An Integrated Computer-Aided Engineering Approach for Parametric Investigation of Locked Plating Systems Design

Locked plating systems have emerged in recent years as effective devices for treating and stabilizing femoral fractures. Nevertheless, clinical failures due to plate yielding and fracture have been observed — particularly with distal femoral plates. The majority of failures are attributed to improper placement, fixation techniques, or plate selection, and to premature weight-bearing by the patient. While the mechanical function of plating systems is well-understood, the optimum design parameters that lead to efficient stability and fracture healing, such as plate geometry, material properties, and fixation techniques (e.g. screw configuration and the use of hole inserts), are unknown. The present paper presents an integrated computer-aided engineering (CAE) approach combining digital imaging, solid modeling, robust design methodology, and finite element analysis in order to conduct a parametric investigation of the design of locked plating systems. The present study allows for understanding the contributions of different design parameters on the biomechanics and reliability of these systems. Furthermore, the present approach will lead to exploration of optimum design parameters that will result in robust system performance. Three-dimensional surface models of cortical and cancellous femoral bone were derived via digital CT image processing techniques and a medical imaging analysis program. A nine orthogonal array matrix simulation (L₉) was conducted using finite element methods to study the effects of the various design parameters on plate performance. The technique was demonstrated on a case study using a Smith & Nephew PERI-LOC distal femur locking plate where the plate thickness and material, the use of screw hole inserts, and the use of an oblique screw angled distally and medially were the design parameters. After creating a distal fracture with bone loss and stabilizing the femur with the plating system, the impact force due to walking was simulated on each of the nine fracture models. Results showed that increasing the plate’s thickness, using titanium alloy for fabrication, and using screw hole inserts in proximity to the fracture site will maximize the overall factor of safety.