Abstract
Objectives We evaluated the biomechanical outcome of different plate fixation strategies (the single plate construct, 45° double-plate construct, 90° double-plate construct, 135° double-plate construct, and 180° double-plate construct) used for the fixation of the femoral shaft nonunion with no cortical support opposite the primary lateral plate. This may help surgeons choose the optimal therapy to the femoral shaft nonunion. Methods The femoral shaft nonunion with no medial support and the models of lateral plate and medial plate was constructed in 3-matic software and UG-NX software, respectively. We then assembled the single plate and different double plates to the fracture model separately to form the fixation models. After meshing the models' elements, we used the ABAQUS software to perform the finite element analysis. Values of the von Mises Stress (VMS) distribution of the implant, peak VMS, and model displacement and deformation were used to capture the mechanical factors in this study. Results Our results indicated that the peak von Mises Stress (VMS) of the lateral plate was concentrated in middle surface of the lateral plate near the fragment of each group. The peak VMS was 5201.0 MPa (the single-plate construct), 3490.0 MPa (45° double-plate construct), 1754.0 MPa (90° double-plate construct), 1123.0 MPa (135° double-plate construct), and 816.5 MPa (180° double-plate construct). The additional short plate dispersed some stress leading to the decrease in the peak VMS of the lateral plate. As angle formed by the double plates increased, the dispersed function of the additional plate was becoming obvious. The bending angles of the lateral plate were 18° versus 12° versus 3° versus 2° versus 1° (the single-plate construct versus 45° double-plate construct versus 90° double-plate construct versus 135° double-plate construct versus 180° double-plate construct). Conclusions Our study indicated that increasing the angle between the plates in a double-plate construct improves the stability of the construct over a single lateral plate when there is no cortical support opposite to the lateral plate. The strongest fixation occurred when the angle between the two plates was greater than ninety degrees.
Highlights
Femoral shaft nonunion is relatively common with a rate between 1% and 20% depending on the type of fracture and on the technique used [1,2,3,4,5]
Stresses appeared to be concentrated in middle surface of the lateral plate (e) near the fragment of each group (Figures 4 and 5)
The additional short plate dispersed some stress leading to the decrease in the peak von Mises Stress (VMS) of the lateral plate
Summary
Femoral shaft nonunion is relatively common with a rate between 1% and 20% depending on the type of fracture and on the technique used [1,2,3,4,5]. Various treatment strategies, including nail dynamization, Ilizarov technique, nail exchange, locking plate osteosynthesis, and the combinations thereof, are available to treat the femoral shaft nonunions and get the success rate ranging between 47 and 100% [2, 6,7,8]. Nail dynamization is suggested for patients without segmental bony defects and suffering from the main complication of bone shortening that can lead to significant leg length discrepancy. Study has reported a 78.3% successful rate of exchange reamed femoral nailing [12]. Plate osteosynthesis can provide the constant fracture compression as well as a chance of sufficient debridement to remove the fibrous scar, which is favored by surgeons with the union rates of 96% [3, 7, 8, 14,15,16]
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