In Silico Analysis of Stress Distribution in Proximal Interphalangeal Joint Arthrodesis in Horses Using a Locking Compression Plate.

The research article presents a simulation study on the impact of different screw types and implantation methods on stress distribution in horse proximal interphalangeal joint arthrodesis procedures, using a locking compression plate. The study also examines the effects of partial or total removal of implants after fusion.

Objective and Methodology of the Study

• The main goal of this research was to investigate and compare stress distribution in proximal interphalangeal joint arthrodesis in horses, specifically focusing on the influence of screw type and implantation methods in the proximal hole of the locking compression plate.
• The authors conducted a finite element analysis, a simulation technique generally used in physics and engineering, enabling detailed assessment of object behavior under various conditions.
• The simulation replicated arthrodesis, a surgical process used to fuse bones in a joint, using a three-hole, 4.5-mm narrow locking compression plate along with two 5.5-mm transarticular screws.

Study Design and Simulation Conditions

• Models were constructed based on the type of screw used (cortex or locking) and method of implantation (uni- or bicortical) in the proximal hole of the locking compression plate.
• The researchers simulated four conditions: Immediate postoperative, ankylosis (joint fusion), ankylosis with partial removal of implants (transarticular screws remaining), and ankylosis with no remaining implants.
• An axial load of 8,700 N was applied in all simulations, and major principal stresses were evaluated in the bones. Additionally, von Mises stress, a theoretical measure used to predict yield failure in ductile materials, was evaluated in the implants.

Findings and Conclusion

• The findings indicated that cortical screws in the proximal hole improved stress distribution, decreasing stress concentration along the diaphysis (shaft) of the proximal phalanx (toe bone) in the immediate postoperative condition.
• The stress pattern between partial and total implant removal did not show any substantial difference.
• High stresses were perceived in the implants, particularly when locking screws were utilized. This stress reduced after the simulation of ankylosis (joint fusion).
• In conclusion, using a cortex screw in the proximal hole can diminish stress concentration in the proximal phalanx. Further, the integrity of bone stress patterns wasn’t negatively affected by maintaining the transarticular screws post-ankylosis.