Does instrumentation removal cause curve progression in patients with adolescent idiopathic scoliosis?

Adolescent idiopathic scoliosis (AIS) is usually instrumented using a posterior approach. Hardware removal may be performed for specific clinical reasons. Little data is available on whether removal influences curve magnitude. The aim of the paper is to evaluate the impact of instrumentation removal on curve progression, and the safety and efficacy of the procedure. We analyzed 59 patients who underwent instrumentation removal. Curve types, reasons for removal, period between procedures, and Cobb angles: at baseline, immediately after correction, after removal and in follow-up were evaluated. Clinical symptoms were also assessed. The mean follow-up period after instrumentation removal was 2.2 years (1-5 years). The mean age at primary surgery was 14.5 years (12-25 years) and the mean Cobb angle after surgery was 24.9 degrees in the thoracic spine, and 17.5 degrees in the lumbar spine. The period between procedures was 46.6 months (11-192 months). The reasons for removal were: fistula (38.9%), pain (35.6%), rib hump removal (13.6%), and hardware failure (11.9%). At the final follow-up, mean thoracic curve was 35.4 degrees and lumbar curve was 26.2 degrees , corresponding to 13.3% and 17.5% curve progression after removal, respectively. Patients with infection had the highest loss of correction (21%). In symptomatic patients, pain subsided in 70% of the cases. In cases of hardware removal > 2 years after fusion, loss of correction was lower than in the < 2 years group. The course of surgery was relatively uneventful.