Joris van Dongen

240 Chapter 10 analysis of true skin elasticity i.e. R7 parameter as a function of age showed a negative correlation preoperative. After treatment with lipofilling, this correlation reversed to a positive correlation, especially in the PRP group. The change from negative to positive correlationwas not significant (p=0.056), probably due to the high number of dropouts. On the other hand, postoperative recovery in this study decreased by the addition of PRP to lipofilling. Thus far, four studies used histological outcomes to evaluate the effect of autologous lipofilling on facial skin. 27,32-34 Three studies only subjectively described the histological outcomes and failed to correlate the histological outcomes to clinical outcomes. 32-34 It is well-known that changes in histology after application of a treatment does not always result in significant observable clinical effects. None of the histology studies used a control group with micro-needling alone. Several clinical and animal studies have shown that microneedling alone has substantial effects to the skin e.g. epidermal thickening and increased dermal density. 35-38 The described effects in the four studies using histological outcomes after autologous lipofilling for facial skin rejuvenation might largely be caused by needling. The definition of ‘skin rejuvenation’ is broad and difficult to describe leading to noncomparable results between different clinical studies. In literature, a clear definition of skin rejuvenation is lacking which contributes to a large number of publications stating that autologous lipofilling improves skin quality e.g. disappearing of wrinkles or dark infraorbital circles. 39,40 These observed effects are volumetric effects rather than ‘true’ skin rejuvenation effects to our opinion. Lipofilling causes an increased subcutaneous volume on the site of injection. Increased subcutaneous volume stretches the overlaying skin thereby reducing wrinkle formation. Moreover, dark infraorbital circles are caused by increased transparency of the orbicularis oculi muscle due to aging related decrease in subcutaneous volume and thinning of the skin. Increasing subcutaneous volume by transplantation of adipose tissue results in a less visible orbicularis oculi muscle and thus decreased dark infraorbital circles. To our opinion, the definition of skin rejuvenation should only be used when ordinary aging related improvements of the skin without any volumetric component is mentioned e.g. improvements of thickness, skin texture, elasticity, pores size or pigmentation. There should also be a clear distinction between ordinary (physiological) aging related changes of the skins and changes due to pathological processes such as traumatic scars, fibrotic diseases or wound healing. All the aforementioned clinical studies used lipofilling as a treatment to enhance skin rejuvenation in patients with ordinary aged skin. To our opinion, aging of the skin is a