Evaluation of a new sagittal classification system in adolescent idiopathic scoliosis.

PURPOSE: The purpose of the present study was to validate a new spinal sagittal classification.
METHODS: We retrospectively included 105 consecutive AIS patients who underwent posterior spinal fusion. Preoperative long-standing EOS radiographs were available on all patients. Patients were classified according to the four suggested sagittal patterns: type 1, 2a, 2b or 3. Several predetermined sagittal parameters were compared between the groups.
RESULTS: The mean preoperative Cobb angle was 64° ± 12°, and 73% of the patients were female. Of 105 patients, 51 were type 1, 14 were type 2a, one was type 2b and 39 were type 3. The distribution of the four sagittal patterns was significantly different compared with the original publication (p < 0.05). However, the two study populations were comparable in terms of Lenke and Roussouly types (p = 0.49 and 0.47, respectively). In our study population, the sagittal groups differed significantly in terms of thoracic kyphosis, length of thoracic and lumbar curves, lumbar lordosis, thoracic slope, C7 slope, pelvic incidence and sacral slope (p < 0.05).
CONCLUSION: The distribution of the four sagittal patterns varies between AIS cohorts. Type 2b was rare, which limits the clinical applicability. Contrary to the original publication, we found that the spinopelvic parameters lumbar lordosis, pelvic incidence and sacral slope were significantly different between the Abelin-Genevois types. Hence, the corrective surgical strategy may need to incorporate these spinopelvic parameters to achieve a balanced spine requiring a minimum of energy expenditure. These slides can be retrieved under Electronic Supplementary Material.