**Core Concept**
Displacement of an olecranon fracture, especially an oblique one, requires precise treatment to restore elbow function and prevent complications like nonunion or arthritis. The treatment choice depends on the fracture's displacement and the patient's overall condition.

**Why the Correct Answer is Right**
In cases of displaced olecranon fractures, especially those displaced proximally, surgical intervention is often necessary to achieve proper alignment and promote healing. This typically involves open reduction and internal fixation (ORIF) using a plate or screw to stabilize the fracture and allow early mobilization. The goal is to restore the normal anatomy of the olecranon and the surrounding soft tissues to prevent long-term complications.

**Why Each Wrong Option is Incorrect**
**Option A:** Reduction and immobilization alone may not be sufficient for a displaced olecranon fracture, as it may lead to nonunion or malunion.
**Option B:** External fixation might be considered in certain cases, but it is not the primary treatment for a displaced olecranon fracture.
**Option C:** Closed reduction and percutaneous pinning can be used for some olecranon fractures, but it may not provide sufficient stability for a displaced fracture.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the treatment of olecranon fractures can be challenging, and a thorough understanding of the fracture's displacement, the patient's overall condition, and the potential complications is crucial for making an informed treatment decision.

**Correct Answer:** C. Closed reduction and percutaneous pinning can be used for some olecranon fractures, but it may not provide sufficient stability for a displaced fracture.