Purpose: To present the description of sagittal alignment of the degenerative human spine and its possible evolution.
Materials and methods: This is a retrospective observational study of degenerative evolution in spinal alignment in low back pain patients. Full spine EOS® sagittal X-rays were analyzed, and pelvic and spinal parameters were measured. Spinal shapes were classified on the hypothesis that the possible sagittal shapes of degenerative spine would be divided into four categories: "classical" Roussouly types 1-4, anteverted types (PT ≤ 5), retroverted types (PT ≥ 25) and kyphotic types.
Results: A total of 331 patients (280 women and 51 men) were included. "Classic" types 1-4 represented the majority in this cohort (71.9%). Retroverted types made the second most common category with 20.8% of the cohort. Kyphosis group (lumbar and global) make only 5.8% of this cohort, while anteverted group make the lowest incidence (1.5%). Retroverted type 2 with thoracic kyphosis should be considered a separate type and made 1.5% of this cohort. Two theoretical subtypes, retroverted type 1 and type 4 were not found.
Conclusions: This is the first description of degenerative spine disease based on its shape and based on the classification of the normal variation in the sagittal alignment of the human lumbar spine described by Roussouly. Eleven types, divided into classical types, anteverted types, false shapes (retroverted) and kyphotic shapes, are described and an evolution pathway is proposed. An evaluation of surgical results in order to propose a treatment algorithm based on this classification should follow.
Level of evidence: Level IV cross sectional observational study.
Keywords: Adult spinal deformity; Degenerative spine; Pelvic parameters; Roussouly classification; Sagittal balance; Scoliosis.