Corrosion and late infection causing delayed paraparesis after spinal instrumentation.

A 28-year-old female patient came to our hospital 14 years after surgical correction of adolescent idiopathic scoliosis with a 316L stainless-steel instrumentation. She presented progressive paraparesis during the last 2 months. Plain radiography, computed tomography scan and computed tomography-scan-guided needle biopsy revealed that a metallotic mass penetrated into the spinal canal, causing compression of the spinal cord at the T5-T6 level. The patient's symptoms were related to corrosion of the implant and infection by Propionibacterium acnes. Through a posterior approach, the instrumentation was retrieved and the metallotic mass and tissues were excised. Six months after the surgery, the patient is completely asymptomatic. Corrosion of stainless-steel implants is a finding more common than supposed. Biocorrosion--or microbially influenced corrosion--is a concept to be taken into account. It is possible that bacteria may modify the rate of corrosion of metals. Early diagnosis of corrosion is essential in order to prevent cases like the one we report, and perhaps, as suggested for total hip arthroplasties, metal levels could be useful to monitor spinal implants.