Knee Replacement: TiN Coating vs. No Coating? 10-Year Study

randomized-controlled-trial PMID: 32367201

Quick Summary: Researchers compared two types of knee replacements: one with a special titanium coating (TiN) and one without. After 10 years, both types worked equally well for pain relief, knee function, and the need for a second surgery.

What The Research Found

This study looked at how well different knee replacements held up over time. The study compared knee replacements made of a metal alloy called CoCrMo, some with a special titanium-nitride (TiN) coating and some without. The researchers found:

Pain Relief: Both types of knee replacements significantly reduced pain.

Knee Function: Both types improved how well people could move and use their knees.

Revision Rate: The need for a second surgery (revision) was about the same for both types of implants.

Study Details

Who was studied: 101 patients who needed a cementless knee replacement.

How long: The study followed patients for 10 years.

What they took: Patients received either a CoCrMo knee replacement with a TiN coating or a CoCrMo knee replacement without the coating.

What This Means For You

If you're considering a knee replacement, this study suggests that the type of coating on the implant might not matter much for your long-term outcome. Both coated and uncoated implants can provide good results in terms of pain relief and knee function. Talk to your doctor about the best option for you, considering factors like cost and your specific needs.

Study Limitations

Not everyone finished the study: Some people didn't complete the full 10 years, which could affect the results.

Small study size: The study wasn't huge, so it might have missed small differences between the two types of implants.

Lab vs. Real Life: The coating looked good in lab tests, but didn't make a big difference in the real world.

Location Matters: The study was done in the Netherlands, so results might be different in other places.

No Molybdenum Supplementation: This study is about the implant material, not about taking molybdenum supplements.

Key Findings

The study found no statistically significant differences in clinical outcomes between titanium-nitride (TiN)-coated and uncoated cobalt-chromium-molybdenum (CoCrMo) cementless mobile-bearing total knee arthroplasty (TKA) implants after 10 years. Both groups showed comparable improvements in pain (mean VAS score decrease: 31.6 ± 22.9), functional scores (Oxford Knee Score increase: 10.9 ± 8.4; Knee Society Score increase: 29.3 ± 31.4), and revision rates (coated: 6% vs. uncoated: 8%). No additional revisions occurred between 5- and 10-year follow-ups.

Study Design

This was a double-blinded, randomized controlled trial (RCT) with a 10-year follow-up period. A total of 101 patients received either TiN-coated or uncoated cementless CoCrMo mobile-bearing TKAs. Outcomes were assessed at 6 weeks, 6 months, 1 year, 5 years, and 10 years post-surgery. The study had a 67% follow-up rate (68 patients) at 10 years.

Dosage & Administration

The study did not involve dietary molybdenum or supplements. Instead, molybdenum was part of the CoCrMo alloy used in knee implants. TiN coating was applied to the implant surface to enhance biomechanical properties. The implants were cementless and mobile-bearing, administered via surgical implantation.

Results & Efficacy

Both groups demonstrated significant improvements from baseline to 10-year follow-up in pain and functional scores (p values not explicitly reported in the summary). However, no intergroup differences were observed:
- VAS pain: Mean decrease of 31.6 (SD ±22.9) overall.
- Oxford Knee Score (OKS): Mean increase of 10.9 (±8.4).
- Knee Society Score (KSS): Mean increase of 29.3 (±31.4).
- Revision rate: 7% overall (coated: 6% vs. uncoated: 8%).
- Adverse events: Similar rates between groups.

The lack of statistical differences suggests TiN coating did not enhance clinical efficacy beyond the uncoated CoCrMo implant.

Limitations

Follow-up attrition: Only 68/101 patients (67%) completed the 10-year assessment, risking selection bias.
Power limitations: Small sample size may have reduced ability to detect minor differences in outcomes.
In vitro vs. clinical discrepancy: TiN coating showed benefits in lab settings but not in real-world clinical performance.
Geographic specificity: Conducted in the Netherlands (trial register: NL2887/NTR3033), limiting generalizability.
Lack of mechanistic data: No analysis of wear debris or biological responses to the implant materials.

Clinical Relevance

For patients and surgeons, this study indicates that TiN coating on CoCrMo cementless knee implants does not confer additional clinical benefits over uncoated implants in terms of pain, function, or revision risk at 10 years. Both implant types demonstrated durable, comparable outcomes, suggesting that TiN coating may not justify added costs or complexity in TKA procedures. The results support the continued use of standard CoCrMo implants for long-term reliability, though further research is needed to validate findings in larger, more diverse populations.

Note: This study focuses on molybdenum as part of an implant alloy, not as a nutritional supplement. Findings are specific to orthopedic surgical outcomes, not systemic molybdenum supplementation.