Split Depression Tibial Plateau Fractures: A Biomechanical Study


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Abstract

ObjectiveTo determine the biomechanical characteristics of four different fixation constructs for split depression fractures of the lateral tibial plateau (OTA classification 41B3.1).DesignLaboratory investigation using a cadaveric simulated split depression tibial plateau fracture model.SettingSplit depression tibial plateau fractures were created, reduced, and instrumented in a matched pair design. Specimens were tested for stiffness using a materials testing machine.InterventionTibias were instrumented with an L-buttress plate, four 3.5-millimeter subchondral raft screws with an antiglide plate, an L-buttress plate with cancellous allograft, or four 3.5-millimeter subchondral raft screws placed through a periarticular plate.Main Outcome MeasurementsVertical subsidence of the lateral tibial plateau was measured for the entire construct and for the local depression. The relative medial and lateral condylar tilt with central loading was also measured.ResultsThere was no significant difference between the four fixation methods for overall longitudinal stiffness of the proximal tibial fracture fixation construct (range, 2,026 to 2,666 newtons per millimeter). The local depression stiffness for the raft–periarticular plate and raft–antiglide plate were 425 newtons per millimeter and 342 newtons per millimeter, respectively, versus 243 newtons per millimeter and 210 newtons per millimeter for the two large fragment buttress constructs. There was no significant difference between the local depression stiffness for the two raft constructs. There was no significant difference between the local depression stiffness for the two buttress plate constructs. Local depression stiffness was found to be significantly greater for the raft–periarticular plate construct when compared with the large fragment buttress plate construct without bone graft (p = 0.0314). Condylar tilt data showed a significant difference between the medial tilt observed in the prefracture specimen and the lateral tilt observed after fixation (p ≤ 0.017) for all constructs.ConclusionsThere was no significant difference in the overall construct stiffness between the four fixation constructs. Fixation constructs with a raft of subchondral screws were more resistant to local depression loads. This supports the use of a raft construct when a central depression is a significant component of the overall fracture pattern. Condylar tilt data showed a persistent weakness in the postfixation lateral plateau regardless of fixation construct when compared with the intact specimen. This supports the current clinical practice of delayed weight-bearing for ten to twelve weeks.

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