Usefulness of slice encoding for metal artifact correction (SEMAC) technique for reducing metal artifacts after total knee arthroplasty

  • Ahmed JawharEmail author
  • Miriam Reichert
  • Michael Kostrzewa
  • Mathias Nittka
  • Ulrike Attenberger
  • Henning Roehl
  • Frederic Bludau
Original Article • KNEE - ARTHROPLASTY



To evaluate the usefulness of a novel MRI sequence strategy in the assessment of the periprosthetic anatomical structures after primary total knee arthroplasty.


Two MR sequences were retrospectively compared for the imaging of 15 patients with implanted cruciate-retaining/fixed-bearing TKAs (DePuy, PFC Sigma): a slice encoding sequence for metal artifact correction (SEMAC) and a standard sequence. Images were acquired on a 1.5-T system. The degree of artifact reduction was assessed using several qualitative (Likert-type scale) (artifact size, distorsion, blur, image quality, periprosthetic bone, posterior cruciate ligament, lateral collateral ligament, medial collateral ligament, patella tendon, popliteal vessels) and quantitative (artifact volume, Insall–Salvati index, length of patella/tendon, prosthesis dimensions) parameters by blinded reads performed by four investigators. The SEMAC sequences were statistically compared with the standard sequence using Wilcoxon test. Additionally, the intraclass correlation coefficient (ICC) for interobserver agreement was calculated.


Higher levels of blurring were found with SEMAC compared to standard sequences (p < 0.001). All other qualitative parameters improved significantly with the application of SEMAC. In comparison with conventional sequences, the artifact volume was reduced by 59% utilizing SEMAC. Thus, the artifact reduction improved the precision of measurements such as Insall–Salvati index and length of patella/tendon (p < 0.001). The dimension of the tibial component (Ti alloy/polyethylene) revealed accurate values with both MRI sequences. A sufficient interobserver agreement among all readers was found with SEMAC, qualitatively ICC 0.9 (range 0.8–1) as well as quantitatively ICC 0.95 (range 0.92–0.98).


SEMAC effectively reduces artifacts caused by metallic implants after total knee arthroplasty relative to standard imaging. This allows for an improved assessment of periprosthetic anatomical structures. This might enable an improved detectability of postoperative complications in the future.

Level of evidence

Diagnostic Study Level III.


Total knee arthroplasty Ligaments Periprosthetic bone SEMAC Artifact reduction 


Compliance with ethical standards

Conflict of interest

Mathias Nittka is an employee of Siemens Healthcare GmbH. The remaining authors declare that there were no conflicts of interest.


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Copyright information

© Springer-Verlag France SAS, part of Springer Nature 2018

Authors and Affiliations

  • Ahmed Jawhar
    • 1
    Email author
  • Miriam Reichert
    • 2
  • Michael Kostrzewa
    • 4
  • Mathias Nittka
    • 3
  • Ulrike Attenberger
    • 2
  • Henning Roehl
    • 1
  • Frederic Bludau
    • 1
  1. 1.Department of Orthopaedics and Trauma Surgery, University Medical Center Mannheim, Medical Faculty MannheimHeidelberg UniversityMannheimGermany
  2. 2.Department of Clinical Radiology and Nuclear Medicine, Institute of Clinical Radiology and Nuclear Medicine, University Medical Center Mannheim, Medical Faculty MannheimHeidelberg UniversityMannheimGermany
  3. 3.Siemens Healthcare GmbHErlangenGermany
  4. 4.Division of Vascular and Interventional Radiology, Department of Medical Imaging, Toronto General Hospital and Mount Sinai HospitalUniversity of TorontoTorontoCanada

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