Total knee arthroplasty is a well established treatment for degenerative
joint disease, which is also performed as a treatment in younger and middle-aged patients who have a significant physical activity and high life expectancy. However, complications may occur due to biological responses to wear particles, as well as local and systemic
hypersensitivity reactions triggered by
metal ions and particles such as
cobalt,
chromium and
molybdenum. The purpose of the study was to perform a highly demanding activities (HDA) knee wear simulation in order to compare the wear characteristics and
metal ion release barrier function of a
zirconium nitride (ZrN) coated knee implant, designed for patients with suspected
metal ion
hypersensitivity, against an uncoated knee implant made out of CoCrMo. The load profiles were applied for 5 million HDA cycles, which represent 15-30 years of in vivo service depending on the activity level of the patient. Results showed a significant wear rate reduction for the coated group (1.01 ± 0.29 mg/million cycles) in comparison with the uncoated group (2.89 ± 1.04 mg/million cycles). The
zirconium nitride coating showed no sign of scratches nor delamination during the wear simulation, whereas the uncoated femurs showed characteristic wear scratches in the articulation areas. Furthermore, the
metal ion release from the coated implants was reduced up to three orders of magnitude in comparison with the uncoated implants. These results demonstrate the efficiency of
zirconium nitride coated knee implants to reduce wear as well as to substantially reduce
metal ion release in the knee joint.