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Model for estimating the threshold mechanical stability of structural cartilage grafts used in rhinoplasty

Authors

  • Allison Zemek BS,

    1. Department of Otolaryngology–Head and Neck Surgery , Division of Facial Plastic Surgery, University of California Irvine, Irvine, California, U.S.A.
    2. Department of Biomedical Engineering , Division of Facial Plastic Surgery, University of California Irvine, Irvine, California, U.S.A.
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    • Ms. Zemek is presently at the Stanford University School of Medicine.

  • Rohit Garg MD,

    1. Department of Otolaryngology–Head and Neck Surgery , Division of Facial Plastic Surgery, University of California Irvine, Irvine, California, U.S.A.
    2. Beckman Laser Institute and Medical Clinic , Division of Facial Plastic Surgery, University of California Irvine, Irvine, California, U.S.A.
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  • Brian J. F. Wong MD, PhD

    Corresponding author
    1. Department of Otolaryngology–Head and Neck Surgery , Division of Facial Plastic Surgery, University of California Irvine, Irvine, California, U.S.A.
    2. Beckman Laser Institute and Medical Clinic , Division of Facial Plastic Surgery, University of California Irvine, Irvine, California, U.S.A.
    3. Department of Biomedical Engineering , Division of Facial Plastic Surgery, University of California Irvine, Irvine, California, U.S.A.
    • Beckman Laser Institute, University of California Irvine, 1002 Health Sciences Road, Irvine, CA 92612
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  • Poster presentation at the Triological Society Western Section Meeting, Las Vegas, Nevada, U.S.A., January 29–31, 2009. Allison Zemek received first prize at this meeting for the best poster presentation.

  • Funding was provided by the National Institutes of Health (D00170, DC005572, RR-01192), the American Society for Laser Medicine and Surgery, and the Air Force Office of Scientific Research (FA9550-04-1-0101). Ms. Zemek was supported by the Undergraduate Research Opportunities Program Grant at the University of California Irvine. The authors have no other funding, financial relationships, or conflicts of interest to disclose.

Abstract

Objectives/Hypothesis:

Characterizing the mechanical properties of structural cartilage grafts used in rhinoplasty is valuable because softer engineered tissues are more time- and cost-efficient to manufacture. The aim of this study is to quantitatively identify the threshold mechanical stability (e.g., Young's modulus) of columellar, L-strut, and alar cartilage replacement grafts.

Study Design:

Descriptive, focus group survey.

Methods:

Ten mechanical phantoms of identical size (5 × 20 × 2.3 mm) and varying stiffness (0.360 to 0.85 MPa in 0.05 MPa increments) were made from urethane. A focus group of experienced rhinoplasty surgeons (n = 25, 5 to 30 years in practice) were asked to arrange the phantoms in order of increasing stiffness. Then, they were asked to identify the minimum acceptable stiffness that would still result in favorable surgical outcomes for three clinical applications: columellar, L-strut, and lateral crural replacement grafts. Available surgeons were tested again after 1 week to evaluate intra-rater consistency.

Results:

For each surgeon, the threshold stiffness for each clinical application differed from the threshold values derived by logistic regression by no more than 0.05 MPa (accuracy to within 10%). Specific thresholds were 0.56, 0.59, and 0.49 MPa for columellar, L-strut, and alar grafts, respectively. For comparison, human nasal septal cartilage is approximately 0.8 MPa.

Conclusions:

There was little inter- and intra-rater variation of the identified threshold values for adequate graft stiffness. The identified threshold values will be useful for the design of tissue-engineered or semisynthetic cartilage grafts for use in structural nasal surgery.

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