Finite Element Analysis of the Septal Cartilage L-Strut

An overview of nasal cartilage bioprinting: from bench to bedside

Nasal cartilage diseases and injuries are known as significant challenges in reconstructive medicine, affecting a substantial number of individuals worldwide. In recent years, the advent of three-dimensional (3D) bioprinting has emerged as a promising approach for nasal cartilage reconstruction, offering potential breakthroughs in the field of regenerative medicine. This paper provides an overview of the methods and challenges associated with 3D bioprinting technologies in the procedure of reconstructing nasal cartilage tissue. The process of 3D bioprinting entails generating a digital 3D model using biomedical imaging techniques and computer-aided design to integrate both internal and external scaffold features. Then, bioinks which consist of biomaterials, cell types, and bioactive chemicals, are applied to facilitate the precise layer-by-layer bioprinting of tissue-engineered scaffolds. After undergoing in vitro and in vivo experiments, this process results in the development of the physiologically functional integrity of the tissue. The advantages of 3D bioprinting encompass the ability to customize scaffold design, enabling the precise incorporation of pore shape, size, and porosity, as well as the utilization of patient-specific cells to enhance compatibility. However, various challenges should be considered, including the optimization of biomaterials, ensuring adequate cell viability and differentiation, achieving seamless integration with the host tissue, and navigating regulatory attention. Although numerous studies have demonstrated the potential of 3D bioprinting in the rebuilding of such soft tissues, this paper covers various aspects of the bioprinted tissues to provide insights for the future development of repair techniques appropriate for clinical use.

Composite Thickness and Stiffness Analysis of the Nasal Septum

Background: The nasal septum supports the structure of the nose and is frequently manipulated during septorhinoplasty. Objective: To compare measurements of thickness and compressive Young's modulus (YM) between different regions of nasal septa from human anatomic specimens. Study Design: Case series. Methods: Cartilaginous septa from human anatomic specimens were dissected. Septum thickness was measured at 24 points with regular intervals using a digital caliper. Compressive YM was determined at 14 regions using a force gauge. Two-tailed student's t-tests were used to compare the average thickness and YM between different regions. Results: Septa from 40 human anatomic specimens were included, with age ranging from 50 to 89. Fifty percent of specimens were female. The mean (standard deviation) thickness of the septum was 1.75 (0.76) mm. The mean YM was 2.38 (1.29) MPa. The septum was thickest near the maxillary crest (3.09 [1.17] mm) and the keystone area (2.52 [0.91] mm) and thinnest near the anterior septal angle (1.29 [0.58] mm). The septum was most stiff posteriorly (2.90 [1.32] MPa) and least stiff anteriorly (1.80 [1.15] MPa). Conclusion: The nasal septum is thickest posteriorly, inferiorly, and along its bony edges. The septum is stiffest posteriorly, ventrally, and along its bony edges.

Effect of Dorsal Preservation Techniques on Septum Strength: An Experimental Animal Study

This experimental animal model study investigates the impact of different methods employed in preservation rhinoplasty (PR) on the strength of the nasal roof, focusing on three techniques: high strip, low strip, and intermediate strip. Using 15 lamb heads as surgical models, the study addresses key questions related to the strengths of each PR techniques, the influence of septal cartilage harvesting on septum strength, and the effectiveness of spreader grafts for stability. The research involves detailed dissection steps and measurements at various nasal points, evaluating the resistance at each stage. Results indicate that the low strip technique demonstrates the most significant reduction in strength. Furthermore, the combination of PR techniques with structural grafts, specifically spreader grafts, is assessed, revealing the classical rectangular spreader graft to be more effective in stabilizing the dorsum. Despite the limitation of using the lamb heads as models, this study offers valuable insights into the effects of PR on nasal septum strength and provides a foundation for further research on the biomechanics of preservation techniques.

A Safe Technique for Excising the Perpendicular Plate of the Ethmoid Bone in Patients with Crooked Nose: A Finite Element Analysis

BACKGROUND

Correction of the crooked nose, especially the perpendicular plate of the ethmoid bone, has the potential to cause skull base injury. At present, the safe and effective method for perpendicular plate resection has not been clearly defined through biomechanics.

METHOD

CT scan data of 48 patients with crooked nose and deviated nasal septum were divided into C-type, angular deformity-type, and S-type based on the morphology of the 3D model. Different types of finite element models of the nasal bony septum and skull base were established. The osteotomy depth, angle, and force mode of the PPE resection were simulated by assembling different working conditions for the models. The von Mises stress of the anterior cranial fossa was observed.

RESULTS

When the osteotomy line length was 0.5 cm, the angle was at 30° to the Frankfurt plane, and 50 N·mm torque was applied, the von Mises stress of the skull base was minimal in the four models, showing 0.049 MPa (C-type), 0.082 MPa (S-type), 0.128 MPa (angular deformity-type), and 0.021 MPa (control model). The maximum von Mises stress values were found at the skull base when the osteotomy line was 1.5 cm, the angle was 50°, and the force was 10 N along the X-axis, showing 0.349 MPa (C-type), 0.698 MPa (S-type), 0.451 MPa (angular deformity-type), and 0.149 MPa (control model).

CONCLUSION

The use of smaller resection angle with the Frankfurt plane, conservative resection depth, and torsion force can better reduce the stress value at the skull base and reduce the risk of basicranial fracture. It is a safe and effective technique for perpendicular plate resection of the ethmoid bone in the correction of crooked nose.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

The Creation of an Average 3D Model of the Human Cartilaginous Nasal Septum and Its Biomimetic Applications

The cartilaginous nasal septum is integral to the overall structure of the nose. Developing our an-atomic understanding of the septum will improve the planning and techniques of septal surgeries. While the basic dimensions of the septum have previously been described, the average shape in the sagittal plane has yet to be established. Furthermore, determining the average shape allows for the creation of a mean three-dimensional (3D) septum model. To better understand the average septal shape, we dissected septums from 40 fresh human cadavers. Thickness was measured across pre-defined points on each specimen. Image processing in Photoshop was used to superimpose lateral photographs of the septums to determine the average shape. The average shape was then combined with thickness data to develop a 3D model. This model may be utilized in finite elemental analyses, creating theoretical results about septal properties that are more translatable to real-world clinical practice. Our 3D septum also has numerous applications for 3D printing. Realistic models can be created for educational or surgical planning purposes. In the future, our model could also serve as the basis for 3D-printed scaffolds to aid in tissue regeneration to reconstruct septal defects. The model can be viewed at the NIH 3D model repository (3DPX ID: 020598, Title: 3D Nasal Septum).

Effect of septal extension graft on nasal tip support: A finite element analysis

BACKGROUND

Septal extension graft (SEG) is an effective method to control the projection, rotation, and shape of the nasal tip. However, the structural mechanics of SEG have not yet been adequately determined.

OBJECTIVES

The purpose of this study was to examine the effect of SEG parameters on nasal tip support using finite element analysis.

METHODS

A multicomponent nasal model was constructed from a computed tomographic scan. A control model without graft and a total of 15 models with different SEGs were created, regarding the direction, length, width, and piece of SEG. The nasal tip compression was simulated to analyze the von Mises stress, reaction force, and strain energy of the tip structure.

RESULTS

The SEG increased the max stress, reaction force, and strain energy of the nasal tip compared to the normal control. The SEG perpendicular to the nasal dorsum resulted in the highest maximum stress, reaction force, and strain energy for the same size of SEG. With the length increasing from 15 × 8 × 1 mm to 25 × 8 × 1 mm, the reaction force remained relatively stable, but the stress on the graft reduced significantly. Adding the width and pieces of the SEG increased the reaction force and strain energy of the tip.

CONCLUSION

The placement of SEG can strengthen the nasal tip support. The direction, length, width, and piece of SEG have an impact on the mechanics.

LEVEL OF EVIDENCE

Diagnostic, III.

Use of nasal septal bone to straighten septal L-Strut in correction of east Asian short nose: A retrospective study

BACKGROUND

The perpendicular plate of ethmoid (PPE) was used to correct short noses in rhinoplasty in Asians, but the safe harvest of the plate and the assessment of its clinical application has been perplexing to plastic surgeons.

AIMS

To explore how to safely cut the perpendicular plate of ethmoid bone and evaluate its application effect.

PATIENTS/METHODS

A finite element model was established to guide the clinical operation. A total of 30 patients with short noses were selected. Among them, 15 patients used autologous septal cartilage to lengthen the nasal tip, and 15 patients used the PPE to strengthen the L-shape nasal septum. The differences in the esthetic parameters of the nose, complications, and patients' satisfaction were compared between the two groups.

RESULTS

Significant differences were noted in the nasal dorsal length (p = 0.001), Goode's ratio (p = 0.001), and nasofrontal angle (p = 0.003) after rhinoplasty, and no significant differences were noted in any of the esthetic parameters between the two groups. The symptoms of nasal obstruction in the experimental group were significantly lighter than those in the control group (p = 0.04). There was no statistically significant difference in the doctors' assessment of outcomes between the two groups (p = 0.48).

CONCLUSION

The safest region to harvest the PPE is in the middle and lower third. Rhinoplasty improves the esthetics of the patient's nose. The PPE used to strengthen the L-shape nasal septum structure has a smaller probability of nasal septal deviation with the time in Asian short noses.

Biomechanics of Septal L-Strut on Lamb Head Models

It is very crucial to know the biomechanics of the septal cartilage and adjacent structures during septoplasty. The aim of this study was to investigate the strength changes of different L-strut models after mucoperichondrium elevation, application of septal extension grafts and spreader grafts on an experimental lamb model. Ten lamb heads were dissected according to a dissection protocol and septal resistances were measured with the newton meter at six zones. Three different L-strut types were designed, and all the L-strut models were created at different widths of 15mm, 10mm, and 5mm. In addition, effects of two different types of septal extension grafts and spreader grafts were compared. After mucoperichondrium elevation and harvesting the septum cartilage, there was a significant decrease in the septum resistance (p <0.05). As the width of the L-strut decreased, the septum strength decreased significantly (p <0.05). There was no significant difference between three chondrotomy types at different widths (p >0.05). There was no significant difference between the overlapping SEG and end-to-end SEG in terms of septum resistance (p >0.05). This was the first study to measure septal resistance in lamb heads. The mucoperichondrium and L-strut width were important structures for maintaining septal resistance. Chondrotomy style was not crucial, but as the width of the L-strut increased, the septal resistance increased. The septal extension grafts regardless of suturing style and the spreader grafts added strength to the caudal septum.

Nuances of Septal Deviation Repair

Septoplasty is one of the most common procedures performed by facial plastic surgeons. Surgical decision-making surrounding septal deviation repair centers around the location of deviation and need for dorsal and/or caudal septal correction. Endonasal approaches are often adequate and external approaches are utilized for significant L-strut involvement. For severe deformities, extracorporeal septoplasty and anterior septal reconstruction can be utilized. We present an overview of septal deviation repair with technical nuances and advanced reconstruction techniques.