Release of Cobalt and Chromium Ions Into the Serum Following Implantation of the Metal-on-Metal Maverick-Type Artificial Lumbar Disc (Medtronic Sofamor Danek)

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Abstract

Study Design.

Cross-sectional study of 10 patients to measure the serum levels of cobalt and chromium after TDA.

Objectives.

To investigate the release of cobalt and chromium ions into the serum following implantation of the metal-on-metal Maverick-type artificial lumbar disc.

Summary of Background Data.

In total hip endoprosthetics and consequently for TDA (total disc arthroplasty), metal-on-metal combinations are used with the aim of reducing wear debris. In metal-on-metal TDA the release of metal ions has until now been secondary to the main discussion.

Materials and Methods.

We investigated the serum cobalt and chromium concentration following implantation of 15 Maverick TDAs (monosegmental L5–S1, n = 5; bisegmental L4–L5 and L5–S1, n = 5; average age, 36.5 years). Five healthy subjects (no metal implants) acted as a control group. The measurements of the metals were carried out using the HITACHI Z-8200 AAS polarized Zeeman atomic absorption spectrometer after an average of 14.8 months.

Results.

The concentrations of cobalt and chromium ions in the serum amounted on average to 4.75 μg/L (SD, 2.71) for cobalt and 1.10 μg/L (SD, 1.24) for chromium. Compared with control group, both the chromium and cobalt levels in the serum showed significant increases (Mann-Whitney U test, P = 0.0120). At follow-up,the Oswestry Disability Score was on average significantly decreased by 24.4 points (L5–S1) (t test, P < 0.05) and by 26.8 points (L4–S1) (t test, P < 0.05). The improved clinical situation is also represented by a significant decrease of the Visual Analog Pain Scale of 42.2 points after the follow-up (t test, P < 0.05).

Conclusion.

Significant systemic release of Cr/Co was proven in the serum compared with the control group. The concentrations of Cr/Co measured in the serum are similar in terms of their level to the values measured in THA metal-on-metal combinations or exceed these values given in the literature. Long-term implication of this metal exposure in unknown and should be studied further.

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