Knee osteoarthritis and other advanced knee problems often lead to severe pain and functional limitations. If conservative measures (physiotherapy, medication, injections, etc.) are no longer sufficient, a knee prosthesis is often considered. There are various forms - from total joint replacement to partial joint replacement (e.g., sledge prosthesis), in which only part of the knee joint is replaced.

For people with a nickel allergy the important question arises: How safe and tolerable are the implant materials? Because many standard implants contain nickel components, and allergic reactions are possible. This is where the idea of nickel-free or low-nickel implants or surface coatings comes into play.

In this article, you will learn how a knee replacement can work with nickel allergy, what materials are available, and how a specialist like Prof. Kutzner at Endoprotheticum Rhein-Main in Mainz can help.

What is a knee replacement?

A knee prosthesis replaces damaged or worn-out joint surfaces in the knee. Depending on the extent of osteoarthritis or damage, there are:

• Total knee arthroplasty (total joint replacement): The entire joint (all compartments) is replaced.
• Partial joint replacement: Only a part of the knee joint is replaced, e.g. an inner or outer area.
• Sled prosthesis (unicondylar replacement, inner or outer sled): Variant of partial joint replacement, in which only one side (inner or outer compartment) is replaced.

Important in this context:

• Preservation of as many natural structures as possible, such as ligaments (e.g., cruciate ligaments), healthy cartilage areas, etc.
• Optimal fit and alignment of the implant.
• Biocompatible materials, good gliding surface (metal-plastic, etc.).

Partial joint replacement and sled prosthesis – definitions & differences

Partial joint replacement generally refers to the replacement of only individual compartments in the knee. The most common forms:

• Unicompartmental (inner or outer) partial joint replacement / sled prosthesis: only one part of the knee joint surface (medially or laterally) is replaced.
• Patellofemoral partial joint replacement: Replacement of the sliding surface between the kneecap and thigh.

Sledge prosthesis is a special form of partial joint replacement, in which a component called a 'sledge' is used, which glides on one side of the joint between the thigh and lower leg. Advantages:

• Less bone removal
• Preservation of cruciate ligaments and other stabilizing structures
• Faster rehabilitation
• More natural knee kinematics

Nickel allergy: Causes, frequency, relevance in knee prostheses

What is nickel allergy?

• Contact allergy to nickel (common skin contact, jewelry, watches, etc.).
• Recognizable by redness, eczema, itching upon skin contact.
• Immunological reaction: Sensitization of the immune system to nickel ions.

Frequency of nickel allergy

• Relatively common in the general population.
• Studies show that women, especially before the age of around 40-50 years, often have higher sensitization rates.
• In patients with knee prosthesis: Surveys in Germany have shown that, in cases of known allergies to nickel or cobalt, allergy implants are already being used in many cases (e.g., 84% of surveyed orthopedists in cases of known allergies).

How relevant is nickel allergy in knee replacements?

• There are case reports in which patients with unicompartmental knee arthroplasty (unicondylar partial prosthesis) or knee prosthesis had persistent complaints, demonstrably caused by nickel allergy.
• Symptoms can include: pain, swelling, joint effusions, dermatitis, delayed wound healing, possibly implant loosening.
• However, not everyone with a nickel allergy reacts to an implant - the system is complex because bone tissue and the surrounding area react differently than skin.

Research & surveys on nickel allergy

• As mentioned, survey in Germany: For known allergies, many orthopedic surgeons use special allergy implants.
• Studies and case reports have shown that implant revision with low-nickel or titanium-based (nickel-free) endoprostheses has led to improvement in some cases.

Controversy and findings: How relevant is the problem of nickel allergy?

What is certain, what is still open

What is certain:

• Nickel allergy exists and is prevalent in a certain proportion of the population.
• There are case reports in which complaints occur after a knee replacement, which were attributed to an allergy.
• In certain patients, the use of nickel-reduced or coated/covered implants can lead to symptom relief.

What is not yet fully confirmed:

• How often a knee prosthesis needs to be revised due to a nickel allergy.
• Whether skin allergy reliably predicts how strongly the immune system reacts in deep tissue and bone.
• Long-term data on the durability and function of allergy implants vs. standard implants are limited.

Data & Surveys

• Survey among members of the Endoprothetik Working Group (Germany): For planned prostheses with known allergy to nickel or cobalt, approximately 84% of surgeons use a so-called "allergy implant".
• However, the proportion of patients who have complaints due to metal allergy with a knee prosthesis is significantly lower according to this survey (e.g., 1.1% of knee arthroplasties in 2009).

Materials & implant variants: nickel-free or low-nickel solutions

If someone has a nickel allergy or wants to rule it out, there are several strategies and materials:

Titanium-based and titanium-coated implants

• Titanium is generally very biocompatible, has low allergenic potential, and can be used in pure form or as a coating.
• Example: Case reports in which a prosthesis was replaced with a titanium-based implant - complaints disappeared.
• Important to check: Even titanium-based implants can contain traces of other metals, depending on the manufacturer and alloy.

Oxinium/Zirconium alloys

• In some clinics, prostheses are used that are made of an Oxinium alloy (Zirconium/Niobium) or have surface technologies with extremely low nickel content. Example: Freiburg Clinic uses materials with very low nickel and chromium content for mono- and double-slider prostheses: Nickel < 0.0035%, Chromium < 0.02%.

Surface coatings / sealings / coatings

• Coatings with titanium or titanium oxide, ceramic, gold coatings, etc., which can act as a barrier between tissue and base metal.
• Some "allergy prostheses" use titanium coatings, for example, to avoid nickel contact.

Low-nickel stainless steels & special alloys

• Stainless steels in prostheses often contain nickel, but there are special alloys with very low nickel content or special treatments that significantly reduce the release of nickel.

Availability and limitations

• Not every hospital/manufacturer offers nickel-free implants as standard.
• The costs can be higher, approvals and documentation are more complex.
• Long-term data are partially not as comprehensive as with standard implants.

Diagnostics: How to detect nickel allergy before and after implantation?

Medical history

• Questions like: Have you ever had eczema after contact with jewelry? Do you react to contact with metals?

Allergological test procedures

• Patch Test for skin contact allergy.
• Lymphocyte transformation test (LTT) – tests the reaction of immune cells to metal ions.
• Histological examination (e.g. during revision operations), tissue samples.

Imaging and laboratory chemical diagnostics

• Exclusion of infections (CRP, ESR, possibly joint aspirate).
• X-ray, scintigraphy, possibly CT or MRI to localize loosening or metal abrasion.
• Monitoring for signs of hypersensitivity reactions: swelling, persistent pain, irritation.

Timing of diagnostics

• Ideally before surgery, if an allergy is known or suspected.
• If complaints occur after implantation, act quickly: rule out mechanical problems, inflammation, infections, and then consider allergy.

Treatment options & surgical planning for nickel allergy

Before surgery

• Allergy testing: Patch test, LTT, detailed medical history.
• Material selection: Discuss with the surgeon which prostheses are offered, which manufacturers have "nickel-free" or very low-nickel implants. Ask about alloy data, coatings.
• Counseling on partial joint replacement vs. total prosthesis: If possible, choose partial joint replacement / sliding prosthesis.

Intraoperative

• Careful selection and documentation of the implant type and material.
• Minimal trauma, shortest possible operation duration, good soft tissue management.

After the operation

• Pain therapy, physiotherapy, mobilization.
• Monitoring for complications: swelling, redness, increased irritability.
• If symptoms occur, re-evaluation for allergy, possibly revision.

Why a knee specialist like Prof. Kutzner / Endoprotheticum Rhein-Main in Mainz

Prof. Dr. med. Karl Philipp Kutzner is a specialist in orthopedic and trauma surgery, specializing in hip and knee arthroplasty. The Endoprotheticum Rhein-Main in Mainz is a specialized institution focusing on joint replacement and joint surgery , with extensive experience in unicompartmental knee arthroplasty, partial joint replacement, and individualized minimally invasive care. endoprotheticum.de

Benefits:

• Specialized practice with high case volume → good routine.
• Expertise in unicompartmental knee arthroplasty / partial knee replacement. (e.g. "unicompartmental knee arthroplasty and partial knee replacement" is part of Prof. Kutzner's surgical spectrum.) endoprotheticum.de
• Possible consultation on allergy implants / special alloys, material selection, etc.
• Good selection of implants and high-quality technical equipment.

Frequently Asked Questions (FAQ)

Question: Can I get a knee prosthesis with a nickel allergy?
Answer: Yes - many patients with nickel allergy receive knee prostheses, and with appropriate material selection (low-nickel, titanium-coated, etc.), allergic reactions can be minimized.

Question: Is a sliding prosthesis always possible?
Answer: Not always - it only makes sense if only one compartment is affected, the ligament structures are intact, and there are no severe deformities.

Question: How "nickel-free" are nickel-free implants really?
Answer: There are low-nickel alloys and implants with very low nickel content (e.g. < 0.0035 %), titanium coatings or titanium-based complete solutions. It is important to obtain manufacturer information. Completely "100 % nickel-free" is often difficult, as traces can occur, but modern solutions are very close.

Question: Do I have to choose a total prosthesis instead of partial joint replacement because of my allergy?
Answer: No, on the contrary - often partial joint replacement is a better choice due to the lower metal load, provided the prerequisites are met.

Conclusion: Nickel allergy is usually not a catastrophe

• A nickel allergy is an important issue with knee prostheses, especially with standard implants containing nickel alloys.
• Partial joint replacement and sledge prosthesis are particularly attractive options for people with nickel allergy - less metal, faster recovery, more natural knee feeling.
• Modern implant materials such as titanium-based or titanium-coated, oxinium/zirconium alloys, and specially coated allergy prostheses offer meaningful ways to minimize risks.
• A thorough diagnosis before and after the operation is essential: allergy test, imaging, anamnesis.
• An experienced knee specialist with a specialization in knee arthroplasty, such as Prof. Kutzner at Endoprotheticum Rhein-Main in Mainz, offers ideal conditions for selecting the right implant and safely performing the operation.