Direct current stimulation of bone production in the pony: observations with a diaphyseal osteotomy model.

The research investigated the impacts of electrically stimulated bone growth in ponies, particularly in the healing of fractures using direct current stimulation. It found that while initial phases showed improvement in healing and vascular development, the overall impact on bone strength and elasticity was not sufficient to recommend this method in clinical settings.

Methodology

• The researchers used a sample of twelve young adult ponies of mixed sex which were divided into two treatment groups (A and B), each containing three stimulated and three control ponies.
• The experiment utilized a third metacarpal diaphyseal osteotomy model, which involved creating a surgically induced fracture in the middle portion of the pony’s third metacarpal bone. This model was combined with internal fixation and postoperative loading.
• The ponies in the stimulated groups received 20 microA of direct current via an implanted bone growth stimulator. Group A was stimulated for 60 days and Group B for 120 days.
• Data was collected using a range of techniques, including radiography for viewing bone healing, nuclear medical bone imaging for assessing bone metabolism, and testing for specific gravity and bending strengths for evaluating mechanical properties of the bone.

Findings

• The biocompatibility of the bone growth stimulator was found to be excellent in all ponies, indicating it did not cause adverse reactions.
• Radiographic observations showed more advanced healing and better vascular development in the 60-day stimulated group compared with controls, suggesting initial promise for the technique. However, there was no discernible difference in the 120-day group compared to the controls.
• Nuclear medical bone imaging highlighted peak uptake at 4 weeks in the stimulated groups which decreased after 8 weeks. Furthermore, radiopharmaceutical uptake was consistently below control uptake throughout the study, indicating that the stimulated bone growth may not have significantly improve bone metabolism.
• Tests on mechanical properties indicated that the specific gravity, ultimate bending strengths, and the flexural moduli of elasticity between control and stimulated groups were not significantly different. This means the bone strength and flexibility in the stimulated groups were not significantly improved, which is crucial for the bone’s ability to withstand physical stresses.

Conclusion

• The researchers concluded that 20 microA of direct current stimulation may not stimulate sufficient bone production to affect the mechanical properties of the bone. This suggests that despite the initial promising signs of accelerated healing and vascular development, the method does not significantly improve the overall quality of the healed bone.
• As a result, the clinical use of bone growth stimulators in fresh fracture management cannot be recommended based on this research.