An artificial neural network model based on standing lateral radiographs for predicting sitting pelvic tilt in healthy adults

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

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.

Sagittal balance in sitting and standing positions: A systematic review of radiographic measures

Background

Sagittal imbalance can be caused by various etiologies and is among the most important indicators of spinal deformity. Sagittal balance can be restored through surgical intervention based on several radiographic measures. The purpose of this study is to review the normal parameters in the sitting position, which are not well understood and could have significant implications for non-ambulatory patients.

Methods

A systematic review was performed adhering to PRISMA Guidelines. Using R-software, the weighted means and 95% confidence intervals of the radiographic findings were calculated using a random effect model and significance testing using unpaired t-tests.

Results

10 articles with a total of 1066 subjects reported radiographic measures of subjects with no spinal deformity in the sitting and standing position. In the healthy individual, standing sagittal vertical axis -16.8°was significantly less than sitting 28.4° (p < 0.0001), while standing lumbar lordosis 43.3°is significantly greater than sitting 21.3° (p < 0.0001). Thoracic kyphosis was not significantly different between the two groups (p = 0.368). Standing sacral slope 34.3° was significantly greater than sitting 19.5° (p < 0.0001) and standing pelvic tilt 14.0° was significantly less than sitting 33.9° (p < 0.0001).

Conclusions

There are key differences between standing and sitting postures, which could lead to undue stress on surgical implants and poor outcomes, especially for non-ambulatory populations. There is a need for more studies reporting sitting and standing radiographic measures in different postures and spinal conditions.