Rigid versus flexible plate fixation for periprosthetic femoral fracture-computer modelling of a clinical case.

A variety of plate designs have been implemented for treatment of periprosthetic femoral fracture (PFF) fixation. Controversy, however, exists with regard to optimum fixation methods using these plates. A clinical case of a PFF fixation (Vancouver type C) was studied where a rigid locking plate fixation was compared with a more flexible non-locking approach. A parametric computational model was developed in order to understand the underlying biomechanics between these two fixations. The model was used to estimate the overall stiffness and fracture movement of the two implemented methods. Further, the differing aspects of plate design and application were incrementally changed in four different models. The clinical case showed that a rigid fixation using a 4.5 mm titanium locking plate with a short bridging length did not promote healing and ultimately failed. In contrast, a flexible fixation using 5.6 mm stainless steel non-locking plate with a larger bridging length promoted healing. The computational results highlighted that changing the bridging length made a more substantial difference to the stiffness and fracture movement than varying other parameters. Further the computational model predicted the failure zone on the locking plate. In summary, rigid fracture fixation in the case of PFF can suppress the fracture movement to a degree that prevents healing and may ultimately fail. The computational approach demonstrated the potential of this technique to compare the stiffness and fracture movement of different fixation constructs in order to determine the optimum fixation method for PFF.