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


METHODS
Descriptive, focus group survey.


METHODS
Ten mechanical phantoms of identical size (5 x 20 x 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.
Department of Otolaryngology-Head and Neck Surgery, Division of Facial Plastic Surgery, University of California Irvine, Irvine, California, USA.
Allison
A
Zemek
Rohit
R
Garg
Brian J F
BJ
Wong
D001696:Biomechanical Phenomena; D002356:Cartilage / Q000637:transplantation*; D004548:Elasticity; D017144:Focus Groups; D006801:Humans; D016015:Logistic Models; D008422:Materials Testing; D008954:Models, Biological; D011140:Polyurethanes; D019736:Prostheses and Implants; D012225:Rhinoplasty / Q000379:methods*; D023822:Tissue Engineering
D011140:Polyurethanes