Unicameral bone cyst in the pelvis: report of a case treated by placement of screws made from a composite of unsintered hydroxyapatite particles and poly-l-lactide

Abstract

Unicameral bone cysts are fluid-filled benign lesions that occur mostly in the long bones. Unicameral bone cysts in the pelvis are extremely rare. Continuous decompression using titanium or hydroxyapatite screws has been reported as a treatment. Screws made from a composite of unsintered hydroxyapatite particles and poly-l-lactide can be used for the treatment. An adolescent male patient presented with a unicameral bone cyst in the ilium extending to a region adjacent to the hip joint. As initial treatment, the cortex was fenestrated when the patient was 13\u2009years old and β-tricalcium phosphate implanted. The cyst first reoccurred when the patient was 15\u2009years old and again when he was 17\u2009years old. During the most recent treatment, unsintered hydroxyapatite particles and poly-l-lactide composite screws were placed, and no recurrence was observed during 2\u2009years of follow-up. The slow biodegradability and absorbability of the screws may allow continuous drainage of unicameral bone cysts.