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LIPOSUCTION TEXTBOOK
The Tumescent Technique By Jeffrey A. Klein MD

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LIPOSUCTION TEXTBOOK

PART IV:
Fundamental Aspects of Tumescent Liposuction
Chapter 25:
Subcutaneous Fat: Anatomy and Histology

The gross anatomy of subcutaneous fat has not been well studied. Anatomists have traditionally regarded subcutaneous tissue as a mere envelope that contains more important structures. Except for an occasional reference to epidural, periorbital, perirenal, buccal, infrapatellar, ischiorectal, and retropubic fat, the gross anatomy of fat is rarely considered. Histology texts describe the individual cellular components of adipose (fat) tissue, but the overall architectural interrelationships among these components are seldom discussed.

Adipose Tissue

On initial inspection the structure of adipose tissue appears to be a random array of coalescing septa (partitions). A predictable pattern exists, however, and the structure of adipose tissue can be represented by a nested family of subsets, as follows:

Fat cell Ì Fat lobule Ì Fat pearl Ì

Fat section Ì Fat compartment

In other words, fat cells are contained within fat lobules, which are within fat pearls, which are contained within fat sections, which are within fat compartments (Figure 25-1).

Fat compartments represent the largest collections of subcutaneous fat. A cross section of fat from a female hip would reveal a deep, thick compartment of subcutaneous fat that is divided into sections by tangentially and obliquely oriented, intersecting collagenous sheets of fibrous tissue. Overlying this deep compartment of fat is the superficial mantle layer of fat, with its palisading columnar fatty pearls.

Fat sections subdivide the deep fatty compartment of fat into subunits. Resembling an orange segment, each section of subcutaneous fat is defined by a thin fibrous membrane consisting of intersecting collagenous sheets of fibrous tissue. The paths of the larger blood vessels, lymphatics, and sensory nerves follow the fibrous partitions that subdivide the fat compartments into fat sections.

Fat pearls subdivide the fat section into subunits. Their size varies with anatomic location (Figure 25-2). The size of fatty pearls seems to increase to a limited extent with the degree of obesity.

Fat lobules are the immediate subunits of the fatty pearl. Each fatty lobule is supplied by a neurovascular bundle of arterioles and venules, which in turn are subdivided into terminal capillaries that course by individual fat cells. A fat lobule represents a grouping of fat cells, all of which are enclosed within a small thin membrane and share the same terminal vascular supply.

Fat cells (adipocytes) are the individual cells that are the ultimate target of the liposuction surgeon. Adipocytes store fat, provide insulation, and physically cushion the body (see later discussion).

Function and Form

Adipose tissue in humans is a type of connective tissue containing adipocytes, blood vessels, nerves, and fibrocytes embedded within a three-dimensional collagenous matrix of intersecting septa. Fat, synonymous with adipose tissue, consists predominantly of adipocytes but also contains significant amounts of collagen (type I and III), blood and lymphatic vessels, and nerves. Approximately half the cells in adipose tissue are adipocytes, and half are vascular and connective tissue cells.1 The triglyceride-filled adipocytes are so much larger than other types of cells, however, that adipocytes represent at least 96% of the adipose tissue mass.

The functions of adipose tissue are as follows:

  1. Store energy
  2. Provide thermal insulation
  3. Act as a physical shock absorber
  4. Provide “sex appeal”

The deep subcutaneous fat in humans has a genderspecific distribution. The development and location of individual pads of depot fat are manifestations of sexual dimorphism. Men have more fat in the upper body, whereas women have more fat on the lower extremities.

The idealized male figure has been represented as athletic, showing a maximum of muscle definition and a minimum of fat. In contrast, the idealized female figure has a softer appearance and more alluring curves. From an aesthetic perspective, it is important that liposuction surgeons allow fat to remain in strategic locations.

Histology of Adipocyte

The embryologic appearance of fat cells occurs after 5 months of gestation, when electron microscopy of subcutaneous tissue reveals spindle-shaped, lipid-free precursor cells and young adipocytes with multiple cytoplasmic droplets. Based on in vitro cell culture studies, these forms seem to represent different stages of lipoblast development.

Fat cells are derived from fibroblasts, which may originate from perivascular sheath cells or perivascular spindle cells. The earliest sign of fat cell differentiation in the adipescent fibroblasts is the appearance of small cytoplasmic vacuoles. The continuing process of lipogenesis causes these vacuoles to expand incrementally and coalesce.

These microscopic vacuoles eventually coalesce into a single, large globule within the mature fat cells with one, large, central lipid droplet and peripheral nucleus.2 These full, unilocular adipocytes are the body’s most efficient long-term depots for storing energy.

When all available fat cells are nearly filled to capacity, the body recruits new fat cells from a population of mesenchymal precursor cells that histologically resemble immature fibroblasts. In the presence of a plethora of dietary fat, excess triglycerides are stored in new adipocytes or lipoblasts.

When an adipocyte becomes depleted of its intracellular fat, the cells become vacuous and again resemble fibroblasts. When a potential patient has lost a considerable amount of weight, the existing fat cells are partially depleted of their triglyceride stores.

Adipocytes have receptors for a number of hormones (cortisol, adrenocorticotropic hormone, thyroxine, glucogon) and cytokines. Lipolysis and capillary dilation are under sympathetic nerve control. Histochemical techniques show an abundance of nerves, typically located perivascularly.

Other types of fat cells include multilocular adipocytes, which contain many small lipid droplets, have a foamy appearance, and are present in the fetus and newborn. Their function appears to be intimately associated with heat production, analogous to the “brown fat” of hibernating animals.

Vascularity of Fat

Special stains reveal that each adipocyte is in direct contact with one or more capillaries. When the ratio of capillary surface to the cellular volume of adipocytes is compared to a similar ratio for striated muscle, the capillary bed of adipose tissue appears to be richer than that of muscle.

In several species, including humans, the blood flow in resting adipose tissue, when there is no vasodilation, ranges from 2 to 14 ml/min/100 g of tissue. In maximally dilated adipose tissue the blood flow is 20 to 50 ml/min/100 g of tissue. With the profound vasoconstriction produced by the tumescent technique, the blood flow through tumescent fat must be much less than 1 ml/min/100 g of tissue.

Blood flow expressed per unit of adipose tissue weight is inversely correlated to the size of the fat cells. In rats, for example, blood flow per unit weight of adipose tissue tends to be greater in fasted animals (shrunken adipocytes) and smaller in fed animals (swollen fat cells). The blood flow per adipocyte, however, seems to be independent of fasting or eating.

Layers of Subcutaneous Fat

Based on my clinical observations and cadaveric dissections, there are three important layers of subcutaneous fat: the apical layer, the mantle layer, and the deep compartment (depot) layer. For the purposes of liposuction surgery, this distinction is a practical way of recognizing and distinguishing the different layers of subcutaneous fat (Figure 25-3).

Apical Layer

The apical layer of subcutaneous fat is a very thin layer contiguous with the deepest aspect of the reticular dermis. Apical fat extends upward into the deep reticular dermis as bumpy, culminant colonnades of fat. No intervening substance or structure exists between apical fat and dermis.

Apical fat includes (1) the thecal, or sheathlike, periadnexal fat surrounding sweat glands and hair follicles and (2) the fat that invests the vascular arcade and lymphatic plexus along the interface between fat and dermis. Apical fat is grossly visible as yellow puncta of fat along the cut surface of a deep, split-thickness, tangential excision of dermis.

Nevus Lipomatosus. An unusual example of apical fat is nevus lipomatosus. Clinically, nevus lipomatosus presents as a typical skin-colored, intradermal, cellular nevus or fibroepithelial polyp. It is a solitary, dome-shaped, soft papule or pedunculated nodule on the trunk or extremities, usually 5 to 10 mm in diameter.

Histologically, nevus lipomatosus is an intradermal nidus of microscopically typical subcutaneous fat located in the middle to upper dermis. It may be loculated and isolated from the subcutaneous fat, or it may be a “fiord”-like extension of fat up into the dermis.

Superficial Liposuction. Despite its intuitive appeal, liposuction of apical fat with dermal trauma does not produce contraction of the dermis. The predictable result of widespread liposuction-induced trauma to the dermal–apical fat interface is injury to the dermal vasculature and possible dermal necrosis.

Erythema ab liporaspiration is a less extreme but more common consequence of excessively superficial liposuction. It is a permanent reticulated erythema, with a clinical appearance similar to erythema ab igne or livedo reticularis (see Figure 8-3).

Although the term superficial liposuction has gained acceptance in recent years, the procedure of superficial liposuction has not been precisely defined. The ability to produce tumescent hemostasis has permitted the use of relatively small, 2-mm to 3-mm cannulas, which in turn has allowed liposuction that is more superficial than the traditional liposuction that used larger, 8-mm or 10-mm cannulas. Safe superficial liposuction avoids injury to the dermis. Excessive superficial liposuction is dangerous and can easily cause either partial-thickness or full-thickness dermal necrosis.

It is a fallacy that an intentional liposuction of the apical fat and deep reticular dermis will result in an aesthetic contraction or shrinkage of the skin. Aggressive superficial liposuction is counterproductive and dangerous (see Chapter 8).

Mantle Layer

The mantle layer of subcutaneous fat is a discrete layer; it is a superficial row of vertically oriented, columnar pearls of fat. Using a cross section of skin and subcutaneous fat, with careful inspection immediately subjacent to the reticular dermis, one can see the distinct blanketlike layer of columnar pearls of fat arranged in a palisading array. The deep margin of the mantle layer consists of a discrete sheet of fascial fibrous tissue.

The mantle layer covers most but not all areas of the body. No significant subcutaneous fat exists in the eyelids (periorbital postseptal fat is not subcutaneous fat), nasal bridge, subungual digits, or penis. The mantle fat layer varies in thickness throughout the body but tends to be uniform over any specific area. It is thicker over areas where it covers deep deposits of subcutaneous fat, such as the hips, thighs, abdomen, and buttocks. Over other areas, such as the leg below the knee, where there are no deep deposits of subcutaneous fat, the mantle layer accounts for nearly all the subcutaneous fat.

Mantle layer fat has the teleologic duty to protect, cushion, and insulate. The individual columnar fat pearls that compose the mantle layer have the structural form of a gabion (cylindric wicker basket filled with rocks and earth for use in fortification and engineering). The body’s ability to withstand the daily assaults of a physically rough environment partly results from the resilient structural design of the mantle layer. Palisaded gabions of fat are closely packed cushions of fat that function as hydraulic shock absorbers. They allow external pressure to be more evenly distributed and more widely dispersed than if the subcutaneous fat were simply a few large, loosely packed “balloons” of fat.

Deep Compartment Layer

The deep compartment layer is the deepest layer of subcutaneous fat. Although this layer is present in obese infants and children, it is often relatively thin until after puberty. With the onset of puberty and adolescence, accumulations of fat begin to appear.

The development and location of individual compartments of fat are manifestations of sexual dimorphism. The eventual size and individual shapes of these depots are a function of genetic predisposition and the individual’s degree of obesity.

The deep fat compartments are capable of enlargement by cell proliferation. Inactivity and a relative abundance of dietary calories tend to augment the size of deep fat compartments, which function as storehouses where excessive dietary energy is saved for later use.

Hierarchical Architecture of Fat

The adipose tissue septa consist of gossamer sheets of fibrous areolar tissue that partition and support an organized series of adipocyte groupings.

The thinnest septa surround fat lobules; they are essentially invisible without magnification. The septa that surround fat pearls are pellucid (translucent) and grossly visible only with great care and attention. The septa that separate fat compartments are thin white sheets; the thinnest are transparent, whereas the thickest (e.g., Scarpa’s fascia) are opaque, white, glistening expanses of tenacious connective tissue.

The taxonomy of fat cell aggregates has a hierarchical pattern vaguely reminiscent of the architectural subdivisions of the lung (see Figure 25-1).

Fat Cell

The individual adipocyte (fat cell) is the smallest unit within the hierarchy of adipose tissue. Histologically the adipocyte has a signet-ring appearance, with an eccentric nucleus and cytoplasm that is less than 1% of the visible fat cell cross section.

Age, gender, and anatomic location influence fat cell size and number. Within any specified anatomic site, fat cells achieve nearly uniform maximum size. In other words, fat cells do not continue to enlarge indefinitely. The size of a fat cell has an upper limit, and once a large proportion of fat cells are almost their maximum size, new fat cells are recruited.

Adipose tissue proliferates by a process of cell multiplication, in contrast to growth by continuous individual cell expansion. With increasing obesity, humans produce new fat cells. New fat cells are created when multipotential fibroblasts become lipoblasts through an overabundance of dietary calories.

Fat Lobule

The fat lobule, next in the hierarchy, is a microscopic structure. The fat lobule consists of a packet of adipocytes partitioned off from adjacent lobules by the thinnest of fibrous septa. The smallest terminal capillaries and an occasional autonomic or sensory nerve fiber meander through the lobule. The smallest lymphatics arise within the interstices between lobules.

The fat lobule is analogous to a compound fruit such as a raspberry, with the adipocyte the smallest individual subsection, or acinus, of the berry.

Fat lobules are easily seen on histologic examination of tissue prepared from a lipoma. When a fatty pearl is sliced open during surgery, fat lobules can be seen as small granules of a yellowish pastelike substance.

Scanning electron micrographs show that each adipocyte is surrounded by a web of collagenous fibers, which are continuous with interlobular septa. With careful inspection, individual fat lobules may be seen without magnification, but the connective tissue membrane that defines a fat lobule is essentially invisible.

Fat Pearl

The fat pearl, encapsulated by a transparent collagenous membrane, is the grossly visible yellow globule of fat that is seen when subcutaneous adipose tissue is transected. The enveloping fibrous membrane gives the fat pearl a shiny, almost pearllike luster. Although somewhat speculative, the fat pearl can be thought of as containing grapelike bunches or clusters of fat lobules.

Although fat pearls are fairly uniform in size within any specific location, they vary in size from one part of the body to another. In the submental chin and cheek areas, fat pearls are about 2 to 3 mm in diameter, whereas in the arms, thighs, and abdomen they may be 1 cm or more in diameter (see Figure 25-2).

Within the same anatomic location, fatty pearls are small in children and larger in adults. Fatty pearls are supplied with small arterioles, venules, and lymphatics. A fat pearl is a lobulose structure; that is, it contains many lobules.

Fat Section

A fat section contains a conglomeration of many fat pearls, packed together between broad, intersecting, visible, pale-white walls of fibrous connective tissue septa. Along these septa course small blood vessels, lymphatics, and nerves.

The three-dimensional size and shape of a fat section are determined by the intersection of multiple fibrous sheets of connective tissue. The fat sections resemble rhomboidal prisms, packed together in a crystal lattice–like fashion.

Fat Compartment

A fat compartment is a grouping of multiple fat sections and is the largest entity within the architectural hierarchy of subcutaneous fat. Some fat compartments are so well recognized that they have been given specific names, such as the hip, outer thigh, buttock, inner thigh, anterior thigh, inner knee, breast, upper abdomen, lower abdomen, and extensor arm.

The size and shape of these fat compartments are responsible for the differences in surface anatomy that exist between adult males and females. When an individual becomes aware that his or her fat compartments are “more than the ideal,” liposuction becomes an option to improve the situation.

Tangential and Oblique Septa

The two types of septal sheets are tangential planes and oblique partitioning walls.

Tangential Planes. These planes of connective tissue are broad, laminated, relatively dense, two-dimensional surfaces that are approximately oriented parallel and tangentially to the subjacent muscle fasciae (see Figure 25-3).

Fascia is the laminated sheet of fibrous tissue that envelops the body beneath the skin. Fasciae also enclose the muscles and groups of muscles and separate their several layers or groups. Subcutaneous fascia is not a functional monolayer of connective tissue; it is a laminate of fibrous sheets, with each lamella a weblike, interwoven film of collagen and fibrocytes. The interfaces between adjacent, loosely adherent lamellae represent potential spaces and become apparent on careful anatomic dissection (Figure 25-4).

These intralamellar potential spaces may be the site of lipoblast formation. A lipoblast is a fibroblast that differentiates into a new fat cell. In the process of adipose tissue proliferation, these lamellae separate and become filled with the new adipocytes.

Oblique Planes. These planes are thinner, smaller, less extensive sheets of tissue that intersect the thicker, tangentially oriented septal planes at oblique angles. They partition fat that is contained between adjacent parallel sheets of tangential septa.

The oblique lamellae might simply arise during the process of fat proliferation within a potential space between two lamellae of a single progenitor tangential septum. A previously parallel lamella becomes an undulating oblique septum, attached in alternating areas between parallel sheets of tangential septa. The new oblique lamella functions as a series of struts that braces and stabilizes the collagenous framework, while concomitantly partitioning and fixing small sections of fat (Figure 25-5).

These sheets of fibrous tissue are intimately attached to both the skin and the deep muscle fasciae, creating a tethering effect on the skin. When the skin and subcutaneous fat of the thigh or buttock are stretched (by gravity or muscle contraction), the resulting irregular distribution of mechanical forces on the tethered skin produces visible dimpling, or cellulite.

Cellulite

As a medical concept, cellulite is not widely recognized, and its anatomic basis is controversial. Many physicians regard the word cellulite as vague and inaccurate. Every woman, however, knows precisely what the term describes: the unattractive, orange peel (peau d’orange), cottage cheese–like, rippling skin of fat thighs.

The Oxford English Dictionary defines cellulite as a “special lumpy form of fat supposed to occur in some women, esp. on the hips and thighs, sometimes producing a yellowish puckering of the skin.” French liposuction surgeons use the words cellulite or cellulitis to designate the human surface anatomy associated with dimpled skin on fat thighs. The French word cellule is translated in English as “cell.” Cellulite is now well established in the English language despite its unscientific origin.

Unproven Treatments

Persons with cellulite despise it and will consider paying for any treatment that promises to remove it. Treatments of dubious value have included acupuncture, exotic diets, special baths, topical creams, and various external massages. Claims of success using external vacuum-roller devices or topical theophylline creams are unproved.

Claims of efficacy have not been supported by objective, reproducible, scientific evidence. If any treatment truly eliminated cellulite, treating only one thigh on a number of women would provide a statistically powerful, wellcontrolled test of efficacy. Until objective, reproducible studies are published, all proprietary claims of successful treatment must be regarded with skepticism. Financial motivation and unsubstantiated claims of dramatic medical success always suggest quackery.

Liposuction. Cellulite cannot be eliminated by liposuction in a predictable manner. Although individual patients might see noticeably improved cellulite, the degree of improvement is usually minimal. An unequivocal elimination of cellulite should not be promised to prospective liposuction patients.

Anatomic Considerations. Cellulite is probably the result of traction on the skin of subcutaneous fibrous septa. Both tangential and oblique planes can insert into the superficial apical and mantle layer septa and the deep fasciae that cover subjacent muscle.

Any attempt to cut the fibrous attachments between skin and adipose tissue is unlikely to give satisfactory long-term results. It is futile to attempt to disconnect the perpendicular septa of the mantle layer from the reticular dermis with the intention of eliminating cellulite. The mantle layer and its vertical fibrous septa will simply readhere to the dermis by a process of scarring fibrosis. Ultimately, with the resolution of postoperative edema, cellulite reappears (see Figure 25-5).

Mantle Layer

The mantle layer of subcutaneous fat is a discrete layer; it is a superficial row of vertically oriented, columnar pearls of fat. Using a cross section of skin and subcutaneous fat, with careful inspection immediately subjacent to the reticular dermis, one can see the distinct blanketlike layer of columnar pearls of fat arranged in a palisading array. The deep margin of the mantle layer consists of a discrete sheet of fascial fibrous tissue.

The mantle layer covers most but not all areas of the body. No significant subcutaneous fat exists in the eyelids (periorbital postseptal fat is not subcutaneous fat), nasal bridge, subungual digits, or penis. The mantle fat layer varies in thickness throughout the body but tends to be uniform over any specific area. It is thicker over areas where it covers deep deposits of subcutaneous fat, such as the hips, thighs, abdomen, and buttocks. Over other areas, such as the leg below the knee, where there are no deep deposits of subcutaneous fat, the mantle layer accounts for nearly all the subcutaneous fat.

Mantle layer fat has the teleologic duty to protect, cushion, and insulate. The individual columnar fat pearls that compose the mantle layer have the structural form of a gabion (cylindric wicker basket filled with rocks and earth for use in fortification and engineering). The body’s ability to withstand the daily assaults of a physically rough environment partly results from the resilient structural design of the mantle layer. Palisaded gabions of fat are closely packed cushions of fat that function as hydraulic shock absorbers. They allow external pressure to be more evenly distributed and more widely dispersed than if the subcutaneous fat were simply a few large, loosely packed “balloons” of fat.

Deep Compartment Layer

The deep compartment layer is the deepest layer of subcutaneous fat. Although this layer is present in obese infants and children, it is often relatively thin until after puberty. With the onset of puberty and adolescence, accumulations of fat begin to appear.

The development and location of individual compartments of fat are manifestations of sexual dimorphism. The eventual size and individual shapes of these depots are a function of genetic predisposition and the individual’s degree of obesity.

The deep fat compartments are capable of enlargement by cell proliferation. Inactivity and a relative abundance of dietary calories tend to augment the size of deep fat compartments, which function as storehouses where excessive dietary energy is saved for later use.

Hierarchical Architecture of Fat

The adipose tissue septa consist of gossamer sheets of fibrous areolar tissue that partition and support an organized series of adipocyte groupings.

The thinnest septa surround fat lobules; they are essentially invisible without magnification. The septa that surround fat pearls are pellucid (translucent) and grossly visible only with great care and attention. The septa that separate fat compartments are thin white sheets; the thinnest are transparent, whereas the thickest (e.g., Scarpa’s fascia) are opaque, white, glistening expanses of tenacious connective tissue.

The taxonomy of fat cell aggregates has a hierarchical pattern vaguely reminiscent of the architectural subdivisions of the lung (see Figure 25-1).

Fat Cell

The individual adipocyte (fat cell) is the smallest unit within the hierarchy of adipose tissue. Histologically the adipocyte has a signet-ring appearance, with an eccentric nucleus and cytoplasm that is less than 1% of the visible fat cell cross section.

Age, gender, and anatomic location influence fat cell size and number. Within any specified anatomic site, fat cells achieve nearly uniform maximum size. In other words, fat cells do not continue to enlarge indefinitely. The size of a fat cell has an upper limit, and once a large proportion of fat cells are almost their maximum size, new fat cells are recruited.

Adipose tissue proliferates by a process of cell multiplication, in contrast to growth by continuous individual cell expansion. With increasing obesity, humans produce new fat cells. New fat cells are created when multipotential fibroblasts become lipoblasts through an overabundance of dietary calories.

Fat Lobule

The fat lobule, next in the hierarchy, is a microscopic structure. The fat lobule consists of a packet of adipocytes partitioned off from adjacent lobules by the thinnest of fibrous septa. The smallest terminal capillaries and an occasional autonomic or sensory nerve fiber meander through the lobule. The smallest lymphatics arise within the interstices between lobules.

The fat lobule is analogous to a compound fruit such as a raspberry, with the adipocyte the smallest individual subsection, or acinus, of the berry.

Fat lobules are easily seen on histologic examination of tissue prepared from a lipoma. When a fatty pearl is sliced open during surgery, fat lobules can be seen as small granules of a yellowish pastelike substance.

Scanning electron micrographs show that each adipocyte is surrounded by a web of collagenous fibers, which are continuous with interlobular septa. With careful inspection, individual fat lobules may be seen without magnification, but the connective tissue membrane that defines a fat lobule is essentially invisible.

Fat Pearl

The fat pearl, encapsulated by a transparent collagenous membrane, is the grossly visible yellow globule of fat that is seen when subcutaneous adipose tissue is transected. The enveloping fibrous membrane gives the fat pearl a shiny, almost pearllike luster. Although somewhat speculative, the fat pearl can be thought of as containing grapelike bunches or clusters of fat lobules.

Although fat pearls are fairly uniform in size within any specific location, they vary in size from one part of the body to another. In the submental chin and cheek areas, fat pearls are about 2 to 3 mm in diameter, whereas in the arms, thighs, and abdomen they may be 1 cm or more in diameter (see Figure 25-2).

Within the same anatomic location, fatty pearls are small in children and larger in adults. Fatty pearls are supplied with small arterioles, venules, and lymphatics. A fat pearl is a lobulose structure; that is, it contains many lobules.

Fat Section

A fat section contains a conglomeration of many fat pearls, packed together between broad, intersecting, visible, pale-white walls of fibrous connective tissue septa. Along these septa course small blood vessels, lymphatics, and nerves.

The three-dimensional size and shape of a fat section are determined by the intersection of multiple fibrous sheets of connective tissue. The fat sections resemble rhomboidal prisms, packed together in a crystal lattice–like fashion.

Fat Compartment

A fat compartment is a grouping of multiple fat sections and is the largest entity within the architectural hierarchy of subcutaneous fat. Some fat compartments are so well recognized that they have been given specific names, such as the hip, outer thigh, buttock, inner thigh, anterior thigh, inner knee, breast, upper abdomen, lower abdomen, and extensor arm.

The size and shape of these fat compartments are responsible for the differences in surface anatomy that exist between adult males and females. When an individual becomes aware that his or her fat compartments are “more than the ideal,” liposuction becomes an option to improve the situation.

Tangential and Oblique Septa

The two types of septal sheets are tangential planes and oblique partitioning walls.

Tangential Planes. These planes of connective tissue are broad, laminated, relatively dense, two-dimensional surfaces that are approximately oriented parallel and tangentially to the subjacent muscle fasciae (see Figure 25-3).

Fascia is the laminated sheet of fibrous tissue that envelops the body beneath the skin. Fasciae also enclose the muscles and groups of muscles and separate their several layers or groups. Subcutaneous fascia is not a functional monolayer of connective tissue; it is a laminate of fibrous sheets, with each lamella a weblike, interwoven film of collagen and fibrocytes. The interfaces between adjacent, loosely adherent lamellae represent potential spaces and become apparent on careful anatomic dissection (Figure 25-4).

These intralamellar potential spaces may be the site of lipoblast formation. A lipoblast is a fibroblast that differentiates into a new fat cell. In the process of adipose tissue proliferation, these lamellae separate and become filled with the new adipocytes.

Oblique Planes. These planes are thinner, smaller, less extensive sheets of tissue that intersect the thicker, tangentially oriented septal planes at oblique angles. They partition fat that is contained between adjacent parallel sheets of tangential septa.

The oblique lamellae might simply arise during the process of fat proliferation within a potential space between two lamellae of a single progenitor tangential septum. A previously parallel lamella becomes an undulating oblique septum, attached in alternating areas between parallel sheets of tangential septa. The new oblique lamella functions as a series of struts that braces and stabilizes the collagenous framework, while concomitantly partitioning and fixing small sections of fat (Figure 25-5).

These sheets of fibrous tissue are intimately attached to both the skin and the deep muscle fasciae, creating a tethering effect on the skin. When the skin and subcutaneous fat of the thigh or buttock are stretched (by gravity or muscle contraction), the resulting irregular distribution of mechanical forces on the tethered skin produces visible dimpling, or cellulite.

Cellulite

As a medical concept, cellulite is not widely recognized, and its anatomic basis is controversial. Many physicians regard the word cellulite as vague and inaccurate. Every woman, however, knows precisely what the term describes: the unattractive, orange peel (peau d’orange), cottage cheese–like, rippling skin of fat thighs.

The Oxford English Dictionary defines cellulite as a “special lumpy form of fat supposed to occur in some women, esp. on the hips and thighs, sometimes producing a yellowish puckering of the skin.” French liposuction surgeons use the words cellulite or cellulitis to designate the human surface anatomy associated with dimpled skin on fat thighs. The French word cellule is translated in English as “cell.” Cellulite is now well established in the English language despite its unscientific origin.

Unproven Treatments

Persons with cellulite despise it and will consider paying for any treatment that promises to remove it. Treatments of dubious value have included acupuncture, exotic diets, special baths, topical creams, and various external massages. Claims of success using external vacuum-roller devices or topical theophylline creams are unproved.

Claims of efficacy have not been supported by objective, reproducible, scientific evidence. If any treatment truly eliminated cellulite, treating only one thigh on a number of women would provide a statistically powerful, wellcontrolled test of efficacy. Until objective, reproducible studies are published, all proprietary claims of successful treatment must be regarded with skepticism. Financial motivation and unsubstantiated claims of dramatic medical success always suggest quackery.

Liposuction. Cellulite cannot be eliminated by liposuction in a predictable manner. Although individual patients might see noticeably improved cellulite, the degree of improvement is usually minimal. An unequivocal elimination of cellulite should not be promised to prospective liposuction patients.

Anatomic Considerations. Cellulite is probably the result of traction on the skin of subcutaneous fibrous septa. Both tangential and oblique planes can insert into the superficial apical and mantle layer septa and the deep fasciae that cover subjacent muscle.

Any attempt to cut the fibrous attachments between skin and adipose tissue is unlikely to give satisfactory long-term results. It is futile to attempt to disconnect the perpendicular septa of the mantle layer from the reticular dermis with the intention of eliminating cellulite. The mantle layer and its vertical fibrous septa will simply readhere to the dermis by a process of scarring fibrosis. Ultimately, with the resolution of postoperative edema, cellulite reappears (see Figure 25-5).

Physiology of Fat

If no postoperative change occurs in dietary energy intake and exercise energy output, a patient’s weight will probably return to its preliposuction magnitude. Unfortunately for obese patients, living organisms are obliged to obey the first law of thermodynamics. Thus, when weight is stable, the following is true:

Energy intake = Energy output

This equation cannot predict how weight changes as a result of a change in either energy intake or energy output. The linear energy balance equation follows:

Change in energy stores = Energy intake – Energy output

This is a static energy balance equation. It seems intuitively valid, but it does not take into account that daily energy expenditure increases with increasing weight. Basal energy expenditure (BEE) is a function of body weight, a relationship described by the Harris-Benedict equation as follows:4

Men: BEE (kcal/day) = 66.47 + 13.75W + 5H + 6.76A

Women: BEE (kcal/day) = 655 + 9.56W + 1.25H + 4.68A

where W is body weight (kg), H is height, and A is age in years.

If the linear energy balance equation were valid, a small increase in energy intake, sustained over many years, would result in a huge weight gain. In reality, after a certain amount of weight gain, a new steady-state equilibrium is attained.

It is more realistic to consider a dynamic energy balance equation. Consider the following differential equation:

dW/dt = dEi/dt – dEo/dt

where dW is rate of change in energy stores, dEi is rate of energy intake, and dEo is rate of energy output. Energy output Eo at time t is also a function of BEE, which in turn is a function of weight.

When the rates of energy intake and output are equal, dW/dt = 0. In other words, weight does not change with time.

After liposuction, weight change is equal to the weight of fat removed surgically. As a result, the body’s BEE will decrease. If a patient does not change the rate of daily food intake or the rate of daily exercise energy expended, the change in BEE will account for a surplus of calories, leading to a net gain in weight. The weight will eventually rise and form a plateau at the preoperative weight.

Analogy and Weight Reduction. A realistic analogy is a tub of water with an open drain, which is in a state of equilibrium when the rate of water inflow and the rate of drainage are equal. In this situation the water level is constant. The rate of water outflow is a function of the height above the drain. Removing a bucket of water from the tub will only lower the water level and slow the rate of drainage temporarily. With the continued steady inflow, however, the water level will rise to the level where the rates of outflow and inflow are again equal.

This analogy helps explain the futility of relying on liposuction as a means of weight reduction. Patients must understand the necessity of either increased exercise or reduced food consumption to maintain any weight reduction achieved by liposuction.

Thus a surgeon should not imply that liposuction alone is a reasonable treatment of obesity. Megaliposuction, besides being risky and expensive, may also be futile.

References

  1. Rodbell M: Metabolism of isolated fat cell. I. Effects of hormones on glucose metabolism and lipolysis, J Biol Chem 239: 375-386, 1964.
  2. Fujita H, Asagami C, Oda Y, et al: Electron microscopic studies of the differentiation of fat cells in human fetal skin, J Invest Dermatol 65:122-139, 1969.
  3. David LR, DeFranzo A, Marks M, Argenta LC: Posttraumatic pseudolipoma, J Trauma 40:396-400, 1996.
  4. Varon AJ, Civetta JM: Physiologic monitoring of the surgical patient. In Schwartz SI, Shires GT, Spencer FC, Cowles-Husser W, editors: Principles of surgery, ed 6, New York, 1994, McGraw-Hill.

Figure 25-1 Hierarchical structure of subcutaneous fat (see text).

Figure 25-2 Size of fat pearls varies according to anatomic site. A, Excision of basal cell carcinoma on male cheek reveals multiple 3-mm to 4-mm fat pearls. B, Site of melanoma excision on extensor arm reveals 6-mm to 10-mm fat pearls.

Figure 25-3 Subcutaneous adipose tissue is bounded superficially by collagenous reticular dermis consisting of closely interwoven collagen fibers arranged in netlike or reticular pattern.

Figure 25-4 Tangential septum of fibrous tissue within midlateral abdominal fat compartment of medium-weight female cadaver. Laminated sheets of diaphanous collagenous tissue form a tangential septum. These laminae can be separated by careful digital dissection.

Figure 25-5 Schematic diagram of tangential and oblique septa within fat compartment.

Figure 25-6 Posttraumatic pseudolipomas. A, Male patient whose right proximal lateral thigh was caught between motorcycle and automobile. B, Female patient whose left distal lateral thigh was injured in automobile collision. C, Another female patient with posttraumatic pseudolipoma caused by automobile accident.

BOX 25-1 Classification of Fibrosis
0    Minimal antitypy, very soft; no effort required to penetrate fat
1    Mild antitypy, soft fat; penetration requires some effort
2    Moderate antitypy, moderately fibrous; penetration requires average effort
3    Significant antitypy, significantly fibrous; penetration requires great effort
4    Extreme antitypy, extremely fibrous; almost impossible to penetrate
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