Thickness and tension of the gluteal aponeurosis and the implications for subfascial gluteal augmentation

Authors


Kun Hwang, Department of Plastic Surgery, and Center for Advanced Medical Education by BK21 project, Inha University School of Medicine, 7-206 Sinheung-dong, Jung-gu, Incheon, 400-711. Korea. T: 82-32-890-3514; F: 82-32-890-2918; E: jokerhg@inha.ac.kr

Abstract

The aim of this study is to elucidate the thickness and tension of the gluteal aponeurosis (GA) as related to subfascial gluteal augmentation. Twenty buttocks from 10 Korean fresh cadavers (age range: 69–92 years, five men and five women) were dissected. Five radial lines were made from the greater trochanter (GT) to the highest point of origin of the gluteus maximus muscle (GM), the posterior inferior iliac spine (PSIS), the piriformis line (P), the coccyx (Co) and the ischial tuberosity (IT). The upper four lines were intersected by three curvilinear lines that divided them by a quarter, half and three-quarters ratios, and the lowest line was divided by a third ratio and a two-thirds ratio. At the 14 intersecting points, the force needed to break the 6 mm width of the GA was measured. The thickness of the GA was also measured with a digital caliper. The GA was widest at the GT–Co line (161.7 ± 15.8 mm), and it was narrowest at the GT–IT line (106.5 ± 21.2 mm). At most of the points (12 among the 14 points), the breaking strength of the GA was greater than 20 Newtons (N). The breaking strength of the GA did not vary significantly according to the locations (= 0.568, anova). The breaking strength of the males (22.8 ± 6.6 N) was significantly greater than that of the females (20.3 ± 7.5 N, P = 0.003, t-test). The thickness of the GA varied according to the locations (0.4 ± 0.2 mm to 0.7 ± 0.3 mm). The thickness of the GA of the upper part (GT–GM line: 0.64 ± 0.24 mm; GT–PSIS line: 0.66 ± 0.23 mm; GT–P line: 0.66 ± 0.24 mm) was significantly greater (= 0.040, 0.017, 0.018, respectively) than that of the lower part (GT–IT line: 0.49 ± 0.18 mm). The GA of the males (0.70 ± 0.23 mm) was significantly thicker than that of the females (0.53 ± 0.21 mm, < 0.001, t-test). We conclude that the GA is capable of holding gluteal implants in the proper position, as the average force to break up the 6 mm width of the GA in females was greater than 20 N.

Introduction

Today women search for an athletic look with well-defined curves in the breast and buttock area. Current standards of beauty include good projection of the buttocks and a contour that, on the frontal view, forms the outline of a natural curve from the waist to the knee (de la Peña et al. 2006). For this reason, requests for gluteal augmentation are increasing. Many types of implants are available, as are several options for their placement.

The techniques of gluteal augmentation have progressed through four anatomic planes: the subcutaneous (González-Ulloa, 1991); submuscular (Robles et al. 1984) ; intramuscular (Vergara & Marcos, 1996; Vergara & Amezcua, 2003); and subaponeurotic (subfascial) planes (de la Peña, 2004; de la Peña et al. 2006).

Subfascial gluteal augmentation (SGA) is based on the anatomy that the thick gluteal aponeurosis (GA) covers the entire gluteal region, and is capable of holding gluteal implants in the proper position because the fascia is stronger at the point of insertion and softer in the middle (de la Peña et al. 2006).

Despite its importance in SGA, the precise anatomy of the GA has not yet been determined.

The aim of this study is to elucidate the thickness and tension of the GA in relation to SGA.

Materials and methods

Materials

Twenty buttocks from 10 Korean fresh cadavers (age range: 69–92 years, five men and five women) were used for the study.

Dissection

Skin incisions were made from the L5 spinous process to the coccyx (Co), and the incisions were extended down to 5 cm below the gluteal fold. The skin flap was elevated laterally toward the greater trochanter (GT), so exposing the GA.

Size of the GA

Five radial lines were made from the GT to the highest point of the origin of the gluteus maximus muscle (GM), the posterior inferior iliac spine (PSIS), the piriformis line (P), the Co and the ischial tuberosity (IT). A curvilinear line from the GT to the IT and traversing the PSIS, P and Co was also made.

The length of the five radial lines and the curvilinear line represented the horizontal and vertical dimensions, respectively (Fig. 1).

Figure 1.

 Measured points. Five radial lines were made from the greater trochanter (GT) to the highest point of the origin of the GM (GM), the posterior inferior iliac spine (PSIS), the piriformis line (P), the coccyx (Co) and the ischial tuberosity (IT). The upper four lines were intersected by three curvilinear lines that divided them by a quarter, half and three-quarters ratios, and the lowest line was divided by a third and two-thirds ratios.

Tension measurement of the GA

The fascial flap was elevated from medial to lateral, and the aponeurotic expansions were exposed.

Five radial lines were made from the GT to the GM, PSIS, P, Co and IT. These lines were intersected by three curvilinear lines that divided them by a quarter, half and three-quarters ratios. The line from the GT to the IT was intersected at a third ratio and a two-thirds ratio (Fig. 1).

At the above 14 points, a #5 silk thread (surgical suture non-absorbable 100% silk; Bakje, Korea) was passed through the GA 6 mm apart, winded, a 3-cm loop was made and this was pulled away using the tensiometer (BFG 20N; Mesmecin, Sinfold, UK). The breaking strength was measured (Fig. 2).

Figure 2.

 Tension measurement of the GA. Silk thread was passed through the GA 6 mm apart, winded, made into a 3-cm loop and pulled using a tensiometer.

Thickness of the GA

At the above 14 points 1-cm cuts were made at the GA, and the GA was detached from the underlying gluteus maximus muscle. The thickness of the GA was measured with an Absolute digimatic caliper (M500-18; Mitutoyo, Kawasaki, Japan).

Results

Size of the GA

The horizontal dimension varied according to the axis from the GT. The GA was widest at the GT–Co line (161.7 ± 15.8 mm) and narrowest at the GT–IT line (106.5 ± 21.2 mm).

The GM–PSIS distance and PSIS–Co distance was 32.3 ± 8.8 mm and 133.6 ± 9.0 mm, respectively (Fig. 3).

Figure 3.

 Size of the GA (mm). Co, coccyx; GM, highest point of the origin of the GM; GT, greater trochanter; IT, ischial tuberosity; P, piriformis line; PSIS, posterior inferior iliac spine.

Tension of the GA

At most of the points (12 among the 14 points), the breaking strength was greater than 20 Newtons (Fig. 4). The breaking strength of the GA did not vary significantly according to their 14 locations (= 0.568, anova). The greatest force was measured at the medial one-third point of the GT–IT line (24.4 ± 6.1 N), while the least force was measured at the medial one-third point of the GT–PSIS line (18.8 ± 7.3 N).

Figure 4.

 Tension of the GA (N). Co, coccyx; GM, highest point of the origin of the GM; GT, greater trochanter; IT, ischial tuberosity; P, piriformis line; PSIS, posterior inferior iliac spine.

The breaking strength of the left side (21.6 ± 6.7 N) did not differ significantly from that of the right side (21.4 ± 7.7 N, = 0.089, t-test).

The breaking strength of the males (22.8 ± 6.6 N) was significantly greater than that of the females (20.3 ± 7.5 N, = 0.003, t-test). The average breaking strength of the GA was 21.5 ± 7.2 N.

Thickness of the GA

The thickness of the GA varied according to the locations (0.4 ± 0.2 mm to 0.7 ± 0.3 mm; Fig. 5). The thickness of the GA of the upper part (GT–GM line: 0.64 ± 0.24 mm; GT–PSIS line: 0.66 ± 0.23 mm; GT–P line: 0.66 ± 0.24 mm) was significantly greater (= 0.040, 0.017, 0.018, respectively) than the lower part (GT–IT line: 0.49 ± 0.18 mm).

Figure 5.

 Thickness of the GA (mm). Co, coccyx; GM, highest point of the origin of the GM; GT, greater trochanter; IT, ischial tuberosity; P, piriformis line; PSIS, posterior inferior iliac spine.

The GA of the males (0.70 ± 0.23 mm) was significantly thicker than that of the females (0.53 ± 0.21 mm, = 0.000, t-test). The average thickness of the GA was 0.61 ± 0.24 mm.

Discussion

de la Peña (2004) described the thick GA as covering the entire gluteal region, and being capable of holding gluteal implants in the proper position because the fascia is stronger at the insertion point and softer in the middle.

We agree with de la Peña in that the GA is capable of holding gluteal implants in the proper position as most of the points (12 out of 14 points) withstood greater than 20 N of force in our study. However, our study did not agree with de la Peña’s conclusion that the fascia is stronger at the insertion and softer in the middle. In the present study, the breaking strength of the GA did not vary significantly according to the locations (= 0.568, anova).

In our previous study (Hwang et al. 2009), the thickness of the gluteus maximus muscle varied according to its location. The medial part (17.1–18.1 mm) was thicker than the lateral (14.5–15.7 mm) or inferior parts (14.5–14.7 mm). Yet, in the present study, the thickness of the GA of the upper part (GT–GM line: 0.64 ± 0.24 mm; GT–PSIS line: 0.66 ± 0.23 mm; GT–P line: 0.66 ± 0.24 mm) was significantly greater (= 0.040, 0.017, 0.018, respectively) than that of the lower part (GT–IT line: 0.49 ± 0.18 mm).

The average thickness of the GA was 0.61 ± 0.24 mm. The GA of the males (0.70 ± 0.23 mm) was significantly thicker than that of the females (0.53 ± 0.21 mm, = 0.000, t-test). Similar to our previous study (Hwang et al. 2009), the breaking strength of the males (22.8 ± 6.6 N) was significantly greater than that of the females (20.3 ± 7.5 N, = 0.003, t-test). It is noteworthy that the average force to break up the 6 mm width of the GM in females was greater than 20 N. It is thought that males have a thicker and stronger GA because males have a greater muscle bulk and a smaller proportion of fat.

The cadavers of this study were of old patients (age range 69–92 years). Most patients seeking plastic surgery are much younger, with patients seeking correction of gluteal ptosis at the age of 40–50 years. This might be one of the limitations of the study, as the breaking strength may decrease with age. Nevertheless, we think the size and relative thickness of the GA do not change with age.

We think the GA is capable of holding gluteal implants in the proper position, as the average force to break up the 6 mm width of the GM in females is greater than 20 N.

Acknowledgement

The abstract of this paper was presented at the ‘Joint meeting of the Anatomical Societies’, Cardiff, 19–21 December 2011. The authors declare that they have no conflicts of interest to disclose. This study was supported by a grant from Inha University (INHA-Research Grant). We are grateful to Kwan Hyun Youn, PhD, medical illustrator, for the illustration.

Author contributions

Sewon Hwang dissected and measured the thickness and tension. Yong Seok Nam analysed the data. Kun Hwang conceived the study and drafted the manuscript. Seung Ho Han revised the manuscript.

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