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.