Does Thoracodorsal Pedicle Dissection Affect Upper-Extremity Lymphatic Drainage? Arm Circumference After Free Latissimus Dorsi Muscle Flap Harvest in Patients Without Axillary Lymphadenectomy.

Background: The free latissimus dorsi (LD) muscle flap remains a workhorse for large soft-tissue defects. Its pedicle, however, must be followed proximally into the axilla-into the immediate vicinity of the lymphatics that drain the arm-and whether this compromises upper-extremity drainage has never been settled. The few studies that examined lymphoedema after LD surgery relied on questionnaires and were confined to breast reconstruction, where axillary clearance and irradiation offer a sufficient explanation for anything they found; the harvest itself has never been isolated. Methods: We identified every patient who underwent free LD muscle flap reconstruction for defect coverage at our institution between September 2017 and December 2022 and examined those who attended a standardized cross-sectional follow-up. None had undergone axillary lymph node dissection, sentinel node biopsy, or axillary irradiation, and none had received cervical or supraclavicular irradiation ipsilateral to the donor side. A single examiner measured upper-arm and forearm circumference bilaterally, 10 cm proximal and 10 cm distal to the medial epicondyle. Patients whose flap had been transferred to an upper limb were excluded, because in them the tape measures the flap rather than the donor site. The contralateral limb served as the intra-individual control. The primary endpoint was the mean side difference in upper-arm circumference with its 95% confidence interval. Results: Forty-one patients (25 women, 16 men; mean age 54.4 ± 16.5 years; mean follow-up 14.4 ± 12.0 months, range 3-48) were included. Upper-arm circumference averaged 27.88 ± 3.26 cm on the donor side and 27.77 ± 3.65 cm contralaterally-a difference of +0.11 cm (95% CI -0.28 to +0.50; p = 0.57). Forearm values were 23.82 ± 2.89 cm and 23.94 ± 3.07 cm (-0.12 cm; 95% CI -0.47 to +0.23; p = 0.49). Two of 41 patients (4.9%; exact 95% CI 0.6-16.5%) crossed the conventional 2 cm threshold at the upper arm-and exactly as many crossed it in the opposite direction, with the donor limb the smaller of the two. Side difference bore no relation to time since surgery. Conclusions: Free LD muscle flap harvest showed no detectable difference in arm circumference at two standardized levels in patients who had never undergone axillary lymphadenectomy. The upper-arm mean difference is compatible with no more than a 0.5 cm increase, and threshold crossings occurred equally often in both directions. Circumference is a coarse surrogate that cannot detect subclinical (International Society of Lymphology [ISL] stage 0) lymphoedema; within that limit, these data give no support for avoiding the flap on lymphatic grounds.