Isolated congenital pseudoarthrosis of the fibula: A comparison of fibular osteosynthesis with distal tibiofibular synostosis

BACKGROUND: Isolated congenital pseudoarthrosis of the fibula is associated with progressive ankle valgus and rare subsequent tibial involvement. Two operative techniques were compared: (1) osteosynthesis with intercalary grafting and (2) distal tibiofibular synostosis. Hemiepiphysiodesis or osteotomy supplemented the primary procedure when necessary. METHODS: A retrospective review of isolated congenital pseudoarthrosis of the fibula-Dooley types 2 (without ankle valgus) and 3 (with ankle valgus); cases with tibial involvement (Dooley types 1 and 4) were excluded. Nine patients were identified (mean age, 7.6 years, follow-up, 6.6 years). One is under observation without bracing (type 2). Five patients (one type 2 and four type 3) were treated with osteosynthesis. Three were treated with distal tibiofibular synostosis (one type 2 and two type 3). One patient in each group also underwent concomitant medial distal tibia hemiepiphysiodesis; 1 patient in the synostosis group underwent distal tibia varus osteotomy with the primary procedure. RESULTS: In the osteosynthesis group (5 patients), mean lateral distal tibial angle (LDTA) improved from 75.6 to 86.6 degrees. Union was achieved in 4; 1 had early graft resorption requiring revision. Four of the 5 had neutral ankle alignment at the final follow-up. Among the 3 patients with primary union and no deformity correction, mean LDTA improved from 81 to 88 degrees over 9.8 years of follow-up. One patient had mild residual valgus (LDTA, 79 degrees) after temporary screw hemiepiphysiodesis. Complications were as follows: nonunion (n = 1), compartment syndrome with mild residual plantar flexion weakness (n = 1), and fibular stress fracture, which healed with immobilization (n = 1).In the synostosis group (3 patients), the mean LDTA improved from 64.3 to 80.0 degrees. One achieved union with distal tibia medial hemiepiphysiodesis (final LDTA, 86 degrees). Two had failure: one synostosis nonunion underwent repeat varus osteotomy (final LDTA, 81 degrees), and the other (Dooley type 2) had crossunion; however, persistent fibular pseudoarthrosis proximal and distal to the synostosis, progressive valgus developed (final LDTA, 73 degrees). CONCLUSIONS: Osteosynthesis with intercalary grafting achieved primary union in 4 of 5 patients; mild residual ankle valgus was present in 1 patient at final follow-up. Synostosis failure with residual ankle valgus at maturity occurred in 2 of 3 patients. Progression to tibial pseudoarthrosis was not observed in either group. In this series, osteosynthesis eliminated fibular discontinuity, allowing correction of ankle valgus. LEVEL OF EVIDENCE: Level III, retrospective comparative study.