Defining a Danger Zone for Iatrogenic Long Thoracic Nerve Injury in Gender-Affirming Mastectomy

SDCC 

Introduction
The Long Thoracic Nerve (LTN) lies immediately deep to the serratus anterior fascia on the lateral chest wall,1 rendering it vulnerable to iatrogenic injury in surgery.2 LTN injury leading to scapular winging is a well-described complication in the breast oncology and thoracic surgery literature.3,4 Expansion of insurance coverage for gender-affirming surgical care has led to rapid increases in the number of gender-affirming mastectomies being performed by plastic surgeons.5 This operation typically involves significant lateral chest contouring placing the LTN at a high risk of injury along the chest wall. In this study, the course of the LTN relative to the lateral border of the pectoralis major muscle was mapped to delineate and define a danger zone for iatrogenic LTN injury in gender-affirming mastectomy.

Methods
Patients undergoing gender-affirming mastectomy by a single surgeon at a single institution were prospectively enrolled. The course of the LTN along the lateral chest wall was mapped using intraoperative nerve stimulation. The distance between the nerve and the lateral border of the pectoralis major muscle was measured and adjacent rib level was determined to define the zone in which the LTN is vulnerable to iatrogenic injury.

Results
Twelve individuals met study criteria and were prospectively enrolled. Study participants were, on average, 23 years old, had an average BMI of 27.8, and 92% had Fischer Grade 3 or 4 ptosis. The LTN was mapped bilaterally and was most reliably located directly lateral to the intersection of the 4th rib and the lateral border of the pectoralis major muscle. The LTN was found an average of 4.3 cm lateral to the pectoralis major at the 3rd rib level, 5.4 cm lateral to the pectoralis border at the 4th rib level, and 6.9 cm lateral to the pectoralis border at the 5th rib level.

Conclusions
This study defines a danger zone for injury to the LTN in gender-affirming mastectomy. Although proximal LTN injury can cause debilitating shoulder dysfunction, more distal LTN injury can cause chronic postoperative shoulder pain and dysfunction without frank scapular winging, making diagnosis and treatment difficult. Therefore, iatrogenic LTN injury is best avoided. With recent increases in the number of plastic surgeons performing gender-affirming mastectomies, awareness of this LTN danger zone is critical to avoid morbidity.

References
1. Tubbs RS, Salter EG, Custis JW, Wellons JC, Blount JP, Oakes WJ. Surgical anatomy of the cervical and infraclavicular parts of the long thoracic nerve. J Neurosurg. May 2006;104(5):792-5. doi:10.3171/jns.2006.104.5.792
2. O J, Kwon HJ, Cho TH, Won SY, Yang HM. Analysis of the positional relationship of the long thoracic nerve considering clinical treatment. Clin Anat. May 2021;34(4):617-623. doi:10.1002/ca.23647
3. Belmonte R, Monleon S, Bofill N, Alvarado ML, Espadaler J, Royo I. Long thoracic nerve injury in breast cancer patients treated with axillary lymph node dissection. Support Care Cancer. Jan 2015;23(1):169-75. doi:10.1007/s00520-014-2338-5
4. Salazar JD, Doty JR, Tseng EE, et al. Relationship of the long thoracic nerve to the scapular tip: an aid to prevention of proximal nerve injury. J Thorac Cardiovasc Surg. Dec 1998;116(6):960-4. doi:10.1016/S0022-5223(98)70047-9
5. Lane M, Ives GC, Sluiter EC, et al. Trends in Gender-affirming Surgery in Insured Patients in the United States. Plast Reconstr Surg Glob Open. Apr 2018;6(4):e1738. doi:10.1097/GOX.0000000000001738

Gender Affirmation

PSTM 2024