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Pelvic index: A new pelvic parameter for assessing sagittal spinal alignment.
Justice U Achonu1, Kenny Ling1, Rohit Bhan1
1Department of Orthopaedics and Rehabilitation, Stony Brook University, HSC-T18, Room 085, Stony Brook, NY 11794-8181, United States.
North American Spine Society Journal
|October 23, 2023
Summary
A new pelvic index measurement aids in classifying spinal deformity types. This length measurement, combined with pelvic incidence, improves differentiation of Roussouly types, particularly low-pelvic incidence categories.
Area of Science:
- Orthopedics
- Spine Surgery
- Radiographic Analysis
Background:
- Correctional surgery for adult spinal deformity (ASD) has risen significantly.
- Pelvic incidence is the standard angular measurement for classifying spinal shapes into Roussouly types.
- Restoring original Roussouly classification is believed to optimize surgical outcomes.
Purpose of the Study:
- To introduce a novel pelvic parameter, the pelvic index, as a length measurement.
- To assess the pelvic index's utility in complementing pelvic incidence for Roussouly type characterization.
- To enhance the accuracy of classifying spinal shapes.
Main Methods:
- Retrospective analysis of sagittal spinal radiographs from 208 patients.
- Measurements included pelvic incidence, sacroacetabular distance, and L5 vertebral height.
- Pelvic index calculated as sacroacetabular distance to L5 height ratio; compared between Roussouly types.
Main Results:
- Pelvic index showed statistically significant differences between Roussouly types 1 and 2 (p=.046), and types 1 and 3 AP (p=.029).
- Pelvic incidence was only significantly different between types 3 and 4 (p<.001).
- Pelvic index did not show significant differences between types 3 and 4 (p=.251).
Conclusions:
- Pelvic index, a ratio of sacroacetabular distance to L5 height, complements pelvic incidence.
- This new parameter assists in differentiating Roussouly types 1 and 2, and 1 and 3 AP.
- Pelvic index offers improved characterization for low-pelvic incidence spinal deformities.
