**Core Concept**
Scaphoid fractures are common wrist injuries, often resulting from a fall onto an outstretched hand. The scaphoid bone is a small, boat-shaped carpal bone in the wrist that plays a crucial role in wrist movement and stability. Complications of scaphoid fractures can arise due to its unique anatomy and blood supply.

**Why the Correct Answer is Right**
The most common complication of scaphoid fractures is **nonunion**, which occurs when the fractured bone fails to heal properly. This is often due to the scaphoid's tenuous blood supply, particularly in the proximal pole. The risk of nonunion is higher in proximal pole fractures, which can lead to persistent pain, limited wrist mobility, and increased risk of osteoarthritis. Nonunion can also be caused by improper immobilization, inadequate reduction, or delayed treatment.

**Why Each Wrong Option is Incorrect**
**Option A:** **Malunion** is incorrect because while it is a complication of scaphoid fractures, it is less common than nonunion.
**Option B:** **Scapholunate ligament injury** is incorrect because, although it can occur concurrently with scaphoid fractures, it is not the most common complication.

**Clinical Pearl / High-Yield Fact**
The scaphoid's unique anatomy and blood supply make it prone to complications, especially nonunion. Early recognition and proper management of scaphoid fractures are crucial to prevent long-term consequences.

**Correct Answer:** C. Nonunion.