Joris van Dongen

264 Chapter 11 two studies lacked a control group 18,24 , four studies used non-validated methods of measurements 19,23,24,96 , two studies did not report any quantitative data 20,22 and two studies did not define the outcome of interest i.e. skin texture. 19,96 Trivisonno et al. defined improved skin texture as decreased wrinkle depth, folds and fine lines when analysed with the profilometry analyser. The observed improved skin texture might therefore be caused by a volumetric effect of lipografting. 24 The volumetric effect of lipografting can decrease wrinkle depth and give the patients’ face a rejuvenated appearance. Decrease in wrinkle depth is not necessarily related to an improved skin quality. Furthermore, each skin parameter e.g. skin texture, wrinkles, pigmentation, pores, is affected by one another. For example, skin texture is defined as softening of the skin which is affected by wrinkles, pores and birthmarks. Hence, the improvement in skin texture is partly caused by a volumetric effect of lipografting due to decreased wrinkle depth. This shows that the definition of “skin rejuvenation” or “skin quality” is rather broad and difficult to confine. The heterogeneity between studies is high caused by the absence of standardization of fat harvesting and processing techniques of lipoaspirates as well as variation in patient demographics. Cell yield and viability of both lipoaspirate and cSVF depend on age, comorbidity e.g. obesity, diabetes mellitus type 2 and probably harvest location and processing techniques such as centrifugation and decantation. 33-38,102 The majority of the included studies did not mention these donor characteristics, which makes comparison of the included study populations difficult. Animal experiments corroborate the clinical findings that administration of adipose tissue or its components is of little influence on skin quality. Two mice experiments demonstrated increased dermal thickening due to increased numbers of type 1 collagen fibers and angiogenesis after lipografting. 103,104 Another study investigating the effect of lipografting, ASC transplantation and ASC-enriched lipografting on the upper eyelid of pigs showed no increase in epidermal thickening. 105 However, the use of ASC- enriched lipografting resulted in an increased dermal thickening as well as increased epidermal cell proliferation, collagen content and number of arterioles in comparison with placebo. 105 In aesthetic plastic surgery, it is challenging to design well-defined prospective randomized clinical trials with the use of validated equipment and questionnaires to assess skin quality. A study on the number of publications in three major plastic surgery journals found only 1.83% of the publications to be randomized clinical trials. 106 Plastic surgery literature consists mainly of relatively small sample sized studies, as compared to the general medical literature. Moreover, a small sample size makes it more difficult