Cobalt-Chromium-Molybdenum Femoral Knee Implant Damage Correlates With Elevated Periprosthetic Metal Concentrations

Total knee arthroplasty (TKA) device systems frequently include cast cobalt chrome alloy (CoCrMo) femoral components. However, compared to total hip arthroplasty (THA), gaps persist in our understanding of the correlations between femoral component damage, local metal release, and potential biological effects. Additionally, it remains unclear how TKA metal release affects clinical success or patient satisfaction. In this study, we investigated the associations between implant damage and metal release in the periprosthetic tissues following TKA. We asked: (1) does damage severity correlate with increased metal concentrations within the periprosthetic tissue? and (2) does the magnitude of metal released from CoCrMo femoral components merit clinical concern?

There were 51 CoCrMo femoral components and synovial samples that were prospectively collected by an institutional review board-exempt retrieval program. Devices received damage scores ranging from minimal (1) to severe (4). Tissue metal concentrations for cobalt (Co), chromium (Cr), molybdenum (Mo), and titanium (Ti) were quantified using inductively coupled plasma mass spectroscopy.

Visual damage correlated with increases in Co, Cr, and Mo concentrations in the periprosthetic tissue (P = 0.0008, 0.029, and 0.007, respectively). Within the tissue adjacent to severely damaged implants, we measured median Co, Cr, and Mo concentrations of 7.81, 5.26, and 0.713 microg/mL, respectively. For minimally damaged implants, we report median Co, Cr, and Mo concentrations of 0.111, 1.80, and 0.179 microg/mL, respectively. In several of the 51 (14%) tissue samples, we measured Co and Cr concentrations > 10 microg/mL. Additionally, within periprosthetic tissues of devices with Ti tibial trays, Ti concentrations increased (P = 0.0052) arising, in part, from tibial-femoral component contact during arthroplasty.

We (1) showed elevated periprosthetic tissue metal concentrations in TKA patients and (2) established a positive correlation between damage severity and subsequent metal release. Measured tissue metal concentrations approached the magnitudes reported following metal-on-metal THA.