What is the most common sinus infection that causes secondary orbital cellulitis?

The most common sinus infection that can lead to secondary orbital cellulitis is ethmoid sinusitis. This is primarily due to the anatomical proximity of the ethmoid sinuses to the orbit. The ethmoid sinuses are located between the eyes and are relatively thin-walled, making it easier for infection to spread from the sinuses to the orbit, particularly in children who often experience upper respiratory infections that can lead to sinusitis.

In cases of ethmoid sinusitis, the infection can cause swelling and inflammation that extends to the periosteum of the orbital cavity, leading to orbital cellulitis. This complication is more likely in pediatric populations due to their anatomical development, where the sinuses are not fully developed, and they are also more prone to upper respiratory infections.

While maxillary, frontal, and sphenoid sinusitis can also occur and may lead to complications, they are less commonly associated with orbital cellulitis compared to ethmoid sinusitis. The maxillary sinuses, while significantly sized, drain posteriorly, and frontal sinuses typically drain into the anterior nasal cavity, making the pathways for infection to reach the orbit longer and more complex. Sphenoid sinusitis is rare and usually does not result in orbital cellulitis as it is located deeper within