<aside>

Avascular necrosis (AVN), also known as osteonecrosis, is a condition resulting from compromised blood supply to bone, leading to bone ischemia, cellular death, and eventual structural collapse of the affected area.

</aside>

https://www.youtube.com/watch?v=qX_J2f9l0AQ

Common Sites

Site Notes
Femoral head Most common site (especially in adults)
Humeral head Often post-traumatic or corticosteroid-induced
Knee (femoral condyles) Often medial femoral condyle
Scaphoid & Lunate Prone due to tenuous vascular supply
Talus Common after fracture (e.g., neck of talus)
Vertebral body Known as Kümmell disease (delayed collapse)

Etiology

Pathophysiology involves interruption of microvascular circulation, leading to bone marrow infarction, trabecular necrosis, and ultimately subchondral collapse.

Category Examples
Traumatic Fractures (esp. femoral neck, talus, scaphoid), dislocations
Non-traumatic Corticosteroids, alcohol abuse, sickle cell disease, SLE, pancreatitis, radiation, Caisson’s disease (diving), chemotherapy, transplant

Untitled

Clinical Features

Stage Symptoms
Early May be asymptomatic or mild pain with activity
Progressive Pain at rest, stiffness, limited ROM
Advanced Joint collapse, secondary osteoarthritis

Radiology

Modality Imaging features
XR Often normal in early stages
  1. Joint effusion (earliest sign)
  2. Patchy or mottled density
  3. ‣: Subchondral lucency (pathognomic, in 20% cases)
  4. Articular surface and joint fragmentation

Later stages: • Sclerosis, flattening of articular surface • Joint space narrowing, secondary OA changes | | MR | Most sensitive for early detection • T1: Low signal in necrotic area (geographic, well-demarcated) • T2/STIR: Double line sign: inner bright (granulation tissue), outer dark (sclerosis) • Post-contrast: Lack of enhancement in necrotic core | | CT | • Useful in surgical planning • Shows subchondral fracture, sclerosis, and collapse clearly | | Bone Scan | • Early: “cold spot” (decreased perfusion) • Late: increased uptake at reactive margins |

![A 9 year-old female with a known history of ‣ presented with a history of pain over the left hip. (a) AP X-ray of the pelvis showed increased opacity secondary to sclerosis at the articular end of the left femoral head without significant deformity. A thin crescenteric radiolucency can be seen in the subchondral region, shown closely in (b) by arrow, consistent with ‣

Case courtesy Dr Supriya Paul & Dr Marrie Pagu // 2025 // #SMCHCase](attachment:00598bb7-e54a-4096-a10a-e56e9468c789:AVN.jpg)

A 9 year-old female with a known history of ‣ presented with a history of pain over the left hip. (a) AP X-ray of the pelvis showed increased opacity secondary to sclerosis at the articular end of the left femoral head without significant deformity. A thin crescenteric radiolucency can be seen in the subchondral region, shown closely in (b) by arrow, consistent with ‣

Case courtesy Dr Supriya Paul & Dr Marrie Pagu // 2025 // #SMCHCase

Staging

Ficat and Arlet Classification for femoral head AVN:

Stage Radiologic Findings
I Normal X-ray, MRI abnormal
II Sclerosis, cysts, no collapse
III Subchondral fracture (crescent sign)
IV Femoral head collapse, joint space narrowing, secondary arthritis