Of the six types of congenital pseudarthrosis, Type II is the most common and lends to poorest prognosis. The basic pathology is an aggressive osteolytic fibromatosis. Failures in these patients are due to recurrence of the osteolytic fibromatosis, which can remove living bone or a dead bone graft. Type III cases have a better prognosis. The gross pathology is a bone cyst, and the microscopic findings resemble fibrous dysplasia. After surgical treatment, generally, the older the child the better the prognosis. Recurrences are rare after skeletal maturity.