Biomechanical Comparison of Polyaxial-Type Locking Plates and a Fixed-Angle Locking Plate for Internal Fixation of Distal Femur Fractures

Abstract

There were no failures of either polyaxial screw-plate interface despite large forces and screw angle did not affect the overall strength of these constructs, supporting the biomechanical soundness of both polyaxial device designs under axial loading. However, the POLYAX supported smaller loads compared with the LISS and NCB while under axial loading. In addition, the mode of failure of the NCB plate, creating an intra-articular fracture propagating from the distal posterior screw hole, may be of some concern. Additional testing is needed to determine the clinical importance of the demonstrated differences among these plate designs.

Implant Material and Design Alter Construct Stiffness in Distal Femur Locking Plate Fixation: A Pilot Study

“…Torsional stiffness again was largest for the steel plate with the AxSOS design. Although Otto et al [16] used a different test setup, under axial loading, they similarly showed LISS (LCP) had 25% greater stiffness than POLYAX. Torsional construct stiffness differed between the implant systems showing 19% to 31% higher values of the constructs with steel implant systems (AxSOS and PERI-LOC) versus constructs with titanium implants.…”

“…However, none of our BICs reached 100,000 cycles and/or forces of 1870 N, which is considered as a loading regimen simulating physiologic forces over a 2-month period [5]. Our fracture model represents an extraarticular fracture, which is classified as a type of distal femur fracture [15] associated with substantial complication rates [16]. This model is used in multiple biomechanical studies [5,11,14,21,25].…”

“…Torsional construct stiffness differed between the implant systems showing 19% to 31% higher values of the constructs with steel implant systems (AxSOS and PERI-LOC) versus constructs with titanium implants. Except the study of Otto et al [16], no further comparisons of the implant systems that we tested were are available in the literature.…”

“…Henderson et al [10] suggested stainless steel locking plates are associated with a higher percentage of nonunions than titanium plates (57% versus 43%, respectively). Many investigators have explored comparisons of distal femur locked plating systems with intramedullary nail systems [19,20,25], angled blade plates [11,24,25], dynamic condylar screws [11], and locked plating constructs with different screw configurations in the condylar fragment of the fracture model [8,16]. However, reported stiffness values for the same implant vary up to more than one order of magnitude, perhaps as a result of differing configurations of the boneimplant constructs (BICs) or test equipment.…”

Mono- versus polyaxial locking plates in distal femur fractures: a prospective randomized multicentre clinical trial

“…Up to now, only utilization and biomechanical observations have been published [10,11], showing low-risk implantation as compared to similar procedures. Unfortunately, studies comparing the available angular stable plating systems are missing [12].…”