Scoliosis requires three dimensional correction at a global level (curve correction) and at a local one (apical axial derotation) as well as sagittal balance management. Except for in situ contouring, previously reported surgical techniques for scoliosis correction hardly deal with all these issues. The aim of the current study was to evaluate long term clinical and radiological outcomes after in situ contouring in 85 patients with severe scoliosis (Cobb= 40 to 110°). Age influence (adults versus adolescents) and surgical approaches (anterior release and posterior correction and fusion versus posterior correction and fusion only) were also assessed. The results of the study show that the in situ contouring is comparable to other surgical techniques in terms of surgery duration and blood loss. Anterior release proved useful in severe scoliosis correction. No difference in peroperative complications was found between age groups nor between approach groups. However, adolescents recover faster than adults. No difference of revision rates in double approach versus posterior approach populations was found. No statistically significant differences were found between the adolescent and adult populations. The mean overall frontal correction reached 68%. The mean loss of correction amounted 5%. No significant evolution was found in sagittal curvatures, emphasizing the difficulties in restoring physiological curvatures in patients with severe scoliosis. Our results suggest the in situ contouring technique is fully appropriate for severe scoliosis correction, regardless of the patient’s age and approach. Besides it will not result in higher morbidity for one specific population and warrants similar outcome when properly applied.