RELEASE OF COBALT AND CHROMIUM IONS INTO THE SERUM FOLLOWING IMPLANTATION OF THE METAL-ON-METAL MAVERICKTM TYPE ARTIFICIAL LUMBAR DISC (MEDTRONIC SOFAMOR DANEK)

Abstract

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

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.

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

Materials and methods: We investigated the serum cobalt and chromium concentration following implantation of 15 Maverick™ TDAs (monosegmental L5/S1 n=5; bisegmental L4/5 and L5/S1 n=5; average age = 36.5 years). 5 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 14,8months.

Results: The concentrations of cobalt and chromium ions in the serum amounted on average to 4.75μg/l (standard deviation 2,71) for cobalt and 1.10μg/l (standard deviation 1,24) for chromium. Compared to the control group, both the chromium and cobalt levels in the serum showed significant increases (Mann-Whitney Rank Sum 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 42,2points after the follow-up (t-test, p< 0,05).

Conclusion: Significant systemic release of Cr/Co was proven in the serum compared to 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 exposuere in unknown and should be studied further.