**Core Concept:** Post-traumatic digital contracture is a clinical condition characterized by contraction of the muscle around a finger joint after injury. It results in joint stiffness and limited movement. In this case, the patient presents with flexion deformity at the proximal interphalangeal joint and hyperextension at the distal interphalangeal joint, indicating a specific type of post-traumatic contracture.

**Why the Correct Answer is Right:** The correct answer is D - Flexion contracture, because a flexion contracture occurs when the muscle around a joint contracts, causing that joint to be pulled into constant flexion. In this scenario, the patient experiences flexion contracture at the proximal interphalangeal joint, leading to limited movement and the described deformity.

**Why Each Wrong Option is Incorrect:**
A. Extension contracture refers to a condition where the muscle contracts and pulls the joint into a position of hyperextension, which is not observed in this case.
B. Dupuytren's contracture is a condition characterized by thickening of the palmar fascia, leading to finger flexion contracture. This is not the primary diagnosis here, as the described deformity involves both flexion and hyperextension, indicating multiple contractures.
C. Ganglion cyst is a benign, fluid-filled, and painless swelling caused by an abnormal connection between the nerve and the tendon sheath. It is unrelated to the described joint deformities and is not the primary diagnosis in this scenario.

**Clinical Pearl:** Post-traumatic contractures should be promptly identified and managed to prevent worsening of the condition and permanent damage to the affected digit. Early intervention involves passive stretching exercises and sometimes surgical release of the contracted tissue.