Precision of an automated surface-based CT-RSA (asCTRSA) for assessing tibial implant migration: a porcine cadaver study and a clinical case

Authors

  • Manou Acke Department of Radiology, Vrije Universiteit Brussel (VUB), Universitair Ziekenhuis Brussel (UZ Brussel), Brussels, Belgium https://orcid.org/0000-0002-8714-1708
  • Benyameen Keelson Department of Radiology, Vrije Universiteit Brussel (VUB), Universitair Ziekenhuis Brussel (UZ Brussel), Brussels, Belgium
  • Lars H W Engseth Faculty of Medicine, University of Oslo (UiO), Oslo; Division for Orthopedic Surgery, Oslo University Hospital (OUH), Oslo, Norway https://orcid.org/0000-0001-8254-5765
  • Frank-David Øhrn Nordmøre and Romsdal Hospital (SNR), Møre and Romsdal Hospital Trust, Hjelsetay, Norway; Department of Neuromedicine and Movement Science (INB), Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology (NTNU), Trondheim, Norway https://orcid.org/0000-0002-7880-8101
  • Gert van Gompel Department of Radiology, Vrije Universiteit Brussel (VUB), Universitair Ziekenhuis Brussel (UZ Brussel), Brussels, Belgium
  • Stephan M Röhrl Faculty of Medicine, University of Oslo (UiO), Oslo, Norway; Division for Orthopedic Surgery, Oslo University Hospital (OUH), Oslo, Norway https://orcid.org/0000-0001-5784-2055
  • Anselm Schulz Faculty of Medicine, University of Oslo (UiO), Oslo, Norway; Akershus University Hospital (Ahus), Department of Radiology, Lørenskog, Norway https://orcid.org/0000-0001-7406-5497
  • Johan de Mey Department of Radiology, Vrije Universiteit Brussel (VUB), Universitair Ziekenhuis Brussel (UZ Brussel), Brussels, Belgium
  • Nico Buls Department of Radiology, Vrije Universiteit Brussel (VUB), Universitair Ziekenhuis Brussel (UZ Brussel), Brussels, Belgium

DOI:

https://doi.org/10.2340/17453674.2026.46156

Keywords:

Arthroplasty, CT-RSA, image processing, image registration, Implant migration, Implants, Knee

Abstract

Background and purpose: Radiostereometric analysis (RSA) is the reference standard for migration analysis, but adoption is limited by invasive marker implantation and specialized equipment. We developed an automated, surface-based CT-RSA (asCTRSA) method that reports a registration quality measure (mean rigid-body fitting error, ME). Our aim was to evaluate the precision by comparing asCTRSA with marker-based RSA and CT-based Micromotion Analysis (CTMA, v25.1).
Methods: Precision was assessed in a retrospective, repeated-measures, zero-migration study using a porcine cadaver tibial implant scanned in 7 positions (21 double examinations). Migration was reported as maximum total point motion (MTPM) for RSA and asCTRSA. CTMA provided maximum total translation (mTT) as an estimate of MTPM. Mean rigid-body fitting error (ME) was calculated for RSA and asCTRSA (acceptability threshold 0.35 mm). The minimal important difference for MTPM/mTT was 0.1 mm. asCTRSA was applied to 1 clinical case with known migration 3 and 8 months postoperatively (NCT04017533).
Results: In the porcine study, precision was 0.09 mm (95% confidence interval [CI] 0.02–0.18) for asCTRSA, 0.08 mm (CI 0.03–0.12) for CTMA, and 0.45 mm (CI 0.20–0.69) for RSA. In the clinical case, asCTRSA detected increasing migration (MTPM 2.5–3.6 mm) and exceeded CTMA’s mTT by 0.4 mm at 8 months. Mean rigid-body fitting error remained below 0.35 mm.
Conclusion: We showed that asCTRSA enables automated, surface-based CT-RSA and demonstrated higher precision than RSA in this zero-migration cadaver setting.

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Published

2026-07-16

How to Cite

Acke, M., Keelson, B., Engseth, L. H. W., Øhrn, F.-D., van Gompel, G., Röhrl, S. M., … Buls, N. (2026). Precision of an automated surface-based CT-RSA (asCTRSA) for assessing tibial implant migration: a porcine cadaver study and a clinical case. Acta Orthopaedica, 97, 484–490. https://doi.org/10.2340/17453674.2026.46156

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