Results through skeletal maturity of planned fibular nonunion for the treatment of genu varum in achondroplasia: An observational retrospective study

Current surgical options for treating genu varum in achondroplasia include tibial and fibular osteotomy and growth modulation using plates and screws. However, a single surgeon consistently treated genu varum using a planned fibular nonunion (PFN). The purpose of this study is to describe his surgical technique and report radiographic and clinical outcomes for the cohort studied. This is an observational retrospective review. The cohort studied included patients with achondroplasia who had PFN surgery for the treatment of genu varum at a young age (<13 years) and was followed through to skeletal maturity. The surgery included meticulous closure of the periosteum over the remaining fibula. The surgery was considered a success if the patient did not require subsequent surgery and had acceptable or improved clinical alignment. Radiographic measures used to determine change in genu varum included the anatomic tibio-femoral angle (aTFA), tibia varus, and tibia-fibula ratio. Clinically, changes in lower limb alignment were defined using a plumb line and 6 categories of alignment ranging from extreme varus to valgus. Statistics were used to validate the plumb line categorization to available radiographic measures. Other appropriate statistical methods were used with P < .05 considered significant. Of the 53 PFN cases (27 patients) included in the study, 34 (64%) did not require subsequent surgery and had acceptable or improved alignment. The average age at surgery and follow-up was 6.1 and 17.0 years, respectively. For the 37 limbs (19 patients) with available radiographs, pre- and post-surgery radiographic measures significantly improved including aTFA (3° varus to 2° valgus, P = .003), tibia varus (2° varus to 3° valgus, P = .004), and the tibia-fibula ratio (0.977 to 1.013, P < .001). Clinically, 32 cases (60%) demonstrated significant improvement by translating into an improved alignment and 9 (17%) remained the same (P < .01). Complications were minimal and insignificant. Failures were readily managed by tibia-fibular osteotomies in adolescence and at maturity. PFN for the treatment of genu varum in young achondroplasia patients significantly improved radiographic and clinical measures of lower limb alignment through skeletal maturity with relatively few complications.