Photoelastic evaluation of pathological axis deviation of the femur in the frontal plane

Sarah Fakher Fakhouri,Antônio Carlos Shimano,Marcos Massao Shimano,Daniel Maranho,Cleudmar Amaral Araujo,José Batista Volpon

doi:10.1177/1687814015572432

Abstract

The objective of this study is to evaluate the repercussions of the pathological deviation of the coxa brevis, femur, and tibia without the pathological deviation of the axis in the femoral or tibial frontal plane. The stress distribution in the proximal and distal joints was evaluated in relation to the deviations using transmission photoelasticity. Two-dimensional femur and tibia models were developed from frontal panoramic radiographs, which were later used to fabricate molds and photoelastic models. A force of 8 N was applied to the top of the femoral head. For the deviation of the coxa brevis and for the femur and tibia without pathological deviation, the stresses were more critical in the calcar region of the proximal femur. In the distal femur and proximal and distal tibia, the stress distributions were in accordance with the models, the proposed fixation conditions, and the long bone geometries. The most important conclusion of this investigation was that joint deviation also alters the stress on all primary joints of the lower extremities. From this study, it will be possible to develop better correction criteria for angular deviations and discharges of bone and joint forces of the lower extremities and to provide refinements to prostheses.

Highlights

The mechanical axis represents the functional discharge of forces from the hip to the ankle, as represented by a straight line that begins in the center of the femoral head and extends to the center of the tibiotalar joint.[1,2,3] In normal conditions, this line should cross the knee up to 9.0 mm medially to the tibial bones.[4,5] The mechanical axis depends on the geometrical alignment between the tibia and the femur, which in turn depends on the anatomy of the bones
A qualitative analysis was performed for the photoelastic models corresponding to the proximal femur (PF), distal femur (DF), proximal tibia (PT), and distal tibia (DT) groups for deviations of the coxa brevis, femur, and tibia without pathological deviations of the axes
For deviations of the coxa brevis and the tibia and femur without pathological deviation of the axes, the locations of the beginning of the fringe orders were in the medial third regions of the femoral heads

Summary

Introduction

The mechanical axis represents the functional discharge of forces from the hip to the ankle, as represented by a straight line that begins in the center of the femoral head and extends to the center of the tibiotalar joint.[1,2,3] In normal conditions, this line should cross the knee up to 9.0 mm medially to the tibial bones.[4,5] The mechanical axis depends on the geometrical alignment between the tibia and the femur, which in turn depends on the anatomy of the bones. For the femur, the mechanical axis is tilted 7 6 2° relative to the anatomical axis, both axes coincide on the tibia.[6].

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Conclusion