In vitro comparison of the use of two large-animal, centrally threaded, positive-profile transfixation pin designs in the equine third metacarpal bone.

This study compares the impact and effectiveness of two different large-animal bone transfixation pins—self-drilling, self-tapping (SDST) and nonself-drilling, nonself-tapping (NDNT)—in equine metacarpal bones, with the NDNT pins demonstrating less bone damage and better stability.

Methodology

• This research centered around an in vitro study, using 25 pairs of adult equine cadaver metacarpal bones.
• Two types of centrally threaded positive-profile transfixation pins were examined: Self-Drilling Self-Tapping (SDST) and Nonself-Drilling Nonself-Tapping (NDNT).
• These pins were inserted into the middiaphysis of the equine metacarpal bones for comparison.
• Several parameters were observed during pin insertion, such as hardware temperature, bone and cortical width, transfixation pin placement and cortical damage.
• The study also measured resistance to axial extraction both before and after cyclic loading, using a material testing system.
• Additionally, microstructural damage caused by the insertion of the transfixation pins was assessed through scanning electron microscopy.

Results

• The results showed a significantly higher temperature following pin insertion for SDST transfixation pins.
• Surface cortical fractures were discovered in 50% of the bones with SDST transfixation pins, while none were found with the NDNT varieties.
• The NDNT transfixation pins demonstrated significantly higher resistance to axial extraction compared to SDST pins, indicative of better transfixation pin stability.
• Macroscopic and microscopic examination revealed that NDNT pins caused less damage to bone and created a more consistent thread pattern during insertion.

Conclusions

• The study argued that in vitro insertion of NDNT transfixation pins results in less macroscopic and microscopic damage to bones than the application of SDST transfixation pins.
• The research also concluded that NDNT pins are superior in terms of initial bone-transfixation pin stability, as reflected in their greater pull-out strength.