Analysis of the risk factors related to coronal plane imbalance after correction of degenerative scoliosis

English Keywords:Degenerative scoliosis  Long-segment fixation and fusion  Coronal imbalance  Risk factor

English Abstract:

  【Abstract】 Objectives: To investigate the risk factors of postoperative coronal plane imbalance in patients with degenerative scoliosis after long-segment fixation and fusion. Methods: The data of 61 patients with degenerative scoliosis underwent long-segment fixation and fusion in our hospital from January 2014 to February 2017 and with complete imaging and follow-up data were reviewed retrospectively. There were 24 males and 37 females with a mean age of 59.0±6.1(53-78 years) and a mean follow up period of 36.4 months(18－85 months). According to the classification of degenerative scoliosis of Nanjing Drum Tower Hospital, 31 cases were of type A , 19 cases of type B, and 11 cases were of type C. Ranges of segment fixation and fusion: T10-L5 in 18 cases, T10-S1 in 6 cases, T10-S2 in 6 cases, T12-L5 in 14 cases, L1-L5 in 8 cases, L1-S1 in 7 cases, and L2-S1 in 2 cases. The patients were divided into two groups of balance group and imbalance group according to the coronal plane conditions at the final follow up. The Cobb angle of main curvature, coronal balance distance(CBD), correction rate, L5 tilt, deformity classification, apical vertebrae of lumbar curvature, rotation of apical vertebrae, grade of osteotomy, number of fixed segments, lower instrumented vertebra, Cobb angle of lumbosacral curvature, and ratio of Cobb angle of main curvature to Cobb angle of lumbo-sacral curvature before operation and at the final follow up were recorded and compared between the two groups, and the differences with statistical significance were analyzed with binary Logistic regression analysis. Results: Of the 61 patients, aggravated coronal plane imbalance or new-onset imbalance occurred in 8 cases at the final follow up. There were no statistical differences between the two groups in terms of preoperative Cobb angle of main curvature, CBD, apical vertebrae of lumbar curvature, rotation of apical vertebrae, grade of osteotomy, number of fixed segments, and lower instrumented vertebra(P>0.05), while there were statistical differences in terms of preoperative Cobb angle of lumbosacral curvature, ratio of Cobb angle of main curvature to Cobb angle of lumbo-sacral curvature, postoperative Cobb angle of main curve, preoperative L5 tilt, deformity correction, and deformity classification(P<0.05). The results of binary Logistic regression analysis showed that the postoperative coronal imbalance was positively correlated with the preoperative Cobb angle of main curvature, lumbosacral angle, and L5 tilt(OR＝1.158, 1.210, 1.322; P<0.05), yet it was not correlated significantly with correction rate, rotation of the apical vertebrae, and the number of fixed segments. Conclusions: Coronal imbalance may occur after long-segment fixation and fusion surgery in the degenerative scoliosis patients. Large Cobb angles of main curvature and lumbosacral curvature before surgery, and large L5 inclination are the risk factors for postoperative coronal plane imbalance or aggravated coronal plane imbalance.