abstractFull article available online at OrthoSuperSite.com/view.asp?rID=36002Traditional treatments for simple bone cysts are associated with signifi cant surgical morbidity and high recurrence rates. The purpose of this study was to evaluate the effectiveness of a percutaneous approach to the treatment of proximal humeral simple bone cysts that includes percutaneous decompression, curettage, and injection of allogeneic cancellous bone combined with autologous bone marrow.Twenty-one children (average age, 10.1±4.6 years) with symptomatic simple bone cysts of the proximal humerus were surgically treated with percutaneous cyst decompression, curettage, and cancellous allograft combined with autologous bone marrow. Patients were observed in-clinic with serial examinations and radiographs. Fracture healing and cyst recurrence were determined at follow-up.All patients returned to activities of daily living with full range of motion and were completely asymptomatic. All fractures healed. There were no surgical complications or refractures. Five patients demonstrated radiographic evidence of partial cyst recurrence and required additional surgical treatment. One patient required a third operative procedure for a second recurrence. Three of 8 active cysts demonstrated partial recurrence. Recurrence was associated with younger age.Our goal in the treatment of proximal humeral simple bone cysts is to prevent cyst recurrence and pathologic refracture. Radiographic evidence of cyst resolution occurred in 75% of our patients using percutaneous curettage and bone grafting, and in 95% of patients with a second procedure. As expected, partial recurrence of active cysts after treatment with this method is high. This percutaneous technique is a safe and effective treatment for humeral simple bone cysts.