Defining sexual dimorphism in masculinizing chest surgery using 3-dimensional imaging.

Area of Science:

• Anatomy
• Plastic Surgery
• Gender-Affirming Care

Background:

• The optimal scar placement and inframammary fold (IMF) position in gender-affirming double-incision mastectomy lack consensus.
• Advances in imaging allow for noninvasive anatomic studies, reducing reliance on cadaveric dissection.
• Understanding chest wall sexual dimorphism can enhance aesthetic outcomes in gender-affirming surgery.

Purpose of the Study:

• To investigate chest wall sexual dimorphism using cadaveric and 3-D CT imaging.
• To provide anatomical data to refine gender-affirming mastectomy techniques.
• To establish consistent landmarks for scar and IMF placement.

Main Methods:

• Analysis of 60 chests (30 cadaveric, 30 3-D CT reconstructions).
• Measurement of chest proportions, correlating surface anatomy with muscular and bony landmarks.
• Utilized Vitrea® software for virtual dissections and 3-D reconstructions.

Main Results:

• Natal male chests are wider and longer than natal female chests on average.
• Pectoralis major muscle dimensions and insertion points showed no significant sex-based differences.
• The male nipple-areolar complex (NAC) was narrower with less projection compared to the female NAC.
• The inframammary fold (IMF) was consistently located between the 5th and 6th ribs in both sexes.

Conclusions:

• Natal male and female inframammary folds are anatomically consistent, located between the 5th and 6th ribs.
• This finding supports a technique for masculinizing the chest by maintaining the IMF at the natal female level.
• Scar placement can be guided by the pectoralis major muscle edges, differing from prior methods.