Association between preoperative concurrent fibular pseudarthrosis and risk of postoperative ankle valgus in patients with congenital pseudarthrosis of the tibia

BACKGROUND: This study evaluated the correlation of preoperative concurrent fibular pseudarthrosis with the risk of ankle valgus deformity in patients with congenital pseudarthrosis of the tibia (CPT) who underwent successful surgical treatment. METHOD: The children with CPT who were treated at our institution between 1 January 2013 and 31 December 2020 were retrospectively reviewed. The independent variable was preoperative concurrent fibular pseudarthrosis, and the dependent variable was postoperative ankle valgus. Multivariable logistic regression analysis was performed after adjusting for variables that might affect the risk of ankle valgus. Subgroup analyses with stratified multivariable logistic regression models were used to assess this association. RESULTS: Of the 319 children who underwent successful surgical treatment, 140 (43.89%) developed ankle valgus deformity. Moreover, 104 (50.24%) of 207 patients with preoperative concurrent fibular pseudarthrosis developed an ankle valgus deformity compared with 36 (32.14%) of 112 patients without preoperative concurrent fibular pseudarthrosis (p=0.002). After adjusting for sex, body mass index, fracture age, age of patient undergoing surgery, surgery method, type 1 neurofibromatosis (NF-1), limb-length discrepancy (LLD), CPT location and fibular cystic change, patients with concurrent fibular pseudarthrosis presented a higher risk of ankle valgus than those without concurrent fibular pseudarthrosis (OR 2.326, 95% CI 1.345 to 4.022). This risk further increased with CPT location at the distal one-third of the tibia (OR 2.195, 95% CI 1.154 to 4.175), age <3 years of patient undergoing surgery (OR 2.485, 95% CI 1.188 to 5.200), LLD <2 cm (OR 2.478, 95% CI 1.225 to 5.015) and occurrence of NF-1 disorder (OR 2.836, 95% CI 1.517 to 5.303). CONCLUSION: Our results indicate that patients with CPT and preoperative concurrent fibular pseudarthrosis have a significantly increased risk of ankle valgus compared with those without preoperative concurrent fibular pseudarthrosis, particularly in those with CPT location at the distal third, age <3 years at surgery, LLD <2 cm and NF-1 disorder.