**Question:** Pesudo fracture of looser's zone is seen in

A. avascular necrosis
B. periostitis
C. osteoporosis
D. Paget's disease

**Core Concept:**

A pseudo fracture, also known as a greenstick fracture, is a type of fracture that occurs when the bone remains intact but is bent or twisted due to external forces. Looser's zone is a transitional zone between the mature compact bone and the immature spongy bone in the epiphyseal region of long bones, particularly in children and adolescents during growth.

**Why the Correct Answer is Right:**

Pseudo fracture of Looser's zone is most commonly seen in the context of avascular necrosis (A), which is characterized by a disruption in blood supply to the affected area, leading to impaired healing and potential bone deformities. In this case, the external force applied to the bone results in bending or twisting without causing a complete fracture.

**Why Each Wrong Option is Incorrect:**

1. Periostitis (B) refers to inflammation of the periosteum, the outer layer of connective tissue covering the bone, rather than a condition associated with pseudo fractures.
2. Osteoporosis (C) primarily affects bone density and strength, increasing the risk of fractures; it is not directly related to pseudo fractures of Looser's zone.
3. Paget's disease (D) is a disorder characterized by abnormal bone remodeling, leading to increased bone density and strength; pseudo fractures are not a typical manifestation of Paget's disease.

**Clinical Pearl:**

Pseudo fractures of Looser's zone are essential to recognize as they can mimic a true fracture on X-rays, leading to unnecessary immobilization and potential complications. In the context of avascular necrosis, clinicians should be vigilant for these pseudo fractures and differentiate them from true fractures when assessing patients with bone pain and deformities.