Knee Implants: New Coating Safe Over 10 Years

observational-study PMID: 35921997

Quick Summary: A new type of coating for knee replacement implants was found to be safe and effective in a 10-year study. The coating, which includes molybdenum, didn't cause any safety issues or increase metal levels in the blood compared to standard implants.

Is Molybdenum in Knee Implants Safe?

This research looked at a new coating for knee replacement implants. This coating includes molybdenum and other materials designed to be gentle on the body. The study wanted to see if this new coating was safe and if it caused any problems over time.

What The Research Found

The study found that the new coating, which includes molybdenum, was safe. Here's what they discovered:

No Safety Issues: The coating didn't cause any significant problems or increase the levels of metals like molybdenum in the blood.

Knee Function Improved: Both groups of patients (those with the new coating and those with standard implants) saw similar improvements in their knee function and quality of life.

Long-Term Success: Almost all patients (98%) had their implants working well after 10 years.

Study Details

Who was studied: 120 people who needed a total knee replacement.

How long: The study followed patients for 10 years.

What they took: Half the patients received a knee implant with the new coating, and the other half received a standard implant.

What This Means For You

If you're considering a knee replacement, this research is good news. It suggests that the new coating, which includes molybdenum, is a safe option. It's designed to be gentle on your body and doesn't seem to cause any harmful metal release. This means you can have confidence in the safety of this new technology.

Study Limitations

It's important to keep these points in mind:

Some Patients Died: A number of patients passed away during the study, which could affect the results.

Metal Levels: The study didn't always specify the exact levels of metals it was measuring.

One Type of Implant: The results might not be the same for all types of knee implants.

Key Findings

The study found no significant safety concerns or increases in serum metal ion levels (including molybdenum) for patients receiving a novel multilayer-coated total knee arthroplasty (TKA) implant compared to standard uncoated implants. Both groups showed similar improvements in knee function (Oxford Knee Score, OKS), quality of life (SF-36), and physical activity (UCLA scale) over 10 years. Cobalt levels in the standard implant group rose slightly at 5- and 10-year follow-ups (p < 0.05), but remained below critical thresholds (<3 μg/L). Cumulative implant survival was 98% in both groups.

Study Design

This was a randomized-controlled trial (RCT) (Level I evidence) involving 120 patients who received either a multilayer-coated or standard TKA implant. Follow-up assessments occurred pre-surgery and at 1, 3, 5, and 10 years post-surgery. 85 patients completed the 10-year follow-up (24 deaths, 1 revision per group). Outcomes included serum cobalt, chromium, molybdenum, and nickel levels, PROs, and implant survival.

Dosage & Administration

Molybdenum was not administered as a supplement. Instead, the study evaluated molybdenum release from a multilayer-coated TKA implant (composed of titanium nitride and other hypoallergenic materials) compared to a standard cobalt-chromium implant. Serum levels were measured via blood tests, with detection limits unspecified in the summary.

Results & Efficacy

Serum metal ions: Most patients had undetectable levels of cobalt, chromium, molybdenum, and nickel. The standard implant group showed a slight increase in cobalt at 5 (p = 0.02) and 10 years (p = 0.01), but values remained <3 μg/L.
Patient-reported outcomes: Both groups improved similarly in OKS (mean 42 pre-op to 18 post-op), SF-36, and UCLA scores, with no significant differences between groups.
Implant survival: 98% survival at 10 years for both groups, with no coating-related failures.

Limitations

High attrition rate: 29% of participants (24/85) died during follow-up, potentially limiting long-term data reliability.
Low sensitivity for metal ions: Detection limits for molybdenum and other metals were not reported, possibly missing subtle increases.
Single implant system: Results may not generalize to other TKA designs or coatings.
Lack of randomization details: Demographics (e.g., age, sex) and baseline characteristics were not specified.
No mechanistic analysis: The study did not explore biological pathways for metal ion release or coating degradation.

Clinical Relevance

This study suggests that the multilayer-coated TKA implant does not lead to clinically relevant molybdenum release, supporting its safety for patients concerned about metal ion exposure from implants. However, the findings do not apply to dietary molybdenum supplementation, as the context is medical device biocompatibility, not nutritional intake. For implant recipients, the coating may reduce allergenic risks without compromising functional outcomes. Further research is needed to assess long-term coating integrity in larger cohorts.

Note: The study’s primary focus was implant safety, not molybdenum’s physiological effects. Supplement users should consult other trials evaluating molybdenum’s role in nutrition or detoxification.

Source: PubMed | Level of Evidence: I | Duration: 10 years