Subperiosteal Hematoma of the Ankle.
BACKGROUND
Periosteal reaction has a long list of differential diagnoses ranging from trauma, infection, metabolic disease to malignancy. The morphology of periosteal reaction shown in imaging studies helps to narrow down the list of differential diagnoses.


METHODS
A 25 year old gentleman had an inversion injury to his left ankle. He complained of lateral ankle and posterior heel pain and swelling after the injury. Radiograph of his left ankle revealed solid, smooth periosteal reaction at posterior aspect of left distal tibia. MRI showed periosteal reaction at the corresponding site, which was better demonstrated in CT scan. Follow up MRI and CT showed maturation of the new bone formation at the site of periosteal reaction. Findings were compatible with subperiosteal hematoma formation from injury, which ossified with time.


CONCLUSIONS
Smooth, thick periosteal reaction favours benign process, while interrupted pattern is an alarming feature for more aggressive causes.
Department of Orthopaedics and Traumatology, North District Hospital 9 Po Kin Road, Sheung Shui, NT, Hong Kong SAR, China.
S H
SH
Hui
Department of Orthopaedics and Traumatology, North District Hospital 9 Po Kin Road, Sheung Shui, NT, Hong Kong SAR, China.
T H
TH
Lui
ankle; periosteal reaction; subperiosteal haematoma