Correlation between postoperative shoulder imbalance and distal adding-on and distal junctional kyphosis in Lenke type 2 adolescent idiopathic scoliosis: a retospective study.

Study design: Retrospective study.

Purpose: This study aimed to evaluate the correlation between postoperative shoulder imbalance (PSI) and distal junctional kyphosis (DJK) in patients with Lenke type 2 adolescent idiopathic scoliosis (AIS).

Overview of literature: Despite reports on several risk factors of postoperative radiographical complications, including PSI, distal adding-on (DA), and DJK in patients with AIS, the correlation between PSI and DJK has not been thoroughly examined.

Methods: This study included 62 patients with Lenke type 2 AIS who underwent posterior correction and fusion surgeries. The patients were categorized into the PSI and non-PSI groups based on their radiographic shoulder height 2 years after surgery. Radiographic parameters, lower end vertebra (LEV), lower instrumented vertebra (LIV), sagittal stable vertebra (SSV), postoperative DA and DJK, and Scoliosis Research Society 22 scores were compared between the two groups using unpaired t -tests or Pearson's chi-square tests.

Results: Twenty-eight patients in the PSI group and 34 in the non-PSI group were evaluated. Three patients had DA in the PSI group and 10 with DA and four with DJK in the non-PSI group. LIV-LEV was higher in the PSI group than in the non-PSI group. Although the LIV-SSV was not significantly different between the two groups, among the three patients with DJK, two had LIV-SSV of -3, one had -1, and one had 0. No significant differences in other examinations were noted between the two groups.

Conclusions: Although more proximal LIV selection might lead to stable DA and DJK, the LIV selection should not be extended distally to prevent DA and DJK because favorable shoulder balance and clinical outcome can still be achieved.