Multilayered injection of calcium hydroxylapatite filler on ischial soft tissue to rejuvenate the previous phase of chronic sitting pressure sore

INTRODUCTION: During a sitting position, the pressure distribution is located below the ischial tuberosity. Many women have skin atrophy on the ischial area. To treat atrophic changes on the skin above the ischium, volumization and improving skin texture are acquired simultaneously. Two methods of automatic and manual injections using a hard filler with a stitmulating effect were administered respectively to both the dermis and subdermis layers. A biopsy study using various straining evaluated histological tissue reactions after the filler injections. METHODS: This study focused on rejuvenating soft tissue on the atrophic ischeal areas, as described by the author as the previous phase of chronic sitting pressure sore, by using the multi-layered injection of calcium-hydroxylapatite (CaHA) filler. Sixteen women (mean, 38.5 years) were treated from 2012 January to 2019 April. Prior to the injection, 1.5cc of Radiesse(®) (calcium hydroxylapatite filler; Merz, Germany) was diluted with 1cc of normal saline and 0.5cc of lidocaine, and 3cc of filler mixture (1:1 dilution) was made. All subjects received the intradermal injection and multi layered subdermal injection with 2.5cc of diluted CaHA filler. A second session for booster treatment was performed at 6 months using the same method. Photography was taken by a camera and a dermascope observation before and 7 months after. Before and 7 months after the first injection, soft tissue depression, skin discoloration, and roughness were assessed. Standard deviations and coefficients of variation were also calculated for changes in depression, discoloration and roughness after the treatment. Biopsy specimens (3×5 mm) were taken from three patients 7 months after the first session. The specimens were analyzed using various stainins. RESULTS: The improvements of skin quality, skin fold, and roughness were visible at physical examination, medical photography and also at high-resolution dermascope examination in all patients. Post-treatment the depressed amounts on the ischial areas reduced with increased volume. CONCLUSION: Depressed soft tissue and skin folds on ischial areas were significantly improved by volumization of subdermal filler injection. The skin quality, roughness, and pigmentation on ischial areas improved, and these improvements may be caused by intradermal micro-droplet injections of CaHA filler which may be influenced by neocollagenesis by numerous fibroblasts and increased micro-blood circulation (neovascularization). This is the first article to show the scientific evidence of neocollagenesis and tissue reaction after an injection of CaHA filler in the dermis, especially using various histological staining and to show various stages of inflammation and foreign body reaction around CaHA particles. Numerous fibroblasts were present around CaHA particles, but plasma cells were not found. Interestingly a few eosinophils were found around CaHA filler. After a significant period of time, multi-layered injections of diluted CaHA tightened and remodeled atrophic ischial skin. The multi layered injection approach was safe and effectively treated ischial soft tissue atrophy without significant side effects, such as infection or delayed swelling or lumps.