Study Design Retrospective cohort analysis. Objectives To evaluate the effectiveness of the Lamartina-Berjano (L-B) classification in reducing mechanical complications in patients with adult spinal deformities, with a minimum follow-up of 10 years. Methods The study included cases of adult deformity with at least 10 years of follow-up. The rate of clinically-relevant mechanical complications, defined as any implant-related issue requiring revision surgery, was estimated. The independent variable was adherence to the treatment guidelines of the L-B classification. The analysis was limited to patients with thoracolumbar deformities, and the population was stratified according to postoperative alignment using GAP scores. Results A total of 121 patients met the inclusion and exclusion criteria. In this cohort, the revision surgery rate for clinically-relevant mechanical complications was 49.6% (60 out of 121 patients). Of these, 90 patients (74%) had surgery following the L-B classification guidelines. A lower risk of complications was observed in aligned patients whose surgeries adhered to the L-B classification. Additionally, the survival curve showed significant differences between patients who followed L-B guidelines and those who did not. Conclusion Our retrospective analysis shows that following the L-B classification guidelines leads to a reduction in mechanical complications in patients with thoracolumbar deformities, particularly in a long-term follow-up scenario.