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- Title
Distances and angles in standing long-leg radiographs: comparing conventional radiography, digital radiography, and EOS.
- Authors
Birkenmaier, Christof; Levrard, Louise; Melcher, Carolin; Wegener, Bernd; Ricke, Jens; Holzapfel, Boris M.; Baur-Melnyk, Andrea; Mehrens, Dirk
- Abstract
Objective: Distances and angles measured from long-leg radiographs (LLR) are important for surgical decision-making. However, projectional radiography suffers from distortion, potentially generating differences between measurement and true anatomical dimension. These phenomena are not uniform between conventional radiography (CR) digital radiography (DR) and fan-beam technology (EOS). We aimed to identify differences between these modalities in an experimental setup. Materials and methods: A hemiskeleton was stabilized using an external fixator in neutral, valgus and varus knee alignment. Ten images were acquired for each alignment and each modality: one CR setup, two different DR systems, and an EOS. A total of 1680 measurements were acquired and analyzed. Results: We observed great differences for dimensions and angles between the 4 modalities. Femoral head diameter measurements varied in the range of > 5 mm depending on the modality, with EOS being the closest to the true anatomical dimension. With functional leg length, a difference of 8.7% was observed between CR and EOS and with the EOS system being precise in the vertical dimension on physical-technical grounds, this demonstrates significant projectional magnification with CR-LLR. The horizontal distance between the medial malleoli varied by 20 mm between CR and DR, equating to 21% of the mean. Conclusions: Projectional distortion resulting in variations approaching 21% of the mean indicate, that our confidence on measurements from standing LLR may not be justified. It appears likely that among the tested equipment, EOS-generated images are closest to the true anatomical situation most of the time.
- Subjects
RADIOGRAPHY; RADIOGRAPHS; EXTERNAL fixators; FEMUR head; ANGLES
- Publication
Skeletal Radiology, 2024, Vol 53, Issue 8, p1517
- ISSN
0364-2348
- Publication type
Article
- DOI
10.1007/s00256-024-04592-9