Abstract
Introduction: 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. Objective: 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. Materials & Methods: 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. Results: 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. Conlusion: 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.
Highlights
The progressively aging population makes higher the probability of operate fractures in patients who have underwent past long bones fixation
Conlusion: 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
The evidence that comes from this study is that stresses in the long bones diaphysis in the middle section were higher in the “kissing” plates configuration and that they could be reduced if the new plate is put for a short portion over the old one
Summary
The progressively aging population makes higher the probability of operate fractures in patients who have underwent past long bones fixation. 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 knowledge of the mechanical characteristics of bone tissue and of the whole bone elements, regarding its behavior under load, is without doubt fundamental for studying it in various physiological and pathological conditions, looking for substitution materials, and for investigating possibilities of coupling with other materials and devices. The structural analysis of skeletal body elements and of the biomechanical systems consisting of a bone element coupled with a prosthesis, an implant or a fracture synthesis device can be performed both numerically and experimentally. Every approach has its own limitations: numerical models can be very complex. We decided to use a finite element numerical model to clarify a couple of intervention methodologies related to a particular case of femoral bone fracture
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