**Core Concept**
Cubitus varus deformity is a common complication of supracondylar fractures of the humerus, characterized by a varus (inward) angulation of the distal humerus. This deformity occurs due to malunion or inadequate reduction of the fracture, leading to a characteristic change in the elbow's alignment.

**Why the Correct Answer is Right**
The correct answer is **C. Coronal tilt**. This occurs when the distal fragment of the humerus is tilted in a coronal plane, resulting in a varus deformity. In a normal elbow, the coronal plane is perpendicular to the sagittal plane, but in cubitus varus, this alignment is disrupted. The coronal tilt is a result of the fracture's displacement and the subsequent malunion, which affects the growth and development of the distal humerus.

**Why Each Wrong Option is Incorrect**
* **Option A:** Posterior displacement refers to the backward movement of the distal fragment of the humerus, which can occur in supracondylar fractures. However, it is not the primary cause of cubitus varus deformity.
* **Option B:** Posterior angulation refers to the backward tilt of the distal fragment, which can also occur in supracondylar fractures. However, it is not the primary cause of cubitus varus deformity.

**Clinical Pearl / High-Yield Fact**
To remember the key concept, recall the mnemonic "COR" for Coronal Orientation and Reduction. Cubitus varus deformity is primarily caused by a coronal tilt, which can be a result of inadequate reduction or malunion of the fracture.

**Correct Answer Line**
✓ Correct Answer: C. Coronal tilt