**Core Concept**
Rigid fixation refers to a surgical technique used to stabilize and immobilize bones, joints, or other tissues, typically after trauma, fracture, or osteotomy. This method involves using rigid implants or devices to maintain proper alignment and promote union without movement.

**Why the Correct Answer is Right**
Rigid fixation is achieved through the use of implants such as plates, screws, rods, or nails that provide stable fixation and prevent excessive movement, allowing for proper healing and union of the affected bone or joint. In orthopedic surgery, rigid fixation is commonly used in procedures such as open reduction and internal fixation (ORIF) to stabilize and immobilize fractures or osteotomies.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not provide a clear method of rigid fixation. Without more context, it is difficult to determine what this option refers to.

**Option B:** This option is incorrect because dynamic fixation involves using implants that allow for some degree of movement, rather than rigid immobilization. Examples of dynamic fixation include elastic stable intramedullary nailing (ESIN) and dynamic hip screws.

**Option C:** This option is incorrect because external fixation involves using external devices, such as pins and frames, to stabilize and immobilize bones or joints. While external fixation can provide some degree of stability, it is not considered a rigid fixation method.

**Option D:** This option is incorrect because arthrodesis involves fusion of a joint, which can provide stability but does not necessarily involve rigid fixation of individual bones or tissues.

**Clinical Pearl / High-Yield Fact**
In orthopedic surgery, rigid fixation is essential for promoting proper healing and union of bones or joints, especially in cases of comminuted fractures or osteotomies. It is crucial to choose the appropriate rigid fixation method based on the specific injury or condition being treated.

**Correct Answer: C. External fixation involves using external devices, such as pins and frames, to stabilize and immobilize bones or joints.