Identification of Predictive Factors for Mechanical Complications After Adult Spinal Deformity Surgery A Multi-Institutional Retrospective Study

Study Design. A retrospective multicenter observational study. Objective. To investigate correction surgeries that were performed in relatively aged patients in terms of mechanical complications (MCs) and their predictive factors. Summary of Background Data. The risk factors associated with MCs have not yet been well examined, especially in aged populations. Methods. We retrospectively reviewed 230 surgically treated ASD patients with an average age of 72.2 years. Twenty-eight patients with ASD caused by vertebral fractures were excluded. The minimum follow-up was 2 years. Postoperative MCs were defined as proximal junction kyphosis, distal junction kyphosis, pseudoarthrosis, rod breakage, and vertebral fractures. We divided all the ASD patients into two groups: patients with MC (the MC (thorn) group) and patients without MC (the MC (-) group). Radiographic parameters were evaluated before and immediately after surgery. The SRS-Schwab ASD classification and global alignment and proportion (GAP) score were also evaluated. Results. Of the 202 patients, 91 (45.0%) had MCs. The age at surgery was significantly higher in the MC (thorn) group than in the MC (-) group. Regarding radiographic parameters, postoperative global tilt (GT), pre- and postoperative thoracolumbar kyphosis (TLK), and postoperative thoracic kyphosis were significantly higher in the MC (+) group than in the MC (-) group. Other parameters, such as the proposed ideal alignment target of PI-LL<10, did not significantly affect MC rates. The GAP score was high in both groups and not significantly related to a higher rate of MC. Forward stepwise logistic regression indicated that the age at surgery, postoperative GT, and preoperative TLK were significant risk factors for MCs. Conclusions. Older age, higher postoperative GT, and higher pre and postoperative TLK can be risk factors for MCs. The GAP score was high in both groups and not significantly related to a higher rate of MC.