Intraspinal metalloma resulting in late paraparesis.

The metal-related complications caused by orthopedic implants have long been a concern, but these problems have been considered mostly in the field of arthroplasty or internal fixation of fractures. The recent prevalence of spinal instrumentation has evoked a similar concern among spine surgeons. Here, we present a case of intraspinal metallosis adjacent to the pedicular hook occurring after treatment of vertebral fracture by posterior spinal instrumentation and fusion, and causing paraparesis at the 3rd postoperative year. Metallic granulomas can appear around the pedicular hooks as in the reported case. Crevice and fretting corrosion are results at the junctions of rod-screw, rod-hook, transverse connector rod and other connector rods in modular spinal implants. Adequate usage of transpedicular screws may inhibit the occurrence of such a complication. For this reason, further studies are necessary to increase metallic corrosive resistance to inhibit crevice and fretting corrosion.