a spacer for delivery into the natural or man - made openings to the frontal , maxillary , sphenoid , anterior or posterior ethmoid sinuses , or other cells or cavities , anatomical regions such as nostrils , nasal cavities , nasal meatus , and other passageways such as the eustachian tubes , naso - lachrymal ducts or airway is described . the bioabsorbable polymeric spacers maintain the opening and / or are useful for delivering drugs or other substances to the natural or man - made openings .