Influence of patient axial malpositioning on the trueness and precision of pelvic parameters obtained from 3D reconstructions based on biplanar radiographs
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Radiographs are often performed to assess pelvic and hip parameters, but results depend upon correct pelvis positioning. Three-dimensional (3D) reconstruction from biplanar-radiographs should provide parameters that are less sensitive to pelvic orientation, but this remained to be evaluated.
Computerized-tomographic scans of six patients were used both as a reference and for generating simulated frontal and lateral radiographs. These simulated radiographs were generated while introducing axial rotations of the pelvis ranging from 0° to 20°. Simulated biplanar-radiographs were utilized by four operators, three times each, to perform pelvic 3D-reconstructions. These reconstructions were used to assess the trueness, precision and global uncertainty of radiological pelvic and hip parameters for each position.
In the neutral position, global uncertainty ranged between ± 2° for pelvic tilt and ± 9° for acetabular posterior sector angle and was mainly related to precision errors (ranging from 1.5° to 7°). With increasing axial rotation, global uncertainty increased and ranged between ± 5° for pelvic tilt and ± 11° for pelvic incidence, sacral slope and acetabular anterior sector angle, mainly due to precision errors.
Radiological parameters obtained from 3D-reconstructions, based on biplanar-radiographs, are less sensitive to axial rotation compared to plain radiographs. However, the axial rotation should nonetheless not exceed 10°.
• Pelvic radiological parameters could be affected by patient malpositioning.
• Biplanar radiograph-based 3D reconstructions were performed at increments of axial rotation.
• Trueness, precision and global uncertainty were evaluated for pelvic and hip radiological parameters.
• Hip parameters were less affected by rotation compared to pelvic parameters.
• Maintaining the pelvis close to the neutral position is recommended to ensure the highest possible accuracy.
KeywordsPelvis Rotation Biplanar X-rays Trueness Precision
The scientific guarantor of this publication is Ismat Ghanem.
The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article. Wafa Skalli is coinventor of the EOS low dose bi-planar X-Ray system, without personal financial benefit.
This study has received funding by the research council of the University of Saint-Joseph (grant number FM276) and the French-Lebanese cooperation for research CEDRE (grant number 11 SCI F 44/L36). The sponsors had no involvement in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the article for publication. No complex statistical methods were necessary for this paper. Institutional Review Board approval was obtained.
Written informed consent was not required for this study because data were previously obtained for clinical purpose and subject gave their informed consent for their further use in research purposes. Methodology: retrospective, observational, performed at one institution.
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