Anterolateral congenital tibial bowing: case report

Abstract Congenital pseudarthrosis of the tibia (CPT) is likely to be a primary periosteal disease and secondary bone disease. The primary goal of treatment is to obtain union, correct the diaphyseal deformity, correct any proximal fibular migration and prevent refracture. The pathobiology demonstrates increased osteoclasis by the surrounding fibrous hamartoma and reduced osteogenesis and bone morphogenic protein production by the bone. This leads to a loss of remodelling potential and gradual bowing and atrophy of the bone with eventual fracture of the tibia and or fibula. This recommends the synergistic use of bisphosphonates and bone morphogenic protein. The pathomechanics of CPT implicate the anterolateral bowing, narrow diameter of the atrophic bone ends and proximal fibular migration. These biomechanical factors can be addressed by means of straightening of the deformity, intramedullary support of both bones, stable fixation and reduction of proximal migration of the fibula. A summary of the literature on CPT shows that the mean probability of achieving primary union without refracture, by most treatments is 50% (12% to 80%). Two recent studies have shown a much higher success rate approaching 100%, by creating a cross-union between the tibia and fibula. The cross-union with intramedullary reinforcement of the bone makes refracture unlikely due to the cross-sectional area of union with its two-bar linkage. A new classification to guide such treatment is also proposed. Level of Evidence V – expert opinion

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.