Biomechanical comparison of two angular stable plate constructions for periprosthetic femur fracture fixation

Fractures of the femur associated with total hip arthroplasty are a significant concern in orthopaedic and trauma surgery. However, little is known about the different biomechanical properties of internal fixation systems in combination with periprosthetic fractures. In this study two new internal fixation systems for periprosthetic fractures are investigated using a cadaver fracture model simulating a Vancouver B1 periprosthetic femur fracture. Nine pairs of fresh-frozen cadaver femurs were scanned by dual X-ray absorptiometry. Cementless total hip prostheses were implanted and a periprosthetic femur fracture was simulated. Fractures were randomly fixed either with the fixed angle locking attachment plate (LAPA (R), Depuy SynthesA (R), Solothurn, Switzerland) or the variable angle non-contact bridging plate (NCBA (R), Zimmer GmbH, Winterthur, Switzerland). Each construct was cyclically loaded to failure in axial compression. Axial stiffness and cycles to failure were significantly higher in the NCB group. Both systems were able to be fixed well around the femoral stem. The two different internal fixation systems for periprosthetic fractures differed significantly in our setup. The non-contact bridging plate system revealed significantly higher failure load and may be the preferred option where high stability and load capacity is needed right after operation.