MeroGel hyaluronic acid sinonasal implants: Osteogenic implications

Objectives/Hypothesis: The study sought to evaluate the effects of MeroGel (Medtronic Xomed Surgical Products, Jacksonville, FL) hyaluronic acid sinonasal implants by using a mouse model. We expected that this material would dissolve, elicit minimal inflammation, and leave intact mucosa. However, pilot data showed that MeroGel may be osteogenic. The present work focuses on the description and quantification of these bony changes. Study Design: Animal experiment. Methods: The effects of MeroGel were evaluated using sinonasal and calvarial implants in C57BL/6 mice. The calvarial experiments employed both light microscopy (bone histomorphometry) and fluorochrome labeling (mineral apposition). Each implant study was subdivided into normal control animals, sham-operated control animals, a foreign body control, and MeroGel implants. MeroGel was also placed within subcutaneous pockets remote from bone. All mice were killed 1 month after surgery. Both percentage of bone area within the sinonasal cavity and total calvarial bone area were quantified and compared. Fluorochrome images and the subcutaneous implants were examined qualitatively. Results: MeroGel placement engendered new bone formation within the nasal lumen of mice. Compared with normal control animals, sham-operated control animals, and a foreign body control, this increase was statistically significant. The calvaria from MeroGel-implanted mice were thickened as compared with normal animals, sham-operated control animals, and a foreign body control. Tetracycline labeling demonstrated mineral apposition along the dorsal and ventral surfaces of the calvaria and within enlarged marrow spaces. MeroGel placed subcutaneously did not engender bone formation. Conclusions: MeroGel, a unique esterified form of hyaluronic acid, induced bone formation within the sinonasal cavity and on the calvaria of mice implanted with it. Our experiments suggest that, when placed adjacent to traumatized, remodeling bone, MeroGel may have osteogenic potential.