• Elke Arts, Han Nijsink, Luc Verhamme, Jan Biert, Mike Bemelman, Lars Brouwers, and Bas van Wageningen.
• Department of Trauma Surgery, Radboud University Medical Centre, Nijmegen, The Netherlands. elke.arts@radboudumc.nl.
• Eur J Trauma Emerg Surg. 2021 Dec 1; 47 (6): 1873-1880.

BackgroundIn patients with acetabular fractures, the reconstructed three-dimensional (3D) model of the contralateral acetabulum could be used as a mirrored template for the anatomical configuration of the affected joint. This has not been validated.ObjectiveTo investigate whether the right and left acetabula, as reconstructed 3D models, are valid mirrored duplicates that can be used as a reference model for the contralateral side.MethodsCT scans of twenty patients with unaffected acetabula were used. The symmetry of the generated 3D models was evaluated through: (1) mirroring of the acetabulum; (2) initial rough matching; (3) automatic optimisation of the matching via surface-based matching; (4) calculation of distances between surfaces by evaluating the Euclidean (straight-line) error distance between the closest points between left and right. The percentages of surface points of the left and right acetabulum with a distance smaller than 0.5, 1.0, 1.5 and 2.0 mm were calculated and evaluated, in relation to Matta's criteria, for acetabular fracture reductions.ResultsThe mean distance deviation was less than 0.75 mm in all 40 comparisons. The calculated distances in 90.7% of the surface points of the left and right acetabulum were below the tolerance threshold of 1.0 mm, based on Matta's anatomical reduction criteria, and 98.7% of the surface points scored below Matta's imperfect tolerance threshold of 2.0 mm.ConclusionThis study demonstrates 3D reconstructed models of healthy left and right acetabula are highly similar and could potentially be used as mirrored duplicates. The next step will be to investigate these results in patients with reduced acetabular fractures.© 2019. The Author(s).

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