The influence of early thoracic fusion on the pulmonary function of patients with idiopathic scoliosis in the early period of the second growth peak with different Risser signs

BACKGROUND: Previous reports confirmed early spinal fusion may compromise pulmonary function and thoracic development in skeletal immature patients with scoliosis. However, the different effects in patients with various Risser signs remain unknown. This study aimed to compare the influence of early thoracic fusion on pulmonary function and thoracic growth in patients with idiopathic scoliosis (IS) with closed triangular cartilage (TRC) and different Risser signs. METHODS: Thirty-six patients with IS and a closed TRC were retrospectively selected and divided into the low Risser (LR, Risser sign ≤2, 22 patients) and high Risser (HR, 2<Risser sign≤4, 14 patients) groups. Patient age, Risser sign, main Cobb angle, thoracic kyphosis, and fusion levels were recorded. Perioperative and minimum of 2-year follow-up pulmonary function and thoracic diameters were compared between both groups. RESULTS: There were no differences in patients’ general characteristics between two groups. The preoperative forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were 2.06±0.43 L and 2.50±0.49 L, respectively, in the LR group, and 2.31±0.49 L (p = 0.067) and 2.74±0.56 L (p = 0.122), respectively, in the HR group. While these values significantly increased postoperatively, to 2.62±0.46 L (p < 0.001) and 3.09±0.69 L (p < 0.001), in the LR group, they remained unchanged in the HR group [2.53±0.56 L (p = 0.093) and 2.70±0.98 L (p = 0.386), respectively]. The FEV1/FVC in both groups was >80% before and after surgery. The T1-T12 and anteroposterior thoracic diameter significantly increased after surgery in both groups, while the maximum inner chest diameter only increased in the LR group at the final follow-up. However, there were no significant differences in respiratory function and thoracic data between both groups. CONCLUSION: For patients with IS, early fusion did not deteriorate pulmonary function or thoracic development in TRC-closed patients whose Risser sign was ≤2 compared with those with a Risser sign >2.