Roussouly classification of adult spinal deformity.

With an estimated prevalence of 68% among healthy adults without a previous diagnosis of scoliosis, adult spinal deformities are a growing concern as the population ages. Our understanding of this growing concern has been historically guided by previous studies performed on the pediatric population. Over time, different classifications have been developed with their own respective limitations. The Roussouly classification was the first classification to describe the shapes of an asymptomatic spine. It considers lumbar lordosis, pelvic incidence, and the inflection point from lumbar lordosis to thoracic kyphosis to attempt to stratify the shapes of an asymptomatic spine. This classification aims to guide treatment, provide information regarding prognosis, allow stratification for research, and be highly reproducible. Overall, the Roussouly classification is a novel way to think about sagittal malalignment, considering the patient's individual anatomy, while allowing for communication between surgeons. Additionally, it has proven to be a reliable system that provides prognostic value for clinicians and may minimize complications when a patient's sagittal alignment is optimized using this classification system.