Metal Ion Concentration Between Coated and Uncoated TKA

Patients are randomized to receive a coated or uncoated TKA. Patients are assessed before surgery, after 3 month, 1 year and 5 years.

Blood samples are collected in 7.5 ml S-Monovette® tubes (for trace metal analysis, Sarstedt AG, Germany) using a specific steel needle for trace metal analysis (Sarstedt AG, Germany). Within one hour, plasma was separated by centrifugation at 2500g for ten minutes. Samples were stored at -20°C before being analysed for chromium, cobalt, molybdenum and nickel content using a graphite furnace atomic absorption spectrometer Z-8270 with Polarisation-Zeeman-Absorption (Hitachi Ltd., Japan). The accuracy and precision of the method is validated to < 10% using the control materials SeronormTM Trace Elements Serum (SERO AS, Norway). The detection limit of the method is estimated at 0.5µg/l for chromium, cobalt and molybdenum, 1.0µg/l for nickel (mean + 3 standard deviations from buffer). All probes having ion levels below the detection limit were adjusted to 0.25µg/l for chromium, cobalt and molybdenum and 0.5µg/l for nickel.

Clinical outcome is measured with the Knee Society Score, Oxford Knee Score, Short-Form 36 and University of Los Angeles Activity Score.

Inclusion criteria

• indication to TKA
• no other metal implant

Exclusion criteria

• no informed consent
• not able to understand study and/or questionnaires
• Need of a higher constrained implant