Anatomic Configuration of Flank Adipose: The “Y” Configuration and Hip Extension

Goals/Purpose:

Since the development of a system 15 years ago to topographically map excess subcutaneous adipose prior to liposuction, we recognized that a consistent anatomic configuration for adipose fullness was present in every patient, and that the differential thickness of these loci in part accounted for feminization or masculinization of form. This locus of adiposity simply referred to as the "flank roll" or the "love handle", has never had its anatomic configuration described in detail. Gender differences have been widely alluded to in the literature, but a definitive analysis of the location and pinch thickness of clinically relevant adipose excess is lacking.

Methods/Technique:

One surgeon (DT) performed pinch testing of subcutaneous fullness to create topographic surface maps using indelible blue ink in 1 cm increments of thickness above baseline. Standardized images on a rotational platform were obtained at 45-degree increments. Patients who presented for primary body contouring over a 10-year period (2004-2013) were reviewed. Revisional cases and patients with HIV lipodystrophy were excluded from consideration. Four preoperative and marked photographic views were selected for analysis (0, 135, 180, and 225 degrees). An independent surgeon (JB) reviewed the images to evaluate the configuration of mapped flank and hip adipose, the presence of a hip extension, and the overall impression of a visually feminine versus masculine form. A third non-author-physician independently assessed the images, confirming the aforementioned parameters.

Results/Complications:

A total of 40 female and 48 male subjects were analyzed. Pinch testing and topographic mapping of subcutaneous adipose thickness showed a "Y"-shaped anatomic configuration of flank fat in 100% of subjects. A consistent pattern was present on each side of the body: 1) fullness of the flank fat begins just anterior to the anterior axillary line; 2) this thickness wraps posteriorly with a maximum fullness just anterior to the posterior axillary line; 3) at this landmark, the "roll" splits into a "Y"-configuration; 4) the upper limb angles superomedially toward the contralateral scapular tip; and 5) the lower limb progresses horizontally across the inferior aspect of the back, stopping just shy of the midline. The average maximal pinch thickness of the flanks in men was 3.4 cm and in women was 3.3 cm.

Eighteen of the 48 men (37.5%) appeared to have a more feminine figure in the truncal region. Of these, 16 were found to have a hip extension (88.9%). Thirty-six of the 40 female subjects (90.0%) appeared visually feminine, with 32 of the 36 having hip extensions (88.9%). The remaining 4 did not (11.1%) have hip fat, but exhibited a visually feminine figure nonetheless, likely due to underlying flare of the bony pelvis. The four women who were visually masculine in the posterior view had neither fullness of hip adipose tissue nor visually evident pelvic flare.

Conclusion:

Flank adipose is consistently "Y"-shaped in both male and female subjects. The presence of a hip extension to flank adiposity renders the impression of a more feminine form in both men and women. Fullness of both limbs of the "Y" configuration with an absence of hip fullness was predominantly seen in those judged to have a masculine shape. Failure to recognize these gender differences and to make appropriate surgical volumetric adjustments has the potential to alter a patient's form toward the opposite sex.

Figure 1

The "Y"-configuration of flank adiposity is present in both subjects. The left image is of a male subject perceived to have a masculine form, without hip extensions. The right image is of a male subject perceived to have more of a feminine form, with the presence of hip extensions.

Figure 2

The "Y"-configuration of flank adiposity is present in both female subjects. The left image is of a female subject perceived to have a feminine form, with the classic presence of hip extensions. The right image is of a female subject perceived to have more of a masculine form, in the absence of hip extensions.