The application of a new intraoperative assessment method of coronal balance in surgical treatment of scoliosis

Abstract

Objective To introduce a new method for assessing coronal balance in surgical treatment of scoliosis, and to explore its effectiveness in preventing postoperative coronal imbalance. Methods The data of forty-six consecutive patients, who underwent posterior surgery for spine deformity correction from January 2016 to December 2016, were retrospectively analyzed. The series included 19 males and 27 females with an average age of 28.24±21.16 years (7-76 years), and with lower instrumented vertebra (LIV) located at the level of L3 or below. Point-line method was used to evaluate coronal balance by determining whether the center of upper instrumented vertebra was located at the measuring rod passing through the centers of symphysis pubis and LIV among all patients during surgery. Preoperative, postoperative 1 week and 3 months Cobb angle, coronal balance distance (CBD), Oswestry Disability Index (ODI), Visual Analogue Scale (VAS), and Scoliosis Research Society Questionnaires-22 (SRS-22) were measured and recorded, and statistical analysis was conducted. And then, subgroup analysis was performed according to preoperative coronal imbalance classification to further evaluate the effectiveness of the new method. Results Among 46 patients in this study, the prevalence of preoperative coronal imbalance was 47.82% (22/46). Of them, ten patients were type B coronal imbalance and eleven patients were type C coronal imbalance. The prevalence of coronal imbalance at one week after operation was 17.39% (8/46), and the prevalence of coronal imbalance at final follow-up was 10.87% (5/46). The results showed that the mean main Cobb angle was 57.24°±26.51° and 14.71°±10.17° at pre-operation and immediate post-operation, respectively. The difference was statistically significant compared to preoperative value (t=13.211, P=0.000), and the average improvement rate was 73.53%±1.88%. Preoperative coronal balance distance CBD ranged from 2.76 mm to 66.73 mm, with an average of 22.54±13.97 mm; the mean CBD was 16.00±14.85 mm at immediate post-operation. The difference was statistically significant (t=3.665, P=0.001), with an average correction rate of 25.58%±52.39%. Our clinical outcome analysis showed that among 46 patients, the preoperative VAS was 8.11±0.89, and the final follow-up VAS was 4.15±0.79. There was a significant difference between pre-operation and the last follow-up (t=21.529, P=0.000). The preoperative ODI score was 49.76±5.84, and the final follow-up ODI score was 25.74±3.92. The difference was statistically significant (t=44.434, P=0.000). The preoperative SRS-22 was 10.57±2.13, and the final follow-up SRS-22 was 21.89±2.35. Compared to pre-operation, the difference was statistically significant (t=24.023, P=0.000). The subgroup analysis showed that in patients with type B coronal imbalance, the mean Cobb angle correction rate was 70.34%±6.02% at immediate post-operation, and there was a significant difference compared to pre-operation (t=5.437, P=0.000); the average CBD correction rate was 37.45%±29.03%, and significant difference was found (t=2.607, P=0.028). In type C patients, the average Cobb angle and CBD correction rate at immediate post-operation was 72.92%±3.67% and 44.79%±5.63%, respectively, and significant difference was found (t=7.319, P=0.000; t=7.545, P=0.000). Conclusion Point-line method was a simple and effective technique for intraoperative assessment of coronal balance, which could assist surgeons to objectively evaluate the result of restoration of the coronal alignment. The use of point-line method is contributed to improve clinical outcomes of spinal deformity correction surgery, and to prevent the occurrence of postoperative coronal imbalance. Key words: Scoliosis; Intervertebral disc degeneration; Spinal fusion; Treatment outcome