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Background: Angular stable plate fixation is a widely accepted treatment option for interprosthetic or periprosthetic femoral fractures with stable implants. This biomechanical study tries to establish a safe distance of the plate from the tip of a femoral prosthesis., Methods: A total of 38 composite femurs were reamed to an inner diameter of 23 mm to create an osteoporotic bone model. A Weber hip stem was cemented into each and a distal femoral NCB plate applied with the distance to the stem varying from 8 cm apart to 6 cm overlap in 2-cm steps. Each specimen was tested in cyclic axial loading (400 N-1500 N) and then cyclic torsion (0.6 Nm-50 Nm). Peak strain on the femur around the tip of the plate was measured with a 3D image correlation system and averaged over 26 cycles (excluding the first 3 and the last cycles). Finally, each femur was axially loaded to failure., Results: Strain increased with decreasing overlap or gap. Seven specimens failed early between 2-cm overlap and 2-cm gap. Results were divided into a far group with a distance of >4 cm and a close group of <4 cm. Strain was significantly higher in the close group for axial (P < .001) and torsional (P < .001) loading. Failure load was significantly lower in the close group (P = .002)., Conclusion: A minimal gap and/or overlap of at least 6 cm is recommended in osteoporotic bone to avoid stress risers., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The aim of this study was to biomechanically evaluate the Locking attachment plate (LAP) construct in comparison to a Cable plate construct, for the fixation of periprosthetic femoral fractures after cemented total hip arthroplasty. Each construct incorporated a locking compression plate with bi-cortical locking screws for distal fixation. In the Cable construct, 2 cables and 2 uni-cortical locking screws were used for proximal fixation. In the LAP construct, the cables were replaced by a LAP with 4 bi-cortical locking screws. The LAP construct was significantly stiffer than the cable construct under axial load with a bone gap (P=0.01). The LAP construct offers better axial stiffness compared to the cable construct in the fixation of comminuted Vancouver B1 proximal femoral fractures., (Crown Copyright © 2015. Published by Elsevier Inc. All rights reserved.)

Periprosthetic femoral fractures (PFF) are a serious complication after total hip arthroplasty. Plate fixation with screws perforating the cement mantle is a common treatment option. The study objective was to investigate hip stem stability and cement mantle integrity under dynamic loading. A cemented hip stem was implanted in 17 composite femur models. Nine bone models were osteotomised just distal to the stem and fixed with a polyaxial locking plate the other eight constructs served as the control group. All specimens were tested in a bi-axial material testing machine (100000 cycles). There were no statistically significant differences in axial nor in medial (varus) stem migration. No cement cracks were detected in both groups. Plate fixation of a PFF with a stable, cemented prosthesis did not lead to cement mantle failure in this in vitro study., (Copyright © 2014 Elsevier Inc. All rights reserved.)