Comparable in vivo joint kinematics between self-reported stable and unstable knees after TKA can be explained by muscular adaptation strategies: a retrospective observational study

  1. Longfeng Rao
  2. Nils Horn
  3. Nadja Meister
  4. Stefan Preiss
  5. William R Taylor  Is a corresponding author
  6. Alessandro Santuz
  7. Pascal Schütz
  1. ETH Zurich, Switzerland
  2. Schulthess-Klinik, Switzerland
  3. Max Delbrück Center for Molecular Medicine, Germany

Abstract

Background: Postoperative knee instability is one of the major reasons accounting for unsatisfactory outcomes, as well as a major failure mechanism leading to total knee arthroplasty (TKA) revision. Nevertheless, subjective knee instability is not well defined clinically, plausibly because the relationships between instability and implant kinematics during functional activities of daily living remain unclear. Although muscles play a critical role in supporting the dynamic stability of the knee joint, the influence of joint instability on muscle synergy patterns is poorly understood. Therefore, this study aimed to understand the impact of self-reported joint instability on tibiofemoral kinematics and muscle synergy patterns after TKA during functional gait activities of daily living.

Methods: Tibiofemoral kinematics and muscle synergy patterns were examined during level walking, downhill walking, and stair descent in eight self-reported unstable knees after TKA (3M:5F, 68.9±8.3 years, BMI 26.1±3.2 kg/m2, 31.9±20.4 months postoperatively), and compared against ten stable TKA knees (7M:3F, 62.6±6.8 years, 33.9±8.5 months postoperatively, BMI 29.4±4.8 kg/m2). For each knee joint, clinical assessments of postoperative outcome were performed, while joint kinematics were evaluated using moving video-fluoroscopy, and muscle synergy patterns were recorded using electromyography.

Results: Our results reveal that average condylar A-P translations, rotations, as well as their ranges of motion were comparable between stable and unstable groups. However, the unstable group exhibited more heterogeneous muscle synergy patterns and prolonged activation of knee flexors compared to the stable group. In addition, subjects who reported instability events during measurement showed distinct, subject-specific tibiofemoral kinematic patterns in the early/mid-swing phase of gait.

Conclusions: Our findings suggest that accurate movement analysis is sensitive for detecting acute instability events, but might be less robust in identifying general joint instability. Conversely, muscle synergy patterns seem to be able to identify muscular adaptation associated with underlying chronic knee instability.

Funding: This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Data availability

Source Data files and related codes have been provided for all Figures and Tables in the supplementary and can be found here: https://doi.org/10.3929/ethz-b-000584582.

The following data sets were generated

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Author details

  1. Longfeng Rao

    Laboratory for Movement Biomechanics, ETH Zurich, Zurich, Switzerland
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-2139-4972
  2. Nils Horn

    Department of lower extremities, Schulthess-Klinik, Zurich, Switzerland
    Competing interests
    The authors declare that no competing interests exist.
  3. Nadja Meister

    Laboratory for Movement Biomechanics, ETH Zurich, Zurich, Switzerland
    Competing interests
    The authors declare that no competing interests exist.
  4. Stefan Preiss

    Department of lower extremities, Schulthess-Klinik, Zurich, Switzerland
    Competing interests
    The authors declare that no competing interests exist.
  5. William R Taylor

    Laboratory for Movement Biomechanics, ETH Zurich, Zurich, Switzerland
    For correspondence
    bt@ethz.ch
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-4060-4098
  6. Alessandro Santuz

    Max Delbrück Center for Molecular Medicine, Berlin, Germany
    Competing interests
    The authors declare that no competing interests exist.
  7. Pascal Schütz

    Laboratory for Movement Biomechanics, ETH Zurich, Zurich, Switzerland
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-1711-7881

Funding

Orthopedic hospital DongXiang (External research fellowship)

  • Longfeng Rao

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Ethics

Human subjects: The project was approved by the Zürich cantonal ethics committee (BASEC no. 2019-01242), and all subjects provided their written informed consent prior to participation.

Copyright

© 2023, Rao et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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  1. Longfeng Rao
  2. Nils Horn
  3. Nadja Meister
  4. Stefan Preiss
  5. William R Taylor
  6. Alessandro Santuz
  7. Pascal Schütz
(2023)
Comparable in vivo joint kinematics between self-reported stable and unstable knees after TKA can be explained by muscular adaptation strategies: a retrospective observational study
eLife 12:e85136.
https://doi.org/10.7554/eLife.85136

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https://doi.org/10.7554/eLife.85136