Nasal tip support: A finite element analysis of the role of the caudal septum during tip depression

Abstract

Objective/Hypothesis Although minor and major tip support mechanisms have been described in detail, no quantitative models exist to provide support for the relative contributions of the structural properties of the major alar cartilage, the fibrous attachments to surrounding structures, and the rigid support structures in an objective manner. Study Design The finite element method was used to compute the stress distribution in the nose during simple tip compression, and then identify the specific anatomic structures that resist deformation and thus contribute to “tip support”. Additionally, the impact of caudal septal resection on nasal tip support was examined. Method The computer models consisted of three tissue components with anatomically correct geometries for skin and bone derived from CT data. Septum, upper lateral cartilages, and major alar cartilages were fitted within the model using 3D CAD software. 5mm nasal tip compression was performed on the models with caudal septal resection (3mm and 5 mm) and without resection to simulate palpation, then the resulting spatial distribution of stress and displacement was calculated. Results The von Mises stress in the normal model was primarily concentrated along medial crural angle. As caudal septum length was reduced, stress was redistributed to adjacent soft tissue and bone, resulting in less force acting on the septum. In all models, displacement was greatest near the intermediate crura. Conclusions These models are the first step in the comprehensive mechanical analysis of nasal tip dynamics. Our model supports the concept of the caudal septum and major alar cartilage as providing the majority of critical load-bearing support. Level of Evidence N/A

Finite Element Model and Validation of Nasal Tip Deformation

“…The geometry of the nose is identical to our previous studies on nasal tip support in response to tip depression 15, 26 . Deformation was recorded using 3d photography and the resulting geometry was compared to results of the finite element model.…”

“…In the nose, the use of finite element analysis to predict the stress and strain distribution under certain loading conditions as a result of simulated surgical modifications 3, 7, 10, 11, 13, 15, 26 has been reported, but with abbreviated anatomic models (incomplete anatomy) and no validation of results with experimental measurements. The majority of the nasal finite element analysis has been limited examining the underlying cartilage tissue alone (septum and alae) and does not consider the effect of the overlying skin-soft tissue envelope or adjacent bone 11, 13 .…”

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

“…Finite element analysis has been used to model complex nasal mechanics and quantify the relative contributions of the classic major nasal tip support mechanisms, 14–20 shape change in laser-cartilage reshaping, 26 cephalic trim on lower lateral cartilage and nasal tip stability, 16,18 and the impact of caudal septal resection. 14 The linkage between physician assessment and outcomes derived from FEA can be established using this 3-D–printed rapid prototype approach. 23 This process opens the possibilities for preoperative detailed computational analysis of the nose before surgery.…”

“…14,15 The patient was a woman of northern European descent with classic facial and nasal features, a relatively thin skin–soft-tissue envelope, and near ideal projection and rotation as outlined by Ahmed et al 25 This study was approved by the institutional review board of the University of California, Irvine, School of Medicine, and all participants provided oral informed consent.…”

“…Gassner et al 13 developed a rhinomanometric device to calculate nasal tip resilience in cadavers. Other investigators 14–19 have used computational modeling and finite element analysis (FEA) to model nasal tip mechanics and to estimate the relative contributions of the classic nasal tip support mechanisms.…”