Open distal femur fractures treated with lateral locked implants: union, secondary bone grafting, and predictive parameters.

Nonunion and secondary reduction loss complicate open distal femur fractures with bone loss. The authors hypothesized that locking plates decrease subsequent bone grafting yet maintain alignment and immediate postfixation radiographic features predict primary union. A retrospective chart/radiographic review was performed at a Level 1 university trauma center. Thirty-four adults with 36 open AO/Orthopaedic Trauma Association (AO/OTA) C-type distal femur fractures were studied. All fractures were treated with open reduction, internal fixation with a lateral locked implant with or without antibiotic beads, and subsequent bone grafting. Union required radiographic bridging callus on at least 2 of 4 cortices. Alignment was assessed on initial and united radiographs. Antibiotic beads within a metaphyseal defect defined clinically important bone loss. Eleven (55%) of 20 fractures with bone loss underwent staged bone grafting to achieve union vs 2 (13%) of 16 fractures without bone loss. Antibiotic bead presence was associated with staged bone grafting (P<.01). Of those with bone loss and grafting, 3 had posterior cortical bone loss only, 3 had medial and posterior cortical bone loss, and 5 had segmental defects. Of 9 fractures with bone loss not requiring grafting, all had radiographic posterior cortical contact and 7 had radiographic medial cortical contact. Posterior cortical continuity was associated with injuries not requiring bone graft (P<.001). Thirty-four had accurate frontal plane reductions and 35 had accurate sagittal plane reductions. 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 are strongly correlated with primary union.