| ObjectiveWith age,the elderly seemed to have common facial characteristics including prominent tear trough deformity,deep nasolabial fold,instead of youthful appearance,causing the fear of aging in people.As far,there were many published studies postulating that volume loss,particularly lipoatrophy,was a primary mechanism of facial aging.With the development of the volumetric theory and the standardization of the technology in fat transplantation by Coleman,facial rejuvenation had been focused on volume restoration by adding some filler to the midface.However,due to the lack of the correct knowledge of aging fat,the detailed number of restoration in midfacial fat was unknown and its degree of standardization was not high enough,which often seemed to result in less natural outcomes in many cases.Therefore,it was necessary to understand the natural distribution of midfacial fat tissue and its age-Related changes correctly.Fat transplantation was one of the effective methods to correct tear trough deformity and nasolabial fold.The highly compartmentalized facial fat did not age as confluent mass,while a volume restoration of each single fat compartment would lead to a volume distribution that resembles the facial appearance in youth.However,lack of the knowledge of the relationship between facial folds and specific fat compartments in midface,it was difficult for surgeons to achieve the most accurate volume filling with minimal adipose tissue and achieve the most satisfactory results with minimal trauma.Based on the above research background,this study selected computed tomography images of 60 healthy women according to strict inclusion criteria by picture archiving and communication systems(PACS),and measured the thickness of different fat compartments by age groups.The aim of this study was to reveal the age-related morphological features of midfacial fat compartments,and to evaluate the anatomy of the specific fat compartments in relation to the tear trough deformity and nasolabial fold,providing new evidence and ideas for rejuvenation strategies based on facial volumetric theory.Materials and methodsData was collected in a retrospective manner from previously acquired head and neck CT scans by PACS at Zhujiang Hospital in Southern Medical University between January 2015 and December 2017,which were categorized into four age groups(20-39 years old,40-59 years old,60-79 years old),and each group included 20 subjects.All images were retransmit to the Mxview work station by 256-row helical CT.Standardization of CT imagesA reference line from the sella through the nasion was drawn,of which the coronal images were perpendicular to.The whole look of the orbital rim was selected as the locating plane.Four vertical lines were drawn:S1 went through 1/4 of the medial orbital rim;S2 went through 1/2 of the orbital rim;S3 went through 1/4 of the lateral orbital rim;S4 went through the lateral margin of the orbital rim.Four horizontal lines were drawn:C1 went through the horizontal line of infraorbital rim;C2 went through the horizontal line of the lower edge of the zygomatic arch;C3 went through the horizontal line of the hard palate;C4 went through the horizontal line of the superior alveolar.Measurement of the fat thicknessInferior orbital fat compartmentThe intersection of S3 and Cl was selected as the medial part of the Inferior orbital fat compartment(marked as A),and the intersection of S4 and C1 was the lateral part of Inferior orbital fat compartment(marked as B).The thickness of superficial and deep fat was measured on sagittal images respectively based on Orbicularis oculi muscle.Nasolabial fat compartmentThe intersection of S1 and C2 was selected as the superior part of nasolabial fat compartment(marked as C),and the intersection of S2 and C3 was selected as the middle part of nasolabial fat compartment(marked as D),and the intersection of S3 and C4 was selected as the inferior part of nasolabial fat compartment(marked as E).The fat thickness at three sites were measured on sagittal images respectively.Cheek fat compartmentIt could identify the levator labii superioris muscle(marked as F)clearly on the S2 sagittal image,and used this muscle as the mark on the superior,middle and inferior segments to measure the thickness of the medial part of cheek fat compartment in both superficial and deep layers.It could identify the zygomaticus major muscle(marked as G)clearly on the S3 sagittal image,and used this muscle as the mark on the upper,middle and lower three segments to measure the thickness of the lateral part of cheek fat compartment in both superficial and deep layers.Grading evaluation of tear trough deformity and nasolabial foldThree-dimensional(3D)reconstruction of the cranial skin and soft tissue were made by adjusting the window width and window level with the multislice spiral computerized tomography volume rendering technique at Mxview workstation.When the 3D images of skull was rotated at 45°,the grading evaluation could be made for the tear trough deformity based on Barton's grading standard and the nasolabial fold based on the Wrinkle Severity Rating Scale.StatisticsAll statistical computations were performed using SPSS 20.0 software.All measurements were expressed as meansąSD.We used Kruskal-Wallis ANOVA or a LSD-t test for the comparison between groups,and a Dunn-Bonferroni test for post hoc comparisons.Spearman correlation was used to analyze the relationship between tear trough deformity and the volume of specific fat compartments as well as the relationship between nasolabial fold and the volume of specific fat compartments.P<0.05 was considered as a significant difference.ResultStatistical analysis of fat thickness in related fat compartmentsFor the Inferior orbital fat compartment,there was a tendency of thickening with age in superficial fat.There was a statistically significant difference in fat thickness between the elderly group and the young group at the medial site,as the same as that between the elderly group and the middle-aged group at the lateral site.In deep fat,it seemed that fat is thickening with age.There was a significant difference in fat thickness between the young group and the middle-aged group at the medial site,as the same as that between the young group and the old group at the lateral site.For the nasolabial fat compartment,there was a tendency of thickening with age.Among them,the elderly group and the young group as well as the middle-aged group showed significant differences in the inferior segment of the nasolabial fat compartment.For the medial part of cheek fat compartment,the superficial layer showed the morphological characteristics of thick in the middle and thin in both ends.The elderly group and the young group,the elderly group and the middle-aged group both tended to atrophy and were significant differences in the middle and inferior segments.For the lateral part of cheek fat compartment,it showed a tendency to atrophy significantly in the middle and inferior segments of the elderly and middle-age groups.For the medial part of deep medial cheek fat(DMCF),the elderly group showed a atrophic changes in the thickness of the superior segment compared with the young group and the middle-age group.The middle-aged group and the elderly group showed atrophic changes both in the middle and in the inferior segment of fat thickness compared with the young group.In the lateral part of DMCF,the elderly group showed a thickening tendency in the middle and inferior segments compared with the young group.Spearman correlation analysis of tear trough deformity and specific fat compartmentsThe severity of tear trough deformity was negatively correlated with the volume of the superior segment of nasolabial fat compartment but it was not closely related to it.The correlation analysis showed the closely negative correlation of the severity of tear trough deformity and the volume of the DMCF.Spearman correlation analysis of nasolabial fold and specific fat compartmentsThe severity of nasolabial fold was positively correlated with the volume of the superior segment of nasolabial fat compartment but the correlation was not close.The correlation analysis showed the closely positive correlation of the severity of nasolabial fold and the volume of the inferior segment of nasolabial fat compartment.There was a positive correlation between the severity of nasolabial fold and the volume changes of the middle and inferior segments of the superficial medial cheek fat compartments,but the correlation was not close.The correlation analysis showed the negatively correlation of the severity of nasolabial fold and the volume of the DMCF,especially closely related in the middle and inferior segment.ConclusionMidfacial fat compartments tended to selective atrophy or hypertrophy with age.Inferior orbital fat compartment tended to be hypertrophy,as the same result with nasolabial fat compartment,especially prominent in the inferior segment.The superficial cheek fat compartments showed the morphological characteristics of thick in the middle and thin in both ends.The inferior segment of DMCF showed an atrophic aging trend.Regardless of whether it was superficial or deep fat layer,the lateral cheek fat compartments showed a tendency to be hypertrophy.The correlation analysis showed the closely negative correlation of the severity of tear trough deformity and the volume of the DMCF.The atrophy of DMCF was one of the causes of hollowing in the infraorbital area,leading a severer tear trough deformity.The correlation analysis showed the closely positive correlation of the severity of nasolabial fold and the volume of the nasolabial fat compartment.The inferior segment of nasolabial fat compartment was hypertrophy with age,leading a severer nasolabial fold.The correlation analysis showed the closely negative correlation of the severity of nasolabial fold and the volume of DMCF.The atrophy of DMCF reduced the support to the superficial fat compartments,causing the collapse of the medial part of nasolabial compartment. |
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