What is the anatomy relevant to breast reconstruction with acellular dermis?

Updated: Jul 29, 2021
  • Author: John Y S Kim, MD, FACS; Chief Editor: James Neal Long, MD, FACS  more...
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Answer

Answer

The significant anatomy of the ADM-assisted expander-implant technique involves the anatomic borders of the breast mound, the associated blood supply, and the nerve supply. See Breast Anatomy for more information.

The breast mound is bordered superiorly by the second rib, inferiorly by the inframammary fold, medially by the sternum, and laterally by the anterior axillary line. The blood supply to the breast is supplied by the internal mammary artery (a branch of the subclavian artery) on the left and the brachiocephalic artery on the right. The primary innervation to the nipple-areola complex is provided by the lateral branch of the fourth intercostal nerve.

The pectoralis major originates from the cartilage of the true ribs, starting at the anterior surface of the clavicle and running down the lateral half of the sternum to approximately the sixth or seventh rib. The fibers end laterally at a flat tendon and insert at the lateral lip of the intertubercular groove of the humerus. This muscle is dually innervated by the medial and lateral pectoral nerves, arising from the brachial plexus.

The serratus anterior originates medially from the upper eighth and ninth ribs and inserts at the costal medial margin of the scapula. It is innervated by the long thoracic nerve, which runs inferiorly along the surface of the muscle. Because this nerve is highly exposed, particular care should be taken during reconstructive procedures, especially if an axillary dissection was performed during mastectomy.

The purpose of using acellular dermis in expander-implant reconstructions is to improve upon or maintain the essential components of breast aesthetics, including the inframammary fold, ptosis, and projection.

The inframammary fold is the inferior landmark of the breast. It is often altered during mastectomy and is a key component in achieving symmetry with the contralateral breast. Ptosis refers to drooping or overlapping skin in the lower pole that extends over the inframammary fold. Ptosis of the breast is caused by the effects of gravity on the breast tissue over time and is usually difficult to replicate with implants.

Finally, projection refers to the fullness of the breast, as measured by the distance from the chest wall to the most anterior point, usually the nipple. Initially, in the setting of tissue expanders, projection is less than was present with the original breast mound. The original projection may be restored with expansion, especially if the nipple is spared at the time of mastectomy.

The inferior border of the matrix is used to recreate the inframammary fold. The superior border is attached to the disinserted pectoralis major to create a complete subpectoral, subgraft pocket for expander placement. The acellular dermal sling provides numerous potential benefits. Complete implant coverage reduces the risk of implant exposure, extrusion, visibility, and palpability. [1, 5, 6] Tethering of the pectoralis major prevents the implant from migrating and creating an unnatural breast stepoff or fold effacement. [1, 5, 6]

The apparent resistance of acellular dermis to capsular contracture also reduces the chances of implant displacement. [1] Ultimately, better control of implant position allows greater lower-pole projection, improved inframammary fold definition, and increased potential for natural-looking ptosis. [1, 4, 5, 6]

Furthermore, it is generally felt that by producing a large pectoralis-dermal pocket, acellular dermis permits greater intraoperative tissue expander fill volumes, leading to fewer postoperative expansions and a subsequent acceleration of the expansion process. [1, 2, 12] However, this sentiment is not completely unanimous. [10]


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