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Original Investigation |

Quantifying Optimal Columellar Strut Dimensions for Nasal Tip Stabilization After Rhinoplasty via Finite Element Analysis

Jessica R. Gandy, BS1,2; Cyrus T. Manuel, BS2; Ryan P. Leary, MD1,2; Brian J.F. Wong, MD, PhD1,2,3
[+] Author Affiliations
1School of Medicine, University of California, Irvine
2Beckman Laser Institute and Medical Clinic, University of California, Irvine
3Department of Otolaryngology–Head and Neck Surgery, University of California, Irvine, Orange
JAMA Facial Plast Surg. 2016;18(3):194-200. doi:10.1001/jamafacial.2015.2261.
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Importance  The contribution of columellar strut grafts (CSGs) to nasal tip support has not been determined via structural mechanics. Optimal graft dimensions have yet to be objectively determined.

Objectives  To use a finite element model (FEM) of the human nose to (1) determine the effect of the CSG on nasal tip support and (2) identify how suture placement contributes to tip support.

Design, Setting, and Participants  A multiple-component FEM of the human nose consisting of bone, skin/soft tissue, and cartilage was rendered from a computed tomographic scan. Then, CSGs of varying sizes were created, ranging from 15 × 4 × 1 mm to 25 × 8 × 1 mm, and placed in the model between the medial crura. Two FEMs were constructed for each strut size: (1) CSGs that were physically attached to the nasal spine, medial crura, and caudal septum and (2) CSGs that were not in direct contact with these structures and free to move within the soft tissue. A control model was also constructed wherein no graft was placed.

Main Outcomes and Measures  Nasal tip support for each model was assessed, and the resultant distribution of von Mises stress, reaction force, and strain energy density with respect to the alar cartilages were calculated.

Results  Compared with the control, the reaction force increased with increasing strut volume, while the strain energy density (calculated over the alar cartilages) generally decreased with increasing CSG volume. Simulations with struts that had suture attachments along the entire length of the graft generated a larger reaction force than the models without any suture attachments. Models with anteriorly placed sutures generated reaction forces similar to that of the fully sutured model, whereas the models with posterior sutures showed reaction forces similar to the fully disconnected model.

Conclusions and Relevance  Insertion of CSGs does effect the amount of force the nasal tip can withstand post rhinoplasty. Moreover, anteriorly placed sutures incur reaction forces similar to struts that are fully connected to the alar cartilage. Thus, our simulations are congruent with clinical practice in that stability increases with graft size and fixation, and that sutures should be placed along either the entire CSG or the anterior most portion for optimal support.

Level of Evidence  NA.

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Figure 1.
Control Finite Element Columellar Strut Graft (CSG) Model

A, Base view of the CSG (red) placement in between alar cartilages (white). B, Frontal view. C, Oblique view. The cartilage, skin, and CSGs in all 3 panels were drawn using Materialise Mimics software (Materialise NV), and the images rendered in COMSOL Multiphysics (COMSOL Inc).

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Figure 2.
Schematic of Strut Placement (Purple) With Regard to the Alar Cartilages

A, Fully connected columellar strut graft (CSG) directly connected to the alar cartilages. B, Anteriorly attached CSG. C, Posteriorly attached CSG. Anterior and posterior attachments (red) were determined by where the graft connected to the alar cartilage in relation to the middle point of the nasal septum.

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Figure 3.
Surface Plot of von Mises Stress of the Cartilage Illustrated in the Oblique and Base Views of the Nose Models

A, Control (no strut) oblique view. B, Fully connected 25 × 8 × 1-mm columellar strut graft (CSG) oblique view. C, Control base view. D, Fully connected 25 × 8 × 1-mm CSG base view. The areas of red indicate high amounts of stress, while the areas in blue indicate low amounts of stress; other colors depict the intervening spectrum of stress levels. Values are represented in kilopascals.

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Figure 4.
Surface Plot of von Mises Stress of the 25 × 8 × 1-mm Columellar Strut Graft

The areas of red indicate high amounts of stress, while the areas in blue indicate low amounts of stress; other colors depict the intervening spectrum of stress levels. Values are represented in kilopascals on the scale and Newtons beneath each image.

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