Biomechanical simulation of correcting primary unilateral cleft lip nasal deformity

Double Reinforcing Strategy with Perpendicular Plate of Ethmoid in Asian Secondary Unilateral Cleft Rhinoplasty: A Finite Element Analysis

BACKGROUND

Deviation and asymmetry relapse after secondary unilateral cleft rhinoplasty with septal extension graft is a common yet serious problem especially among Asian patients. Therefore, finding an effective approach to reduce deformity relapse remains a great challenge to plastic surgeons.

METHODS

In this study, authors established finite element models to simulate different nasal cartilage-corrected options and different reinforcing strategies in secondary unilateral cleft rhinoplasty. A load of 0.01N was given to the nasal tip to simulate the soft tissue pressure, while two loads of 0.5N were separately given to the anterior and posterior part of the septal extension graft to simulate the rhinoplasty condition. Maximum deformations were evaluated to make stability judgments.

RESULTS

The maximum deformation of different cartilage correction models in ascending order was: UCL deformity with septum correction, normal nasal cartilage, UCL nasal deformity, and UCL nasal deformity with lower lateral cartilage correction. When applied L-strut reinforcement graft was harvested from the perpendicular plate of the ethmoid bone, the maximum deformation of the models decreased significantly, and strong fixation of the septum could further enhance this decreasing effect.

CONCLUSIONS

Correcting the septum and lower lateral cartilage together could improve the structural stability and symmetry in secondary unilateral cleft rhinoplasty. To keep the corrected septum stable and thus reduce deformity relapse, reinforcing the L-strut with perpendicular plate of ethmoid graft while strongly anchoring the septal cartilage to the anterior nasal spine was proved to be effective in both finite element analysis and clinical observation.

LEVEL OF EVIDENCE IV

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ChatGPT for shaping the future of dentistry: the potential of multi-modal large language model

The ChatGPT, a lite and conversational variant of Generative Pretrained Transformer 4 (GPT-4) developed by OpenAI, is one of the milestone Large Language Models (LLMs) with billions of parameters. LLMs have stirred up much interest among researchers and practitioners in their impressive skills in natural language processing tasks, which profoundly impact various fields. This paper mainly discusses the future applications of LLMs in dentistry. We introduce two primary LLM deployment methods in dentistry, including automated dental diagnosis and cross-modal dental diagnosis, and examine their potential applications. Especially, equipped with a cross-modal encoder, a single LLM can manage multi-source data and conduct advanced natural language reasoning to perform complex clinical operations. We also present cases to demonstrate the potential of a fully automatic Multi-Modal LLM AI system for dentistry clinical application. While LLMs offer significant potential benefits, the challenges, such as data privacy, data quality, and model bias, need further study. Overall, LLMs have the potential to revolutionize dental diagnosis and treatment, which indicates a promising avenue for clinical application and research in dentistry.

Airflow of the Two-Port Velopharyngeal Closure: Study Using Computational Fluid Dynamics

Posterior pharyngeal flap palatoplasty is used to restore the function of velopharyngeal (VP) closure, after which 2 ports remain between the nasal and oral cavity. The authors hypothesized that the airflow dynamics of the upper airway is different in PPF patients compared to health subjects, who only has 1 movable port. Twenty adults who have multislice spiral computed tomography scan were included in this study. Two cylinders (radius, 2.00 mm; height, 4.5 mm) were used to recapitulate the 2-port VP structure after PPF palatoplasty. The areas of ports were modified by changing the radius of 2 cylinders. Real-time computational fluid dynamics simulation was used to capture the airflow velocity and pressures through the 2 ports. The airflow velocity and pressure of upper airway were recorded as the total areas of 2 VP ports increased. The total orifice areas of the 2-port VP closure for 4 VP conditions, including adequate closure, adequate/borderline closure, borderline/inadequate closure, and inadequate closure, were demonstrated. Significant differences between the 2-port VP function for demonstrating PPF reconstruction and the 1-port VP function were found. Airflow dynamics is dependent on the VP structure. The 2-port airflow model for mimicking VP closure after PPF palatoplasty demonstrated airflow characteristics that were significantly different from the 1-port model in normal VP closure.

An anatomical composite nasal lining subunit technique in primary cleft nose correction

Current primary cleft nose correction techniques are associated with a significant rate of long term alar collapse. The nasal lining on the cleft side has been observed to be distorted and deficient. Nasal endoscopy was used to map the two dimensional topography of the anterior nasal airway lining in a normal and patient with unilateral cleft lip. The vestibular nasal subunit was noted to have a triple structural overlap (Lateral crus, valve and vestibule units). A nasal lining subunit based surgical strategy was designed, based on the subunit principle. The lateral crural tethering was released and differential repositioning of the cartilage/lining complex performed. The difference in domal height between the cleft and non-cleft sides was translated into a superior and medial advancement of the cartilage/lining composite subunit. The valve sub-unit defect was resurfaced with a vermilion full thickness graft, taken at the time of primary cleft lip repair. Primary septal relocation was performed and no percutaneous cartilage sutures were done. Pre and post-operative anthropometry measurements were obtained, and repeated at follow up. Complete nasal correction was seen in the unilateral cleft lip patient and was noted to be stable at 1 year follow-up. A novel nasal cartilage/lining subunit topographical map is proposed and forms the basis for a surgical strategy addressing comprehensive correction of the unilateral cleft nasal deformity.

Computational technology for nasal cartilage-related clinical research and application

Surgeons need to understand the effects of the nasal cartilage on facial morphology, the function of both soft tissues and hard tissues and nasal function when performing nasal surgery. In nasal cartilage-related surgery, the main goals for clinical research should include clarification of surgical goals, rationalization of surgical methods, precision and personalization of surgical design and preparation and improved convenience of doctor-patient communication. Computational technology has become an effective way to achieve these goals. Advances in three-dimensional (3D) imaging technology will promote nasal cartilage-related applications, including research on computational modelling technology, computational simulation technology, virtual surgery planning and 3D printing technology. These technologies are destined to revolutionize nasal surgery further. In this review, we summarize the advantages, latest findings and application progress of various computational technologies used in clinical nasal cartilage-related work and research. The application prospects of each technique are also discussed.

A FEA-Based Methodology to Predict the Osteotome Wear Status during Nasal Bone Surgical Operations

A FEA-based methodology was developed in order to predict the wear status of an osteotome (surgical instrument) during its use in a lateral nasal bone osteotomy considering its fatigue strength. The latter parameter was determined by appropriate FEM-evaluation of the perpendicular impact test results. For the simulation of the surgical procedure, two scenarios were examined: (i) when utilizing a brand new osteotome and (ii) when utilizing an already used osteotome characterized by decreased fatigue strength. The actual nasal bone geometry used in the FEA model was obtained from a high-resolution, maxillofacial, computed tomography (CT) scan of a single patient. In both cases examined, depiction of fracture patterns for the osteotome and the nasal bone were obtained. The wear of a new osteotome and an already used osteotome was also calculated and compared. The developed von Mises stresses in both the osteotome and nasal bone were depicted. The proposed methodology allowed an accurate prediction of the critical number of impacts that the osteotome can receive during the lateral nasal osteotomy which is followed in all rhinoplasties. Based on the developed methodology, a preventive replacement of the osteotome before its extensive fracture can be determined, thereby minimizing the risk of postoperative complications.

Computational Fluid Dynamic Analysis of Different Velopharyngeal Closure Patterns

Objective:

Velopharyngeal (VP) closure has high impact on the quality of life, especially in patients with cleft palate. For better understanding the VP closure, it is important to understand the airflow dynamics of different closure patterns, including circular, coronal, sagittal, and circular with a Passavant’s ridge. The purpose of this study was to demonstrate the airflow characteristics of different velopharyngeal closure patterns.

Methods:

Sixteen adults with no notable upper airway abnormality who needed multislice spiral computed tomography scans as part of their clinical care. Airways were reconstructed. A cylinder and a cuboid were used to replace the VP port in three models of VP port patterns. Flow simulations were carried using computational fluid dynamics. Airflow pressures in the VP orifice, oral cavity and nasal cavity, as well as airflow velocity through the velopharyngeal orifice, were calculated.

Results:

The airflow dynamics at the velopharynx were different among different velopharyngeal patterns as the area of the velopharyngeal port increased from 0 to 25 mm2. The orifice areas of different closure conditions in four velopharyngeal closure patterns were significantly different. The maximal orifice area for adequate velopharyngeal closure was 7.57 mm2 in the coronal pattern and 6.21 mm2 in the sagittal pattern.

Conclusions:

Airflow dynamics of the velopharynx were correlated to the velopharyngeal closure patterns. Different closure patterns had different largest permitted orifice areas for getting the appropriate oral pressures for normal speech.

Biomechanical analyses of common suspension sutures in primary cleft lip rhinoplasty

Background

For a better understanding of common suspension sutures during primary cleft lip nasal rhinoplasty, the biomechanical consequences of those sutures need to be demonstrated.

Methods

A finite element model of the infant specimen was established. The closure of cleft lip and four different specific suspension sutures were simulated by loading different forces on the model: 1. F1 to simulate the suture fastening both medial crura together; 2. F2 to simulate the suture which sewed both medial crura and the non-cleft-side upper lateral cartilage together; 3. F3 to simulate the suture elevating the alar cartilage cranially; 4. F4 to simulate the suture elevating the alar cartilage superiorly. The deformation and stress distribution consequent to each maneuver were analyzed in details.

Results

The deviation of columella was restored through the closure of cleft lip. Different suspension sutures had different biomechanical effects on the nasal structure. All suspension sutures had the function on elevating the alar cartilage. F2 had no function on restoring the collapse of the nasal tip. The suture which fastened both medial crura together leaded to the lowest stress on the skin envelope.

Conclusions

Each suspension suture had its characteristics respectively. The simulation suggested that F1, the suture which fastened both medial crura, could be the most potential maneuver for cleft lip rhinoplasty because it can symmetrically restore the shape of the nose without incurring a significant increase in stress.

Analysis of Velopharyngeal Functions Using Computational Fluid Dynamics Simulations

Objectives:

Competent velopharyngeal (VP) function is the basis for normal speech. Understanding how VP structure influences the airflow during speech details is essential to the surgical improvement of pharyngoplasty. In this study, we aimed to illuminate the airflow features corresponding to various VP closure states using computed dynamic simulations.

Methods:

Three-dimensional models of the upper airways were established based on computed tomography of 8 volunteers. The velopharyngeal port was simulated by a cylinder. Computational fluid dynamics simulations were applied to illustrate the correlation between the VP port size and the airflow parameters, including the flow velocity, pressure in the velopharyngeal port, as well as the pressure in oral and nasal cavity.

Results:

The airflow dynamics at the velopharynx were maintained in the same velopharyngeal pattern as the area of the velopharyngeal port increased from 0 to 25 mm2. A total of 5 airflow patterns with distinct features were captured, corresponding to adequate closure, adequate/borderline closure (Class I and II), borderline/inadequate closure, and inadequate closure. The maximal orifice area that could be tolerated for adequate VP closure was determined to be 2.01 mm2.

Conclusion:

Different VP functions are of characteristic airflow dynamic features. Computational fluid dynamic simulation is of application potential in individualized VP surgery planning.