Periarticular raft constructs and fracture stability in split-depression tibial plateau fractures

Objectives: To evaluate relative fracture stability yielded by screws placed above a lateral plate, as well as locking and non-locking screws placed through a plate in a split depression tibia plateau fracture model. Methods: Cadaver tibia specimens (mean age 74.1 years) were randomised across 3 groups: Groups 1: raft-construct outside the plate, 2: non-locking raft screws through the plate, and 3: locking raft screws through the plate. Displacement of the depressed fragment was recorded with force values from 400 N to 1600 N in increasing 400 N increments. The force required to elicit lateral plateau fragment displacement of 5 mm, 10 mm, and 15 mm was also recorded. Results: None of the mechanical testing results demonstrated statistical significance with p-values of <0.05. Cyclic testing of Groups 1, 2, and 3 at 400 N revealed displacements of 0.54 mm, 0.64 mm, and 0.48 mm, respectively. At 800 N, displacements were 1.36 mm, 1.4 mm, and 1.4 mm, respectively. At 1200 N, displacements were 2.4 mm, 1.9 mm, and 2.1 mm, respectively. At 1600 N, displacements were 2.8 mm, 2.5 mm, and 2 mm, respectively. Resistance to displacement data demonstrated the mean force required to displace the fracture 5 mm in Groups 1, 2, and 3 were 250 N, 330 N, and 318 N, respectively. For 10 mm of displacement, forces required were 394 N, 515 N, and 556 N, respectively. For 15 mm of displacement, forces required were 681 N, 853 N, and 963 N, respectively. Compared to combined groups using screws through the plate, Group 1 demonstrated lower displacement ≤800 N, but demonstrated greater displacement >800 N. Group 2 demonstrated greatest resistance to plateau displacement of 5 mm compared to Group 1 or 3, while Group 3 was most resistant to greater displacement. The combined group using screws through the plate (Groups 2 + 3) was consistently more resistant than Group 1 at all levels of displacement. Conclusions: Designs utilising screws through the plate trended towards statistically significant improved stability against plateau displacement relative to utilising screws outside the plate. Our study also suggests that there is no significant benefit of locking screws over non-locking screws in this unicondylar tibia plateau fracture model.