Rotational alignment of the lower extremity in the presence of total knee endoprosthesis: Reproducibility of torsion analyses using ultra-low-dose photon-counting CT

Theresa Sophie Patzer; Andreas Steven Kunz; Henner Huflage; Karsten Sebastian Luetkens; Nora Conrads; Pauline Pannenbecker; Axel Jakuscheit; Stephan Reppenhagen; Süleyman Ergün; Thorsten Alexander Bley; Jan-Peter Grunz

doi:10.1016/j.ejrad.2023.111055

Rotational alignment of the lower extremity in the presence of total knee endoprosthesis: Reproducibility of torsion analyses using ultra-low-dose photon-counting CT

Eur J Radiol. 2023 Oct:167:111055. doi: 10.1016/j.ejrad.2023.111055. Epub 2023 Aug 19.

Affiliations

¹ Department of Diagnostic and Interventional Radiology, University Hospital Würzburg, Oberdürrbacher Straße 6, 97080 Würzburg, Germany. Electronic address: Patzer_T@ukw.de.
² Department of Diagnostic and Interventional Radiology, University Hospital Würzburg, Oberdürrbacher Straße 6, 97080 Würzburg, Germany.
³ Department of Orthopaedic Surgery, Koenig-Ludwig-Haus, University of Würzburg, Brettreichstrasse 11, 97074 Würzburg, Germany.
⁴ Institute of Anatomy and Cell Biology, University of Würzburg, Koellikerstraße 6, 97070 Würzburg, Germany.

PMID: 37632998
DOI: 10.1016/j.ejrad.2023.111055

Abstract

Purpose: Leg torsion analysis can provide valuable information in symptomatic patients after total knee arthroplasty. However, extensive beam-hardening and photon-starvation artifacts limit diagnostic assessability and dose reduction potential. For this study, we investigated the reproducibility of rotational measurements in ultra-low-dose photon-counting CT with spectral shaping via tin prefiltration.

Material and methods: Employing a first-generation photon-counting CT, eight cadaveric specimens were examined with an established three-level scan protocol (hip: Sn 140, knee: Sn 100, ankle: Sn 100 kVp). In three body donors with unilateral knee endoprostheses, additional modified settings were applied (Sn 140 kVp at knee level). Protocols were executed with three dose levels (hip-knee-ankle, high-quality: 5.0-3.0-2.0 mGy, low-dose: 0.80-0.30-0.26 mGy, ultra-low-dose: 0.25-0.06-0.06 mGy). Six radiologists performed torsion analyses, additionally reporting their diagnostic confidence. Intraclass correlation coefficients (ICC) were calculated to assess interrater reliability.

Results: No significant differences were ascertained for femoral (p = 0.330), tibial (p = 0.177), and overall leg rotation measurements (p = 0.358) among high-quality, low-dose, and ultra-low-dose protocols. Interrater reliability was excellent for torsion of the femur (ICC 0.915, 95% confidence interval 0.871-0.947), tibia (0.960, 0.938-0.976), and overall leg (0.967, 0.945-0.981). In specimens with total knee endoprostheses, absolute rotational measurements were unaffected by dose level and tube voltage despite superior diagnostic confidence on the ipsilateral and contralateral sides with modified settings (p < 0.001).

Conclusions: Combining the advantages of photon-counting CT and spectral shaping, reliable leg torsion analyses are feasible with ultra-low radiation exposure even in the presence of total knee endoprostheses.

Keywords: Leg rotation; Photon-counting; Radiation dosage; Tomography, x-ray computed; Torsion measurement.

MeSH terms

Humans
Knee Joint / surgery
Lower Extremity*
Prostheses and Implants
Reproducibility of Results
Tomography, X-Ray Computed* / methods