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Original Investigation |

Estimation of Nasal Tip Support Using Computer-Aided Design and 3-Dimensional Printed Models

Eric Gray, BS1,2; Marlon Maducdoc, MD, MBA2,3; Cyrus Manuel, BS2; Brian J. F. Wong, MD, PhD2,3
[+] Author Affiliations
1Medical student, University of California, Irvine, School of Medicine
2Beckman Laser Institute and Medical Clinic, University of California, Irvine, School of Medicine
3Department of Otolaryngology–Head and Neck Surgery, University of California, Irvine, School of Medicine
JAMA Facial Plast Surg. 2016;18(4):285-291. doi:10.1001/jamafacial.2016.0215.
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Importance  Palpation of the nasal tip is an essential component of the preoperative rhinoplasty examination. Measuring tip support is challenging, and the forces that correspond to ideal tip support are unknown.

Objective  To identify the integrated reaction force and the minimum and ideal mechanical properties associated with nasal tip support.

Design, Setting, and Participants  Three-dimensional (3-D) printed anatomic silicone nasal models were created using a computed tomographic scan and computer-aided design software. From this model, 3-D printing and casting methods were used to create 5 anatomically correct nasal models of varying constitutive Young moduli (0.042, 0.086, 0.098, 0.252, and 0.302 MPa) from silicone. Thirty rhinoplasty surgeons who attended a regional rhinoplasty course evaluated the reaction force (nasal tip recoil) of each model by palpation and selected the model that satisfied their requirements for minimum and ideal tip support. Data were collected from May 3 to 4, 2014.

Results  Of the 30 respondents, 4 surgeons had been in practice for 1 to 5 years; 9 surgeons, 6 to 15 years; 7 surgeons, 16 to 25 years; and 10 surgeons, 26 or more years. Seventeen surgeons considered themselves in the advanced to expert skill competency levels. Logistic regression estimated the minimum threshold for the Young moduli for adequate and ideal tip support to be 0.096 and 0.154 MPa, respectively. Logistic regression estimated the thresholds for the reaction force associated with the absolute minimum and ideal requirements for good tip recoil to be 0.26 to 4.74 N and 0.37 to 7.19 N during 1- to 8-mm displacement, respectively.

Conclusions and Relevance  This study presents a method to estimate clinically relevant nasal tip reaction forces, which serve as a proxy for nasal tip support. This information will become increasingly important in computational modeling of nasal tip mechanics and ultimately will enhance surgical planning for rhinoplasty.

Level of Evidence  NA.

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Figure 1.
Creation of a Digital Nose Model From an Individual Computed Tomographic (CT) Scan

After acquisition of the CT scan, a computer-aided design program (3-D Slicer) is used to segment the bone and soft-tissue components. Addition of the bone and soft-tissue volumes is used to render the composite digital model.

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Figure 2.
The Silicone Casting Process

A, Silicone is poured over printed nasal soft tissue. B, After silicone has set for 12 hours, the printed nasal soft tissue is removed from the negative mold. C, Silicone of the desired stiffness is poured into a sealed negative mold, and then the casted silicone is removed and placed on the printed nasal skeleton. D, A complete nasal model.

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Figure 3.
Nose Model Undergoing Reaction Force Testing

The nasal tip was depressed by cylindrical plunger (CP) while on a platform paired to a load cell (LC) to determine reaction force to nasal tip depression.

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Figure 4.
Young Modulus Selected Based on Surgeon Skill Level

The Young modulus is selected for the absolute minimum and ideal requirements for good nasal tip support.

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Figure 5.
Reaction Force to Nasal Tip Depression

Reaction force (0-8 mm) is depicted for all 5 nasal models.

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