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Validation of a novel blinding method for measuring postoperative knee articular cartilage using magnetic resonance imaging



To test PEEK implant-associated MRI artifacts, a method for blinding MRI readers, the repeatability of cartilage thickness measures before and 6 weeks after high tibial osteotomy (HTO), and the sensitivity to change of cartilage thickness 12 months after HTO.

Materials and methods

Ten patients underwent HTO using a PEEK implant and 3 T-MRI before, 6 weeks and 12 months after surgery. Masks were applied to hide implant visibility on 48 MRI pairs, which were assessed by 7 readers (blinded to time). One blinded reader measured femorotibial cartilage thickness from masked MRIs.


No artifacts were produced. Readers were unable to identify scans by time greater than by chance. Cartilage thickness before and 6 weeks after surgery was not significantly different and indicated excellent repeatability. Medial cartilage thickness increases 12 M postoperatively approached statistical significance (p = 0.06), with no lateral changes observed. Half of the participants had an increase in medial cartilage thickness at 12 M that exceeded the minimal detectable change. Standardized response mean values were moderate-to-large.


Postoperative measures of cartilage thickness are repeatable, consistent and sensitive to change when artifact is eliminated, and a validated blinding technique is used. These results provide proof of concept for accurately measuring increases in medial knee articular cartilage after medial opening wedge HTO.

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This work was supported in part by the Canadian Institutes of Health Research (FRN-133489) (Operating Grant), the Arthritis Society (SOG-13-20) and Canada Research Chairs Program. Funding sources were not involved in the conduct of the study.

Author information




RM: study conception and design, acquisition of data, analysis and interpretation of data, drafting of manuscript, critical revision. TB: study conception and design, acquisition of data, analysis and interpretation of data, drafting of manuscript, critical revision. FE: study conception and design, analysis and interpretation of data, drafting of manuscript, critical revision. WW: acquisition of data, analysis and interpretation of data, drafting of manuscript, critical revision. SM: acquisition of data, analysis and interpretation of data, drafting of manuscript, critical revision. BC: acquisition of data, analysis and interpretation of data, drafting of manuscript, critical revision. JRG: study conception and design, analysis and interpretation of data, drafting of manuscript, critical revision

Corresponding authors

Correspondence to Rebecca Moyer or Trevor Birmingham.

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Conflict of interest

Drs. Birmingham and Giffin report Grants from Canadian Institutes of Health Research and Grants from The Arthritis Society, outside of the submitted work. Dr. Birmingham also reports Grants from Canada Research Chairs Program, outside of the submitted work. Dr. Eckstein reports Grants from NIH, Grants from EU FP7-PEOPLE-2013-ITN, during the conduct of the study; personal fees from Chondrometrics GmbH, Ainring, Germany, personal fees from MerckKGaA, personal fees from Samumed, personal fees from Tissuegene, personal fees from Servier, personal fees from Roche, personal fees from Medtronic, Grants from Orthotrophix, Grants from MerckKgaA, Grants from Samumed, Grants from Tissuegene, Grants from Boston Imaging Core Lab, outside the submitted work. Drs. Wirth and Maschek report personal fees from Chondrometrics GmbH, Ainring, Germany. Drs. Moyer and Chronik have nothing to disclose.

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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

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Informed consent was obtained from all individual participants included in the study.

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Moyer, R., Birmingham, T., Eckstein, F. et al. Validation of a novel blinding method for measuring postoperative knee articular cartilage using magnetic resonance imaging. Magn Reson Mater Phy 32, 693–702 (2019).

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  • Osteoarthritis
  • Knee
  • Articular cartilage
  • Magnetic resonance imaging
  • Osteotomy