Ineffectiveness of acute scalp expansion

The aim of this study was to test the ex vivo biomechanical properties of acutely expanded scalp flaps 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 scalp underwent acute intermittent expansion (a 3-minute expansion/3-minute rest cycle was performed three times with the maximum expansion achievable); the contralateral flap served as a control. After the expansion process, the acutely expanded flaps were measured to assess whether applied biomechanical stress caused any changes in flap 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. No change of length nor gain in compliance was observed in the acutely expanded flaps as compared with control scalp flaps. In the authors' opinion, a possible explanation (to be further validated) for the lack of effect of acute scalp expansion might be that the inelastic galea aponeurotica did not allow mechanical creep to exploit the inherent elastic properties of the overlying scalp skin.