Pediatric free fillet of leg flap for external hemipelvectomy coverage: A case report and systematic review

Background: External hemipelvectomy leaves large composite defects that are difficult to reconstruct. The free fillet of leg flap repurposes soft tissue from the amputated limb to provide durable coverage without additional donor-site morbidity. Pediatric applications are rarely reported. Methods: We conducted a PRISMA-guided systematic review (1999–2025) across PubMed and Google Scholar. Inclusion criteria were external hemipelvectomy reconstructed with a free flap and reporting at least flap survival and/or complications. Data were extracted at the case and study levels. We computed pooled proportions (Wilson 95% Confidence Intervals) for primary outcomes (flap survival/complications) overall and by flap category. We complement this synthesis with a detailed pediatric case from our institution. Results: Forty-three studies comprising 94 cases met inclusion. Among cases with explicit reporting, pooled flap survival was 95% (65/69; 95% CI 86.0–97.7), and any complication occurred in 44% (28/64; 95% CI 32.3–55.9). By flap category, survival was reported in 36/38 fillet-of-leg, 7/8 fillet-of-leg with fibula only, 3/3 fillet-of-leg with fibula and tibia, 7/7 anterolateral thigh (ALT)/anterior thigh, 6/6 latissimus dorsi, 2/3 medial thigh, 3/3 other/unspecified, and 1/1 free vascularized fibular graft (FVFG) cases. Complications occurred in 14/34 fillet-of-leg, 5/7 fillet-of-leg with fibula only, 2/3 fillet-of-leg with fibula and tibia, 1/7 ALT/anterior thigh, 3/6 latissimus dorsi, 1/3 medial thigh, 3/3 other/unspecified, and 1/1 FVFG reconstructions. Our case involved an 11-year-old boy who underwent external hemipelvectomy with a free fillet-of-leg flap, achieving full healing by 6 weeks and ambulation by 5 months. Conclusions: Fillet-of-leg free flaps offer reliable, donor-site-sparing coverage for hemipelvectomy defects with high flap survival. This pediatric case supports feasibility and highlights strategies to minimize ischemia and manage venous congestion.