The effect of varied electrical current densities on lumbar spinal fusions in dogs.

BACKGROUND CONTEXT

The use of electrical stimulation has been shown to increase the rate of successful spinal fusions. It is possible that increasing the current density of these stimulators may increase the speed and success rate of these fusions.

PURPOSE

This study evaluated the effects of varied current densities on the speed and success rate of spinal fusion in dogs.

STUDY DESIGN/SETTING: Three different current densities (0.83 microA/cm, 4 microA/cm and 10 microA/cm) were used to stimulate spinal fusions in a canine model over a 12-week period.

OUTCOME MEASURES

Radiographic and histologic assessments were used to determine the degree of facet fusions at each time period.

METHODS

Fifteen dogs underwent spinal facet fusion bilaterally at the level of L1-2 and L4-5. Each fusion site was electrically stimulated using one of three current densities. At 6, 9 and 12 weeks, the specimens were evaluated using high-resolution radiography and routine histology. The fusion masses were graded and then statistically evaluated.

RESULTS

The results demonstrate a dose response of fusion mass scores to increasing current density. The highest current density (10 microA/cm) demonstrated a statistically higher fusion scores than the lowest currently density (0.83 microA/cm) at 6 weeks and statistically greater than both the middle (4 microA/cm) and lowest (0.83 microA/cm) current densities at 9 weeks. No differences were noted at 12 weeks, because all groups showed complete fusion.

CONCLUSIONS

This controlled study suggests that speed of fusion may be further improved by increasing the current density of the electrical stimulation.