Unicameral bone cyst of the proximal tibia in a five year old girl
A 5-year-old girl presented to our clinic (Kashani hospital, Isfahan, Iran, 2011) with a history of 4-month pain around her right knee. She had a painful limping. There was no history of any specific infection or trauma. She did not have any similar complain previously. The pain was constant throughout the day but was alleviated by analgesics. There was a moderate tenderness in the proximal of tibia in palpation without any warmth or change in color of the skin in the suspicious area. There was no limitation in arc of motion of her right knee and hip. The child was not febrile and there was no sign or symptom of systemic illness. Hematological investigations (include leukocyte count, cell profile, erythrocyte sedimentation rate, calcium, phosphorus and alkaline phosphatase) were normal.\nBefore referring to our clinic, she had been visited 3 months ago by an orthopedic surgeon, and a plain radiography had been requested. At that time, the plain radiography of the right knee demonstrated a small well-circumscribed eccentric lesion in the proximal medial metaphyseal region of the tibia without disruption of the cortex (), and the patient had been treated conservatively with suspicious of fibrous cortical defect.\n3 months later she was referred to our clinic with a new plain radiography, which demonstrated a large well-defined centric lytic lesion with involvement of both medial and lateral portion of proximal tibial metaphysis, without disruption of cortices and physis (). There was no evidence of fallen leaf sign or obvious sclerotic border. Furthermore, there was no obvious septation but to some extent cortical expansion. Because of rapid progression of the lytic lesion, a magnetic resonance imaging (MRI) was requested. MRI reported an expansile centric, septated cystic lesion in metadiaphyseal part of the right tibia without fracture or secondary changes in muscular component (). Signal of lesion was high on T2-weighted and low on T1-weighted.\nThe patient was admitted to orthopedics ward for open biopsy. Macroscopically, there was blood accompanied by epithelial lining without straw fluid or infective discharge. Histological examination revealed highly vascular thin membranous lining composed primarily of epithelium-like cells and giant cells accompanied with hemosiderin deposition ().\nAfter confirmation of the diagnosis, the patient underwent curettage and grafted with bone substitute (). The risk of progressive valgus deformity discussed with patient's parents thoroughly before proceeding with surgery and they were justified to be followed and evaluated postoperatively. At 3 months follow-up, the patient was asymptomatic and clinical examination was normal. The patient was able to walk without limping and pain.