The association between fibular status and frontal plane tibial alignment post-union in congenital pseudarthrosis of the tibia

PURPOSE: Controversy exists regarding fibular status related to tibial alignment after congenital pseudarthrosis of the tibia (CPT) achieves union. We aimed to determine whether fibular status affected frontal plane tibial alignment post-CPT union. METHODS: Between January 2010 and December 2013, we followed 36 patients treated using a combined surgical technique (mean 6.6 years (2.2 to 9.4)). Outcome measures comprised medial proximal tibial angle, tibial diaphyseal angulation, lateral distal tibial angle (LDTA), relative intramedullary rod length and relative fibula length discrepancy. RESULTS: The frequency of proximal tibial valgus deformity and ankle valgus deformity were significantly lower in the fibular integrity group than in the fibular un-integrity group (proximal tibial valgus deformity: 2/17 versus 11/19; p = 0.006; ankle valgus deformity: 10/17 versus 18/19; p = 0.016). The mean LDTA was notably higher in the fibular integrity group than in the fibular un-integrity group (81.2° (sd 6.7°) versus 71.3° (sd 6.6°); p < 0.001). A statistically significant difference was observed in relative fibula length discrepancy between patients with fibular integrity (0.06 (0 to 0.11); Malhotra grade 0, n = 6; Malhotra grade I, n = 11) and those without (0.24 (0.01 to 0.36); Malhotra grade 2, n = 2; Malhotra grade 3, n = 17; p < 0.001). Ankle valgus deformity had a significant positive correlation with proximal tibial valgus deformity (r = 0.402; p = 0.015). Patients with an intact and normal length fibula had a lower frequency of ankle valgus deformity than those with an intact but shortening fibula (1/6 versus 9/11; p = 0.035). CONCLUSION: Shortening or pseudarthrosis of the fibula was associated with ankle valgus and proximal tibial valgus deformities post-CPT union. LEVEL OF EVIDENCE: III