Prognosis of thoracic curve in Lenke 5+ type adolescent idiopathic scoliosis after posterior selective fusion

English Keywords:Lenke 5  Adolescent idiopathic scoliosis  Spontaneous correction  Selective fusion  Non-selective correction

English Abstract:

  【Abstract】 Objectives: To compare the clinical and radiological outcomes after selective and non-selective fusion in Lenke 5+ AIS and to investigate the prognosis of thoracic curve in Lenke 5+ adolescent idiopathic scoliosis(AIS) patients after posterior selective fusion(PSF). Methods: Lenke 5+ AIS patients who received correction surgery in our hospital from January 2010 to December 2018 with a minimum of 2 years follow up were retrospectively reviewed. There were 80 cases, including 13 males and 67 females. According to the surgical strategy, patients were classified into non-selective fusion(NS) group(n=21) and the selective fusion(S) group(n=59). Then, the patients in S group were subdivided into two groups of progressive(P) group with thoracic curve progression >5° and non-progressive(NP) group with progression ≤5° at the final follow-up. Comparison analysis was made in terms of radiological and clinical outcomes between well-matched patients in S group and NS group and between patients of P group and NP group. SRS-22(scoliosis research society-22) was used to evaluate clinical outcomes. Imaging parameters included chest bend flexibility, thoracolumbar/lumbar curve(TL/L), thoracic curve(T), apical vertebrae translation of thoracic curve(AVT-T), apical vertebrae translation of thoracolumbar curve(AVT-TL), shoulder tilt(ST), coronal balance(CB), uppermost instrumented vertebrae(UIV) or UIV+1 tilt angle, thoracic kyphosis(TK), lumbar lordosis(LL). Spearman correlation analysis was used to analyze the related factors of thoracic curvature progression, and binary Logistic regression was used to explore the risk factors of thoracic curvature progression. Results: Both groups demonstrated significant corrections in thoracolumbar curve and in thoracic curve comparing with the conditions before operation(P＜0.05). Comparing with S group, NS group demonstrated greater correction rate in thoracic curve(12.8°±5.6° vs 20.6°±4.0°, P<0.001), and the thoracic curve and thoracolumbar curve of most patients were found stable during follow-up. 9 patients(P group, 15.2%) in the S group demonstrated progression more than 5° in thoracic curve while 50 patients(NP group, 84.8%) maintained a well-corrected thoracic curvature at the final follow-up. Comparing with NP group, patients in P group were younger(14.0±0.6 vs 15.4±1.1, P=0.004), with a lower Risser sign(2.3±1.3 vs 3.9±0.7, P<0.001) and greater postoperative UIV+1 tilt(22.7±4.5 vs 19.7±3.5, P<0.05). Logistic regression analysis showed Risser sign≤2(P=0.003) and UIV+1 tilt(P=0.042) and UIV-UEV(upper end vertebrae)＜0(P=0.028) were independent risk factors of thoracic curve progression. Self-image scores were improved after selective surgery in both P group and NP group, but there was no significant difference(P＞0.05). Conclusions: Satisfying correction could be achieved regardless of selective or non-selective strategy in Lenke 5+ type AIS. Spontaneous correction of thoracic curve could be achieved after selective surgery in Lenke 5+ type AIS and remained stable during minimum of 2 years′ follow up. However, selective fusion should be carefully considered for patients with younger age and lower Risser sign.