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A biomechanical assessment of plate fixation, with insufficient bony support
Author(s) -
Beaupré Gary S.,
Carter Dennis R.,
Dueland Rudolph T.,
Caler William E.,
Spengler Dan M.
Publication year - 1988
Publication title -
journal of orthopaedic research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.1100060515
Subject(s) - materials science , tension (geology) , compression (physics) , bending , dynamic compression plate , bending of plates , femur , diaphysis , internal fixation , composite material , anatomy , structural engineering , engineering , surgery , medicine
The use of an internal fixation plate in the presence of a bone defect was studied using a theoretical model of an idealized long bone having a circular cross section and loaded using a combination of axial and bending loads. The analysis showed that the “bending‐open” loading mode does not occur if, in the normal unplated bone, the line of action of the resultant axial load passes within the outer cortex at the location where the plate is to be applied. In this situation the fracture will deform in a “bending‐closed” mode regardless of whether the plate is attached to the tension or the compression side. If bony contact cannot be achieved, lower plate stress is always encountered when the plate is attached to the compression side instead of the tension side. In vivo verification of the model was addressed in a pilot experiment using instrumented metal plates applied bilaterally to the femora of one dog. Bilateral bone defects were created in the midfemoral canine diaphysis. On one leg the plate was applied to the lateral aspect (“tension” side), and on the other leg the plate was applied to the medial aspect (“compression” side). The plate attached to the lateral aspect deformed plastically in the bending‐closed mode. The contralateral plate that was attached to the medial aspect (compression side) of the femur did not show signs of plastic deformation. Furthermore, the plate strains were lower in the plate attached to the medial aspect than those in the plate attached to the lateral aspect. The results and analysis of this study suggest that when applying plates to diaphyseal fractures where bony stability cannot be achieved, it may be acceptable or even desirable to attach the plate to the compression side of the bone.