1. UNICAMERAL BONE CYST JULY 2012UNICAMERAL BONE CYST

2. AETIOLOGY Unknown Venous obstruction leading to transudate of fluid Fluid contains high levels of IL-1 & IL-6, which stimulate osteoclasts JULY 2012UNICAMERAL BONE CYST

3. FEATURES Benign lesion during growth 20% of benign bone lesions 5-15 years Not in adults Male:Female 3:1 Most common prox. Humerus, followed by prox. femur Sometimes in calcaneus JULY 2012UNICAMERAL BONE CYST

4. PATHOLOGY UBC’s are thin walled cavities filled with blood tinged fluid Lining cells are cuboidal Endosteal osteoclastic activity Periosteal new bone formation JULY 2012UNICAMERAL BONE CYST

5. FEATURES Active or latent : Active: Located near growth plate Latent: Further away from growth plate and inactive JULY 2012UNICAMERAL BONE CYST

6. PRESENTATION Asymptomatic OR Present as pathological fracture JULY 2012UNICAMERAL BONE CYST

7. RADIOGRAPHIC FEATURES Well defined Central osteolytic area Thin sclerotic margin Metaphyseal in young  Towards diaphysis with growth Fallen fragment sign with pathological fracture JULY 2012UNICAMERAL BONE CYST

8. RADIOGRAPHIC FEATURES JULY 2012UNICAMERAL BONE CYST Metaphysis Thin walled Central Well defined

9. RADIOGRAPHIC FEATURES JULY 2012UNICAMERAL BONE CYST MRI Proximal humerus

10. DIFFERENTIAL Dx Depending on the location : NOF, enchondroma, Fibrous dysplasia Sometimes bone abscess JULY 2012UNICAMERAL BONE CYST

11. TREATMENT AIM : Minimize # risk until cyst heals Steroid injection 60-80 % success rate Curettage and bone graft ? Bone marrow aspirate JULY 2012UNICAMERAL BONE CYST