Predictability of spontaneous thoracic curve correction after anterior thoracolumbar correction and fusion in adolescent idiopathic scoliosis. A retrospective study on a consecutive series of 29 patients with a minimum follow-up of 2 years.

Background Context: According to the Lenke classification, a Type 5 adolescent idiopathic scoliosis can be surgically treated with selective anterior thoracolumbar or lumbar fusion.

Purpose: This study aims to predict the spontaneous correction of the unfused thoracic curve after anterior thoracolumbar fusion and to study whether age is of influence on this predictability.

Study Design: Retrospective study on a consecutive series of patients.

Patient Sample: Of a consecutive series of 38 patients with idiopathic thoracolumbar scoliosis, Lenke type 5, 29 patients were included in the study. All patients were treated with anterior spinal fusion and instrumentation. A minimum follow-up of 2 years was available for all patients (mean, 4 years; range, 2-17 years). To investigate the influence of age on the outcome, we divided the group into two subgroups: an adolescent (n=13) and an adult age group (n=16). The mean age in the adolescent group was 17 (range, 13-21 years) and 38 years (range, 22-54 years) in the adult group.

Outcome Measures: Physiological measures include coronal Cobb angle, apical vertebral translation (AVT) and apical vertebral rotation (AVR), shoulder tilt, trunk shift, L4 tilt, and pelvic tilt. Relative corrections were computed for the thoracolumbar and thoracic curves in each patient using the following formula: (preoperative curve-postoperative curve)/preoperative curve×100 (%). The correlation coefficient between the relative (%) corrections of the thoracic and thoracolumbar curves was calculated for the whole group as for the two age subgroups.

Methods: For radiographic evaluation, we used standing anteroposterior and lateral projections of the thoracolumbar spine to determine Cobb angle, AVT and AVR, and coronal balance.

Results: Both the thoracolumbar and thoracic curves in the whole group improved after surgery (45% and 19%, respectively, p<.01). In the adolescent age group, a significant correlation between the relative (%) correction of the thoracolumbar curve and the relative (%) correction of the thoracic curve was found (R=0.704; p=.01) and between age and relative (%) correction of the thoracic curve (R=-0.805; p<.01).

Conclusions: These results show that the spontaneous correction of the thoracic curve is a reflection of the thoracolumbar curve correction in adolescent thoracolumbar idiopathic scoliosis. Moreover, the predictability of the thoracic curve correction in the individual patient seems to decrease with increasing age of the patient.