Certain fillers are currently used as biostimulatory agents when injected into different parts of the body. The filler’s most commonly used today are PLLA which is Poly-L- Lactic Acid or Sculpta and CaHA or Calicium Hydroxyapatite which is Radiesse. PMMA is Polymethymetacrylate which is Bellafill. These fillers tighten and improve the appearance of the skin and are being used on various parts of the body besides the face.

When these fillers are injected to cause fibroblast proliferation, they are usually diluted more than when used in the face. The dilution ratios depend on where you are working on the body and the thickness of the skin. Skin that is thin like the decolletage will require a slightly higher dilution ratio of 1:4 to prevent nodular formation.

When injecting these fillers one should get into the habit of always drawing back to decrease the risk of injecting into a vessel. This decreases the risk of vascular compromise and embolization. It is also important to try to inject in a uniform layer in the subdermal plane. This will give the rest result.

These fillers work by stimulating a histiocytic and fibroblastic response and a scaffold is created much like platelet rich fibrin where new collagen and elastin is produced to improve the appearance of the skin. PRF (Platelet Rich Fibrin) can also be added to the filler to improved the appearance of the skin by sustained growth factor release.

It is believed that collagen type I gradually replaces collagen type III which is the collagen that causes fibrosis or scarring. The new collagen synthesis occurs as early as 4 weeks and has been observed up to 12 months after treatment. The highest deposition occurs at 4 months and is stable by 9 months after injection. One might require up to 3 sessions for opotimal results. Maintenance injections every 12-18 months might be needed afterwards.

In the buttocks biostimulatory fillers target sagging and skin controus irregularities, especially cellulite and stretch marks. Some of patients that have had fat grafting to the buttocks still have some contour irregularities and are difficult to correct with fat eventhough subcision is performed .

Below is a photograph of a patient that has had 3 sessions of filler injected into her butt.
One is also treat the neck, decolletage, upper inner arms, superior knees, anterior thighs and hands.

References:
Goldie K, Peeters W, Alghoul M. et al. Global Consensus Guidelines for Injection of Diluted and Hyperdiluted Calium Hydroxylapatie for Skin Tightening. Dermatologic Surg 2018;44:S32-S41.