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{\textquoteright}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.
Acke, M, Keelson, B, Engseth, LHW, Øhrn, F-D, Van Gompel, G, Röhrl, S, Schulz, A, De Mey, J & 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, vol. 97, pp. 484–490. https://doi.org/10.2340/17453674.2026.46156
Acke, M., Keelson, B., Engseth, L. H. W., Øhrn, F.-D., Van Gompel, G., Röhrl, S., Schulz, A., De Mey, J., & 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
@article{7a2603ae3c9048ada5259a8322e760db,
title = "Precision of an automated surface-based CT-RSA (asCTRSA) for assessing tibial implant migration: a porcine cadaver study and a clinical case",
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{\textquoteright}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.",
keywords = "arthroplasty, CT-RSA, Image processing, Image registration, implant migration, Implant, Knee",
author = "Manou Acke and Benyameen Keelson and Engseth, \{Lars H.W.\} and Frank-David {\O}hrn and \{Van Gompel\}, Gert and Stephan R{\"o}hrl and Anselm Schulz and \{De Mey\}, Johan and Nico Buls",
year = "2026",
month = jul,
day = "16",
doi = "10.2340/17453674.2026.46156",
language = "English",
volume = "97",
pages = "484–490",
journal = "Acta Orthopaedica",
issn = "1745-3674",
publisher = "Informa Healthcare",
}