Persistently Raised Serum Titanium Levels After Spinal Instrumentation in Children

Study Design. Prospective study of patients undergoing elective spinal deformity surgery with repeated testing for circulating metal ions including preoperative levels acting as controls. Objective. The aim was to determine if levels of particular circulating metal ions are maintained to two years postsurgery including different implant systems and rods. Summary of Background Data. Adults having hip replacements, especially metal-on-metal bearings, may develop high metal ion levels. Pediatric spinal implants are known to cause circulating metal ions, notably titanium, chromium, cobalt, and nickel. Materials and Methods. Fifty-six children having spinal deformity surgery were studied with repeated testing for circulating metal ions, using high-resolution inductively coupled plasma mass spectrometry. Linear mixed-effects models adjusting for repeated measurements over time were used to analyze levels of titanium, cobalt, chromium, and nickel. Results. Titanium levels showed a rapid increase by seven days and a peak at 30 days that was essentially maintained at the two-year assay. At two years, titanium levels were 5.14 times greater compared with the presurgery control level (P<0.0001). Cobalt levels were shown to gradually rise to a peak at 30 days and then slowly decline but remained 1.74 times above mean baseline level at two years (P=0.0004), with a declining trajectory. Chromium and nickel levels rose immediately postoperatively and then steadily declined to baseline by six months and remained at baseline at two years. The five implant systems tested had generally equivalent results. Conclusion. The persistent and rising levels of titanium, in a predominantly female population, is concerning. Titanium is known to cross the placental barrier and enter the circulation of the fetus in rodents and humans, and to accumulate in solid organs especially the liver, spleen, heart, and lymph nodes in humans. This potentially exposes the offspring of mothers with spinal implants to titanium, with potential teratogenic effects.