A Cross Sectional Study On The Characteristics Of Primary Inframammary Fold In 131 Women

Objective(s): The inframammary fold(IMF)is the fold formed between the breast skin and the chest wall when it moves to the chest wall,which is the lower edge of the breast.IMF is an important visual focus of the breast in addition to the nipple and areola complex.However,due to various reasons such as congenital dysplasia,megamastia,therapeutic breast surgery,etc.,especially for women after mastectomy,the original IMF structure may not be obvious,displaced,partially or completely destroyed,and the breast appearance is not ideal.Therefore,in the plastic surgery and reconstruction of breast tumors,we need to find the ideal IMF location and get good shape for patients with no obvious,displacement,partial or complete destruction of the IMF.At present,there are not many studies on the IMF at home and abroad,and there is little information about the IMF anatomical structure,IMF location and morphology,and these results are still controversial,without clear description and standards.The purpose of this study is to collect the characteristic information of a certain number of domestic women’s primary IMF,including the position of IMF in the chest wall,manifestation,whether there is standing and lying movement,and the incidence of asymmetry,and further explore its influencing factors,so as to provide reference for the preoperative evaluation of IMF and the formulation of operation plan.Methods: From June 2022 to December 2022,131 women were enrolled in the Department of Breast Surgery,the First Affiliated Hospital of Kunming Medical University,according to the inclusion criteria and exclusion criteria.The breast characteristic data of the subjects were collected,including the distance between the nipple and the inframammary fold,the distance between the sternal notch and the nipple,the breast height,the skin stretch(APSS),and the degree of breast sag.The breast volume was calculated according to the modified BREAST-V formula.Study the IMF characteristic information separately: 1.TAP index,namely the ratio of the vertical distance from the sternum notch to the lowest point of the IMF and the vertical distance from the sternum notch to the upper edge of the umbilicus.The higher the TAP index,the lower the position of IMF in the chest wall;2.The classification of IMF manifestations is based on whether there is visible IMF when the arm is on both sides of the body in standing position and when it is raised upward;3.Whether the IMF moves from the standing position to the supine position;4.The incidence of IMF asymmetries,including the asymmetries of manifestations and chest wall positions.The database was established by SPSS 25.0 statistical software and the following statistical analysis was carried out: t test and analysis of variance were used to compare whether the TAP index had significant differences in general demographic characteristics,breast characteristics and clinical examination.Multi-factor linear regression analysis was used to screen independent variables step by step forward and backward regression,and the optimal regression equation of TAP index was established;Pearson’s chi-square test and Fisher’s exact test were used to compare whether there were significant differences in IMF performance and whether the IMF had standing and lying movement in general demographic characteristics,breast characteristics and clinical examination,and binary logistic regression analysis was used to further analyze the influencing factors.Results:1.The average value of TAP index of 131 subjects(262 breasts)in this survey was 0.580 ± 0.050(95% CI 0.580-0.590).The statistical results showed that there was a statistical difference in TAP index in BMI,breast volume,and breast prolapse(P<0.05).The independent influencing factors related to TAP index were: APSS(b=-0.013,t=-2.893,P=0.004),breast volume(b=0.000281,t=7.348,P<0.001),breast ptosis II(b=-0.073,t=-4.601,P<0.001),breast ptosis III(b=-0.069,t=-4.649,P<0.001).TAP index regression equation: TAP index=0.563+0.000281 × Breast volume(ml)-0.013 × APSS(cm)-0.073 × Breast ptosis Class II-(0.069 × Breast ptosis Class III).2.In the classification of IMF performance,type 2 IMF is the most common subtype(n=99,37.8%),type 0 IMF(n=6,2.3%),type 1 IMF(n=68,26%),and type 3IMF(n=89,34%).The statistical results showed that there were statistical differences in IMF manifestations in BMI,breast volume,degree of breast ptosis,APSS,and breast feeding(p<0.05),among which 40 sagging breasts were 2/3 type IMF.The four types of IMF manifestations were divided into two groups: type 0 IMF and type 1IMF were a group(IMF manifestations were not clear group),type 2 IMF and type 3IMF were a group(IMF manifestations were clear group).The regression analysis of222 breasts without breast prolapse showed that the independent factors related to IMF manifestations were: breast volume and APSS,OR were 1.022(95% CI1.01-1.03,P<0.001)and 3.160(95% CI 1.54-6.50,P=0.002),respectively,BMI and breast feeding were not significant.3.In the study of whether the IMF has standing and lying movement,84% of the breasts(n=220)did not move,and 16% of the breasts(n=42)moved.Statistics showed that there were statistical differences in BMI,breast volume,breast sagging degree,and breast feeding(P<0.05).The independent influencing factors of IMF movement were: breast ptosis grade II and grade III,with OR of 29.915(95% CI4.60-194.63,P<0.001)and 11.740(95% CI 2.21-62.37,P=0.004),respectively.However,breast ptosis grade I was not related to the movement of IMF(OR=3.002,95% CI 0.72-12.49,P=0.131).4.131 women,the asymmetric incidence of IMF manifestations was only 1.6%(n=2),and the asymmetric incidence of IMF in chest wall position was 93.9%(n=123).Among them,61.1% of women(n=80)have left IMF below the right IMF,and the average vertical distance of the lowest point is 0.8cm(range: 0.1-2.0cm).32.8%of women(n=43)have the right IMF located below the left side,with the average vertical distance of the lowest point of 0.7cm(range: 0.1-2.0cm).Among the 123 women who showed asymmetric position of the left and right IMF,the average vertical distance of the lowest point was 0.8cm(range: 0.1-2.0cm).74.8% of women(n=92)had a vertical position difference between the left and right IMF within 1.0 cm,and 34.0% of women(n=42)had a vertical position difference within 0.5 cm.Conclusion(s):1.The TAP index objectively evaluates the position of IMF in the chest wall,and suggests that it is related to APSS,breast volume,and breast sag.The TAP index regression equation: TAP index=0.563+0.000281 × Breast volume(ml)-0.013 ×APSS(cm)-0.073 × Breast ptosis grade II-(0.069 ×Breast ptosis grade III).The index can be used as a way to evaluate the ideal position of the IMF,which is objective and simple.2.The apparent morphology of the IMF is diverse,and is significantly related to APSS,breast volume,and the degree of breast ptosis.When APSS is large,breast volume is large,or breast ptosis,the IMF shape often presents 2/3 type.3.The IMF position of most women does not move with the change of body position,and the movement is abnormal,and the sagging of breast II and III is a significant factor affecting the IMF movement.When such patients need an ideal IMF position,the impact of body position on the IMF should be considered.4.Most women’s bilateral IMF positions are asymmetrical.Because their breasts are not completely symmetrical,the symmetry of IMF should be taken into account when the perfect breast shape is needed.