Segmental Pelvic Correlation (SPeC): a novel approach to understanding sagittal plane spinal alignment

Area of Science:

• Orthopedics
• Radiology
• Spine Surgery

Background:

• Lumbar lordosis (LL) is linked to pelvic morphology, with higher LL associated with cranial shifts in inflection points.
• Understanding the specific relationship between each lumbar segment and pelvic morphology is crucial.

Purpose of the Study:

• To determine if a direct relationship exists between pelvic morphology and lumbar segmental angulation in the sagittal plane.
• To investigate the predictive value of pelvic incidence on lumbar spine alignment.

Main Methods:

• Retrospective analysis of 41 lateral whole spine radiographs with normal sagittal profiles.
• Measurement of spinopelvic parameters: pelvic incidence (PI), LL, thoracic kyphosis (TK), and segmental angulation (L1-S1).
• Pearson correlation coefficients were used to analyze relationships between pelvic parameters and segmental angulation.

Main Results:

• A strong correlation was observed between pelvic incidence (PI) and lumbar lordosis (LL).
• PI showed a strong correlation with L1 and L2 motion segments, particularly intervertebral discs.
• The contribution of L4-L5 and L5-S1 to total LL decreased as PI increased.

Conclusions:

• Pelvic incidence is a significant predictor of lumbar segmental angulation.
• While L4-L5 and L5-S1 traditionally contribute most to LL, cephalad segments (L1-L2) play an increasingly vital role in fine-tuning LL as PI rises.
• This understanding facilitates identification of segmental abnormalities and informs anatomical reconstruction strategies for degenerative adult spinal deformity.