Changes of the non-fused proximal thoracic curve and its relationship with clinical shoulder balance after main thoracic curve correction in adolescent idiopathic scoliosis

English Keywords:Adolescent idiopathic scoliosis  Upper thoracic curve  Spontaneous curve correction  Cronal balance  Shoulder balance

English Abstract:

  【Abstract】 Objectives: To investigate the change of non-fused upper thoracic curve after correction of main thoracic curve in adolescent idiopathic scoliosis(AIS) patients, and its relationship with the clinical shoulder balance. Methods: A retrospective review of consecutive patients treated with posterior pedicle screw fixation and deformity correction from January 2008 to December 2010 was carried out. This study included the patients with an age from 10 to 18 years old, all cases had a type Lenke 1, 2, 3, 4 with right thoracic curve of less than 80°, and all had upper thoracic instrumented vertebra at or lower than T4. The follow-up was more than two years. Patients underwent osteotomy correction, and revision surgery were excluded. According to the Lenke classification, these patients were subdivided into structure upper thoracic curve(UTC) group and non-structure UTC group. Clinical shoulder height difference(CSH) and radiographic features between two groups were measured and compared at preoperative, 3-month follow-up and final follow-up. Results: 62 patients with an average age of 14.4 years old were included in this study. The follow-up ranged from 24 to 62 months, with a mean of 36.4 months. There were 17 cases in structure UTC group, and 45 cases in non-structure UTC group. At final follow-up, the upper thoracic curve in both groups decreased spontaneously from 27.9° to 19.4°, T1 tilt increased from -0.21° to 4.7°, first rib tilt(FRT) from 0.4° to 3.7°, clavicle angle(CA) from -1.5° to 0.8°, and CSH decreased from -13.0mm to 5.2mm. These changes all had significant differences(P=0.000). The Pearson′s correlation analysis suggested that there was strong correlation between the change of T1 tilt(post T1 tilt - pre T1 tilt) and the change of CSH(post CSH - pre CSH) (r=0.624, P=0.000), moderate correlation of correction rate of main thoracic curve and postoperative FRT with the change of CSH(r=0.437, 0.345, P=0.007, 0.006), only weak correlation between preoperative main thoracic Cobb angle and the change of CSH(r=0.262, P=0.040). There was no statistically significant correlation of UTC Cobb angle, flexibility, T1 tilt, flexibility of main thoracic curve with the change of CSH. Conclusions: After posterior main curve correction, spontaneous correction occurrs in both structure and non-structure upper thoracic curve. However, the T1 tilt, FRT and CSH difference may increase. There is moderate to strong correlation of the elevation of left shoulder with postoperative T1 tilt change, correction rate of main thoracic curve, FRT.