BIOMECHANICAL EVALUATION OF PLATE OSTEOSYNTHESIS FOR AO TYPE C2 FRACTURE OF THE DISTAL RADIUS — A CADAVER STUDY

Biomechanical investigation of a novel hybrid dorsal double plating for distal radius fractures by integrating topology optimization and finite element analysis

BACKGROUND

Currently available dorsal locking plates for the treatment of distal radius fractures are far less then volar locking plates, and there is limited evidence about biomechanical strength of dorsal plates. The aim of this study is to develop a novel hybrid dorsal double plating, which enhance biomechanical strength in the articular fixation region and achieve the minimally invasive surgical technique requirement of distal radius fracture treatment by combining weighted topology optimization and finite element (FE) analysis METHODS: A dorsal template bone plate design (based on dorsal double plating (DDP)) was constructed to perform weighted topology optimization and FE analysis under six fracture models with 50%, 30%, and 20% weighting of the joint subjected to axial, bending, and torsion moments, respectively. A novel hybrid dorsal double plating (HDDP) was generated using the union of six single dorsal plates to subtract the intersection of the original template dorsal model. A 100 N axial load with 1 Nm bending and torsion moments were applied at the end of the distal radius onto six fracture FE models to investigate the biomechanical differences between the DDP and HDDP approaches.

RESULTS

Results of weighted topology optimization showed that the profile of the HDDP presented a "Y" shape. Simulation results showed that the bone plate stress values for the distal radius fractures fixed with HDDP was much smaller than those with DDP regardless of the type of bone fractures and load conditions. The maximum bone stress value of the DDP approach was much higher than that of HDDP when the distal radius was a complete sagittal articular fracture and partial articular fracture involving lunate fossa. The corresponding maximum bone stress values for different loads might be higher than the ultimate strength of bone (150  MPa) and induced the risk of future bone fractures.

CONCLUSIONS

It is concluded that the novel HDDP demonstrated better resistance to functional loads, provided sufficient screw fixation at the articular surface, and can be placed on the dorsal site of the distal radius through the standard dorsal approach to minimize invasive surgeries and eliminate tendon irritations.

Biomechanical evaluation of the modified double-plating fixation for the distal radius fracture

BACKGROUND

Distal radius fracture is among the most common type of skeletal injuries. To conquer the surgical and biomechanical complications of the most-frequent used double-plating operation for this fracture, modified double-plating technique was proposed in this study. The aim of this study was to investigate the biomechanical interactions of double-plating, modified double-plating and traditional single plating fixations coupled with various load conditions using nonlinear finite element analysis.

METHODS

A three-dimensional finite element distal radius fracture model with three fixation methods (double-plating, modified double-plating and single) was generated based on computer tomography data. After model verification and validation, frictional (contact) elements were used to simulate the interface condition between the fixation plates and the bony surface. The rigidity, stress values and displacements at the radius end were observed under axial, bending and torsion load conditions.

FINDINGS

The simulated results showed that the modified double-plating model demonstrated the highest rigidity and the least displacement among the three techniques in bending, but not in axial compression (similar results across the three) and torsion (modified double-plating technique possessed lowest rigidity). The maximum von Mises stress for bone was lower in modified double-plating model as well. These results indicated that modified double-plating technique demonstrated a better structural strength against bending with the least potential of fracture fragments and screw loosening.

INTERPRETATION

Although a lower torsional rigidity, modified double-plating technique was a better choice in distal radius fracture fixation since the bending force, which has the potential to separate the fracture ends, is more detrimental in hindering fracture healing.

Buttressing angle of the double-plating fixation of a distal radius fracture: a finite element study

Treatment of a distal radius fracture should consider principles including stable fixation and early motion. The aim of this study was to investigate the biomechanical interactions of plate-fixation angles in the internal double-plating method coupled with various load conditions using non-linear finite element analysis (FEA). A 3D finite element distal radius fracture model with three separation angles (50, 70, and 90 degrees ) between the buttressed L- and straight plates was generated based on computed tomography data. After model verification and validation, frictional (contact) elements were used to simulate the interface condition between the fixation plates and the bony surface. The stress/strain distributions and displacements at the radius end were observed under axial, bending, and torsion load conditions. The simulated results indicated that the bending and torsion increased the stress values more than the axial load. The radius and straight plate stress values decreased significantly with increasing fixation angles for all load conditions. However, the L-plate stress values increased slightly under the bending buckling effect. The displacements at the radius end and strains at the fracture healing interface decreased with increasing fixation angles for axial and torsion conditions but displayed a slight difference for the bending condition. The findings using FEA provide quantitative evidence to identify that much larger plate fixation angles could provide better mechanical strength to establish favorable stress-transmission and prevent distal fragment dislocation.