• William W Cross, Bruce A Levy, Joseph A Morgan, Bryan M Armitage, and Peter A Cole.
• Department of Orthopaedic Surgery, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, United States.
• Injury. 2013 Jun 1;44(6):796-801.

ObjectivesTo 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.MethodsCadaver 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 400N to 1600N in increasing 400N increments. The force required to elicit lateral plateau fragment displacement of 5mm, 10mm, and 15mm was also recorded.ResultsNone of the mechanical testing results demonstrated statistical significance with p-values of <0.05. Cyclic testing of Groups 1, 2, and 3 at 400N revealed displacements of 0.54mm, 0.64mm, and 0.48mm, respectively. At 800N, displacements were 1.36mm, 1.4mm, and 1.4mm, respectively. At 1200N, displacements were 2.4mm, 1.9mm, and 2.1mm, respectively. At 1600N, displacements were 2.8mm, 2.5mm, and 2mm, respectively. Resistance to displacement data demonstrated the mean force required to displace the fracture 5mm in Groups 1, 2, and 3 were 250N, 330N, and 318N, respectively. For 10mm of displacement, forces required were 394N, 515N, and 556N, respectively. For 15mm of displacement, forces required were 681N, 853N, and 963N, respectively. Compared to combined groups using screws through the plate, Group 1 demonstrated lower displacement ≤800N, but demonstrated greater displacement >800N. Group 2 demonstrated greatest resistance to plateau displacement of 5mm 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.ConclusionsDesigns 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.Copyright © 2013 Elsevier Ltd. All rights reserved.

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