Precision of an automated surface-based CT-RSA (asCTRSA) for assessing tibial implant migration: a porcine cadaver study and a clinical case
DOI:
https://doi.org/10.2340/17453674.2026.46156Keywords:
Arthroplasty, CT-RSA, image processing, image registration, Implant migration, Implants, KneeAbstract
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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Copyright (c) 2026 Manou Acke, Benyameen Keelson, Lars H W Engseth, Frank-David Øhrn, Gert van Gompel, Stephan M Röhrl, Anselm Schulz, Johan de Mey, Nico Buls
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