Monitoring lymphatic reconstitution in free latissimus dorsi flap for lower extremity defects repair in pediatric patients: a case series.

Background: The circulation in free flap is mainly studied on blood perfusion, but lack of exploring contributory factor of lymphatic drainage. This study aimed to monitor lymphatic reconstitution of free latissimus dorsi (LD) flaps for lower extremity defects repair, using indocyanine green (ICG) lymphography and assessing its relationship with post-operative flap edema.

Methods: Patients who underwent lower extremity defects repair with free LD flap between January 2021 and April 2024 were included. The inclusion criteria were as follow: (I) lower extremity defects; (II) wound repaired by free LD flap; (III) more than 6 months of follow-up. ICG lymphography was performed to monitor lymphatic reconstitution at different timepoints (postoperative 3^rd day, 7^th day, 10^th-14^th day, 1^st month, and 3^rd month). Changes in flap limb circumference were recorded at different timepoints (operation day, 3^rd day, 7^th day, 14^th day, 1^st month, and 3^rd month).

Results: Of the 12 patients examined (mean age: 10.3±2.7 years old, range from 7 to 16 years old; male to female ratio: 7:5), LD flap edema reached its peak on 3^rd day postoperatively, and involuted in one week. Lymphedema was initially observed between 10 and 14 days (average: 11.5±1.7 days). Flap swelling was not found decreased from 7^th day to 1st month, but involuted remarkably between 1^st month and 3^rd month postoperatively. The overall time of spontaneous lymphatic reconstitution in LD flap ranged from 11 to 16 weeks (average: 12.8±1.6 weeks), and flap edema resolution ranged from 12 to 16.5 weeks (average: 13.6±1.3 weeks).

Conclusions: Lymphedema forms without obvious decrease of flap swelling in plateau period, and flap edema resolves gradually after lymphatic reconstitution, which is crucial to edema resolution of free LD flap, and the findings in this research may aid in understanding option of symptomatic management in flap edema.