**Core Concept**
Tardy ulnar nerve palsy is a delayed onset ulnar nerve dysfunction, often resulting from a pre-existing anatomical or mechanical deformity that gradually worsens over time, leading to nerve compression and subsequent palsy.

**Why the Correct Answer is Right**
The most common cause of tardy ulnar nerve palsy is cubitus valgus, a congenital or post-traumatic deformity of the elbow where the ulna is angled outward, causing the ulnar nerve to be stretched or compressed as it passes through the cubital tunnel. This compression can lead to nerve damage, resulting in symptoms such as weakness, numbness, and atrophy of the hand muscles innervated by the ulnar nerve.

**Why Each Wrong Option is Incorrect**
**Option A:** Traumatic injuries can cause acute ulnar nerve damage, but they do not typically result in tardy ulnar nerve palsy.
**Option B:** Cervical spine injuries can cause ulnar nerve damage due to radiculopathy, but this is not a characteristic feature of tardy ulnar nerve palsy.
**Option C:** Diabetic neuropathy can cause various forms of nerve damage, but it is not typically associated with tardy ulnar nerve palsy.

**Clinical Pearl / High-Yield Fact**
Be aware that tardy ulnar nerve palsy often presents with a delayed onset, typically several years after the initial deformity, making it a classic example of a "tardy" presentation in orthopedic and neurosurgical practice.

**Correct Answer: C. Cervical spine injuries can cause ulnar nerve damage due to radiculopathy, but this is not a characteristic feature of tardy ulnar nerve palsy.