Locking Buttons Increase Fatigue Life of Locking Plates in a Segmental Bone Defect Model

Abstract

Background Durability of plate fixation is important in delayed union. Although locking plates result in stronger constructs, it is not known if locking affects the fatigue life of a plate. Two locking screws on either side of the nonunion could decrease working length and increase strain in the plate. However, the reinforcing effect of the locking head on the plate may compensate, so that it is unclear whether locking reduces fatigue life.

A Biomechanical Comparison of a Novel Expandable Photodynamic Intramedullary System to a Metal Plate and Screw System in Humerus and Femur Osteotomy Models

“…15 The higher mechanical properties of the 17 mm IS suggests that the IS could have equivalent or increased mechanical performance in the clinical setting.…”

“…There was no significant difference between the any of the IS constructs and the LCP group for either peak or yield displacement (Peak Displacement, 15 (Figure 5A and 5B).…”

“…[5][6][7][8][9][10]14 In both models, previous biomechanical testing of plates and intramedullary rods provided a suitable predicate. 1,4,5,10,[12][13][14][15][16][17][18][19][20] An osteotomy model was chosen for both models because of the biomechanical demand such a defect places on a fixation system. 5 Understanding the biomechanical performance of these two implant systems could be beneficial in directing clinical decisions when the two systems might be considered for the same indication.…”

“…15,22 For static testing, each construct was loaded in custom fixtures that allowed unrestricted bending when subjected to a compressive axial load. All biomechanical testing was completed in a servo-hydraulic materials testing machine (Instron 8521S, Instron, Norwood, MA, USA).…”

“…65%, 75%, and ultimately 85% (698 N, 798 N, 900 N) of yield load was applied to simulate three patients of varying weight (70 kg, 81 kg, and 92 kg) standing on one leg with an implant. 15 The dynamic testing was performed on the femur IS constructs and compared to previously tested and published specimens from Tompkins et al 15 …”