[Intraoperative expansion of scalp flaps. Quantitative assessment]

The aim of this study was to test the ex-vivo biomechanical properties of acutely expanded scalp flaps, in order to quantitatively assess the efficacy of acute scalp expansion.

A total of 14 fresh male cadavers were used for the study. In each cadaver, a rectangular (4 x 10 cm), laterally-based flap was designed on each side of the scalp, starting from the superior margin of the external auditory canal. One randomly-selected flap per each scalp underwent acute-intermittent expansion (3-minute expansion-3-minute rest cycle per three times with the maximal expansion achievable), while the contralateral flap served as control. After the expansion process, the acutely-expanded flaps were measured to assess if the applied biomechanical stress have determined any changes in their dimensions. The biomechanical properties (stress/strain ratio, mean stiffness) of both expanded and control flaps were then assessed by means of a dynamometer and a force-transducer.

The obtained data showed that the biomechanical benefits provided by acute scalp expansion were not statistically different (p < 0.05) from those obtained by simple subgaleal undermining. Neither any change of length nor any gain in the compliance have been observed in the acutely-expanded flaps as compared to control scalp flaps.

In our opinion, a possible explanation (to be further validated) for the lack of effect of acute scalp expansion might be that inelastic galea aponeurotica did not allow the mechanical creep to exploit the inherent elastic properties of the overlying scalp skin.