Background

The aesthetics of the human nose is highly dependent on the complex structure of the lower lateral cartilages (LLC). Understanding optimum shape and mechanical properties of the LLC is pivotal to achieving satisfactory results in nasal tip rhinoplasty.

Objective

The authors introduce an ex vivo animal model to replicate the shape and mechanics of human nasal LLC as a tool for research and surgical education.

Methods

Seven fresh pig heads were obtained from a local butcher shop. Nasal cartilage was harvested in a replicable manner and fashioned into appropriate shapes and dimensions based on the authors' human cadaver studies. Sutures were placed to approximate the cartilage pairs into appropriate human anatomical position.

Results

The porcine cartilage model replicated analogous structures, including the medial crura and the lateral crura, with appropriate cephalic orientation and domal angles. The anterior-posterior dimensions of the medial crura, intermediate crura, and lateral crura were 4 mm, 6 mm, and 10 mm, respectively. Cartilage thickness was approximately 1 mm throughout the specimen. Cephalic orientation of the lateral crura was sculpted to 45°. The average angle of divergence was 54° and varied according to the physiological shape of the porcine nasal vault (range, 43-74°). Average interdomal distance was 13.3 mm (range, 9-18 mm), and average domal width was 6.2 mm (range, 5-7 mm).

Conclusions

This novel porcine model mimics human LLC and is inexpensive, easy to construct, and highly replicable. This model can be used as a valuable educational resource for training novice surgeons in the principles of nasal tip rhinoplasty. Additionally, our construct has broad applications in studying LLC geometry and mechanics.

Objective

To determine how mechanical stability changes in the lower lateral cartilage (LLC) after varying degrees of cephalic resection in a porcine cartilage nasal tip model.

Methods

Alar cartilage was harvested from fresh porcine crania (n = 14) and sectioned to precisely emulate a human LLC in size and dimension. Flexural mechanical analysis was performed both before and after cephalic trims of 0 (control), 4, and 6 mm. Cantilever deformation tests were performed on the LLC models at 3 locations (4, 6, and 8 mm from the midline), and the integrated reaction force was measured. An equivalent elastic modulus of the crura was calculated assuming that the geometry of the LLC model approximated a modified single cantilever beam. A 3-dimensional finite element model was used to model the stress distribution of the prescribed loading conditions for each of the 3 types of LLC widths.

Results

A statistically significant decrease (P = .02) in the equivalent elastic modulus of the LLC model was noted at the most lateral point at 8 mm and only when 4 mm of the strut remained (P = .05). The finite element model revealed that the greatest internal stresses was at the tip of the nose when tissue was flexed 8 mm from the midline.

Conclusion

Our results provide the mechanical basis for suggested clinical guidelines stating that a residual strut of less than 6 mm can lead to suboptimal cosmetic results owing to poor structural support of the overlying skin soft-tissue envelope by an overly resected LLC.