenting from April 1994 to June 2020 at a single institution and treated with a Providence orthosis. A predictive logistic regression model was developed utilizing the following candidate features: age, sex, body mass index, Risser classification, Lenke classification, curve magnitude at brace initiation, percentage correction in a brace, and total months of brace use. Model performance was assessed using the area under the receiver operating characteristic curve, accuracy, sensitivity, and specificity. The importance of individual features was assessed using the variable importance score.

Results: There were 329 consecutive patients with IS with a mean age of 12.8 ± 1.4 years that met inclusion and assessment criteria. Of these, 113 patients (34%) ultimately required surgery. The model's area under the curve (AUC) was 0.72 on the testing set, demonstrating good discrimination. The initial curve magnitude (Importance score: 100.0) and duration of bracing (Importance score: 82.4) were the 2 most predictive features for curve progression leading to surgery. With respect to skeletal maturity, Risser 1 (Importance score: 53.9) had the most predictive importance for future surgery. For the curve pattern, Lenke 6 (Importance score: 52.0) had the most predictive importance for future surgery.

Conclusion: Out of 329 patients with IS treated with a Providence nighttime orthosis, 34% required surgery. This is similar to the findings of the BrAist study of the Boston orthosis, in which 28% of monitored braced patients required surgery. In addition, we found that predictive logistic regression can evaluate the likelihood of future spine surgery in patients treated with the Providence orthosis. The severity of the initial curve magnitude and total months of bracing were the 2 most important variables when assessing the probability of future surgery. Surgeons can use this model to counsel families on the potential benefits of bracing and risk factors for curve progression.