Distraction osteogenesis for nonunion after high tibial osteotomy.

The purpose of this study was to determine whether distraction osteogenesis can be used to treat hypertrophic nonunion associated with angular deformity and shortening after Coventry style high tibial osteotomy. Five consecutive patients were retrospectively reviewed. In all patients the alignment had collapsed into excessive varus or valgus and leg length discrepancy was present. The leg length discrepancy, malalignment, and nonunion were treated simultaneously with distraction. Union was achieved by the time of fixator removal, which averaged 4.4 months. The Hospital for Special Surgery knee score significantly improved from 42 to 89. The mechanical axis deviation significantly improved by 5 cm. The coronal plane deformity significantly improved by 13 degrees, and leg length discrepancy improved significantly from 2.3 to 0.5 cm. Metaphyseal bone stock increased by 43%, and the Insall-Salvati ratio increased from 1.1 to 1.2 and remained within normal limits. All patients were satisfied with the procedure, and none have had or need a total knee replacement at an average followup of 4 years. Distraction osteogenesis of nonunion after high tibial osteotomy is a minimally invasive and successful procedure. It leads to bony union with correction of deformity and leg length discrepancy and prevents the need for total knee replacement at intermediate-term followup. The increase in metaphyseal bone stock may make total knee replacement technically easier.