Knee arthrodesis with lengthening: experience of using Ilizarov techniques to salvage large asymmetric defects following infected peri-articular fractures.

AIM: We present four patients with large bone defects due to infected internal fixation of knee condylar fractures. All were treated by debridement of bone and soft tissue and stabilisation with flap closure if required, followed by bone transport arthrodesis of the knee with simultaneous lengthening.

METHODS: Four patients (three male and one female), mean age 46.5 years (37-57 years), with posttraumatic osteomyelitis at the knee (three proximal tibia and one distal femur) were treated by debridement of infected tissue and removal of internal fixation. Substantial condylar bone defects resulted on the affected side of the knee joint (6-10 cm) with loss of the extensor mechanism in all tibial cases. Two patients required muscle flaps after debridement. All patients received intravenous antibiotics for at least 6 weeks. Bone transport with a circular frame was used to achieve an arthrodesis whilst simultaneously restoring a functional limb length. In three cases a 'peg in socket' docking technique was fashioned to assist stability and subsequent consolidation of the arthrodesis.

RESULTS: Arthrodesis of the knee, free of recurrent infection, was successfully achieved in all cases. None has since required further surgery. Debridement to union took an average of 25 months (19-31 months). The median number of interventions undertaken was 9 (8-12). Two patients developed deep vein thrombosis (DVT), one complicated by PE, which delayed treatment. Two required surgical correction of pre-existent equinus contracture using frames. The median limb length discrepancy (LLD) at the end of treatment was 3 cm (3-4 cm). None has required subsequent amputation.

CONCLUSION: Bone loss and infection both reduce the success rate of any arthrodesis. However, by optimising the host environment with eradication of infection by radical debridement, soft-tissue flaps when necessary and bone transport techniques to close the defect, one can achieve arthrodesis and salvage a useful limb. The residual LLD can result from not accounting for later impaction at peg and socket sites, which had the effect of increasing LLD beyond the desirable amount. We therefore recommend continuing the lengthening for an additional 1-2 cm to allow for this.