The Art and Science of Dangling: A Systematic Review of Free Flap Protocols

Dangling protocols are widely used in the postoperative management of lower extremity free flaps to promote microvascular adaptation. To optimize outcomes, surgeons use dangling protocols, gradually increasing limb dependency, to enhance venous adaptation. However, wide variability exists in their design, and the impact of dangling duration and frequency on complication rates remains unclear.

A systematic meta-analysis was performed to evaluate pooled complication rates associated with dangling protocols and to assess whether protocol duration (minutes per session) or frequency (number of sessions) was associated with adverse outcomes. Following PRISMA 2020 guidelines, we searched Medline, Embase, Web of Science, and Cochrane for relevant studies published through 2024. Then, a random-effects model was used to estimate pooled rates of partial flap loss, total flap loss, venous congestion, arterial compromise, hematoma, infection, wound dehiscence, return to the operating room, and donor site complications. Meta-regression was performed to examine associations with dangling protocol characteristics.

Across pooled studies, overall complication rates were low, including total flap loss (0.30%), arterial compromise (0.30%), and venous congestion (0.73%). No statistically significant associations were found between dangling duration and any complication type. While increased frequency of dangling was significantly associated with higher return-to-OR rates in the full model (slope = 0.0224; p = 0.0002), this relationship was entirely driven by a single study reporting 24 sessions/day. When this outlier was excluded, the association became non-significant.

Dangling protocols appear safe and well tolerated, with low rates of major complications. While the duration of dangling sessions does not affect complication risk, higher frequency may increase the likelihood of surgical re-intervention. These findings support the need for standardized, evidence-based protocols and further research into the physiologic and clinical thresholds guiding postoperative flap care. A meta-analysis of lower extremity free flap studies demonstrated low complication rates across common endpoints including total flap loss (0.30%), arterial compromise (0.30%), and venous congestion (0.73%).