Effect of the screw tightening sequence on the stress distribution of a dynamic compression plate: A pilot finite element study

Biomechanical evaluation of composite reduction plates with variable positioning using the Henry and Thompson approaches for transverse radial fracture surgery

BACKGROUND

Radius fractures are challenging to stabilize due to complex muscle-loading conditions, requiring optimized plate positioning and material selection for effective treatment. This study addresses the biomechanical impact of plate positions (anterior, posterior, lateral) and materials in transverse radial fractures.

HYPOTHESIS

Plate positioning and material selection significantly influence stress distribution and displacement, with lateral positioning and WE43 alloy offering biomechanical advantages.

METHODS

Finite element analysis was used to evaluate Ti6Al4V titanium alloy and WE43 magnesium alloy bone plates positioned on the anterior, posterior, and lateral sides of the radius under a 50 N axial load. Stress distribution and displacement were analyzed.

RESULTS

Posterior reductions exhibited the highest stress and displacement, indicating potential instability, with maximum von Mises stress increasing by 32.5% compared to anterior reduction. Lateral reductions provided more uniform stress distribution and lower displacement, though von Mises stress was still 20% higher than in the anterior reduction. WE43 alloy demonstrated effective stress reduction in non-posterior positions, while Ti6Al4V exhibited greater stiffness and resistance to deformation.

DISCUSSION

Lateral and anterior plate positions demonstrated superior biomechanical stability, suggesting their preference for optimizing fracture healing and reducing complications. WE43 alloy's stress-reducing and biodegradable properties make it suitable for temporary fixation, while Ti6Al4V provides greater structural integrity for long-term support. These findings highlight the importance of plate positioning and material selection in improving clinical outcomes for transverse radial fracture fixation.

LEVEL OF EVIDENCE

V; expert opinion, controlled laboratory study.

Finite element modeling of fracture compression by compression plates

Dynamic compression plating is a common type of fracture fixation used to compress between bone fragments. The quality of compression across the fracture is important for postoperative stability and primary bone healing. Compression quality may be affected by surgical variations in plate prebend, screw location, screw torque, fracture gap, and implant material. Computational modeling provides a tool for systematically examining these factors, and for visualizing the mechanisms involved. The purpose of this study was to develop a finite element model of dynamic compression plating that includes screw insertion under torque control, establish model credibility through sensitivity analyses and experimental validation, and use the model to examine the effects of surgical variables on fracture compression and postoperative stability. Model-predicted compressive pressures had good agreement with corresponding synthetic bones experiments under a variety of conditions. Models demonstrated that introducing a 1.5 or 3 mm plate prebend (using a 4.5 mm narrow LCP plate) eliminated gapping at the far cortex, which is consistent with clinical recommendations. However, models also revealed that plate prebend led to sharp decreases in fracture compressive force, exceeding 80% in some cases. A 1.5 mm plate prebend resulted in the most uniform pressures across the fracture. Testing of a simplified model form used in previous computational modeling studies showed large inaccuracies for constructs with plate prebend. This study provides the first experimentally validated computational models of dynamic compression plate fracture fixation, and reveals important effects of plate prebend and fracture gap on fracture compression quality.

Biomechanical evaluation of the screw preload values used in the plate placement for bone fractures

The purpose of this study is to examine the effects of screw preload values on the bone-plate system. The preload value was taken differently in the literature range from 50 N to 3000 N. These preload value were examined in this study. The finite element method was used to calculate the strain and stress on the models. The long bone, plate and screws were modeled as 3D using CAD software. The finite element models were created using Ansys Workbench software. The convergence and validation study were made for the correct results. The 400 N axial load was applied to the proximal end of bone. The distal end of the bone fixed for boundary condition. The preload values were applied to the screws differently. The results of the finite element analysis were compared and evaluated. The results showed that when the preload values increased, the von Mises stresses and strains on the bone and plate system increased. The critical preload value of the screw is the 500 N. The upper values of this critical value can be damaged bone and plate system. The critical region of the bone is the holes where the screw inserted. In conclusion, the preload values of the screw should not exceed the 500 N for the successful fixation.