Zone-Dependent Architecture and Biochemical Composition of Decellularized Porcine Nasal Cartilage Modulate the Activity of Adipose Tissue-Derived Stem Cells in Cartilage Regeneration.

Previous anatomical studies have shown different functional zones in human nasal septal cartilage (NC). These zones differ in respect to histological architecture and biochemical composition. The aim of this study was to investigate the influence of these zones on the fate of stem cells from a regenerative perspective. Therefore, decellularized porcine septal cartilage was prepared and subjected to histological assessment to demonstrate its equivalence to human cartilage. Decellularized porcine NC (DPNC) exposed distinct surfaces depending on two different histological zones: the outer surface (OS), which is equivalent to the superficial zone, and the inner surface (IS), which is equivalent to the central zone. Human adipose tissue-derived stem cells (ASCs) were isolated from the abdominal fat tissue of five female patients and were seeded on the IS and OS of DPNC, respectively. Cell seeding efficiency (CSE), vitality, proliferation, migration, the production of sulfated glycosaminoglycans (sGAG) and chondrogenic differentiation capacity were evaluated by histological staining (DAPI, Phalloidin, Live-Dead), biochemical assays (alamarBlue®, PicoGreen®, DMMB) and the quantification of gene expression (qPCR). Results show that cell vitality and CSE were not influenced by DPNC zones. ASCs, however, showed a significantly higher proliferation and elevated expression of early chondrogenic differentiation, as well as fibrocartilage markers, on the OS. On the contrary, there was a significantly higher upregulation of hypertrophy marker MMP13 (p < 0.0001) and GAG production (p = 0.0105) on the IS, whereas cell invasion into the three-dimensional DPNC was higher in comparison to the OS. We conclude that the zonal-dependent distinct architecture and composition of NC modulates activities of ASCs seeded on DPNC. These findings might be used for engineering of cartilage substitutes needed in facial reconstructive surgery that yield an equivalent histological and functional structure, such as native NC.

Sonoelastographic Evaluation of the Lower Lateral Nasal Cartilage Lateral Crus, Auricular Conchal Cartilage, and Costal Cartilage.

We investigated the sonoelastographic features of the lower lateral nasal cartilage lateral crus (LLNC-LC), auricular conchal cartilage (ACC), and costal cartilage (CC). In this prospective study, group 1 consisted of 60 participants (30 males and 30 females) between 18 and 35 years of age. Group 2 consisted of 60 participants (30 males and 30 females) between 35 and 50 years of age. Strain elastography (SE) and shear wave elastography (SWE) were performed. For all LLNC-LCs and ACCs, type I SE was detected more in group 2, type II SE was detected more in group 1, and type III SE was detected more in group 1 (p < 0.05). For CC, type I SE was detected more in both groups (p < 0.05). For LLNC-LC, type I SE was detected more in males compared with females in both groups (p < 0.05). For all LLNC-LC, ACC and CC, the SWE modulus of group 2 was significantly higher than that of group 1 (p < 0.05). In older participants, the SWE modulus increased. We recommend using ACC mainly in rhinoplasty operations for primary and revision cases as its SWE modulus is similar to that of the LLNC-LC. However, due to the higher SWE modulus of CC, CC grafts should not be used as the first choice in rhinoplasties, especially in the reconstruction of the nasal tip contour, but may be used in nasal dorsum augmentation.

Addition of decellularized extracellular matrix of porcine nasal cartilage improves cartilage regenerative capacities of PCL-based scaffolds in vitro.

Composite scaffolds can improve regenerative capacities of scaffolds in various tissue-engineering approaches. In order to generate a 3D printable scaffold that is capable of cartilage regeneration, decellularized extracellular matrix (DECM) of porcine nasal cartilage was added to 3D printed polycaprolactone (PCL) scaffolds. Subsequently, scaffolds (PCL, PCL/DECM and DECM) were seeded with human primary nasoseptal chondrocytes and differentiated with cartilage inductive medium for up to 42 days in vitro. Afterwards samples were analyzed with scanning electron microscopy, histology, biochemical assays and gene expression analysis. In short, results showed cell attachment and proliferation on all scaffolds. There was a trend towards ossification on pure PCL scaffolds, whereas we found evidence for cartilage tissue formation on DECM scaffolds as well as on PCL/DECM scaffolds. Moreover, biochemical analysis indicated an enhanced differentiation on novel PCL/DECM scaffolds. In conclusion, the addition of DECM to 3D printable PCL scaffolds may yield a new composite material for regenerative approaches in cartilage for facial reconstructive surgery. Further research will be necessary to evaluate these findings in vivo.

Fibrin-Genipin Hydrogel for Cartilage Tissue Engineering in Nasal Reconstruction.

OBJECTIVES: Nasal reconstruction is limited by the availability of autologous cartilage. The aim is to investigate an adhesive biomaterial for tissue engineering of nasal cartilage by evaluating mechanical properties of hydrogels made of fibrin crosslinked with genipin as compared to native tissue. METHODS: Hydrogels of fibrin, fibrin-genipin, and fibrin-genipin with extracellular matrix (ECM) particles were created and evaluated with mechanical testing to determine compression, tensile, and shear properties. Rabbit nasal septal cartilage was harvested and tested in these modalities for comparison. Transmission electron microscopy characterized hydrogel structure. RESULTS: Fibrin-genipin gels had higher compressive, tensile, and shear moduli compared to fibrin alone or fibrin-genipin with ECM. However, all hydrogel formulations had lower moduli than the rabbit nasal septal cartilage. Electron microscopy showed genipin crosslinking increased structural density of the hydrogel and that cartilage ECM created larger structural features with lower crosslinking density. CONCLUSION: The addition of genipin significantly improved mechanical properties of fibrin hydrogels by increasing the compressive, tensile, and shear moduli. The addition of cartilage ECM, which can add native structure and composition, resulted in decreased moduli values. Fibrin-genipin is a bioactive and biomechanically stable hydrogel that may offer promise as a scaffold for cartilage tissue engineering in nasal reconstruction, yet further augmentation is required to match material properties of native nasal cartilage.

Histological and Anthropometric Changes in the Aging Nose.

BACKGROUND: Rhinoplasty in the elderly requires different surgical approaches due to the morphological and structural changes affecting the nose over time. OBJECTIVES: In this study, the authors aimed to evaluate the age-related cellular and architectural changes of nasal cartilages and soft tissue attachments. METHODS: This prospective study included 80 patients who underwent rhinoplasty. Patients were divided into 2 groups according to age. Group I included 40 patients ranging in age from 19 to 39 years. Group II included 40 patients aged at least 40 years. Samples from nasal cartilages (upper lateral, lower lateral, and septum) and nasal attachments (interdomal, inter-cartilaginous, and septo-crural) were taken. All specimens were evaluated histologically to detect age-related changes. A modified version of the Mankin grading scale was used to score each nasal cartilage sample. All attachment samples were examined by image analysis for quantitative assessment. The results were correlated to preoperative anthropometric measurements of nasolabial angle and nasal projection. RESULTS: Histologically, in group II, the cartilage matrix showed fibrinoid degeneration with a significant decrease in the number of chondrocytes and increased perichondrial fibrosis compared with group I. Attachments in group II showed a lower number of blood vessels and decreased percentage of collagen bundles. Modified Mankin scores were significantly higher in group II, indicating weak cartilages compared with group I. There was negative correlation and significance between projection, nasolabial angle, cartilages, and attachments in study groups. The linear regression model revealed that the lower lateral cartilage is the cartilage that is most affected by the aging process. CONCLUSIONS: These findings not only enhance our current understanding of the natural changes that occur in the nose during aging but may also affect surgical decision-making when grafting or suturing are considered during rhinoplasty.Level of Evidence: 2.

The impact of surgical manipulation on lower lateral cartilage stiffness.

BACKGROUND: Cephalic trimming of the alar (or lower lateral) cartilage may cause weakening leading to external nasal valve collapse. Numerous methods have been proposed to combat this weakening in order to maintain lateral crural stiffness. The purpose of this study was to quantify the effect of mucosal stripping, cephalic trimming, cephalic turn-in flap, and lateral crural strut grafting on lateral crural stiffness. METHODS: In situ cyclic compressive loading was performed on eight lateral crura in 4 fresh frozen cadaveric specimens. Testing was performed on the unaltered degloved cartilage (intact) and following each of the following interventions: mucosal stripping, cephalic turn-in flap, cephalic trimming, and lateral crural strut grafting. Linear regression of the generated force-displacement curves was used to calculate stiffness. Each intervention was compared to the intact cartilage. RESULTS: Alar cartilage of all of the specimens demonstrated a linear response to compressive loading. Intact cartilage had a mean stiffness of 3.53 N/mm. Mucosal stripping and cephalic turn-in flaps yielded similar stiffness values to intact cartilage. Cephalic trimming reduced stiffness in all cases by a mean of 1.09 N/mm (p = 0.003). Lateral crural strut grafting significantly increased stiffness by a mean of 3.67 N/mm (p = 0.0001). CONCLUSIONS: Cephalic trimming leads to decreased lateral crural stiffness in cadaveric specimens. Cephalic turn-in flaps restore pre-trimmed stiffness, and lateral crural strut grafting increases overall stiffness of the cartilage. These findings should be considered in patients undergoing rhinoplasty, particularly if there are concerns regarding potential external valve collapse.

The Caucasian Nasal Septum: An In Vivo Computed Tomography Study.

BACKGROUND: The nasal septum is composed of cartilaginous and bony components and an understanding of each component volume is essential in both functional and cosmetic surgery. OBJECTIVES: We sought to radiographically measure septal dimensions on cross sectional computer tomography (CT) images, establishing average parameters for normal anatomy among a single, Caucasian population group. METHODS: One hundred and fifty consecutive sinus CT scan images were examined and 100 cases with appropriate sagittal views were included in the study. On each septum, the sagittal CT images were assessed and 14 points were identified and 23 lengths measured and tabulated. Trigonometric formulae were used to accurately calculate surface areas of 11 resulting triangles which constituted the components of the nasal septum. RESULTS: Measurements from 100 patients were included, with a mean age of 50.2 years, constituting 47 males and 53 females. Our surface area mapping established the following areas for both males and females respectively (mm2): quadrangular cartilage 1148 and 981; vomer 894 and 741; perpendicular plate of ethmoid bone 1244 and 1006; and total surface area 3287 and 2728. Our only statistically significant comparison in the series was found in the female series when age and reducing quadrilateral cartilage size were compared, highlighting reducing size with age (P = 0.04). CONCLUSIONS: The study presents the largest published data series representing nasal septal measurements on CT images in a living Caucasian population. Our data demonstrates that septal size remains constant after adolescence, throughout our age-varied series (18-79 years), except in the female population where the quadrilateral cartilage reduces in size with age.

Yield Strength Testing in Human Cadaver Nasal Septal Cartilage and L-Strut Constructs.

IMPORTANCE: To our knowledge, yield strength testing in human nasal septal cartilage has not been reported to date. An understanding of the basic mechanics of the nasal septum may help surgeons decide how much of an L-strut to preserve and how much grafting is needed. OBJECTIVES: To determine the factors correlated with yield strength of the cartilaginous nasal septum and to explore the association between L-strut width and thickness in determining yield strength. DESIGN, SETTING, AND PARTICIPANTS: In an anatomy laboratory, yield strength of rectangular pieces of fresh cadaver nasal septal cartilage was measured, and regression was performed to identify the factors correlated with yield strength. To measure yield strength in L-shaped models, 4 bonded paper L-struts models were constructed for every possible combination of the width and thickness, for a total of 240 models. Mathematical modeling using the resultant data with trend lines and surface fitting was performed to quantify the associations among L-strut width, thickness, and yield strength. The study dates were November 1, 2015, to April 1, 2016. MAIN OUTCOMES AND MEASURES: The factors correlated with nasal cartilage yield strength and the associations among L-strut width, thickness, and yield strength in L-shaped models. RESULTS: Among 95 cartilage pieces from 12 human cadavers (mean [SD] age, 67.7 [12.6] years) and 240 constructed L-strut models, L-strut thickness was the only factor correlated with nasal septal cartilage yield strength (coefficient for thickness, 5.54; 95% CI, 4.08-7.00; P < .001), with an adjusted R2 correlation coefficient of 0.37. The mean (SD) yield strength R2 varied with L-strut thickness exponentially (0.93 [0.06]) for set widths, and it varied with L-strut width linearly (0.82 [0.11]) or logarithmically (0.85 [0.17]) for set thicknesses. A 3-dimensional surface model of yield strength with L-strut width and thickness as variables was created using a 2-dimensional gaussian function (adjusted R2 = 0.94). Estimated yield strengths were generated from the model to allow determination of the desired yield strength with different permutations of L-strut width and thickness. CONCLUSIONS AND RELEVANCE: In this study of human cadaver nasal septal cartilage, L-strut thickness was significantly associated with yield strength. In a bonded paper L-strut model, L-strut thickness had a more important role in determining yield strength than L-strut width. Surgeons should consider the thickness of potential L-struts when determining the amount of cartilaginous septum to harvest and graft. LEVEL OF EVIDENCE: NA.

A Model to Estimate L-Strut Strength With an Emphasis on Thickness.

IMPORTANCE: To perform and teach septorhinoplasty, one must have a principled understanding of the mechanics of the nasal septum. The thickness of the L-strut and how it changes septal strength have not been adequately quantified, yet calculating septal strength based on changes to thickness and size is vital in maintaining lasting nasal strength and integrity. OBJECTIVE: To establish standards for the nasal septal cartilage thickness, dorsal and caudal septum length, and Young's modulus. To provide a basis for quantitative, operative decision making, a mathematical model of L-strut strength is presented based on changes in thickness and width. DESIGN, SETTING, AND PARTICIPANTS: Nasal septal cartilages from 30 fresh cadavers were used to measure thickness at clinically relevant points and length of dorsal and caudal L-strut arms. The Young modulus was directly measured using a force gauge. Statistical analyses were performed to compare thicknesses in anatomically relevant areas. Using a cantilevered beam construct, the spring constant of the L-strut dorsal and caudal arms were estimated individually with width and thickness as variables. MAIN OUTCOMES AND MEASURES: Thickness, dorsal and caudal length, and the Young modulus of nasal septal cartilage. Spring constants of dorsal and caudal L-strut arms with different combinations of thickness and width. RESULTS: The mean (SD) age at death of the 30 cadavers was 79.2 (13.6) years (range 50-97 years). Of these, 17 (57%) were male, and 13 (43%) were female. The mean (SD) nasal septal cartilage thickness in the 30 cadavers was 1.45 (0.54) mm. Mean (SD) thickness of points along the 2-mm L-strut line was 1.49 (0.56) mm and was significantly thicker than points along the 5-mm L-strut line (mean [SD] thickness, 1.29 [0.52] mm) but significantly thinner than points along the 15-mm L-strut line (mean [SD] thickness, 1.68 [0.53]). Mean (SD) thicknesses of the posterior dorsal and caudal cartilage points were 1.52 (0.45) mm and 1.71 (0.69) mm and were significantly thicker than the anterior dorsal and caudal points (mean [SD] thickness, 1.28 [0.42] mm and 1.31 [0.44] mm, respectively). Mean (SD) dorsal and caudal L-strut arm lengths were 21.9 (3.7) mm and 20.9 (3.5) mm, respectively. The mean (SD) Young modulus was 2.03 (1.3) MPa. A model was generated demonstrating the thickness required to maintain a desired strength at a given dorsal or caudal arm width. CONCLUSIONS AND RELEVANCE: Although thickness was not uniform throughout the nasal septum, there is a predictable pattern. Thickness of the L-strut contributes more to septal strength than does L-strut width. The model generated in this study can be used in planning, performing, or teaching the applied mechanics of septorhinoplasty. LEVEL OF EVIDENCE: NA.

Quantifying Changes in Nasal Tip Support.

IMPORTANCE: Imparting surgical change to the nasal tip remains one of the most challenging aspects of rhinoplasty. The surgeon must assess the tip preoperatively and execute the necessary maneuvers to impart the desired change. OBJECTIVE: To assess nasal tip resistance to compression in a cadaveric model before and after specific rhinoplasty maneuvers using a novel method. DESIGN, SETTING, AND MATERIALS: Open rhinoplasty maneuvers were performed at an academic tertiary care center on 6 fresh-thawed cadaver heads. Assessment of tip support was performed with a motorized, computer-controlled test stand equipped with a digital load cell. Tip support was assessed by compression to a depth of 2.5 mm from contact both preoperatively and after each surgical maneuver. All force data were recorded in pound-force and converted to newtons (N) following analysis. MAIN OUTCOMES AND MEASURES: Nasal tip support, measured as resistance to compression, before and after various rhinoplasty maneuvers. RESULTS: Following the elevation of the skin-soft-tissue envelope with septoplasty, resistance to compression (1.82 N) was not significantly different from the preoperative assessment (1.60 N for all specimens). Tip support following placement of a caudal extension graft was significantly different from all other conditions (3.16 N; P < .01), showing support increased by more than 66% from preoperative assessment. Placement of columellar strut (1.28 N) did not show significant increase in tip support. Tip support was decreased slightly after placement of intradomal sutures, which was significant (1.22 N; P < .01). CONCLUSIONS AND RELEVANCE: This study demonstrates the use of materials testing equipment to assess and quantify change in tip support after several rhinoplasty maneuvers. Minor supporting maneuvers that rely on healing and scar do not significantly alter tip support in a cadaveric model. Caudal extension graft is an important maneuver imparting significant effect on nasal tip support. LEVEL OF EVIDENCE: NA.

Model to Estimate Threshold Mechanical Stability of Lower Lateral Cartilage.

IMPORTANCE: In rhinoplasty, techniques used to alter the shape of the nasal tip often compromise the structural stability of the cartilage framework in the nose. Determining the minimum threshold level of cartilage stiffness required to maintain long-term structural stability is a critical aspect in performing these surgical maneuvers. OBJECTIVE: To quantify the minimum threshold mechanical stability (elastic modulus) of lower lateral cartilage (LLC) according to expert opinion. METHODS: Five anatomically correct LLC phantoms were made from urethane via a 3-dimensional computer modeling and injection molding process. All 5 had identical geometry but varied in stiffness along the intermediate crural region (0.63-30.6 MPa). DESIGN, SETTING, AND PARTICIPANTS: A focus group of experienced rhinoplasty surgeons (n = 33) was surveyed at a regional professional meeting on October 25, 2013. Each survey participant was presented the 5 phantoms in a random order and asked to arrange the phantoms in order of increasing stiffness based on their sense of touch. Then, they were asked to select a single phantom out of the set that they believed to have the minimum acceptable mechanical stability for LLC to maintain proper form and function. MAIN OUTCOMES AND MEASURES: A binary logistic regression was performed to calculate the probability of mechanical acceptability as a function of the elastic modulus of the LLC based on survey data. A Hosmer-Lemeshow test was performed to measure the goodness of fit between the logistic regression and survey data. The minimum threshold mechanical stability for LLC was taken at a 50% acceptability rating. RESULTS: Phantom 4 was selected most frequently by the participants as having the minimum acceptable stiffness for LLC intermediate care. The minimum threshold mechanical stability for LLC was determined to be 3.65 MPa. The Hosmer-Lemeshow test revealed good fit between the logistic regression and survey data (χ23 = 0.92, P = .82). CONCLUSIONS AND RELEVANCE: This study presents a novel method of modeling anatomical structures and quantifying the mechanical properties of nasal cartilage. Quantifying these parameters is an important step in guiding surgical maneuvers performed in rhinoplasty. LEVEL OF EVIDENCE: 5.

Prediction of cartilage compressive modulus using multiexponential analysis of T(2) relaxation data and support vector regression.

Evaluation of mechanical characteristics of cartilage by magnetic resonance imaging would provide a noninvasive measure of tissue quality both for tissue engineering and when monitoring clinical response to therapeutic interventions for cartilage degradation. We use results from multiexponential transverse relaxation analysis to predict equilibrium and dynamic stiffness of control and degraded bovine nasal cartilage, a biochemical model for articular cartilage. Sulfated glycosaminoglycan concentration/wet weight (ww) and equilibrium and dynamic stiffness decreased with degradation from 103.6 ± 37.0 µg/mg ww, 1.71 ± 1.10 MPa and 15.3 ± 6.7 MPa in controls to 8.25 ± 2.4 µg/mg ww, 0.015 ± 0.006 MPa and 0.89 ± 0.25MPa, respectively, in severely degraded explants. Magnetic resonance measurements were performed on cartilage explants at 4 °C in a 9.4 T wide-bore NMR spectrometer using a Carr-Purcell-Meiboom-Gill sequence. Multiexponential T2 analysis revealed four water compartments with T2 values of approximately 0.14, 3, 40 and 150 ms, with corresponding weight fractions of approximately 3, 2, 4 and 91%. Correlations between weight fractions and stiffness based on conventional univariate and multiple linear regressions exhibited a maximum r(2) of 0.65, while those based on support vector regression (SVR) had a maximum r(2) value of 0.90. These results indicate that (i) compartment weight fractions derived from multiexponential analysis reflect cartilage stiffness and (ii) SVR-based multivariate regression exhibits greatly improved accuracy in predicting mechanical properties as compared with conventional regression.

Mechanical behavior of bovine nasal cartilage under static and dynamic loading.

Abnormal mechanical loading may trigger cartilage degeneration associated with osteoarthritis. Tissue response to load has been the subject of several in vitro studies. However, simple stimuli were often applied, not fully mimicking the complex in vivo conditions. Therefore, a rolling/plowing explant test system (RPETS) was developed to replicate the combined in vivo loading patterns. In this work we investigated the mechanical behavior of bovine nasal septum (BNS) cartilage, selected as tissue approximation for experiments with RPETS, under static and dynamic loading. Biphasic material properties were determined and compared with those of other cartilaginous tissues. Furthermore, dynamic loading in plowing modality was performed to determine dynamic response and experimental results were compared with analytical models and Finite Elements (FE) computations. Results showed that BNS cartilage can be modeled as a biphasic material with Young's modulus E=2.03 ± 0.7 MPa, aggregate modulus HA=2.35 ± 0.7 MPa, Poisson's ratio ν=0.24 ± 0.07, and constant hydraulic permeability k0=3.0 ± 1.3 × 10(-15)m(4)(Ns)(-1). Furthermore, dynamic analysis showed that plowing induces macroscopic reactions in the tissue, proportionally to the applied loading force. The comparison among analytical, FE analysis and experimental results showed that predicted tangential forces and sample deformation lay in the range of variation of experimental results for one specific experimental condition. In conclusion, mechanical properties of BNS cartilage under both static and dynamic compression were assessed, showing that this tissue behave as a biphasic material and has a viscoelastic response to dynamic forces.

Shape fidelity of native and engineered human nasal septal cartilage.

OBJECTIVE: To test engineered and native septal cartilage for resistance to deformation and remodeling under sustained bending loads and to determine the effect of bending loads on the biochemical properties of constructs. STUDY DESIGN: Prospective, basic science. SETTING: Laboratory. SUBJECTS AND METHODS: Human septal chondrocytes from 6 donors were used to create 12-mm constructs. These were cultured for 10 weeks and subjected to bending for 6 days. Free-swelling controls and native tissue from 6 donors were used for comparison. Shape retention, photo documentation, live-dead staining, and biochemical properties were measured. RESULTS: Live-dead staining showed no difference in cell survival between loaded constructs and free-swelling controls. The immediate shape retention of the constructs was 39.0% versus 24.4% for native tissue (P = .13). After 2 and 24 hours of relaxation, the constructs possessed similar shape retention to native tissue (26.9% and 16.4%; P = .126; 21.7% and 14.4%; P = .153). There was no significant change in construct shape retention from immediately after release to 2 hours of relaxation (39.0% and 26.9%, respectively; P = .238). In addition, the retention did not change significantly between 2 and 24 hours of relaxation (26.9% and 21.7%; P = .48). There was no significant difference in biochemical properties between loaded constructs and controls. CONCLUSION: The shape retention properties of human septal neocartilage constructs are comparable to human native septal cartilage. In addition, mechanical loading of neocartilage constructs does not adversely affect cell viability or biochemical properties. This study demonstrates that neocartilage constructs possess adequate shape fidelity for use as septal cartilage graft material.

Flexural properties of native and tissue-engineered human septal cartilage.

OBJECTIVE: To determine and compare the bending moduli of native and engineered human septal cartilage. STUDY DESIGN: Prospective, basic science. SETTING: Research laboratory. SUBJECTS AND METHODS: Neocartilage constructs were fabricated from expanded human septal chondrocytes cultured in differentiation medium for 10 weeks. Constructs (n = 10) and native septal cartilage (n = 5) were tested in a 3-point bending apparatus, and the bending moduli were calculated using Euler-Bernoulli beam theory. RESULTS: All samples were tested successfully and returned to their initial shape after unloading. The bending modulus of engineered constructs (0.32 ± 0.25 MPa, mean ± SD) was 16% of that of native septal cartilage (1.97 ± 1.25 MPa). CONCLUSION: Human septal constructs, fabricated from cultured human septal chondrocytes, are more compliant in bending than native human septal tissue. The bending modulus of engineered septal cartilage can be measured, and this modulus provides a useful measure of construct rigidity while undergoing maturation relative to native tissue.

Mechanical analysis of cartilage graft reinforced with PDS plate.

OBJECTIVES/HYPOTHESIS: This study attempts to characterize the biomechanical properties of a PDS-cartilage composite graft for use in septorhinoplasty. STUDY DESIGN: Experimental Study. METHODS: This study used a PDS analog, porcine cartilage cut to 1 × 5 × 20 mm, and a mechanical testing platform to measure flexure of a composite graft. Samples were assessed in four groups based on variations in suture pattern and orientation. The platform measured the force required to deflect the sample 2 mm in single cantilever beam geometry before and after the polymer was affixed to the specimen. Elastic Moduli were calculated before and after application of the polydioxanone polymer. RESULTS: The average modulus of the cartilage alone was 17 ± 0.9 MPa. The modulus of the composite cartilage-polymer graft with 2 suture fixation was 21.2 ± 1.5 MPa. The 3-suture configuration produced an increase to 25.8 ± 2.23 MPa. The four-suture configuration produced 23.1 ± 3.19 MPa. The five-suture configuration produced 25.7 ± 2.6 MPa. The modulus of the analog alone was 170 ± 30 MPa. The modulus of the 0.5 mm PDS was 692 ± 37.4 MPa. The modulus of the 0.15 mm perforated PDS was 447 ± 34.8 MPa. CONCLUSIONS: The study found that suturing a polymer plate to cartilage resulted in enhanced stiffness of the composite. Under the conditions of the study, there was no significant difference in elastic moduli between suture configurations, making the two-suture linear configuration optimal in the one-plane cantilever deflection model.

The influence of a Le Fort I impaction and advancement osteotomy on smile using a modified alar cinch suture and V-Y closure: a prospective study.

A previous report from the authors' department showed that a modified alar cinch suture combined with a muco-musculo-periosteal V-Y closure (mACVY) improves nasolabial mobility. To test if the improvements were equal to the range of nasolabial mobility in non-dysgnathic persons, a prospective study was carried out in 56 patients: 31 with mACVY, 25 with simple closing sutures (SCS) and 18 non-operated, angle class I volunteers. Standardized full facial frontal photographs, taken immediately preoperatively and 18 months postoperatively were used. The landmarks, alare, crista philtri and cheilion were analysed. The test has a standard deviation of 0.9 mm. Intra-group changes, paired t-test, and inter-group differences, unpaired t-test (p<0.05) were statistically analysed. The results show significant preoperative differences in nasolabial mobility compared with the control group, for both groups. Postoperative mobility improved in both groups, but significantly with mACVY with horizontal movement of cheilion and alare, and the vertical movement of crista philtri and less so for the vertical movement of crista philtri with SCS. Postoperative inter-group differences in mobility were small and significant for SCS vs the control group. It can be concluded that using mACVY improves orofacial movement to the level of normal class I volunteers.

Mechanical analysis of the effects of cephalic trim on lower lateral cartilage stability.

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.

Determining the most suitable costal cartilage level for rhinoplasty: an experimental study.

OBJECTIVE: The aim of this study was to compare the biomechanical properties of septal cartilage (SC) and costal cartilage (CC) grafts harvested from different ribs and to find at which level CC has characteristics closest to SC. STUDY DESIGN: Experimental cadaver study. SETTING: Istanbul Training and Research Hospital. MATERIAL AND METHOD: Cartilage grafts were harvested from the 6th, 7th, and 8th ribs and the SC of 10 fresh cadavers. Shaped cartilage grafts were subjected to a bending test. Results were measured, and the force-deflection curve was plotted. Flexural strength (σ(f)) and flexural modulus of elasticity (E(f)) were determined. Fractured surfaces were evaluated by scanning electron microscopy (SEM). RESULTS: According to F(max), it was determined that ribs 6, 7, and 8 have significantly more durability compared with the SC (Ps = .030, .004, and .001). With regard to deflection, there was no significant difference between the SC and the 6th and 7th ribs and between the 6th and 7th ribs (Ps = 1.000, .088, and .306), while a significant difference was found between the SC and the 8th rib (P = .001). According to σ(f), no differences were seen between the 6th and 7th rib (P = .782), while difference was detected between the 6th and 8th and the 7th and 8th ribs (p = .001). Similar trends were established in E(f) values as in σ(f.) These results were confirmed by SEM images. CONCLUSION: The 7th CC can be used as autograft because it shows similar properties to SC. However, the 6th CC is preferred if more flexibility is desired, and the 8th CC is preferred where more strength is needed.