What are the key aspects of surgical anatomy to consider in a female patient with a history of mastectomy and possible radiation therapy undergoing second stage breast reconstruction?

Surgical Anatomy Primer for Second Stage Breast Reconstruction

Critical Pre-Operative Anatomical Assessment

Before scrubbing into second stage breast reconstruction, you must understand the altered anatomy from the first stage and identify key structures that determine your surgical approach, particularly the musculofascial pocket boundaries, the position of the tissue expander, and any radiation-induced tissue changes. 1

First Stage Anatomy Review

The tissue expander from stage one creates a musculofascial pocket that typically involves:

• Pectoralis major muscle coverage superiorly and medially, which has been elevated and stretched during expansion 2
• Serratus anterior fascia or muscle laterally, providing lateral pocket support 2
• Inferior fasciotomy site where the pectoralis major was released from its inferior origin to allow adequate expansion and proper implant positioning 2
• Acellular dermal matrix (ADM) or synthetic mesh inferiorly and laterally if used during first stage, which now forms part of the capsule 2

Radiation-Altered Anatomy

If the patient received post-mastectomy radiation therapy (PMRT), expect significantly altered tissue characteristics:

• Fibrotic, less pliable skin with reduced vascularity and elasticity 1
• Thickened, contracted capsule around the expander with increased risk of capsular contracture (significantly higher rates) 1
• Compromised blood supply to the mastectomy skin flaps, increasing risk of wound breakdown 3
• Adherent tissue planes making dissection more difficult and increasing bleeding risk 4

In previously radiated patients, autologous tissue reconstruction is strongly preferred over implant exchange due to unacceptably high rates of capsular contracture, malposition, poor cosmesis, and implant exposure with tissue expanders/implants. 1, 5

Key Anatomical Landmarks for Implant Exchange

When performing the exchange procedure (replacing expander with permanent implant), identify:

The inframammary fold (IMF) position:

• The IMF must be precisely set or reset during exchange, as this determines breast projection and shape 2
• Measure from the sternal notch and midclavicular line to ensure symmetry 2
• The IMF may have migrated superiorly during expansion and requires release and repositioning 2

The capsule anatomy:

• A circumferential capsulotomy is often necessary to achieve proper implant positioning and breast shape 2
• The capsule is thickest inferiorly and laterally where ADM/mesh was placed 2
• Anterior capsulotomy (removing anterior capsule) improves implant projection 2
• Inferior capsulotomy allows proper IMF positioning 2

The inferolateral breast contour:

• This area requires specific attention to define natural breast shape 2
• The lateral border of the pectoralis major and the serratus fascia junction define this region 2
• Inadequate release here results in a "boxy" or unnatural breast shape 2

Vascular Anatomy Considerations

Critical vessels to preserve or avoid:

• Internal mammary perforators medially (typically 2nd-4th intercostal spaces) - these may be the primary blood supply to the mastectomy skin flaps 1
• Lateral thoracic artery branches laterally, running along the lateral border of pectoralis major 6
• Thoracoacromial artery branches superiorly, supplying the pectoralis major 6

In radiated patients, these vessels may be compromised or thrombosed, explaining the higher complication rates with implant-based reconstruction in this population. 3, 4

Chest Wall Anatomy

Understand the underlying chest wall structures:

• Ribs and intercostal spaces - the implant pocket sits directly on these structures 2
• Pectoralis major muscle - its inferior origin (typically 5th-6th rib) has been released during first stage 2
• Serratus anterior muscle - provides lateral coverage and should be preserved 2

Nipple-Areolar Complex (NAC) Anatomy (if preserved)

If the patient had NAC-sparing mastectomy:

• The NAC blood supply comes from subdermal plexus and is tenuous 1
• Avoid undermining or excessive manipulation of the NAC during exchange 1
• NAC necrosis rates are similar in radiated and non-radiated patients (low overall) 3

Donor Site Anatomy (if Converting to Autologous Reconstruction)

If converting from implant to autologous tissue due to radiation complications or patient preference:

DIEP/TRAM flap anatomy:

• Deep inferior epigastric vessels (source vessels) arise from external iliac vessels 1, 7
• Perforators through rectus abdominis muscle (DIEP) or muscle itself (TRAM) 7, 6
• Abdominal wall fascia must be closed to prevent hernia 7, 6

Latissimus dorsi flap anatomy:

• Thoracodorsal vessels (source vessels) from subscapular artery 1
• Latissimus dorsi muscle with overlying skin paddle from back 1
• Creates donor site on back requiring separate incision 6

Common Pitfalls to Avoid

Do not underestimate radiation effects: Even if radiation was completed months or years ago, tissue changes are permanent and significantly increase complication risk with implants. 1, 5, 3

Do not inadequately release the capsule: Insufficient capsulotomy results in malposition, poor shape, and patient dissatisfaction. 2

Do not improperly set the IMF: This is the most critical determinant of final breast shape and projection. 2

Do not proceed with implant exchange in heavily radiated patients: Strongly consider conversion to autologous reconstruction instead. 1, 5

Surgical Approach Algorithm

For non-radiated patients:

• Proceed with standard implant exchange 1
• Perform circumferential capsulotomy as needed 2
• Set IMF precisely 2
• Select appropriate implant size and profile 2

For radiated patients:

• Strongly consider conversion to autologous tissue reconstruction (DIEP, TRAM, latissimus dorsi) rather than implant exchange 1, 5
• If patient insists on implant, counsel extensively about high complication rates (capsular contracture >40%, malposition, poor cosmesis, implant exposure) 1
• Expect thickened, fibrotic capsule requiring extensive release 4
• Consider ADM reinforcement if proceeding with implant 4

For patients with expander complications (infection, exposure, malposition):

• Remove expander and capsule completely 5
• If radiated, convert to autologous reconstruction 5
• If not radiated, may attempt re-expansion after healing 5