Spinopelvic Parameters Depending on the Angulation of the Sacral End Plate Are Less Reproducible Than Other Spinopelvic Parameters in Adult Spinal Deformity Patients

Tanvir Johanning Bari; Dennis Winge Hallager; Niklas Tøndevold; Ture Karbo; Lars Valentin Hansen; Benny Dahl; Martin Gehrchen

doi:10.1016/j.jspd.2018.12.002

Spinopelvic Parameters Depending on the Angulation of the Sacral End Plate Are Less Reproducible Than Other Spinopelvic Parameters in Adult Spinal Deformity Patients

Spine Deform. 2019 Sep;7(5):771-778. doi: 10.1016/j.jspd.2018.12.002.

Authors

Tanvir Johanning Bari¹, Dennis Winge Hallager², Niklas Tøndevold², Ture Karbo², Lars Valentin Hansen², Benny Dahl³, Martin Gehrchen²

Affiliations

¹ Spine Unit, Department of Orthopedic Surgery, Rigshospitalet, University Hospital of Copenhagen, Copenhagen, Denmark. Electronic address: [email protected].
² Spine Unit, Department of Orthopedic Surgery, Rigshospitalet, University Hospital of Copenhagen, Copenhagen, Denmark.
³ Department of Orthopedics and Scoliosis Surgery, Texas Children's Hospital and Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA.

PMID: 31495478
DOI: 10.1016/j.jspd.2018.12.002

Abstract

Study design: Reproducibility study.

Objectives: To report the agreement and reliability for commonly used sagittal plane measurements.

Summary of background data: Spinopelvic parameters and sagittal vertical axis (SVA) are commonly used parameters for preoperative planning and postoperative evaluation of patients with adult spinal deformity (ASD). Previous reproducibility studies have focused on describing the reliability using intraclass correlation coefficients (ICCs), thus quantifying the methods' ability to distinguish between individuals. To our knowledge, no previous study in patients with ASD has reported the measurement error in terms of limits of agreement. The current study aimed to report the agreement and reliability for measurements of pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), and SVA in ASD patients.

Methods: In a consecutive, one-center cohort of 64 patients referred for ASD evaluation, a blinded test-retest study was performed. Reliability was assessed using ICCs, whereas 95% limits of agreement (LOAs) were used to quantify agreement.

Results: We found "excellent" (ICC > 0.9) results in all analyses of reliability except for interrater PI, which was classified as "good" (ICC = 0.89). However, considerable interrater measurement error was observed for parameters depending on the angulation of the sacral end plate (95% LOA of ±11° and ±14° for SS and PI, respectively) compared with ±5° for PT and ±7 mm for SVA, which depends on the location of the sacral end plate. Intrarater agreement was only slightly better.

Conclusion: These are to our knowledge the first estimates of measurement error for sagittal spinopelvic parameters in ASD patients. Despite near excellent ICCs, we found considerable measurement error for parameters depending on the angulation rather than the location of the sacral end plate.

Level of evidence: Level II.

Keywords: Adult; Agreement; Reliability; Reproducibility; Spine.

MeSH terms

Adult
Cohort Studies
Female
Humans
Male
Middle Aged
Pelvis / diagnostic imaging*
Preoperative Care / standards*
Radiography / standards
Reproducibility of Results
Sacrum / diagnostic imaging*
Spinal Curvatures / diagnostic imaging*
Young Adult