A novel parameter for predicting postoperative shoulder balance in Lenke Type 1 and 2 adolescent idiopathic scoliosis patients

PurposeTo evaluate the predictive value of the thoracic spine-clavicle angle (TSCA) and the thoracic cage-clavicle angle (TCCA) for immediate postoperative shoulder balance. MethodsA total of 154 Lenke type 1 and 2 AIS patients who underwent corrective surgery in our hospital were included. The degree of clavicle angle (CA), thoracic spine tilt angle (TSTA), thoracic cage tilt angle (TCTA), proximal thoracic curve (PTC) Cobb angle, and main thoracic curve (MTC) Cobb angle were measured on standing full-length posteroanterior spine radiographs before and after surgery. Five parameters, TSCA, TCCA, correction rate of PTC, correction rate of MTC, relative PT/MT residual Cobb angle (RRCA), were calculated. Multinomial Logistic Regression was used to determine the risk factors of PSB. A p-value of less than 0.05 was considered statistically significant. ResultsFor TCCA, in group R (vs group B), pre-op right high (vs pre-op left high) (OR=8.102, 95%CI [1.650, 39.786], p=0.01) and RRCA (OR=1.015, 95%CI [1.004, 1.026], p=0.009) are risk factors. Pre-op left high (vs pre-op right high) (OR=0.123, 95%CI [0.025, 0.606], p=0.01) and correction rate of MTC (OR=0.886, 95%CI [0.809, 0.971], p=0.009) are protective factors. Correction rate of PTC shows no significant effect. In group L (vs group B), pre-op left high (vs pre-op right high) (OR=2.648, 95%CI [1.084, 6.469], p=0.033) is a risk factor. Pre-op right high (vs pre-op left high) (OR=0. 378, 95%CI [0. 155, 0.922], p=0. 033) is a protective factor. Correction rate of PTC, correction rate of MTC, and RRCA show no significant effect. ConclusionPreoperative shoulder balance, as defined by the TCCA, serves as an independent risk factor for PSB. Using postoperative balanced shoulders as the reference group, preoperative left shoulder high (vs right high) significantly increased the risk of postoperative left shoulder high, while significantly reducing the risk of postoperative right shoulder high. Preoperative right shoulder high (vs left high) significantly increased the risk of postoperative right shoulder high, while significantly reducing the risk of postoperative left shoulder high. The correction rate of MTC was an independent protective factor against postoperative right shoulder high, whereas RRCA was an independent risk factor for postoperative right shoulder high.