A Flat Sagittal Spinal Alignment Is Common among Young Patients with Lumbar Disc Herniation

Background: Recent studies suggest a correlation between spinal sagittal alignment and different types of lumbar pathologies due to different load patterns on the lumbar spine. The main objective of this study was to investigate the preoperative spinal sagittal alignment in young patients (<25 years) undergoing lumbar disc herniation surgery. Methods: Information regarding preoperative clinical examinations was collected from the patient medical charts. Preoperative MRI examinations were used to classify lumbar types according to four sagittal spinal alignment groups (1: a long thoracic kyphosis, 2: a flat back, 3: a normal spine and 4: an increased thoracic kyphosis). Other MRI findings were also noted. Classification of lumbar types was performed independently by three spine surgeons. To compare two sample proportions the 2-sample z-test was performed. Results: The distribution of lumbar curve types was: Type 1, 17% (9 patients); Type 2, 62% (33 patients); Type 3, 17% (9 patients) and Type 4, 4% (2 patients). The distribution of operated levels was: L3 L4, 2% (1 patient); L4 L5, 47% (25 patients); L5 S1, 42% (22 patients) and L4 L5 + L5 S1, 9% (5 patients). Conclusions: A majority of the young patients (62%) that underwent surgery due to herniated disc in the lumbar spine were classified as Type 2 indicating a flat back. Future studies are needed to increase the knowledge about spinopelvic sagittal alignment and the correlation to spinal pathologies.