Volumetric representation of the malar fat pad (MFP) in neutral and smiling positions. Composite image showing a representative subject with superimposed 3-dimensional representations of the MFP in (A) the neutral position and (B) smiling position. The right MFP is represented in blue, the left in red. Note the gross change in MFP morphologic traits with smiling, with reduction in vertical height being most evident.
Barrera JE, Most SP. Volumetric Imaging of the Malar Fat Pad and Implications for Facial Plastic Surgery. Arch Facial Plast Surg. 2008;10(2):140-142. doi:10.1001/archfacial.2007.20
The malar fat pad (MFP) establishes an important aesthetic norm easily identified as the cheek mound by the untrained eye. Although it is frequently manipulated as a part of contemporary facial aesthetic and reconstructive procedures,1- 4 a paucity of research exists that describes the static volumes and dynamic anatomic changes that occur with facial movement.
A prospective, institutional review board–approved, nonrandomized, case-control series included 11 subjects recruited from the Department of Otolaryngology, Stanford University, Stanford, California. The study was employed to determine the usefulness of a new technology in measuring volumetric norms of the MFP. We examined MFP volumes and compared volumes across sex and body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared) using magnetic resonance imaging (MRI). In addition, conformational changes of the MFP were examined from a neutral to smiling posture. To our knowledge, this is the first study to demonstrate dynamic conformational changes in the MFP.
All the MRI investigations were performed with the subject in the supine position in a 0.5 T MRI scanner (GE Medical Systems, Waukesha, Wisconsin). The subjects were advised not to swallow and not to move while assuming a neutral or nonsmiling posture. Of the 11 subjects, 4 consented to undergo a second MRI while assuming a smiling posture. A multiplanar localizing sequence, followed in sagittal and coronal orientation using a turbo spin echo sequence, was performed for determining structure volumes. The total acquisition time was 10 minutes. Volumetric calculations were performed using a 3-dimensional (3D) image analysis application (Dextroscope, Volume Interactions, Republic of Singapore) to circumscribe areas, orient dimensions, and calculate volumes of the MFP. The MRI data were imported into the virtual reality environment and rendered as a 3D object in a monoscopic or stereoscopic view using proprietary glasses. A line measurement tool was used to manually circumscribe the MFP in the sagittal plane per image slice. A volume tool automatically estimated the volume of the previously configured sagittal slices in cubic centimeters. The computation of the volume takes into account all voxels with a transparency value greater than 0.01 (transparency range, 0-1.0). The volume of the MFP per subject was calculated and compared across the case series in terms of sex, BMI, and differences between the right and left sides. The volumes in neutral position were compared with those in the smiling position per subject. The horizontal and vertical distances and anterior-posterior (A-P) depth of the MFP were compared in neutral and smiling positions.
The paired t test for normal continuous variables was used to test the null hypothesis that differences between groups (right- vs left-sided MFP volumes and sex differences) were equal to zero. All results of continuous variables are expressed as mean (SD). The Pearson correlation coefficient was used to associate BMI and total MFP volume.
Demographic results for the 11 subjects in the study (7 men and 4 women) revealed a mean (SD) age of 33.5 (6.1) years (33.3 years for men and 33.8 years for women). The mean total MFP volume for men was 24.3 cm3 vs 17.9 cm3 in women (Table 1). Although there was a trend toward increased MFP volumes in men, the mean MFP showed no significant difference (P = .21).
The mean (SD) BMI was 25.1 (5.2) (27.7 for men and 20.7 for women). The BMI correlated with MFP volume (Pearson correlation coefficient , 0.76). As BMI increased, the relative volume of the MFP also increased. There was no statistical difference when comparing left-sided vs right-sided MFP volumes per individual (Table 1).
To measure any changes in MFP dimensions with movement, 4 subjects were measured in the smiling position. There was no change in MFP volume as measured in neutral and smiling positions (Table 2). A minimal increase in horizontal length (47.3 [5.0] mm to 49.1 [3.0] mm) and a trend toward decrease in the vertical dimension (38.1 [4.0] mm to 32.7 [3.0] mm) and shortening in the A-P dimension (14.4 [3.0] mm to 12.4 [3.0] mm) in the smiling position were noted (Table 2). The volume of the MFP was consistent in the neutral and smiling positions.
Our preliminary study demonstrates a novel technique for measuring the volume of the MFP. Furthermore, we demonstrate conformational changes in the MFP shape during dynamic positional changes in facial expression (Figure). In the literature,5- 7 there are only a few articles dealing with the evaluation of the facial fat deposits with MRI, none evaluating the MFP alone. These studies did not discriminate BMI with MFP volume, nor did they evaluate dynamic changes in position.
In the current study, we demonstrate a correlation between BMI and MFP volume. We note a trend toward increased volume in men compared with women, although this did not reach statistical significance (P = .21). A more appropriate comparison is that of BMI and MFP volume, for which a correlation was found. It remains to be seen if changes in BMI within a given subject result in changes in MFP volume. Another novel finding was changes of MFP conformation with smiling. The validity of our measurements of the MFP volume is bolstered by our finding that measured volumes of the MFP remain consistent in the neutral and smiling positions. As visualized in the Figure, the MFP grossly shortens in the vertical dimension with smiling. We also show minimal lengthening in the horizontal direction and shortening in the A-P direction with smiling. Because the MFP volume does not change with position, we assume that the volume is distributed over a wider horizontal area. Our measurement did not detect this, but it may be secondary to our small sample size. Further studies in facial fat deposits using this technique may answer this question.
Our study shows a novel approach to evaluate the MFP in subjects. There was no notable difference in volumes when comparing left vs right sides, demonstrating internal consistency. However, MFP volume was associated with increased BMI. Comparing neutral vs smiling postures, changes in MFP conformation were found. Such studies may help us understand the complexity of this dynamic structure, as well as changes in the MFP with aging, and possibly guide surgical planning.
Correspondence: Dr Barrera, Division of Facial Plastic and Reconstructive Surgery, 801 Welch Rd, Stanford, CA 94305 (firstname.lastname@example.org).
Financial Disclosure: None reported.