Angular Improvement with Bracing Over 7 Years in Anterolateral Tibial Bowing without Neurofibromatosis Type 1: A Case Report.

INTRODUCTION: Congenital anterolateral bowing of the tibia is a rare dysplasia of the tibia that is strongly associated with neurofibromatosis type 1 (Nf1). It produces two deformities, angulation and limb shortening, which are usually reported together and corrected surgically. We report a child without NF1, managed non-operatively, in whom these two courses diverged: The angular deformity improved while the shortening did not. To the best of our knowledge, this dissociation has not previously been documented over more than7 years of continuous non-operative management in a prenatally detected case without a genetic association. CASE REPORT: An 8-year-old Hispanic boy had right-sided anterolateral bowing of the tibia detected on obstetric ultrasound at 27 weeks of gestation. Genetic testing showed only variants of uncertain significance, and no systemic condition, cutaneous stigma, or family history of NF1 was found. Serial radiographs demonstrated mid-diaphyseal bowing of the tibia with a patent medullary canal and no fracture or pseudarthrosis over more than 7 years, corresponding to Paley type 1. Magnetic resonance imaging showed normal ossification without pathological periosteum. He was managed with a right total contact orthosis and a graduated shoe lift. Tibial angulation improved radiographically and in the appearance of the limb, without a bone defect. Limb length discrepancy was unaffected by bracing, measuring 4.4 cm at latest follow-up, and corrective surgery is now warranted. CONCLUSION: Angular deformity in anterolateral bowing of the tibia can be managed conservatively. Limb length inequality can follow an independent course, because the shortening arises from growth inhibition in the affected segment rather than from the angulation. An intact and straightening tibia should therefore not be read as protection against shortening. Limb length warrants projection to skeletal maturity and a separate operative plan from the first consultation, a lesson that applies to every clinician who follows a bowed tibia to maturity.