Does controlled, gradually increased venous pressure exposure (dangling) of the lower extremity after free flap reconstructions reduce partial flap loss? A multicenter randomized controlled trial

Introduction: Controlled, gradually increased venous pressure exposure of lower extremity free flaps (dangling) is common, based on the assumption that this reduces (partial) flap loss. Dangling protocols potentially increase length of hospital stay and resource utilization. We investigated whether: (1) the proportion of partial flap loss 6 weeks after lower extremity free flap reconstruction is non-inferior after uncontrolled exposure compared to gradually increased venous pressure exposure; (2) there is a difference in length of hospital stay and major or minor adverse events 3 months after surgery. Materials and Methods: For this multicenter randomized controlled trial patients who underwent lower extremity free flap reconstruction were included. Seven days after surgery 39 were randomized to dangling and 36 mobilized without limitations. Partial flap loss was assessed 6 weeks after surgery (primary outcome), length of stay, and major and minor adverse events 3 months after surgery. An absolute increase of 12% partial flap loss was considered inferior. Results: Uncontrolled exposure was non-inferior to controlled, gradually increased venous pressure exposure (absolute risk difference: 2.4%, 95% CI -10%-15%, partial flap loss dangling: 5.1% (n=2) vs. non-dangling: 2.8% (n=1)). There was no difference in length of stay and major or minor complications. Conclusion: Seven days after surgery, dangling the lower extremity after free flap reconstruction seems unnecessary. Surgeons and patients can consider forgoing a formal dangling protocol at that time. Future research is warranted to assess whether forgoing dangling is also safe earlier after free tissue transfer possibly reducing length of hospital stay and resource utilization.