The effect of pulsed electromagnetic fields on instrumented posterolateral spinal fusion and device-related stress shielding.

STUDY DESIGN

This study was designed to examine stress-shielding effects on the spine caused by rigid implants and to investigate the effects of pulsed electromagnetic fields on the instrumented spine.

OBJECTIVES

To investigate the effects of pulsed electromagnetic fields on posterolateral spinal fusion, and to determine if osteopenia induced by rigid instrumentation can be diminished by pulsed electromagnetic fields.

SUMMARY OF BACKGROUND DATA

Although device-related osteopenia on vertebral bodies is of a great clinical importance, no method for preventing bone mineral loss in vertebrae by stiff spinal implants has been effective.

METHODS

Twenty-eight adult beagles underwent L5-L6 destabilization followed by posterolateral spinal fusion. The study was divided into four groups: 1) Group CNTL: without instrumentation, without pulsed electromagnetic fields, 2) Group PEMF: without Steffee, with pulsed electromagnetic fields, 3) Group INST: with Steffee, without pulsed electromagnetic fields, 4) Group PEMF + INST: with Steffee, with pulsed electromagnetic fields. At the end of 24 weeks, the dogs were killed, and L4-L7 segments were tested biomechanically without instrumentation. Radiographs and quantitative computed tomography assessed the condition of the fusion mass.

RESULTS

Stress shielding was induced in the anterior vertebral bodies of L6 with the Steffee plates; bone mineral density was increased with the addition of pulsed electromagnetic fields, regardless of the presence or absence of fixation. A decrease in flexion and bending stiffness was observed in the Group INST; pulsed electromagnetic fields did increase the flexion stiffness regardless of the presence or absence of fixation, although this was not statistically significant.

CONCLUSIONS

Use of pulsed electromagnetic fields has the potential to minimize device-related vertebral-bone mineral loss.