Matching correction of main and compensatory curves is critical for immediate postoperative coronal balance in correction of severe adult idiopathic scoliosis.

PURPOSE:To analyze the correlation between immediate postoperative coronal imbalance and the matching degree of the correction rates of the main curve and compensatory curves in the surgical treatment of severe adult idiopathic scoliosis. METHODS:Patients were categorized into three types based on the preoperative coronal balance status (type A = balance, type B = shifted to cave side and type C = shifted to convex side), and each type was further divided into two subgroups based on the postoperative coronal balance status (balance and imbalance). Different coronal parameters before and after operations were calculated and compared. RESULTS:The rate of postoperative CIB was highest in type C patients (53.8%) and lowest in type A patients (31.5%). To avoid postoperative CIB, the value of the postoperative CRmain should fall within the range of 1.001 × CRcomp ± 2.84% in type A patients, 1.112 × CRcomp + 3.3% ± 5.02% in type B patients and 0.907 × CRcomp - 2.5% ± 4.38% in type C patients. CONCLUSION:Mismatch between the correction rates of the main curve and compensation curves is a critical cause of immediate postoperative CIB. The relatively equal correction of the main curve and compensatory curves is essential for type A patients to achieve postoperative coronal balance, while the correction rate of the main curve should be higher than the compensatory curves in type B patients and vice versa in type C patients. Three formulas for the three different types were developed to provide helpful guidance information for surgical planning.