Purpose: Non-union and secondary reduction loss complicate open distal femur fractures with bone loss. We hypothesize that locking plates decrease subsequent bone grafting in these injuries, yet maintain alignment; immediate post-fixation radiographic features predict primary union.

Method: From 2001 to 2004 inclusive, 34 adults with 36 open AO/OTA C-type distal femur fractures were reviewed. All were treated with locking plates and 3-month minimum follow-up. Union required radiographic bridging callus on 2/4 cortices combined with lack of symptoms. Alignment was assessed on initial and united radiographs. Antibiotic beads within a metaphyseal defect defined clinically important bone loss.

Results: Eleven of 20 fractures with bone loss (55%) underwent staged bone grafting to achieve union, versus two of 16 fractures without bone loss (13%). The presence of antibiotic beads was significantly associated with staged bone grafting (p< 0.01). Of those with bone loss and staged grafting, three had posterior cortical bone loss, and only three had medial and posterior cortical bone loss, and five had segmental defects. Of nine fractures with bone loss not requiring grafting, all had radiographic posterior cortical contact; seven had radiographic medial cortical contact. Posterior (p< 0.001) and medial (p< 0.025) cortical continuity were associated with injuries not requiring bone graft. Thirty-four had accurate frontal plane reductions; thirty-five had accurate sagittal plane reductions. Complications included two non-unions, and one reduction loss.

Conclusion: Despite metaphyseal bone loss, locking plates obviate the need for routine bone grafting of some open distal femur fractures. Those with radiographic posterior cortical contact and/or medial cortical contact are strongly correlated with primary union.