Static Magnetic Fields within Spinal Interbody Cages for the Promotion of Spinal Arthrodesis: A Pilot Study

Background: Spinal arthrodesis is a commonly performed spinal operation. Spinal arthrodesis can be complicated by pseudoarthrosis and resultant hardware failure. Static magnetic fields (SMF) have the ability to improve bone fusion. We seek to assess the feasibility of the construction and implantation of a lumbar interbody cage equipped with a SMF in a caprine model.

Methods: Six skeletally mature female Boer goats underwent a lateral approach for placement of an interbody graft at lumbar (L) 1-2 and 3-4. The goats were divided into 2 groups of 3 animals. The interbody graft contained a neodymium iron boron magnet in the experimental group and a nonmagnetic titanium sham in the control group. Both groups contained a synthetic bone graft. Blinded radiographic and histologic evaluation was performed at predetermined timepoints to assess degree of bony fusion and osseointegration.

Results: All 6 goats underwent successful placement of lumbar interbody grafts. At the 1-month postoperative computed tomography, 1 goat in the experimental group and 1 goat in the control group were noted to have dislodged their intervertebral cage. Qualitative radiographic and histologic evaluation identified enhanced bone formation, bone density, and osteointegration of the graft in the experimental group.

Conclusions: A spinal interbody cage containing a neodymium iron boron magnet for the production of a local SMF is feasible. Preliminary data suggests enhanced bone formation, bone density, and osseointegration of the graft.