Clinical, histologic and electron microscopic findings after injection of a calcium hydroxylapatite filler.

BACKGROUND Calcium hydroxylapatite (CaHa) is one of many newly available soft tissue fillers. OBJECTIVE We have, in this pilot study, evaluated the clinical, histologic and electron microscopic ultrastructural changes seen with CaHa at 1 and 6 months after skin injection. METHODS Each of the three subjects was injected in the postauricular area with 0.1 cc of CaHa gel. A 3-mm punch tissue biopsy was taken at 1 and 6 months post-injection. Biopsies were analyzed by histopathology and electron microscopy. Clinical results after injection of the nasolabial folds were also evaluated. RESULTS CaHa particles were found to persist at 6 months with evidence of new collagen formation being seen. Patients still showed clinical improvement at this time. CONCLUSION This study is the first in vivo ultrastructural analysis of the biologic response to CaHa in human skin. CaHa shows clinical, histologic and electron microscopic evidence of persistence at 6 months.