Implications of Malignancy, Radiation, and Timing of Major Nasal Reconstruction.

Owing to the complex, multilayered anatomy of the nose in the central face, major nasal reconstruction can pose a significant challenge for reconstructive surgeons. It is the responsibility of reconstructive surgeons to have an understanding of the most common cutaneous malignancies and excisional techniques that may lead to complex nasal defects. The purpose of this article is to discuss these malignancies, excisional techniques, and impacts of radiation on tissue that has implications for reconstructive surgeons.

Anatomical and Ultrasonographic Analyses of the Levator Labii Superioris Alaeque Nasi Muscle at the Level of the Nasal Ala / Análisis Anatómico y Ecográfico del Músculo Elevador Nasolabial a Nivel del Ala Nasal

SUMMARY: We aimed to determine the width of the levator labii superioris alaeque nasi muscle (LLSAN) at the level of the nasal ala through cadaveric dissections and ultrasonography (US), to provide essential anatomical information for use during both invasive and noninvasive procedures in the nasal ala region. The LLSAN was investigated in the 40 hemifaces of 20 Korean cadavers, comprising 10 males and 10 females with a mean age of 73.6 years. The LLSAN width of the 40 specimens at the level of the midpoint of the nasal ala was 5.02±2.35 mm (mean±standard deviation), and ranged from 1.45 mm to 10.11 mm. The LLSAN widths were 5.96±2.36 mm and 3.93±1.89 mm in males and females, respectively, with ranges of 2.40-10.11 mm and 1.45-6.96 mm, respectively. The LLSAN widths on the left and right sides were 4.77±2.72 mm and 5.26±1.99 mm, respectively. The proportions of the LLSAN fibers inserting into the nasal ala and upper lip were similar in 13 specimens (32.5 %), while more fibers inserted into the nasal ala in 11 specimens (27.5 %) and more fibers inserted fibers of the LLSAN into the upper lip in 16 specimens (40 %). When clinicians need to target or avoid the LLSAN, the present width and range data can be helpful for ensuring the efficacy and safely of both invasive and noninvasive procedures. In addition, the possibility of asymmetry in the width of the LLSAN in the nasal ala region should be confirmed by US before performing such procedures.

Nuestro objetivo fue determinar el ancho del músculo elevador nasolabial (MENL) a nivel del ala nasal mediante disecciones cadavéricas y ecografía, para proporcionar información anatómica esencial, para su uso durante procedimientos invasivos y no invasivos, en la región del ala nasal. El MENL se estudió en 40 hemicaras de 20 cadáveres coreanos (10 hombres y 10 mujeres) con una edad media de 73,6 años. El ancho de MENL de las 40 muestras a nivel del punto medio del ala nasal fue de 5,02 ± 2,35 mm (media ± desviación estándar) y osciló entre 1,45 mm y 10,11 mm. Los anchos de MENL fueron 5,96 ± 2,36 mm y 3,93 ± 1,89 mm en hombres y mujeres, respectivamente, con rangos de 2,40 a 10,11 mm y 1,45 a 6,96 mm, respec- tivamente. Los anchos de MENL en los lados izquierdo y derecho fueron 4,77 ± 2,72 mm y 5,26 ± 1,99 mm, respectivamente. Las proporciones de fibras de MENL que se insertaban en el ala nasal y en el labio superior fueron similares en 13 muestras (32,5 %), mientras que se insertaron más fibras en el ala nasal en 11 muestras (27,5 %) y además, se insertaron fibras de MENL en el labio superior en 16 ejemplares (40 %). Cuando los médicos necesitan apuntar o evitar el MENL, los datos actuales de ancho y rango pueden ser útiles para garantizar la eficacia y seguridad de los procedimientos, tanto invasivos como no invasivos. Además, la ecografía puede ser utilizada para confirmar una posible asimetría en el ancho del MENL en la región del ala nasal antes de realizar los procedimientos.

Longitudinal changes of the natural craniofacial and dentoalveolar complex in the fourth decade of life.

INTRODUCTION: This study aimed to longitudinally examine the changes in craniofacial and dentoalveolar regions during the third and fourth decades of life. METHODS: The data from this study constitute the cephalometric films and plaster models of 8 female and 8 male dental students or dentists. The mean chronological ages of the subjects at the first observation period was 22.09 years for females and 22.64 years for males. The material was collected over 3 intervals: 1985-1989, 1998-2000, and 2016-2017. The observation period was approximately 28 years. Acquired cephalometric recordings and dental models were assessed for subjects in their 20s (baseline), 30s, and 40s. Maxillary, mandibular, maxillomandibular, soft-tissue, and dentoalveolar cephalometric variables were measured with a cephalometric analysis software, and dental cast measurements were made with a digital caliper. Changes in the cephalometric films and dental casts were evaluated statistically. RESULTS: Statistical analysis showed that the length of the midfacial region increased with age. The height of the lower face increased significantly in females and the mandible can be seen mildly rotating to the posterior as it increased in length. The nose moved slightly forward and downward in males and females. Upper lip height was significantly increased in females; however, there was a significant reduction in upper lip thickness for males and females. Soft-tissue pogonion measurements showed a significant forward and downward chin movement in females. Overjet was significantly increased in females, whereas the mandibular arch length was significantly decreased for both sexes, although it was more prominent in females. There was a loss of space in the anterior segments of males and females, resulting in increased crowding. However, the loss of space was only significant in the mandible. CONCLUSIONS: We observed significant changes in skeletal, soft-tissue, and dentoalveolar variables of subjects in their third and fourth decades of life. The fact that many changes have occurred throughout this study demonstrates that the process of maturation and aging is ongoing.

Regression analysis of nasal shape from juvenile to adult ages for forensic facial reconstruction.

The nose is a prominent feature for facial recognition and reconstruction. To investigate the relationship of the nasal shape with the piriform aperture in Korean adults and juveniles, we performed regression analysis. By regression analysis, prediction equations for nasal shape were obtained in relation to the shape of the piriform aperture considering sex and age groups. Three-dimensional skull and face models, rendered from computed tomography images, were assessed (331 males and 334 females). Juveniles (<20 years) were divided into three age groups according to the development of the dentition. Adults were divided into three age groups of two decades each, according to their age. To measure the nasal area, nine landmarks and nine measurements were chosen, while seven landmarks and five measurements were selected to measure the piriform aperture area. Four measurements were defined to explain the direct relationship between the nasal aperture and nasal shape. First, descriptive statistical analyses were performed according to sex and age groups. Subsequently, the correlation of nasal soft tissue measurements with piriform measurements was analyzed. Last, we performed a linear regression analysis of the measurements with higher correlations, considering sex and age groups as variables. Prediction equations were used to estimate the nasal bridge length, height, protrusion, and width. Equations considering sex and age groups showed better explanation ability. Measurements related to the height of the nasal bridge presented improvement. This study may assist in the more accurate approximation of nasal shape in facial reconstruction.

[Effect of alar base cinch suture based on anatomic landmarks on the morphology of nasolabial region in patients after orthognathic surgery].

OBJECTIVE: To study the effect of a modified alar base cinch suture (ABCS) based on nasal musculature anatomy on the three-dimensional morphology of nasolabial region in patients after Le Fort Ⅰ osteotomy. METHODS: In the study, 30 patients[11 males and 19 females, with an average age of (23.23±2.98) years]with skeletal Class Ⅲ malocclusion underwent orthognathic surgery between August, 2019 and January, 2020 to have the maxilla advanced no more than 4 mm in the Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology were involved and were divided into the test and control groups based on the random number table.In the test group, the nasal musculature was identified and labeled before dissection and the ABCS was according to the label, while in the control group, the nasal musculature was directly sutured and knotted in the midline of nose without prepend labeling.All the patients underwent three-dimensional facial photos preoperatively and 6 months postoperatively by using 3dMD face system.On the three dimensional image, soft tissue landmarks of nasolabial region was identified by the same examiner.Fourteen measurements including straight distance, curve distance, angle and ratio were measured.Statistical analysis was done by using SPSS 22.0. RESULTS: There were significant differences between the two groups in cutaneous height of upper lip (P=0.023) and in nasal tip protrusion-alar width (P=0.012).The increase rate of cutaneous height of upper lip and the decrease rate of nasal tip protrusion-alar width in the control group were significantly higher than that in the test group.The alar width and alar base width of the both groups were significantly increased compared with the preoperative level (P < 0.05).The nasolabial angle in the control group was significantly higher compared with the normal value, while there was no significant difference between the test group and the normal value. CONCLUSION: Compared with the conventional suture method, this modified alar base cinch suture is more favorable for the postoperative nasal coordination and nasolabial morphology in patients who need mild to moderate maxillary advancement, and it has certain advantages in operability and objective accuracy.So it could become a modified and accurate method of alar base cinch suture and be widely applied in clinical practice.

The Assessment of External Nasal Valve Efficiency After Le Fort I Surgery.

BACKGROUND: The present study investigated how external nasal valve function is affected after Le Fort I osteotomy using external nasal valve efficiency (ENVE) index. MATERIALS AND METHODS: Twenty-one patients who underwent Le Fort I osteotomy with or without mandibular osteotomy were included in the retrospective study. Preoperative and postoperative standardized videos of basal view of the nose during breathing were recorded, and 2 screenshots were taken, 1 in the resting position and the other after deep inspiration. External nasal valve efficiency was calculated at preoperative and postoperative periods for each patient. RESULTS: Of the 21 patients, 12 were women and 9 were men (mean age, 26.63 ± 8.20 years). The mean ENVE index was 0.75 ± 0.16 for the preoperative period and 0.82 ± 0.17 for the postoperative period. There was a significant difference between these values ( P = 0.002). When the correlation of the ENVE with maxillary movements was analyzed, the ENVE was negatively affected by maxillary impaction ( P = 0.011, r = -0.540). CONCLUSIONS: These findings imply that Le Fort I osteotomy positively affects the ENVE index. However, because of the antagonistic relation between maxillary impaction and ENVE, higher maxillary impaction amounts or isolated maxillary impaction should be carefully planned in patients with low ENVE index.

Análisis de las Variaciones Anatómicas y Dimensionales del Canal Nasopalatino Mediante Tomografía Computarizada de Haz Cónico / Analysis of the Anatomical and Dimensional Variations of the Nasopalatine Canal by Cone Beam Computed Tomography

El conocimiento anatómico del canal nasopalatino (CNP) es fundamental para la realización de cirugías en el sector anterior del maxilar y así prever posibles complicaciones. El objetivo de este trabajo es evaluar y determinar las variaciones anatómicas y dimensionales del CNP según sexo, edad y estado dental. Este estudio transversal analizó un total de 251 imágenes de TCHC obtenidas de la base de datos del Servicio de Imagenología Oral y Maxilofacial de la Facultad de Odontología de la Universidad Andrés Bello, Viña del Mar, Chile. Para evaluar la asociación estadística entre variaciones del CNP con sexo, edad y estado dentario se realizó la prueba T de Student, chi-cuadrado y ANOVA (p0,05). Además, se detectó diferencia significativa entre el estado dentario y la dimensión de la tabla vestibular en relación con el CNP (p<0,01). Se deben considerar las variaciones de CNP para evitar posibles complicaciones durante los procedimientos quirúrgicos.

SUMMARY: Anatomical knowledge of the nasopalatine canal (PNC) is essential for performing surgeries in the anterior sector of the maxilla and thus anticipating possible complications. The objective of this work is to evaluate and determine the anatomical and dimensional variations of the CNP according to sex, age and dental status. This cross-sectional study analyzed a total of 251 CBCT images obtained from the database of the Oral and Maxillofacial Imaging Service of the Faculty of Dentistry of the Andrés Bello University, Viña del Mar, Chile. To evaluate the statistical association between CNP variations with sex, age and dental status, the Student's T test, chi-square and ANOVA (p0.05). In addition, a significant difference was detected between the dental state and the dimension of the vestibular table in relation to the CNP (p<0.01). CNP variations should be considered to avoid potential complications during surgical procedures.

Anthropometric analysis of orbital and nasal parameters for sexual dimorphism: New anatomical evidences in the field of personal identification through a retrospective observational study.

Orbital and nasal parameters among modern humans show considerable variation, which affects facial shape, and these characteristics vary according to race, region, and period in evolution. The aim of the study was to ascertain whether there are sex differences in the orbital and/or nasal indexes and/or the single measurements used to calculate these in a Kosovar population. The following parameters were taken into consideration: orbital height (OH), orbital width (OW), nasal height (NH), and nasal width (NW). The ratios between orbital index/nasal index (RONI) were calculated. All measurements were obtained from a population sample comprising 408 individuals. The accuracy in sex prediction was 52.86% (CI95% = 45.05%-60.67%) for NW and 64.96% for NH (CI95% = 57.50%- 72.42%). The difference between male and female indexes was statistically significant (P < 0.05). The anthropometric study revealed that only NW and NH are configured as predictors of sexual dimorphism. It could be useful to increase the number of samples to test the discriminant function in other population groups.

Analysis of select esthetic nasal parameters in virtually planned orthognathic patients.

PURPOSE: Bony changes after orthognathic surgery are always followed by changes of the overlying soft tissues. Therefore, morphologic changes of the nose may be expected after procedures involving the maxilla. The purpose of this study was to evaluate the changes in the nasal region due to orthognathic surgery using computed tomography (CT) images of virtually planned patients. METHODS: 35 patients who underwent Le Fort I osteotomy, with or without bilateral sagittal split osteotomy, were included. 3D measurements on preoperative and postoperative images were performed and analyzed. RESULTS: The results revealed that aesthetically acceptable results can be achieved by orthognathic surgery alone. CONCLUSIONS: According to the results of this study, it can be concluded that it is best to reserve decisions on rhinoplasty to the post-orthognathic period.

Beyond Alar Base Resection: Contouring of the Alar Rim and Base.

SUMMARY: Alar base surgery is approached with hesitancy and is often avoided by many surgeons because of inexperience and a lack of understanding. However, with a thorough knowledge of the anatomy and dynamic nature of the lower third of the nose, alar base resection can achieve favorable and reproducible results. Beyond correcting alar flare, an appropriately diagnosed and performed alar base procedure serves to contour both the alar rim and the alar base. The following article presents a case series of 436 consecutive rhinoplasties from a single surgeon, 214 of which underwent alar base surgery. The outcomes demonstrate that the procedure is safe and yields desirable results without a single revision being required. As the third in a series of three articles on alar base surgery by the senior author (R.J.R.), this article unifies the management of the alar base. An intuitive approach to the classification and management of alar flare and the implications of alar base surgery on contouring of the alar base and alar rim is presented. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

Nasal Sesamoid Cartilages: Fact or Fiction? An Anatomical Study of the Lateral Nasal Ala.

OBJECTIVES: To evaluate the presence of cartilage in the lateral nasal ala (LNA) via histological analysis of alar Mohs surgical specimens. An accurate understanding of nasal anatomy is essential to optimize esthetic and reconstructive surgical outcomes. LNA anatomy is typically pictured to include discreet accessory and sesamoid cartilages; however, the authors debate the actual presence of these structures. METHODS: A blinded reviewer analyzed 101 lateral nasal alar histologic specimens from 362 tissue blocks using a Hematoxylin and Eosin (H&E) stain to assess for the presence of cartilage. RESULTS: Out of the 362 tissue blocks histologically analyzed, only 1 included cartilaginous components. CONCLUSIONS: We conclude that the presence of sesamoid and accessory cartilages in the LNA within our sample set is exceedingly rare.

Comparison of Effects between Total Maxillary Setback Osteotomy and Anterior Maxillary Segmental Osteotomy on Nasolabial Morphology.

BACKGROUND: The authors aimed to compare the effects of total maxillary setback osteotomy (TMSO) and anterior maxillary segmental osteotomy (AMSO) on nasolabial morphology. METHODS: This retrospective clinical trial enrolled 130 patients undergoing maxillary surgery using TMSO or AMSO. Ten nasolabial-related parameters and nasal airway volume were measured preoperatively and postoperatively. The soft-tissue digital model was reconstructed using Geomagic Studio and Dolphin image 11.0. Statistical analysis was performed using IBM SPSS Version 27.0. RESULTS: A total of 75 patients underwent TMSO, and 55 underwent AMSO. Both techniques achieved optimal repositioning of the maxilla. Except for the dorsal nasal length, the dorsal nasal height, the length of the nasal columella, and the upper lip thickness, the remaining parameters were significantly different in the TMSO group. In the AMSO group, only the nasolabial angle, the alar base width, and the greatest alar width showed significant differences. There was a significant difference in the nasal airway volume for the TMSO group. The results of matching maps are consistent with the statistical results. CONCLUSIONS: TMSO has a more significant impact on both nose and upper lip soft tissues, whereas AMSO has a more significant impact on the upper lip and less on the nasal soft tissue. There is a significant decrease in nasal airway volume after TMSO, whereas AMSO showed less decrease. This retrospective study is helpful for clinicians and patients to understand the different changes in nasolabial morphology caused by the two interventions, which is essential for effective intervention and physician-patient communication. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Comparative evaluation of various nasal shapes and angles in different vertical growth patterns - A Cephalometric Study.

Background: Factors affecting the appearance of the nose and the size of the nasal angles are different. The aim of this study was to examine the influence of the vertical developmental pattern on the nose appearance. Material and methods: Lateral cephalogram from 144 adult Caucasian subjects from the central Balkan were analyzed (72 male and 72 female), with orthognathic jaw relationship - class I and different types of divergence pattern. The profile type of nose, the shape of the nasal dorsum and the value of the nasal angles (nasofrontal, nasofacial, nasolabial and nasal tip angle) were determined for each person. Subjects were divided into three groups based on the values of ANB angle (sagital relation between the maxilla and mandible), Wit's appraisal, SN/GoGn (the angle of mandibular divergence pattern). These groups are subjects with hypodivergent, normaldivergent and hyperdivergent growth pattern. Statistical analysis included differences separately for each gender between different types of divergence. Results: The results indicated that some nasal forms are more common in certain types of divergence, but that these differences did not show statistical significance, in contrast to the results of authors from other areas. Conclusions: The clinical implication of current study relates to the fact that nasal reconstruction should not be based on the type of divergence, but on other factors.

Morphology of pig nasal structure and modulation of airflow and basic thermal conditioning.

Mammals have presumably evolved to adapt to a diverse range of ambient environmental conditions through the optimized heat and mass exchange. One of the crucial biological structures for survivability is the nose, which efficiently transports and thermally preconditions the external air before reaching the internal body. Nasal mucosa and cavity help warm and humidify the inhaled air quickly. Despite its crucial role, the morphological features of mammal noses and their effect in modulating the momentum of the inhaled air, heat transfer dynamics, and particulate trapping remain poorly understood. Tortuosity of the nasal cavity in high-olfactory mammalian species, such as pigs and opossum, facilitates the formation of complex airflow patterns inside the nasal cavity, which leads to the screening of particulates from the inhaled air. We explored basic nasal features in anatomically realistic nasal pathways, including tortuosity, radius of curvature, and gap thickness; they show strong power-law correlations with body weight. Complementary inspection of tortuosity with idealized conduits reveals that this quantity is central in particle capture efficiency. Mechanistic insights into such nuances can serve as a tipping point to transforming nature-based designs into practical applications. In-depth characterization of the fluid-particle interactions in nasal cavities is necessary to uncover nose mechanistic functionalities. It is instrumental in developing new devices and filters in a number of engineering processes.

Five-Principle and Five-Step Liquid Rhinoplasty.

SUMMARY: Liquid rhinoplasty, otherwise known as nonsurgical or filler rhinoplasty, has earned increased attention for its ability to provide surgical rhinoplasty results at a fraction of the cost and without incising the skin. However, significant complications can arise, such as tissue necrosis, filler embolus, and vascular compromise if the procedure is performed without consideration of the principles and anatomy of the face and nose. As demonstrated in this article, a stepwise and patient-specific approach to performing liquid rhinoplasty will ensure safe, consistent, and desirable results.

The Impact of Alar Flare Reduction Goes Beyond Just the Ala.

BACKGROUND: Alar flare reduction (AFR) is a widely used technique in rhinoplasty. Although the impact of AFR on the alar base has been well studied, its effect on the surrounding tissues is largely unknown. This study aims to elucidate the potential effect of AFR on the overall nasal and perinasal anatomy. METHODS: AFR was performed on cadavers ( n = 7) with sequential crescent-shaped alar excisions of 2, 4, and 6 mm. Two- and three-dimensional photographs were obtained at baseline and subsequent intervals. Analysis was performed with Adobe Photoshop and Vectra. Standardized landmarks were placed at the nasal tip point (NTP) and alar base point to quantify NTP vector distances, NTP surface distances, and alar crease angle. RESULTS: The surface and vector distances between the NTP and alar base point decreased for increasing AFR intervals. AFR created a surface decrease of 1.90 ± 1.60, 3.54 ± 1.85, and 4.91 ± 1.89 mm, respectively. AFR created a vector decrease of 1.50 ± 1.14, 2.83 ± 1.37, and 3.97 ± 1.38 mm, respectively. NTP projection decreased by 0.54 ± 0.31 mm for 6-mm excision. AFR led to cheek elevation of 0.87 ± 0.70, 1.25 ± 0.60, and 1.96 ± 0.48 mm, respectively. This alar crease elevation blunted the transition between the cheek and upper lip skin at the level of the alar rim with the angle of this transition increasing 26.62 ± 12.78 degrees from baseline to 6 mm. CONCLUSIONS: Three-dimensional analysis demonstrates the influence of AFR on the alar base and surrounding perinasal contour. AFR results in nasal tip deprojection, alar crease elevation, and alar flare width narrowing. Further investigation into the impact of modifying the alar base on surrounding structures is warranted.

Lymphoid enhancer binding factor 1 is associated with nose color in Yunong black pigs.

Yunong black pig is an indigenous black pig breed being cultivated that has a pure black whole body. However, some individuals appear with a white spot on the nose. We performed case-control association studies and FST approaches in 76 animals with nose color records (26 white-nosed pigs vs. 50 black-nosed pigs) by Illumina Porcine SNP50 BeadChip data. In total, 76 SNPs, which included 2 genome-wide significant SNPs and 18 chromosome-wide suggestive SNPs, were identified by association study. The top-ranked 0.1% windows of FST results as signals under selection and 24 windows were selected. The lymphoid enhancer binding factor 1 was identified as candidate gene with strong signal in analyses of genome-wide association study and FST in black- and white-nosed pigs. Overall, our findings provide evidence that nose color is a heritable trait influenced by many loci. The results contribute to expand our understanding of pigmentation in pigs and provide SNP markers for skin color and related traits selection in Yunong black pigs. Additional research on the genetic link between nose pigmentation is needed.

Nasal Anthropometric Analysis in Turkish Rhinoplasty Patients.

This study aimed to determine the mean values of the nasal anthropometric measurements through 2-dimensional photogrammetry in for rhinoplasty patients. The study group included 72 healthy individuals, 36 men, and 36 women. The patients were aged 18 to 42 years. All patients had undergone primary rhinoplasty in our clinic between 2013 and 2020. Seven landmarks were identified from the preoperative photographs taken with the patient's head in neutral position in the frontal and lateral planes. Five distances (total nasal length, nasal bridge length, morphological nose width, alar length, and nasal tip protrusion) and 2 angles (nasofrontal and nasolabial) measurements were calculated. We noted a statistically significant difference between the male and female sexes in terms of total nasal length and morphological nose width (P<0.05). The results were compared with the nasal anthropometric measurements reported in the literature for the Turkish population as well as other ethnic groups. We believe results of this study may facilitate preoperative planning in Turkish patients who request rhinoplasty and improve the success rate of the surgery.

Application of 3-Dimensional White-Light Scanning to Observe the Lip and Nose Morphology of Chinese Children.

OBJECTIVE: To establish a database and study the growth and development of Chinese children's nasolabial units by 3-dimensional (3D) white-light scanning technology. MATERIALS AND METHODS: From January 2018 to January 2019, 528 patients were selected preoperatively in our hospital, without cranial or maxillofacial deformities. The patients were placed in supine positions in a state of sedation, and the authors used a 3D white-light scanner to scan the children's faces to measure the 3D morphological structure of their nasolabial areas. The results were presented with Graphpad Prism 8.0.2 to explore correlations and analyze trends. RESULTS: The selected Chinese children consisted of 356 males (67.4%) and 172 females (32.6%). All nasolabial subunits grew fastest at 0 to 2 years old and at a slower rate from 2 to 15 years old, whereas the relevant growth of different sex was similar among contemporaries. CONCLUSIONS: Three-dimensional white-light scanning can quickly and accurately gain 3D imaging of nasolabial soft tissue to build a normal morphology database. Furthermore, every nasolabial subunit grows fastest at the age of 0 to 2 years.