**Core Concept**
Cubitus varus deformity, also known as gunstock deformity, is a complication of supracondylar fracture of the humerus. This deformity occurs when the distal fragment of the humerus is displaced posteriorly, resulting in a varus (inward) angulation of the elbow joint.

**Why the Correct Answer is Right**
The correct answer is associated with the mechanism of injury and the anatomy of the supracondylar fracture. When a supracondylar fracture occurs, the distal fragment of the humerus is displaced posteriorly due to the pull of the flexor muscles. This displacement leads to a varus deformity, which can be exacerbated by improper reduction and immobilization. The fracture occurs just above the elbow joint, making it prone to this type of displacement.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because supracondylar fractures, not epiphyseal fractures, are associated with cubitus varus deformity. Epiphyseal fractures occur at the growth plate and do not typically result in this type of deformity.
* **Option B:** This option is incorrect because Monteggia fractures involve the ulna and radius bones, not the humerus. While they can be complex injuries, they are not typically associated with cubitus varus deformity.
* **Option C:** This option is incorrect because lateral condyle fractures can result in cubitus valgus deformity, not varus deformity. Cubitus valgus occurs when the distal fragment of the humerus is displaced anteriorly, resulting in an outward angulation of the elbow joint.

**Clinical Pearl / High-Yield Fact**
Supracondylar fractures are a common injury in children and can be associated with significant complications if not properly managed. Early recognition and treatment of these fractures are crucial to prevent deformities and long-term functional impairment.

**Correct Answer:** C. Supracondylar fracture of the humerus.