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.

METHODS

Level III, retrospective comparative study.