"Cured" patients with early-onset idiopathic scoliosis after serial casting are at risk of recurrence at intermediate follow-up.

Purpose: Serial casting limits curve progression while preserving spinal growth, delaying or even eliminating the need for surgery. Some patients with EOIS can be "cured" with curve reduction under 15°. However, no long-term studies have defined whether "cured" patients maintain small curves or if they are at risk of progression. We examined if casting patients remained "cured" following treatment.

Methods: We identified 40 EOIS patients who were treated with serial casting, achieved curves under 15° and had minimum 2 years of follow-up after completing the treatment. Failure was defined as an increase > 6° resulting in a curve magnitude > 15° at any point during follow-up, requiring cast/brace treatment after cessation of initial cast/brace, or undergoing surgery. Average curve magnitude at the time of cure was 11.1°. Kaplan-Meier survival analysis was used to identify failure rates over time.

Results: 10 patients (25.0%) met criteria for failure. Mean time from cure to last follow-up was 4.3 years. 3 patients (7.5%) completed bracing and were later re-braced while 2 (5.0%) required surgery. Mean curve magnitude of "failed" patients was 27.4° with an average increase of 15.6°. At 5.1 years, probability of successful treatment is 64.2%. For "failed" patients, median time to failure was 2.4 years. Successful patients were braced for median 1.4 years, while "failed" patients had a median of 1 year.

Conclusion: While EOIS patients may be "cured" with serial casting, this may not be sustained. The percentage of "failures" likely will increase with longer follow-up through skeletal maturity, and patients must be closely monitored after concluding casting/bracing.