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Finite element analysis of different repair methods of Vancouver B1 periprosthetic fractures after total hip arthroplasty
Injury, 06/21/2012
Chen DW et al. – Better fixation power is achieved by using both proximal and distal screws (the locking–plate concept) in treating Vancouver type B1 periprosthetic fracture after total hip arthroplasty (THA).
Methods- An artificial femur was used as the basis for the solid model; U2 series femoral stem (United Orthopedic Corporation, Hsinchu, Taiwan) was used for modelling of the prosthesis; and the modelling of the cable plate, wires and screws was based on information given in the manufacturer's catalogue (Zimmer, Warsaw, IN, USA).
- The analysis model was constructed using the ANSYS software, and all material settings were based on literature values.
- A six–orifice cable plate, unicortical screws (20mm long and 4.5mm in diameter) and bicortical screws (50mm long and 4.5mm in diameter) were constructed.
- Four analysis models were defined.
- The basic model had a plate and three cable wires above the fracture line and two bicortical screws below the fracture line.
- In the second model, two unicortical screws were added above the fracture line.
- In the third model, three wires were added below the fracture line.
- In the fourth model, both the proximal screws of the second model and the distal wires of the third model were added to the basic model.
- To ensure that the numerical values produced by analysis reached convergence, mesh convergence was tested.
- Adding two proximal unicortical screws to the basic Ogden construct (plate, proximal wires and distal screws) lessened displacement of the fracture and decreased the von Mises stress on the repair.
- Adding three distal wires to the basic construct had no noticeable effect.