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Award-Winning Research Questions the Rationale of Nickel-Free Total Knee Arthroplasty

 

Charles M. Lawrie, MD
Orthopedic Surgeon

Baptist Health Miami Orthopedics & Sports Medicine Institute's Orthopedic surgeon, Charles M. Lawrie, MD, MSc, won the 2021 James A. Rand, MD Young Investigator’s Award presented at the 2021 Annual Meeting of the American Association of Hip and Knee Surgeons (AAHKS) on November 13, 2021, in Dallas. His research project entitled, “Questioning the ‘Nickel-Free’ Total Knee Arthroplasty,” was selected for the award from more than 1,000 submissions. The manuscript will be published in the Journal of Arthroplasty’s “Proceedings of AAHKS” in 2022. 

The study focused on the controversial topic of metal allergy or hypersensitivity reaction in total knee replacement failure. The study’s results demonstrate that nickel and chromium levels in the joint are elevated by the actual performance of TKA from instruments such as saw blades and cutting guides. This discovery calls into question the rationale of utilizing more expensive, hypoallergenic, lower-nickel content components based on a suspected nickel allergy.

The idea for the study came in 2018 during a TKA when Dr. Lawrie noted metal staining on some of the bones after doing cuts. “It occurred to me that interference between saw blades and cutting blocks may generate a large number of intraarticular metal ions during the actual procedure,” he said. “This could lead to high post-operative levels of metal ions in the knee joint.”

To Dr. Lawrie’s surprise, no study to date had quantified the metal content in knee replacements  performed with “nickel free” implants and standard instruments. Dr. Lawrie and his colleagues designed a study to determine post-operative intraarticular levels of nickel, cobalt and chromium generated during primary TKA performed with stainless steel cutting guides, saw blades and jigs. The two-cohort study included 40 patients and four orthopedic surgeons. 

Patients with self-reported or known nickel allergies had TKA performed with a nickel-sensitive implant (oxidized zirconium/titanium, or OxZr/Ti). Those without a known or reported nickel allergy had TKA performed with a non-hypoallergenic implant (cobalt-chromium, or Co-Cr). Fluid was sampled from the knee joint prior to opening the joint in surgery and on the morning after surgery. Researchers also conducted a wear analysis of a representative sample of six saw blades, using a scanning electron microscopy and an optical three-dimensional surface profiler.

Among their findings:

  •        The Co-Cr implant group had statistically higher levels of cobalt, chromium and nickel postoperatively compared to preoperatively.
  •        The OxZr/Ti patients had 9.5x significantly higher chromium and 5.1x higher nickel postoperatively versus preoperatively. As expected, the cobalt level was not significantly different after TKA due to the absence of cobalt in the components.
  •        Cutting blocks were the main source of the nickel, with 10x as much nickel as a standard Co-Cr femoral component.
  •        Performing a TKA with standard saw blades and cutting blocks dramatically releases metal ions (nickel and chromium) into the knee joint that are still present the following morning.

“This study shows significant levels of chromium and nickel ions are generated by the performance of total knee arthroplasty with standard instrumentation,” Dr. Lawrie said. “Cutting blocks, and to a lesser extent saw blades, appear to be the major sources of these metal ions. Therefore, the use of hypoallergenic implants does not mitigate this generation of metal debris into the knee joint. Furthermore, standard TKA implants contain less than 0.5% nickel, are polished and hardened, and articulate against plastic, and are therefore unlikely to represent a significant source of intraarticular nickel ions in the long term. Standard cutting blocks contain eight to ten times as much nickel as the standard TKA implants and liberate substantial micron and submicron size debris from abrasion by the harder saw blade. Our results indicate that the generation of metal ions, specifically nickel, during performance of TKA may be more significant than the nickel generated by a well-functioning TKA over time. This calls into question the rationale of using hypoallergenic implants, as the level of intraarticular metal ions on postoperative day one is elevated even with these implants.”

About Baptist Health Miami Orthopedics & Sports Medicine Institute

Miami Orthopedics & Sports Medicine Institute offers comprehensive services for athletes and non-athletes – from physical and cognitive evaluation to rehabilitation and surgical reconstruction. The Institute is the sports medicine provider for the Miami Dolphins, Miami HEAT, Florida Panthers, Florida International University athletics, Orange Bowl, Miami Open Tennis, Miami Marathon and Half Marathon and Miami-Dade County Public Schools.

Miami Orthopedics & Sports Medicine Institute is part of Baptist Health South Florida, the largest healthcare organization in the region, with 11 hospitals, more than 23,000 employees, 4,000 physicians and 100 outpatient centers, urgent care facilities and physician practices spanning across Miami-Dade, Monroe, Broward and Palm Beach counties. Baptist Health has internationally renowned centers of excellence in cancer, cardiovascular care, orthopedics and sports medicine, and neurosciences. In addition, it includes Baptist Health Medical Group; Baptist Health Quality Network; and Baptist Health Care On Demand, a virtual health platform. A not-for-profit organization supported by philanthropy and committed to its faith-based charitable mission of medical excellence, Baptist Health has been recognized by Fortune as one of the 100 Best Companies to Work For in America and by Ethisphere as one of the World’s Most Ethical Companies.