The unicompartmental knee replacement has established itself in modern orthopaedic surgery as a proven alternative to total knee replacement (TKR), particularly for isolated osteoarthritis of the knee joint. Nevertheless, numerous myths about alleged disadvantages of unicompartmental prostheses circulate in public perception and among patients. This blog examines the most common prejudices and refutes them with scientific facts. The aim is to comprehensively inform patients about unicompartmental knee replacement and its advantages as well as alleged disadvantages.

The sled prosthesis is often considered a minimally invasive alternative to total endoprosthesis (TEP), but many alleged disadvantages and myths surrounding this special prosthesis are widespread. This blog comprehensively clarifies the alleged disadvantages, provides a fact check, and examines what is actually scientifically founded.

If you are considering a unicompartmental knee arthroplasty or want to explore its benefits and potential risks, you are in the right place. Our careful analysis ensures that you can make an informed decision.

Introduction to the Sled Prosthesis

What is a sled prosthesis?

The sled prosthesis, also called a unicondylar knee prosthesis, is a partial prosthesis that replaces only one joint side (usually the inner or medial side) of the knee joint. It is used primarily when the joint wear is limited to one half of the joint.

Benefits of the partial knee replacement at a glance:

Preservation of healthy bone and cartilage structures.

Rapid rehabilitation and mobilization.

Less invasive than a total knee replacement (TKR).

The partial knee replacement is considered an ideal solution for patients who do not have extensive damage to ligaments and bones. Nevertheless, there are many prejudices that are repeatedly discussed.

Disadvantage Myth 1: "The unicompartmental knee arthroplasty does not last as long as a total knee arthroplasty."

The accusation:

A common disadvantage cited for the unicompartmental knee arthroplasty is its allegedly shorter durability compared to total knee arthroplasty. Critics argue that the mechanical stress is concentrated on a smaller area, leading to faster wear and tear.

The fact check:

Modern unicompartmental prostheses are made of extremely durable materials such as highly cross-linked polyethylene and high-quality metal. Studies have shown that the durability rate of unicompartmental prostheses can now be 20 to 30 years or more, which is comparable to the lifespan of total knee replacements in many cases. The key is proper patient selection and surgical technique.

In addition, the unicompartmental prosthesis offers the advantage that it can be easily replaced with a total knee replacement in the event of a revision, which means a less invasive procedure.

Disadvantage Myth 2: "A partial knee replacement always has to be replaced with a total knee replacement at some point."

The accusation:

Another widespread argument against unicompartmental knee arthroplasty is that it is only a temporary solution and will inevitably need to be replaced by a total knee replacement at some point.

The fact check:

This myth is not entirely correct. While there are cases where a switch to a total knee replacement is necessary, this depends on the individual diagnosis and the progression of osteoarthritis. For example, in cases of isolated medial meniscus damage, Ahlbäck's disease, or a congenital genu varum, unicompartmental knee replacements can be a permanent solution. Here, the osteoarthritis is limited to a single compartment of the knee, so that other areas of the joint can remain undamaged in the long term.

Modern surgical techniques and precise preoperative diagnoses contribute to the fact that sled prostheses do not necessarily lead to a total endoprosthesis. Patients often benefit from improved kinematics and faster rehabilitation. However, continuous follow-up care is important to identify and address potential problems early on.

Disadvantage Myth 3: "Unicompartmental knee replacements have a higher revision rate than total knee replacements."

The accusation:

Critics claim that the revision rate - i.e., the probability that the prosthesis needs to be replaced or corrected - is significantly higher for sled prostheses than for total endoprostheses.

The fact check:

It is correct that studies sometimes show higher revision rates for unicompartmental prostheses. However, this is often due to the selection of patients. The actual reasons for revisions range from mechanical complications to the progression of osteoarthritis in other joint areas. Unicompartmental prostheses require precise indication and very accurate implantation to ensure optimal results.

The main reason for the higher revision rate is that initially only a small part of the knee joint is replaced with a prosthesis and over the course of life, the arthritis can progress to other parts of the joint. If this is the case, there is still a chance to expand the prosthetic therapy to a total knee replacement. The threshold is lower for unicompartmental prostheses. If a total knee replacement causes problems, the threshold for deciding on a complete replacement of the prosthesis is significantly higher and is therefore less frequently made.

Advantages of unicompartmental knee replacement over total knee replacement

Beyond the myths, there are numerous documented advantages of unicompartmental knee replacement:

Shorter surgery time:

The reduced invasiveness enables a shorter operation duration.

Less blood loss:

Less tissue damage during surgery.

Faster rehabilitation:

Many patients are mobile again more quickly and regain a high quality of life.

Preservation of natural biomechanics: Healthy structures are preserved.

Better mobility:

A correctly implanted partial knee replacement allows most patients to have almost normal mobility. Many even return to sporting activities such as cycling, hiking, and swimming. Since only part of the knee is replaced, the natural movement pattern is preserved, which significantly improves functionality and subjective well-being.

Less foreign body sensation:

In addition, many patients report less foreign body sensation compared to a total endoprosthesis, as more natural joint structures are preserved.

For whom is the partial knee replacement suitable?

Patients who benefit from a unicompartmental knee replacement typically exhibit the following characteristics:

Limited osteoarthritis to one joint compartment.

Intact ligaments, especially cruciate and collateral ligaments.

No pronounced axial malalignments or systemic diseases.

An experienced orthopedist or endoprosthetics specialist can select the best treatment option through careful diagnosis and consultation.

Conclusion – What is really true?

Many myths surrounding unicompartmental knee arthroplasty are based on outdated information or misinterpretations. Modern medicine has significantly improved the technique and success rate of unicompartmental knee arthroplasty. With proper indication and expert implementation, unicompartmental knee arthroplasty is an excellent option for patients with limited osteoarthritis.

For an informed decision, a thorough consultation with a specialist is essential. Speak with an expert to determine if unicompartmental knee replacement is the right choice for you.

The unicompartmental knee arthroplasty is an excellent option for patients with isolated osteoarthritis in one knee compartment. Many of the perceived disadvantages are either exaggerated or simply incorrect upon closer inspection. The right patient selection, modern surgical techniques, and thorough aftercare are crucial for success. It is worth it for patients to receive individual counseling and carefully weigh the pros and cons before making a decision.