Direct current stimulation of bone production in the horse: preliminary study with a “gap healing” model.

This study investigated the impact of a 20-microA direct-current (DC) bone growth stimulator (BGS) on healing gaps in horse bones. The results suggested that the method did not significantly enhance bone production, paving the way for further research into electrical stimulation techniques for promoting bone healing in horses.

Study Design

• The study took place using seven adult horses. The researchers created a “gap healing” model using the right and left 4th metatarsal bones (Mt-4) of each horse. A 4-mm section of the Mt-4 bone was surgically removed (reseected) on each side.
• The researchers then surgically implanted the BGS into the left Mt-4 defects, leaving the right MT-4 defects as control sites.
• The study lasted for 16 weeks, with six of the seven horses surviving the full duration of the experimental period.

Observations and Findings

• Throughout the 16 weeks, none of the horses showed signs of pain, decreased range of limb motion, or lameness. This suggests that the BGS did not cause any observable adverse health effects.
• Direct current (20 microA) did not increase bone production. Although none of the animals showed complete healing radiographically, four of the stimulated sites showed less periosteal reaction (bone inflammation) and two showed greater reaction than the control sites.
• The bone resorption (breakdown and absorption into the blood) was primarily seen around the screws and plates implanted in both groups.
• The BGS proved excellent biocompatibility, indicating it was well-tolerated by the biological systems of the horses. However, there was one instance of a broken cathode wire in a horse, and all polyethylene cathode sheaths were found to be fluid-filled at the end of 16 weeks.
• There was no significant difference between the control limbs and the limbs with implanted BGS in terms of the histomorphometric values measured. These included mineralization rates and bone formation activity.

Conclusions and Future Directions

• The results suggested that the direct current BGS does not significantly increase bone production in horses.
• However, the findings provide a useful starting point for future research on the effectiveness of electrical stimulation for treating fractures in horses and for exploring potential dose-response relationships.