Knee osteoarthritis and other advanced knee problems often lead to severe pain and limited mobility. When conservative treatments (physiotherapy, medication, injections, etc.) are no longer sufficient, a knee replacement often considered. There are various types of knee replacements – from total knee replacement to partial knee replacement (e.g., unicompartmental knee arthroplasty ), in which only part of the knee joint is replaced.

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

This article explains how a knee replacement can work in cases of nickel allergy, what materials are available, and how a specialist like Prof. Kutzner at the Endoprotheticum Rhein-Main in Mainz can help.

What is a knee prosthesis?

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

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

The following are important:

• 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 sliding surface (metal-plastic etc.).

Partial joint replacement and unicompartmental knee replacement – ​​definitions & differences

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

• Unicompartmental (inner or outer) partial knee replacement / unicompartmental knee replacement : only part of the knee joint surface (inner or outer) is replaced.
• Patellofemoral partial joint replacement : Replacement of the gliding surface between the kneecap and thighbone.

A partial knee replacement is a special type of knee replacement in which a component called a "slide" is implanted that 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 replacements

What is a nickel allergy?

• Contact allergy to nickel (frequent 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 those under the age of approximately 40-50, often have higher sensitization rates.
• In patients with knee replacements: Surveys in Germany showed that in many cases of known allergies to nickel or cobalt, allergy implants are already being used (e.g., 84% of the orthopedic surgeons surveyed in cases of known allergies).

How relevant is nickel allergy in knee replacements?

• There are case reports in which patients with a partial knee replacement (unicondylar partial prosthesis) or knee prosthesis had persistent symptoms, demonstrably caused by nickel allergy.
• Symptoms may include: pain, swelling, joint effusion, dermatitis, delayed wound healing, and possibly implant loosening.
• However, not everyone with a skin nickel allergy will react to an implant – the system is complex, as bone tissue and the surrounding area react differently than skin.

Research & surveys on nickel allergy

• As mentioned, a survey in Germany found that many orthopedic surgeons use special allergy implants for patients with known allergies.
• Studies and case reports show 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 common in a certain percentage of the population.
• There are case reports in which complaints occur after knee replacement surgery that have been attributed to an allergy.
• In certain patients, the use of low-nickel or coated/covered implants can lead to symptom relief.

What is not yet fully secured:

• How often a knee prosthesis needs to be revised due to a nickel allergy.
• Can skin allergies reliably predict 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 Working Group for Endoprosthetics (Germany): In planned prostheses with a known allergy to nickel or cobalt, approximately 84% of surgeons use a so-called "allergy implant".
• However, according to this survey, the proportion of patients who experience problems due to a metal allergy after receiving a knee prosthesis is significantly lower (e.g., 1.1% of knee endoprostheses in 2009).

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

If someone has a nickel allergy, or if you want to rule this out, there are several strategies and materials available:

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 titanium-based
• Important to check: Even titanium-based implants can contain traces of other metals, depending on the manufacturer and alloy.

Oxinium / Zirconium alloys

• Some clinics use prostheses made from materials such as an oxinium alloy (zirconium/niobium) or with surface technologies that have extremely low nickel content. For example, the Freiburg Clinic uses materials with very low nickel and chromium content for its mono- and bipartite dentures: nickel < 0.0035%, chromium < 0.02%.

Surface coatings / sealants / coatings

• Coatings with titanium or titanium oxide, ceramics, gold plating, etc., which can form a barrier between tissue and base metal.
• Some “allergy-friendly dentures” use, for example, titanium coatings to avoid contact with nickel.

Low-nickel stainless steels & special alloys

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

Availability and limitations

• Not every hospital/manufacturer offers nickel-free implants as standard.
• The costs may be higher, and permits and documentation are more complex.
• Long-term data is sometimes not as comprehensive as for standard implants.

Diagnostics: How can a nickel allergy be detected before and after implantation?

Medical history

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

Allergy testing procedures

• Epicutaneous test (patch test) for skin contact allergy.
• Lymphocyte transformation test (LTT) – tests the response of immune cells to metal ions.
• Histological examination (e.g., in revision surgeries), tissue samples.

Imaging and laboratory diagnostics

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

Timing of diagnosis

• Ideally, this should be done before the operation if an allergy is known or suspected.
• If problems arise after implantation, act quickly: rule out mechanical problems, inflammation, infections, and then consider allergies.

Treatment options & surgical planning for nickel allergy

Before the operation

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

Intraoperative

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

After the operation

• Pain therapy, physiotherapy, mobilization.
• Watch for complications: swelling, redness, increased irritability.
• If symptoms occur, further testing for allergies is necessary, and revision may be required.

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

Prof. Dr. Karl Philipp Kutzner is a specialist in orthopedics and trauma surgery, with a focus on hip and knee replacement. The Endoprostheticum Rhein-Main in Mainz is a specialized facility that focuses particularly on joint replacement and joint surgery , with extensive experience in unicompartmental knee replacement, partial joint replacement, and customized, minimally invasive procedures. endoprotheticum.de

Advantages:

• Specialized practice with a high volume of cases → good routine.
• Expertise in unicompartmental joint replacement (e.g., "unicompartmental joint replacement and partial joint 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 replacement if I have a nickel allergy?
Answer: Yes – many patients with nickel allergies receive knee replacements, and with appropriate material selection (low nickel, titanium-coated, etc.), allergic reactions can be minimized.

Question: Is a partial knee replacement always possible?
Answer: Not always – it is only advisable 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 information from the manufacturer. Completely "100% nickel-free" is often difficult to achieve, as trace amounts may be present, but modern solutions come very close.

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

Conclusion: Nickel allergy is usually not a catastrophe

• Nickel allergy is an important issue with knee prostheses, especially with standard implants containing alloys that contain nickel.
• Partial knee replacement and unicompartmental knee replacement are particularly attractive options for people with nickel allergies – less metal, faster recovery, more natural knee feel.
• Modern implant materials such as titanium-based or titanium-coated, oxinium/zirconium alloys and specially coated allergy prostheses offer sensible ways to minimize the risks.
• Careful diagnostics before and after the operation are essential: allergy test, imaging, medical history.
• An experienced knee specialist with expertise in knee endoprosthetics, such as Prof. Kutzner at the Endoprotheticum Rhein-Main in Mainz, offers ideal conditions for selecting the right implant and for safely performing the operation.