Automatic measurements of volar tilt and radial inclination of the distal radius on 3D models - validation against manual methods

Sep 30, 2026

Uploaded by Riley

Assessing distal radius malunions relies on measuring volar tilt and radial inclination in 2D radiographs, but projection errors and landmark ambiguity limit reliability. This study validated an algorithm for automatic 3D measurements on virtual models using a defined 3D coordinate system and anatomical landmarks that replicate conventional 2D definitions. Automatic results from 16 participants were compared with consensus manual 2D measurements and independent manual 3D measurements.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages13

Reading Time33 min

AccessFree to download

Background

Limits of 2D radiographic measurements

Promise of 3D measurement techniques

Method validation

Coordinate system and landmark definitions

Participants and comparison design

Agreement and discrepancy analysis

[www. nature.com/scientificreports](www. nature.com/scientificreports) OPEN Automatic measurements of volar tilt and radial inclination of the distal radius on 3D models: validation against manual methods Emilia Gryska1,2􀀍, Katleen Libberecht1,2, Johan Andersson3, Charlotte Stor Swinkels1,2,3, Peter Axelsson1,2 & Anders Björkman1,2 Assessing distal radius malunions traditionally relies on measuring volar tilt and radial inclination in 2Dradiographs. Reliability of these parameters is limited by projection errors and landmark ambiguity. Using 3D models allows more precise quantification of these parameters. This study validated an algorithm for measuring volar tilt and radial inclination on 3D virtual models of malunited and healthy radii. The algorithm establishes a 3D coordinate system and anatomical landmarks replicating conventional 2D definitions to maintain clinical compatibility. Automatic 3D measurements on models from 16 participants were compared with manual measurements on 2D radiographs (by three surgeonsin consensus) and on 3D models (by two independent raters). Agreement was assessed using Bland– Altman analysis, and landmark discrepancies were quantified. Mean differences between automatic 3D and manual 2D measurements were small: for volar tilt, 2.0° in malunited and 3.5° in healthy radii; for radial inclination, 1.5° and 2.3°, respectively. Strong agreement was also found between automatic and manual 3D measurements. Landmark deviations ranged from 0.5 to 2.8 mm, with an average longitudinal axis difference of 2.5°. This open-source algorithm provides a reproducible 3D assessment of distal radius alignment. By closely matching 2D standards, the algorithm has a high potential for clinical integration. Keywords Distal radius, 3D, Automatic, Volar tilt, Radial inclination, Anatomic landmarks Three-dimensional (3D) virtual surgical planning (VSP) and the use of patient-specific surgical guides have been increasingly adopted, particularly for reconstructing complex malunions in the upper extremity1–4. Compared with conventional two-dimensional (2D) planning and freehand osteotomy, 3D planning has demonstrated superior accuracy of correction1,5 and more favourable functional outcomes2. This is likely because planning corrections on 3D models facilitates more anatomically precise reconstructions than when relying on 2D images and radiographic parameters from these images for planning. Although 2D radiographic measurements are considered the gold standard in preoperative planning, they suffer from low reliability6–9. Studies by Fox et al. and MacDermid et al. have demonstrated that providing detailed measurement instructions can improve consistency7, 10, however, measurement protocols are not well standardized6, 10. Furthermore, image quality issues, such as inaccurate projections11–13, cast artefacts, healed fracture lines, or obscured anatomical landmarks, may compromise measurement accuracy, especially in complex skeletal deformity7. Due to these limitations, 2D methods may not reliably measure the true extent of a malunion or the correction outcome, especially within clinically acceptable ranges of 5° for volar tilt and 2 mm for ulnar variance14–16. 3D measurement techniques offer a promising alternative, having shown good-toexcellent inter-and intra-rater reliability17–19. While 3D measurements are generally more reproducible than 2D, manual placement of landmarks to estimate 3D radiographic parameters is affected by inter-rater variability, especially for volar tilt20. Algorithms that automatically identify landmarks and calculate radiographic parameters offer a promising solution to reduce this variability19,21–24. A few studies have demonstrated the reliability of automatic 3D methods compared with manual approaches in healthy radii21–23 and one in both malunited and healthy radii19. 1Department of Hand Surgery, Sahlgrenska University Hospital, Länsmansgatan 20, Mölndal 431 30, Sweden. 2In

FAQs

Why are volar tilt and radial inclination measurements difficult using 2D radiographs?

2D measurements can suffer from projection errors and landmark ambiguity, reducing reliability. Image quality issues and inconsistent measurement protocols can further compromise accuracy.

How does the study make the 3D measurements clinically comparable to 2D standards?

The algorithm establishes a 3D coordinate system and anatomical landmarks that replicate the conventional 2D definitions. This design maintains direct comparability with established clinical guidelines.

How were the automatic 3D measurements evaluated in the study?

Automatic 3D measurements on models from 16 participants were compared with manual measurements on 2D radiographs (three surgeons in consensus) and manual measurements on 3D models (two independent raters). Agreement was analyzed using Bland–Altman methods, and landmark discrepancies were quantified.

Sep 30, 2026

Uploaded by Riley