A Traversing Nerve Branch Within the Deltopectoral Interval Anatomically Consistent with a Possible Lateral Pectoral Nerve Variant: A Cadaveric Study

Background/Objectives: The deltopectoral approach is widely used in shoulder surgery. Safe exposure during this approach requires recognition of neurovascular structures within the operative field. A traversing nerve branch within the deltopectoral interval, anatomically consistent with a possible lateral pectoral nerve variant, remains poorly characterized. This study evaluated its observed frequency, course, and relationship to surgical landmarks. Methods: Bilateral deltopectoral dissections were performed in 6 cadavers (12 shoulders). The interval was identified using the cephalic vein and the plane between the deltoid and pectoralis major. Candidate branches were traced proximally and distally when feasible, and presence, laterality, and unilateral or bilateral occurrence were recorded. Distances from the coracoid process, proximal border of the pectoralis major insertion, and sternoclavicular joint were measured. Results: A traversing nerve branch was identified in 3 of 12 shoulders (25.0%; 95% CI, 5.5–57.2%) and 2 of 6 cadavers (33.3%; 95% CI, 4.3–77.7%). It was present in one left and two right shoulders; one cadaver demonstrated bilateral presence, and one demonstrated unilateral right-sided presence. In the three positive shoulders, the branch coursed inferiorly through the deltopectoral interval with variable positioning. The mean distance from the coracoid process was 7.0 cm (range, 6.5–8.1 cm), from the proximal border of the pectoralis major insertion was 2.7 cm (range, 1.6–3.9 cm), and from the sternoclavicular joint was 12.5 cm (range, 11.0–13.3 cm). Conclusions: A traversing nerve branch anatomically consistent with a possible lateral pectoral nerve variant was present in 3 of 12 shoulders in this cadaveric series. The observed location, approximately 6.5–8.1 cm distal to the coracoid process, may be relevant to anatomical understanding of the deltopectoral interval during surgical exposure; however, the small sample size precludes defining a reproducible surgical risk zone. Larger anatomical and clinical studies are required to establish the frequency, identity, and clinical significance of this branch. Given the limited sample size and incomplete anatomical confirmation, these findings should be considered exploratory and hypothesis-generating and should not be interpreted as estimates of population frequency or established clinical significance.