Unicameral Bone Cysts: Treatment Rationale and Approach:

Unicameral bone cyst (UBC) is a benign cystic lesion, most commonly diagnosed in the proximal aspects of the humerus and femur of growing children. Medullary venous obstruction is the leading pathogenesis theory, resulting in fluid accumulation, bone resorption, and cortical thinning. Most UBCs are asymptomatic and likely go undiagnosed, while the most common presentation is a pathologic fracture, either complete or insufficiency/stress. Younger children tend to present with active lesions, which are uniloculated, abut the physis, and have a higher recurrence or persistence rate after treatment. Lesions in older children tend to migrate away from the growth plate (latent), and might become multiloculated, especially if they recur after treatment. Radiographs are often diagnostic and reveal a centrally-located, lucent metaphyseal lesion with cortical thinning, although advanced imaging is also helpful is some cases. Most UBCs do not need treatment and are amenable to observation alone. Management ranges from aspiration and steroid injection to decompression, curettage, grafting, and internal fixation. Percutaneous or open surgical approaches are acceptable, and often yield good results, although high recurrence rates should be expected, especially in younger children with active lesions.