Learning curve and long-term outcomes of minimally invasive correction and fusion for adolescent idiopathic scoliosis.

Study design: Retrospective analysis.

Objective: This study sought to report the long-term outcomes of patients that underwent minimally invasive surgery (MIS) correction for Adolescent Idiopathic Scoliosis (AIS) in terms of radiographic, clinical, and patient-reported outcomes. Furthermore, we examined the learning curve of MIS technique over the course of 13 years. Both MIS and open techniques are used to surgically address AIS. MIS techniques are purported to preserve the midline spinal musculature and to decrease estimated blood loss (EBL) and hospital length of stay (LOS).

Methods: Data were collected at a single tertiary care center of all consecutive AIS patients undergoing deformity surgery from January 2008 to October 2021. Demographic, clinical, and radiographic data were collected at various intervals. Descriptive and inferential analyses were conducted.

Results: 70 AIS patients were included in the study. Mean patient age was 16.2 years of which 95.7% were female, with a mean BMI of 21.7. The majority of the patients were Lenke type 1A (60%) followed by Lenke 1B (18.6%) with mean preop Cobb angle as 52.2°. The mean follow-up was approximately 6 years with 35.7% of our cohort meeting the long-term follow-up landmark (> 5 years, 2-11). The mean number of spinal levels treated was 9.3 with mean ASA score of 1.7. Overall, mean EBL was 151 cc with mean OR of 308 min. The mean LOS was 3.94 days with postop Day 1 as the initiation of ambulation. Overall, the percent correction at the last visit was significantly greater than preop (Cobb: 77.6%, p < 0.05). Mean loss of correction on follow-ups was less than 5º. The overall revision rate was 2.9%. At 2 years postop, 98.6% (69/70) of the patients achieved fusion with 100% (24/24) at 5 years, and 96% (24/25) beyond the 5-year mark. Surgeon's technical proficiency in performing MIS for the treatment of AIS corrections was achieved after 23 cases.

Conclusions: Based on our cohort's 2-11 year follow-up data, we conclude that MIS provides an effective treatment option for AIS reconstruction. Our study indicates that MIS can achieve adequate deformity correction and positive long-term clinical outcomes as indicated by Cobb angle, VAS, ODI, and SRS-22r scores during follow-ups. If the individual goals of AIS surgery can be achieved, consideration should be given to less-invasive techniques.

Level of evidence: IV.