Unicameral Bone Cyst

Question 1

What is the most common location for a unicameral bone cyst?

Answer 1

Proximal humerus of person <20yo; also proximal femur

Question 2

How does a unicameral bone cyst present a majority of the time?

Answer 2

Pain from pathologic fracture (50-75%)

Question 3

What are the imaging and histological characteristics of a unicameral bone cyst?

Answer 3

1) Central lesion, usually contained within cortex, in metaphysis
2) “fallen leaf” sign in pathologic fracture
3) histo shows cyst with thin fibrous lining

Question 4

How are unicameral bone cysts treated?

Answer 4

1) many resolve with growth maturity
2) steroid or marrow injection if near physis (still high recurrence rate)
3) ORIF if proximal femur fx (high refracture rate if non-op)
4) Immobilization if proximal humerus fx