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. 2025 Apr 26;15(1):14685.
doi: 10.1038/s41598-025-98819-x.

Spinopelvic parameters in the lateral decubitus are different from standing and sitting positions

Mohammadreza Razzaghof  1   2 , Alireza Moharrami  1 , Ahmad Abbaszadeh  1 , Mostafa Houshmand  1 , Seyed Mohammad Javad Mortazavi  3   4   5
Affiliations

Spinopelvic parameters in the lateral decubitus are different from standing and sitting positions

Mohammadreza Razzaghof et al. Sci Rep. .

Abstract

To investigate how spinopelvic parameters change when transitioning between standing, sitting, and lateral decubitus (LD) positions, providing insights for optimizing acetabular cup placement in total hip arthroplasty (THA). A retrospective study was performed on 140 patients undergoing primary THA from 2023 to 2024. Lateral spinopelvic radiographs were taken in standing, sitting, and LD positions, measuring SS, PT, pelvic incidence (PI), and ante-inclination (AI). Measurements were performed by two independent reviewers using mediCAD® software, with inter-rater reliability assessed (ICC range: 0.83-0.91). Paired t-tests were used to compare spinopelvic parameters (SPP) values across positions, and associations with demographic factors, spinopelvic mobility, and other clinical variables were analyzed using Chi-square, ANOVA, and Kruskal-Wallis tests. We included 90 men (mean age 44.93 ± 13.28 years) and 50 women (mean age 43.10 ± 12.17 years). Mean BMI was 26.4 ± 3.1 kg/m². SS, PT, and AI showed significant differences across positions (P < 0.001). From standing to LD, SS decreased (<-5°) in 51.4% of patients, remained consistent (-5 to + 5°) in 35.7%, and increased ( > + 5°) in 12.9%. AI decreased in 26.4% of patients, remained consistent in 25.7%, and increased in 47.9%. Changes in AI correlated with SS (P = 0.02) and PT (P = 0.001). No significant associations were found between SPP changes and age, gender, BMI, or spinopelvic mobility. Our study showed that pelvic position and, consequently, acetabular orientation may change in LD, indicating that SPPs in LD cannot be assumed to be the same as in standing. It has implications for surgeons performing THA in LD, as intraoperative pelvic shifts may influence implant positioning and potentially impact postoperative stability and functional outcomes.

Keywords: Lateral decubitus; Pelvic Tilt; Pelvic incidence; Sacral slope; Spinopelvic; Total hip arthroplasty.

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Conflict of interest statement

Declarations. Competing interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Standing position for lateral spinopelvic radiographic imaging.
Fig. 2
Fig. 2
Sitting position for lateral spinopelvic radiographic imaging.
Fig. 3
Fig. 3
Lateral decubitus position for lateral spinopelvic radiographic imaging.
Fig. 4
Fig. 4
Patterns of change in sacral slope (SS), pelvic tilt (PT), ante-inclination (AI) between standing and lateral decubitus position.
Fig. 5
Fig. 5
The contingency table showing changes in ante-inclination (AI) across pelvic tilt (PT) between the standing and lateral decubitus positions.
See this image and copyright information in PMC

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