Re-raising muscle flaps: A randomised controlled animal study

In the experience of our centre, 33% of reconstructed compound lower limb injuries will need an orthopaedic revision.¹ A flap may be re-raised through numerous methods, and historically, the approach of choice has been based on the principle of protecting the vascular pedicle rather than the inset. Our aim was to determine whether a marginal versus a split approach to re-raising inferred a higher risk of flap necrosis and whether more attention should be paid to protecting the inset of the flap, particularly at the distal portion.

A pedicled pectoralis profundus muscle flap was raised in 32 Sprague-Dawley rats and transposed to the lateral chest wall. After 21 days, the flaps were randomised into one of four treatment groups according to the surgical approach and whether or not the anatomical vascular pedicle was ligated. Necrosis was assessed 48 h later, both clinically and through the analysis of digital photographs.

The rate of necrosis in the marginal group was higher than that in the split group (63% vs 0%, p < 0.001, McNemar). More necrosis occurred in the former when the pedicle was ligated (p < 0.001, Fisher's exact test). Measured necrosis was also higher in the marginal group (18% vs 0%, p = 0.002, Wilcoxon signed-rank test). Twenty-nine percent more flap could be raised using the split approach (p = 0.001, Mann-Whitney U test).

Splitting a muscle flap produces significantly less necrosis than incising the inset, regardless of whether the pedicle is in flow. It also offers wider exposure of structures deep to the flap. These findings provide a detailed model for human trials, which is presented as a proposed management algorithm. It also highlights conditions that must be met for translation to a human population.