Serum Titanium Levels Remain Elevated 6 Years and Beyond From Spinal Instrumentation in Children.

Background: Paediatric spinal implants are known to cause circulating metal ions. A previous prospective study by the authors demonstrated elevated chromium, cobalt, nickel, and especially persistence of titanium serum levels at a median of 5.4 times baseline level.

Methods: A continuation of prospective study of children undergoing spinal deformity surgery with repeated testing for circulating metal ions including preoperative levels as controls. Thirty-four of 56 participants returned beyond 6 years from surgery for 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 analyse titanium, chromium, cobalt, and nickel serum levels.

Results: Median titanium levels at 6 years decreased significantly to 0.46 times that of 2-year levels (95% CI: 0.32-0.67, P<0.001); however, they remained 2.40 times higher compared with the presurgery control levels (95% CI: 1.47-3.92, P<0.001). In comparison, median chromium levels at 6 years were significantly increased from 2 years (1.45 times) but were not significantly different to baseline (1.13 times). Cobalt levels at 6 years remained significantly higher than baseline (1.32 times), but also decreased significantly compared with 2-year levels (0.76 times). Nickel levels at 6 years did not differ significantly from baseline or from 2-year levels.

Conclusions: Titanium remains raised at beyond 6 years from spinal instrumentation in children. The effects on a person's health through deposition in solid organs including the brain or on the offspring of persons with spinal instrumentation remains unclear. Curiously, chromium levels increased at 6-year sampling in "all titanium" constructs which may be explained by metallurgical irregularities.

Level of evidence: Level II.