Metal ion levels after metal-on-metal hip resurfacing: A single-center longitudinal study of Chinese patients.

This study aimed to investigate the long-term serum metal ion levels of patients who received metal-on-metal hip resurfacing arthroplasty (MoM HRA). We conducted a retrospective study of 99 patients (110 hips) from March 2006 to May 2017 who underwent MoM HRA. The Harris Hip Score (HHS) and the University of California at Los Angeles (UCLA) activity score were measured, and the patients underwent clinical and radiological management. Serum levels of cobalt (Co), chromium (Cr), and molybdenum (Mo) were measured using inductively coupled plasma mass spectrometry (ICPMS) at 1, 6, and 12 months, and each year follow-up after prosthesis implantation. Patients were followed up from 1 to 156 months, with a mean of 98 months. No complications occurred. Metal ion analysis revealed significantly elevated levels compared to preoperative levels. The metal ions levels increased and reached a peak after surgery, and then the levels began to decline gradually. Approximately 84-108 months after surgery, the metal ion levels increased again to approximately peak levels. Then, up to 156 months after surgery, the metal ions levels will drop approximately to preoperative levels. The serum levels of Cr in women were higher than those in men, with the difference being statistically significant. Patients with a body mass index (BMI) of ≥24.9 kg/m2 Co levels were significantly higher than those of normal-weight patients. The serum levels of metal ions showed no significant differences between the prostheses. The use of the MoM HRA was clinically effective, and the Co, Cr, and Mo levels increased significantly after HRA; however, upon long-term follow-up, serum metal ion levels tended to decrease to preoperative levels. Longer follow-up periods and larger study samples are needed to establish the long-term outcome of patients undergoing HRA with MoM bearings. Level IV, Therapeutic Study.