**Question:** When performing a DCR, the osteum is created at the level of

A. Nasal wall
B. Orbital wall
C. Ethmoid bulla
D. Frontal process of ethmoid bone

**Correct Answer:** D. Frontal process of ethmoid bone

**Core Concept:** Dacryocystorhinostomy (DCR) is a surgical procedure used to create a communication between the lacrimal sac and the nasal cavity for the purpose of draining the accumulated tears and relieving the symptoms of acquired or congenital nasolacrimal duct obstruction.

**Why the Correct Answer is Right:**

DCR involves creating an osteum, which is a bony opening, at a specific level to ensure effective drainage of the lacrimal sac contents into the nasal cavity. In this case, the osteum is created at the level of the frontal process of the ethmoid bone. The frontal process is located superior to the lacrimal sac, ensuring that tears drain into the nasal cavity and bypass the obstructed nasolacrimal duct. This allows for proper drainage and relieves the patient's symptoms.

**Why Each Wrong Option is Incorrect:**

A) Nasal wall: Creating the osteum at this level would not allow for a direct connection between the lacrimal sac and the nasal cavity, leading to inadequate drainage.

B) Orbital wall: Similar to option A, placing the osteum at the orbital wall would not provide an optimal route for tear drainage.

C) Ethmoid bulla: The ethmoid bulla is located within the nasal cavity, not superior to the lacrimal sac, so creating the osteum at this level would not effectively drain tears.

**Clinical Pearl:**

Understanding the anatomy of the lacrimal system is crucial when planning and performing a DCR. By creating the osteum at the level of the frontal process of the ethmoid bone, surgeons ensure that tears can drain directly into the nasal cavity, bypassing the obstructed nasolacrimal duct and effectively treating the patient's symptoms.