Serum Metal Concentrations in Patients With Titanium Ceramic Composite Cervical Disc Replacements.

STUDY

DESIGN

Prospective longitudinal study.

OBJECTIVE

The serum titanium (Ti) concentrations were examined in patients implanted with a PRESTIGE LP Cervical Disc System (Medtronic, Inc., Memphis, TN). The metal-on-metal disc with ball-in-trough articulation is made of titanium alloy/titanium carbide composite (Ti-6Al-4 V/TiC).

SUMMARY OF BACKGROUND DATA: Cervical disc arthroplasty provides a motion-preserving treatment alternative to anterior cervical discectomy and fusion for degenerative cervical disc disease. The articulating surfaces have a tendency to generate in vivo wear in the form of insoluble particulates (debris) and soluble metal ions. Not much information is available on the long-term metal concentrations observed in cervical disc arthroplasty and how these compare with the metal concentrations in Ti-based posterior fixation devices and other joint replacement implants.

METHODS

Thirty patients were enrolled after strict exclusion criteria that included no previous permanent metal implants and no professional exposure to metal particles. High-resolution inductively coupled plasma-mass spectrometry was used to assay blood serum titanium concentrations preoperatively and at 3, 6, 12, 24, 36, 60, and 84 months after surgery. The detection limit for Ti was 0.2 ng/mL. The Friedman test was used to make longitudinal statistical comparisons.

RESULTS

The median serum Ti concentrations determined preoperatively, and at 3, 6, 12, 24, 36, 60, and 84 months were 0.10, 1.22, 1.15, 1.27, 1.21, 1.46, 1.34, and 1.42 ng/mL, respectively. The serum Ti concentrations at all postoperative time points were significantly higher than that at the preoperative time point (Friedman P < 0.01).

CONCLUSION

The long-term postoperative serum Ti concentrations were significantly higher than the preoperative concentrations. The observed serum Ti concentrations in this study are lower than the reported concentrations in patients receiving posterior spinal instrumentation and metal or ceramic-on-polyethylene hip prostheses with Ti-alloy based stems and acetabular components.

LEVEL OF EVIDENCE: 3.