## **Core Concept**
Nonunion in bone healing refers to the failure of a fractured bone to heal properly, resulting in persistent separation of the bone fragments. Several factors can impede the bone healing process, leading to nonunion. Understanding these factors is crucial for managing and preventing nonunion.

## **Why the Correct Answer is Right**
Prostaglandins, particularly those in the prostaglandin E series, are known to play a role in the inflammatory phase of bone healing. They can actually enhance bone healing by promoting the differentiation of osteoblasts and the formation of new bone tissue. Therefore, prostaglandins are not typically considered factors that facilitate nonunion; instead, they can support the healing process.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Infection is a well-known factor that can lead to nonunion. It creates an environment that is not conducive to healing, often resulting in chronic inflammation and tissue damage that prevents bone union.
- **Option B:** Poor blood supply can significantly impede the healing process. Bone tissue requires a good blood supply to deliver oxygen, nutrients, and growth factors necessary for healing. A deficiency in blood supply can lead to nonunion.
- **Option C:** Excessive movement at the fracture site can prevent the formation of a stable callus and subsequent bone union. Stability is crucial for the healing process, and excessive mobility can lead to nonunion.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that electrical stimulation and ultrasound therapy are sometimes used as adjunctive treatments to enhance bone healing in cases of nonunion. These treatments aim to stimulate the healing process by promoting cellular activity and bone growth.

## **Correct Answer:** D. Prostaglandins.