• Paul J Dougherty, Do-Gyoon Kim, Steve Meisterling, Christopher Wybo, and Yener Yeni.
• Department of Orthopaedic Surgery, Henry Ford Hospital, Detroit, Michigan 48202, USA. pauldoug@med.umich.edu
• J Orthop Trauma. 2008 Jul 1; 22 (6): 399-403.

ObjectiveThe purpose of this study was to compare the biomechanical properties of bicortical with unicortical screws in a proximal tibial fracture cadaveric model.SettingBiomechanics laboratory at a Level 1 trauma center.Patients/ParticipantsEight pairs (4 male and 4 female) of elderly (average age, 79 years; range, 63 to 104 years) cadaveric tibiae.InterventionOsteotomies were performed in the proximal tibia to reproduce a 41-C2 bicondylar fracture pattern. The 4.5-mm proximal tibial periarticular locking plates (Smith-Nephew, Memphis, TN) were applied to the tibiae with 4 proximal bicortical or unicortical locking screws and 3 screws distal to the fracture site. The fixed tibiae were tested by using a materials testing machine (Instron, Canton, MA) with the axial load on the medial condyle.Outcome MeasurementsThe bicortical and unicortical constructs were compared for stiffness, yield load and displacement, and maximum load and displacement to failure.Results: Bicortical screw placement significantly outperformed unicortical screw placement in stiffness (53.1 +/- 6.7 N/mm versus 35.6 +/- 7.2 N/mm, P < 0.002) and maximum load (476.5 +/- 83.8 N versus 258.9 +/- 62.1 N, P < 0.001) but the yield properties and the ultimate displacement were not significantly different.ConclusionBicortical screw placement may provide a biomechanically superior construct than unicortical screw placement for the stabilization of unstable proximal tibia fractures.

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