Semipermanent Volumization By Hyaluronic Acid Fillers: Onlay Injection Technique to the Bone

Goals/Purpose: Hyaluronic acid (HA) fillers have become the most popular tool for facial rejuvenation over the past several years, although a downside of HA is absorption of the material within 6-12 months that necessitates repeated treatments to maintain the effects. On the other hand, any permanent filler result in long-term complications such as foreign body granulomas. Then, we found that onlay injection of HA fillers to the bone could provide semi-permanent volumizing outcomes by year's experiences. We herein demonstrate the efficacy and safety of the technique, and consider the underlying mechanism of the effects.

Methods/Technique: HA was injected onto the bone for volumization with small 30-gauge needles to examine the long-lasting effects. Of 63 Japanese patients (58 females and 5 males), 51 had HA injection for cosmetic purposes and 12 suffered from facial deformity such as localized scleroderma, lupus erythematosus profundus, Parry-Romberg syndrome and post-surgical craniomaxillofacial deformity. The mean age of the patient was 59.8, and all patients were followed up for 12 months or more. Ninety-seven treated sites included the forehead, temple, nasal root, mentum, tear trough and infraorbital sulcus.

Results/Complications: After long-term follow-up (12 to 93 months, mean=21.6), persistent volumizing effects were observed in most patients though the final volume retention was relatively less than the original injection volume. In fact, 86.6% of the treated sites showed >50% volume retention and 49.5% showed >75% retention. No serious complication occurred. Magnetic resonance imaging (MRI) in some patients showed that the injected spaces were still augmented with heterogeneous materials, which were similar but not identical intensity to HA syringe. Additionally, MRI quantitative T2 maps in another patient indicated that much of the injected HA was capsulated, and gradually replaced with other materials.

Conclusion: Our clinical and imaging findings suggest that injection of HA on the bone induced formation of capsule, fibrosis and calcification/ ossification, which contributed to persistent volumization. It is suspected that immune response surrounding injected HA may activate resident stem cells in the periosteum and induce gradual replacement of HA with fibrogenesis and osteogenesis. We should be aware of the potential use of an absorbable filler injection for semi-permanent volumization and this may also become an alternative to bone, cartilage or fat grafting.