A light and electron microscopic evaluation of Zyderm collagen and Zyplast implants in aging human facial skin. A pilot study.

Four patients received Zyderm collagen implant (ZCI) or Zyplast implant (ZI) in preauricular and infraauricular regions of facial skin periodically between one and nine months. Both materials were identified microscopically in the mid- to deep dermis at all points of the study and, in 60% to 70% of the injected sites, some material was also present subdermally. A slow, gradual colonization of ZCI by fibroblasts was noted compared with a delayed intense interaction of these cells with ZI. Also, there was some new collagen deposition associated with remodeling of the ZI, while no demonstrable synthetic activity occurred in relationship to ZCI. The results suggest that ZCI and ZI "migrate" deeper and eventually move into the subcutaneous plane. This movement could explain the loss of correction at six to nine months that is noted when this implant is used for age-related changes.