Introduction: Unsuccessful preventive treatment of adolescent idiopathic scoliosis, including brace treatment, often results in the decision to perform surgery. The aim of the presented study was to determine whether using a SpineCor dynamic brace has an effect on further surgical correction of the main curve, as well as whether the length of time a patient stops using the brace before the surgical procedure and the length of preventive treatment have any effect on the final outcome of the surgery. Methods: The study encompassed patients who underwent surgery to correct lateral curve deformation of the spine. The study group (Group A) comprised patients who underwent preventive treatment with a SpineCor dynamic brace. The rest of the patients, who did not undergo preventive treatment, constituted the control group (Group B). The magnitude of curve deformation was assessed based on the Cobb angle in X-ray images taken in a standing position from the anteroposterior view. Measurements were taken before the surgical procedure (measurement 1), directly after the surgery (measurement 2), and 12 months after the surgery (measurement 3). Subsequently, the correction of the curve was calculated at both one week and 12 months after the surgery. Results: Satisfactory correction was obtained in Groups A and B, as shown from both measurements: one week (71 ± 13 in Group A and 66 ± 15 in Group B) and 12 months after the surgical procedure (68 ± 20 in Group A and 65 ± 17 in Group B). Differences between the groups were not statistically significant. On average, brace treatment in the experimental group lasted 25 ± 8 months. No statistically significant correlation between the length of brace treatment and the correction of the curve was observed. On average, the non-brace period before the surgical procedure was 7.5 ± 4.9 months and it did not have a significant effect on the course and final outcome of surgical treatment. Conclusions: As far as adolescent idiopathic scoliosis is concerned, preventive treatment with a SpineCor brace before the surgery did not have a significant effect on the course and final result of the surgical correction of the curve, either immediately or within one year after the surgical procedure.