Model to Estimate Threshold Mechanical Stability of Lower Lateral Cartilage.
OBJECTIVE
In rhinoplasty, techniques used to alter the shape of the nasal tip often compromise the structural stability of the cartilage framework in the nose. Determining the minimum threshold level of cartilage stiffness required to maintain long-term structural stability is a critical aspect in performing these surgical maneuvers.


OBJECTIVE
To quantify the minimum threshold mechanical stability (elastic modulus) of lower lateral cartilage (LLC) according to expert opinion.


METHODS
Five anatomically correct LLC phantoms were made from urethane via a 3-dimensional computer modeling and injection molding process. All 5 had identical geometry but varied in stiffness along the intermediate crural region (0.63-30.6 MPa).


METHODS
A focus group of experienced rhinoplasty surgeons (n = 33) was surveyed at a regional professional meeting on October 25, 2013. Each survey participant was presented the 5 phantoms in a random order and asked to arrange the phantoms in order of increasing stiffness based on their sense of touch. Then, they were asked to select a single phantom out of the set that they believed to have the minimum acceptable mechanical stability for LLC to maintain proper form and function.


METHODS
A binary logistic regression was performed to calculate the probability of mechanical acceptability as a function of the elastic modulus of the LLC based on survey data. A Hosmer-Lemeshow test was performed to measure the goodness of fit between the logistic regression and survey data. The minimum threshold mechanical stability for LLC was taken at a 50% acceptability rating.


RESULTS
Phantom 4 was selected most frequently by the participants as having the minimum acceptable stiffness for LLC intermediate care. The minimum threshold mechanical stability for LLC was determined to be 3.65 MPa. The Hosmer-Lemeshow test revealed good fit between the logistic regression and survey data (χ23 = 0.92, P = .82).


CONCLUSIONS
This study presents a novel method of modeling anatomical structures and quantifying the mechanical properties of nasal cartilage. Quantifying these parameters is an important step in guiding surgical maneuvers performed in rhinoplasty.


METHODS
5.
Beckman Laser Institute, Department of Otolaryngology, University of California, Irvine.
James Hakjune
JH
Kim
Beckman Laser Institute, Department of Otolaryngology, University of California, Irvine.
Ashley
A
Hamamoto
Beckman Laser Institute, Department of Otolaryngology, University of California, Irvine.
Nicole
N
Kiyohara
Beckman Laser Institute, Department of Otolaryngology, University of California, Irvine.
Brian J F
BJ
Wong
D055119:Elastic Modulus; D017144:Focus Groups; D006801:Humans; D008953:Models, Anatomic; D055171:Nasal Cartilages / Q000502:physiology* / Q000601:surgery*; D012225:Rhinoplasty / Q000379:methods*; D011795:Surveys and Questionnaires; D014110:Touch