OBJECTIVE: Pelvic morphology is an important element in determination of spinal alignment. We retrospectively examined the correlation between spinal alignment, severity, and pelvic morphology in lumbar disc herniation (LDH) surgery. METHODS: The study included 62 cases of paramedian LDH surgeries (L4-5: 19 cases; L5-S1: 43 cases). For all cases, we performed x-ray imaging of the whole spine in the standing position preoperatively and 1 week postoperatively and measured spinopelvic parameters. Comparing preoperative parameters of patients with 82 healthy subjects, we examined changes before and after surgery. We also examined the relationship between preoperative severity and parameters. RESULTS: Compared with healthy subjects, patients with LDH exhibited significantly decreased lumbar lordosis and sacral slope and increased pelvic tilt and sagittal vertical axis (P < 0.01). Japanese Orthopaedic Association score improved from 16.1 ± 4.6 preoperatively to 23.5 ± 3.2 1 week postoperatively (P < 0.01). Spinopelvic parameters observed preoperatively improved significantly 1 week postoperatively (P < 0.01). Correlation analysis did not confirm any correlation of severity with preoperative pelvic tilt, sagittal vertical axis, or pelvic incidence. However, cases with high pelvic tilt/pelvic incidence were significantly more likely to be severe cases (R2 = 0.08, P = 0.027). A significant decrease in pelvic tilt was observed in cases with a large improvement in postoperative Japanese Orthopaedic Association score (P = 0.031). CONCLUSIONS: For LDH cases, pelvic retroversion is important to avoid pain. The range of mobility for pelvic retroversion varies depending on pelvic morphology of individuals. In cases of LDH, ratio of pelvic tilt to pelvic incidence correlates strongly with severity.
OBJECTIVE: Pelvic morphology is an important element in determination of spinal alignment. We retrospectively examined the correlation between spinal alignment, severity, and pelvic morphology in lumbar disc herniation (LDH) surgery. METHODS: The study included 62 cases of paramedian LDH surgeries (L4-5: 19 cases; L5-S1: 43 cases). For all cases, we performed x-ray imaging of the whole spine in the standing position preoperatively and 1 week postoperatively and measured spinopelvic parameters. Comparing preoperative parameters of patients with 82 healthy subjects, we examined changes before and after surgery. We also examined the relationship between preoperative severity and parameters. RESULTS: Compared with healthy subjects, patients with LDH exhibited significantly decreased lumbar lordosis and sacral slope and increased pelvic tilt and sagittal vertical axis (P < 0.01). Japanese Orthopaedic Association score improved from 16.1 ± 4.6 preoperatively to 23.5 ± 3.2 1 week postoperatively (P < 0.01). Spinopelvic parameters observed preoperatively improved significantly 1 week postoperatively (P < 0.01). Correlation analysis did not confirm any correlation of severity with preoperative pelvic tilt, sagittal vertical axis, or pelvic incidence. However, cases with high pelvic tilt/pelvic incidence were significantly more likely to be severe cases (R2 = 0.08, P = 0.027). A significant decrease in pelvic tilt was observed in cases with a large improvement in postoperative Japanese Orthopaedic Association score (P = 0.031). CONCLUSIONS: For LDH cases, pelvic retroversion is important to avoid pain. The range of mobility for pelvic retroversion varies depending on pelvic morphology of individuals. In cases of LDH, ratio of pelvic tilt to pelvic incidence correlates strongly with severity.