Wide anatomical variability of PI normative values within an asymptomatic population: a systematic review

Kari Odland, Sharon C Yson, David W. Polly

Research output: Contribution to journalReview articlepeer-review

2 Scopus citations


Purpose: Studies on sagittal alignment parameters have solely focused on patients with preexisting spinal deformity. Limited data in the literature have analyzed pelvic incidence (PI) values in an asymptomatic patient population. The purpose of this study was to: (1) systematically review the literature to analyze normative PI values in asymptomatic patients; and (2) provide a more definitive geometric measurement guide for determining surgical interventions. Methods: A systematic review of retrospective studies was performed by searching PubMed to identify studies that analyzed PI measurements in asymptomatic subjects. The following search phrases were used: (pelvic incidence, pelvic tilt, sacral slope, sagittal alignment, radiograph, asymptomatic, normative values, and adults) using Boolean operators AND, OR and NOT. Patients with pathology involving the osseous pelvic anatomy (including fracture, infection, tumor, previous surgery, and lumbosacral fusion) that would prevent measurement of the selected parameters were not included. Pelvic incidence (PI) values were analyzed. Results: A total of 29 studies met inclusion criteria, including 3629 asymptomatic subjects who underwent standing lateral radiographs (mean age, 41.1 years; range, 24–69 years) for the purposes of analyzing pelvic incidence values. Overall, the mean PI value was 50.0° (range, 24–69) which is consistent with reported values in the literature. Conclusion: Wide anatomical variability and broad clinical interpretation of PI normative values do little to guide surgical planning for successful outcomes. However, this systematic review has presented PI-stratified normative values in a large sample of asymptomatic subjects which can serve as a grounded geometric reference for spine surgeons when considering surgical intervention approaches.

Original languageEnglish (US)
Pages (from-to)559-566
Number of pages8
JournalSpine Deformity
Issue number3
StatePublished - May 2023

Bibliographical note

Funding Information:
This systematic review was funded by SI-Bone, Inc. The grant was used for the salary of a full-time research associate during the initial stages of the study.

Publisher Copyright:
© 2023, The Author(s), under exclusive licence to Scoliosis Research Society.


  • Normative values
  • Pelvic incidence
  • Radiographs
  • Sagittal
  • Spinopelvic measurements

PubMed: MeSH publication types

  • Systematic Review
  • Journal Article
  • Review


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