Overlapping Versus “Kissing” Plates in Femur: A FEM Study

The progressively aging population makes higher the probability of operate fractures in patients who have underwent past long bones fixation. Surgeons may consider not to remove the past implant because of poor bone quality and low life expectancy, but attention must be paid to avoid the origin of new dangerous stresses. There is still a lack of evidence in determining which is the best relation between a plate already implanted in the past and a new fixation device.

The purpose of this study was to investigate how the bone-implant stress distribution changes with two different plate configurations: overlapped (the tip of new plate covering part of the old one) versus “kissing” (the tips of the plates in close contact).

This study was based on a finite element analysis by means of Rhinoceros^® and Ansys Work bench software programs. In order to reduce confusing factors, the femur was considered to be not fractured.

Different features have been tested: bone quality, plate materials, and plate configurations. The study was conducted by evaluating stress values in different femur sections. The same parameters were evaluated in a femur without plates. Three phases of gait were simulated: Heel-strike, midstance, and toe-off.

Heel-strike phase has shown to reach the highest stresses. In general, stresses are lower in the overlapping plates configuration when compared to the “kissing” plates one.

The main evidence shown in this study is that, in silico, the overlapped configuration can decrease the stress under the plates intersection, without increasing the stress shielding.