Anatomy for plastic surgery of the breast

1 Anatomy for plastic surgery of the breast







Ideal breast architecture


The appearance of the ideal breast is somewhat subjective. Each patient has their own opinion as to the aesthetics of their breasts, which should be given consideration with any operative alteration of the breast. Reconstruction or cosmetic enhancement of the breast encompasses not only the way the breast looks, but also how it feels to the touch. Size, symmetry, proportionality and the location of the breast and its landmarks on the chest wall all play a role in the attractiveness of the breast. Statistical standards for the dimensions of the breast have been analyzed and reported by various authors (Fig. 1.1).17 The distance from the sternal notch to the nipple and the distance from the midclavicular line are each 19–21 cm. The distance from nipple to the inframammary fold is 5–7 cm (Fig. 1.1). The distance from the nipple to the midline is 9–11 cm. These measurements offer guidelines for altering the breast, which must be individualized, based on proportionality, variances in chest wall anatomy, posture and patient preference (Fig. 1.2).




The breast mound is situated over the pectoralis major muscle between the second and sixth ribs in the nonptotic state. Important landmarks include the upper pole, location of the nipple areolar complex, inframammary fold and lateral breast fold. The upper pole of the breast extends from just below the clavicle to the level of the nipple. The contour should be neither concave nor convex, but a plane that extends out to the point of maximum projection of the breast at the level of the nipple. In the ideal breast form, the nipple areolar complex should be cephalad to the level of the inframammary fold.



Development of the breast


The breast originates from the ectoderm, the germinal layer which forms the initial breast bud. The connective tissue is derived from the mesoderm. A group of glands, derived from the epidermis, develops within the dermis and underlying fascia. Breast development occurs along the milk line, which extends from the axilla to the groin. The normal breast develops at the level of the fourth intercostal space on the anterolateral chest wall. Supernumerary breast formation can occur anywhere along the milk line (Fig. 1.3). The most common location of supernumerary breast formation is at the inframammary crease on the left side, but additional breast formation can occur in the axilla as well.



Following a brief period of activity shortly after birth in response to maternal hormones, breast development is quiescent until puberty. Onset of puberty occurs at approximately 9 years of age (Fig. 1.4). Typically, by age 14, parenchymal growth has extended to its mature borders. These include the clavicle at the superior border, the sternum at the medial border, the inframammary fold for the inferior border and the anterior border of the latissimus dorsi for the lateral border. Breast tissue can extend beyond the borders particularly medially and inferiorly. The breast tissue that extends laterally through the axillary fascia into the axillary fat pad is referred to as the “tail of Spence.” Mature breast morphology projects from the chest wall in a conical fashion with its greatest point of projection at the nipple areolar complex (Fig. 1.5).




Development of breast shape is dependent on many factors, including fat content, volume, muscular and skeletal contour and skin and connective tissue compliment. In particular, the Cooper’s ligaments provide structural support for the breast parenchyma. These structures combine to provide the final breast shape; it is dependent in large part on heredity and will change with age as the suspensory structure become lax and the breast becomes more ptotic (Fig. 1.6).




Parenchyma


The glandular tissue of the breast is dispersed through a significant amount of adipose tissue.8 The glands themselves consist of millions of lobules clustered together into 20–25 lobes. Interlobular ducts join to form approximately 20 primary lactiferous ducts that open onto the nipple areolar complex. The lactiferous ducts converge into a specialized ductile network, which stores the milk prior to lactation. The glandular parenchymal ducts are lined with cuboidal cells which transition to stratified squamous epithelium in the ductile and sinus network (Fig. 1.5).


The functioning parenchyma produces milk in the post-partum period. Adipose tissue comprises a significant amount of the breast volume, representing 50–70% of the breast volume. With age and the hormonal changes of menopause, the glandular tissue of the breast involutes, increasing the adipose to parenchymal tissue ratio. The consistency of the breast softens with the increased fatty tissue accumulation.


An intricate fascial layer supports the breast tissue. The parenchyma is fixed in placed by the superficial fascial system, which extends cephalad from the abdomen, diverges into a superficial and deep component enveloping the breast tissue and maintaining its attachment to the breast wall (Fig. 1.7). The superficial fascial layer is an extension of Scarpa’s fascia, which envelopes the glandular tissue deep to the dermal layer. The superficial fascial layer and the dermis can be difficult to distinguish. Subcutaneous fatty tissue between the dermis and the superficial fascia distinguish the two layers. The deep layer diverges at the level of the sixth rib, where the inframammary fold is the inferior border of the parenchyma.



The Cooper’s ligaments provide numerous interconnections between the deep and superficial fascial layers. These ligaments pass through ad invest in the breast parenchyma securing to the pectoralis fascia. With attenuation of these support structures, breast ptosis will develop (see Fig. 1.14). Regnault delineated a classification system for mammary ptosis describing the relative positions of the nipple and the inframammary fold.9




Some authors have reported a distinct anatomic entity holding the inframammary fold in place, however surgically, this ligamentous structure is not readily apparent. The circumference of the dermis at this level does however, contribute to the effect of allowing the tissue of the breast to drop over at the level of the inframammary fold.



Nipple areola complex


The nipple areola complex is the primary landmark of the breast. As previously stated, it is located at the prominence of the breast mound. The nipple itself may project as much as ≥1 cm, with a diameter of approximately 4–7 mm. The areola consists of pigmented skin surrounding the nipple proper and is on average approximately 4.2–4.5 cm in diameter. The areola consists of keratinized, stratified epithelium and contains not only the lactiferous sinus openings, but also sebaceous glands and the Montgomery glands. The Montgomery glands are intermediate in their nature with characteristics of both the lactiferous gland and the sebaceous gland.


The lactiferous glands extend from their opening on the surface of the nipple down to the parenchyma. The lining of the ducts transition from stratified epithelium on the surface to cuboidal cells within the ducts, and ultimately to columnar cells of the lactiferous gland itself. The nipple and areolar have a network of connecting myoepithelial cells arranged surrounding the sinus opening. This myoepithelium lies between the surface epithelium and the basal lamina. In addition, deep to the nipple and areolar there are smooth muscle fibers which are arranged circumferentially and radially. These fibers are attached to the thick connective tissue of the areola and are responsible for nipple erection.


Because the nipple is the focus of the breast, maximizing its location and maintaining its function are of critical importance when performing breast surgery of any type. Fortunately, the blood supply to the nipple, as with the breast parenchyma, is redundant and rich. The internal mammary perforator, lateral thoracic perforators, and the intercostal perforators from both the anterolateral and anteromedial origins all provide arterial supply to the subdermal plexus of the nipple.10

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Feb 21, 2016 | Posted by in General Surgery | Comments Off on Anatomy for plastic surgery of the breast
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