Pelvico-Sacro-L1 Angle: An Index for Rapid Evaluation of Spinopelvic Sagittal Balance

Articles in Press

Document Type : RESEARCH PAPER

Authors

1 a Joint Reconstruction Research Center, Tehran University of Medical Sciences, Tehran, Iran b Department of Orthopedic Surgery, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran

2 Joint Reconstruction Research Center, Department of Orthopedic Surgery, Tehran University of Medical Sciences, Keshavarz Boulevard, Tehran, Iran

10.22038/abjs.2025.84981.3868

Abstract

Purpose: This study aims to evaluate the Pelvico-Sacro-L1 angle (PSLA) as a direct parameter for assessing PI-LL mismatch, a key determinant of sagittal balance.

Methods: In this retrospective study, adult patients scheduled for total hip arthroplasty (THA) underwent spinopelvic lateral X-rays. PSLA was defined as the angle between a line passing through the center of the femoral head to the center of the superior endplate of S1 and the superior endplate of L1. The deviation from 90° was termed the modified PSLA, an alternative to PI-LL mismatch. Two independent orthopedic surgeons measured spinopelvic parameters, then re-evaluated the radiographs four weeks later.

Results: We included 92 patients (average age: 57.4 ± 9.9 years, 50 females). The Bland–Altman plot indicated no significant systematic difference between the two measurement sets, suggesting good agreement between methods. The intraclass correlation coefficient (ICC) for PSLA in both inter- and intraobserver reliability was greater than 0.9, indicating excellent agreement.

Conclusions: The PSLA demonstrated a strong agreement with the PI-LL mismatch, confirming the reliability of this approach. This approach provides a more straightforward and easily interpretable measurement

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Main Subjects

The Archives of Bone and Joint Surgery

Articles in Press, Accepted Manuscript
Available Online from 16 September 2025

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History

  • Receive Date: 28 December 2024
  • Revise Date: 05 September 2025
  • Accept Date: 16 June 2025

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