Unicompartmental knee arthroplasty MRI: impact of slice-encoding for metal artefact correction MRI on image quality, findings and therapy decision

Christoph A. Agten, Filippo Del Grande, Sandro F. Fucentese, Samuel Blatter, Christian W.A. Pfirrmann, Reto Sutter

Research output: Contribution to journalArticlepeer-review


Objectives: To evaluate the impact of slice-encoding for metal artefact correction (SEMAC) on image quality, findings, and therapy decision in patients with unicompartmental knee arthroplasty (UKA). Methods: Forty-five painful UKAs were examined at 1.5T-MRI (STIR, proton-density(PD)-weighted sequence, each with SEMAC and high-bandwidth). Artefact size, image quality, anatomic depiction, and clinically relevant findings were compared between SEMAC and high-bandwidth (2 readers). In 30 patients, therapy decision was retrospectively assessed by two orthopaedic surgeons without MRI, with high-bandwidth-MRI, and with SEMAC-MRI. Results: SEMAC reduced mean artefact size for STIR (11.8 cm2 vs. 37.7 cm2) and PD (16.8 cm2 vs. 18.9 cm2), p < 0.0005 for both comparisons. SEMAC showed more blurring than high-bandwidth, p < 0.0005. STIR-SEMAC revealed more bone marrow oedema (29 vs. 18 patients, p = 0.001, 30 vs. 13 patients, p < 0.0005, for reader 1 and 2 respectively). PD-SEMAC was worse in detecting meniscal lesions (6 missed, p = 0.031, 9 missed, p = 0.004, by reader 1 and 2 respectively) than PD-high-bandwidth. Revision-surgery was chosen in 12 and 11 patients without MRI (surgeon 1 and 2), with high-bandwidth-MRI in 15 and 14 patients, and with SEMAC-MRI in 19 and 14 patients. Conclusions: STIR-SEMAC was useful in detecting bone marrow oedema and influenced the orthopaedic surgeons’ decisions towards surgery, while PD-SEMAC showed no clinical benefit. Key Points: • Slice-encoding for metal artefact correction (SEMAC) MRI reduces metal-induced artefact size. • STIR SEMAC detects more bone marrow oedema in painful unicompartmental knee arthroplasty. • STIR SEMAC can help the orthopaedic surgeon with decision making. • PD SEMAC suffers from blurring of images, potentially masking relevant meniscal lesions. • PD SEMAC does not improve cartilage lesion detection in the non-operated compartments.

Original languageEnglish (US)
Pages (from-to)2184-2193
Number of pages10
JournalEuropean radiology
Issue number7
StatePublished - Jul 8 2015
Externally publishedYes


  • Artefacts
  • Decision making
  • Knee replacement arthroplasty
  • MRI

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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