The surface replacement at the hip (capping prosthesis, hip cap, McMinn, resurfacing) was considered a promising method for a long time, which was intended to offer an alternative to the classic total hip replacement, particularly for younger and active patients. So far, this type of implant has not been able to assert itself due to many significant complications.

In recent years, the approach has been brought back into focus through modern materials such as ceramic. However, despite the potential, significant challenges continue to arise that should not be overlooked. In this blog, we take a comprehensive look at the principle of surface replacement, discuss experiences and complications from the past, and analyze what speaks against current use with ceramic materials. We also highlight the disadvantages of the more invasive surgical technique compared to modern minimally invasive approaches and present the short stem prosthesis as a progressive alternative.

What is hip resurfacing?

Functionality and objectives

In surface replacement (resurfacing), the entire femoral head is not removed, as is the case with a total hip replacement. Instead, the damaged surface of the femoral head is ground down and covered with a cap made of metal or ceramic. The acetabular component (hip socket) is also provided with an inlay.

Target group for hip resurfacing

Originally, the method was developed for younger patients with a good bone structure who are exposed to high physical stress and wanted to optimise the lifespan of a hip prosthesis. The greatest advantage was seen in preserving as much natural bone material as possible.

Difference to short stem

The short stem, on the other hand, not only replaces the femoral head but also a part of the femoral shaft. Nevertheless, more bone remains than with a conventional prosthesis, and the implantation can be performed minimally invasively, for example, via an AMIS or ALMIS approach.

Retrospective on surface replacement: Experiences from the past

Failure of metallic surface replacements

The first generation of hip resurfacing implants failed on several fronts. In particular, metallic materials had significant disadvantages:

Abrasion particles and metal ions: Metal-metal pairings led to increased metal ion concentrations in the blood. These particles caused inflammatory reactions and tissue damage.

Higher revision rate: In comparison to hip TEP, surface replacements had to be revised more frequently due to complications.

Technically demanding: The correct placement of the implants was complex and prone to errors.

Image loss and current developments

The disproportionate number of complications led to the fact that surface replacement almost completely disappeared from the market. Meanwhile, a revival is being sought through the use of new materials like ceramic. Nevertheless, skepticism remains.

New approaches to surface replacement with ceramic – can it work?

Advantages of ceramic as a material

Ceramic materials have excellent properties:

High biocompatibility: Ceramic does not cause toxic reactions.

Minimal wear: In comparison to metal, significantly less wear occurs.

Long durability: Ceramic surfaces are extremely robust and wear-resistant.

Current limitations

Despite the advantages, there are significant problems:

Lack of long-term data: There are still no reliable medium-term or long-term studies on ceramic surface prostheses.

Mechanical challenges: Ceramic is more brittle than metal, which increases the risk of fractures or material failure.

Cost factor: The production and processing of ceramics are complex and expensive.

The surgical technique of surface replacement:

A step backward in minimally invasive surgery

Comparison of surface replacement vs. minimally invasive techniques

The surgical technique of hip resurfacing requires a significantly more invasive approach compared to modern minimally invasive methods such as the ALMIS or AMIS access. This is due, among other things, to the necessary complete exposure of the femoral head and the acetabulum in order to be able to precisely implant the special surface components. A particularly stressful measure in this context is the surgical dislocation, i.e. the targeted dislocation of the natural femoral head. This step is absolutely necessary in order to gain access to the entire joint surface and to enable the preparation for the application of the new joint surface.

However, the dislocation of the femoral head requires extensive manipulation and stretching of soft tissues and muscles. In particular, the external rotator musculature as well as sensitive structures such as the hip joint capsule tissue and nearby nerves can be stressed or even damaged. This increases the risk of postoperative complications such as instability, pain, or loss of function. In addition, the rehabilitation process is often delayed because the muscles and soft tissues require a longer healing time.

In comparison, minimally invasive approaches such as ALMIS and AMIS are significantly gentler, as they do not require dislocation of the femoral head and largely preserve the integral structures of the hip joint. The less invasive technique results in faster mobilization and less postoperative pain, making it the preferred choice in modern endoprosthetics. This shows that surface replacement represents a significant step backward in terms of surgical technique and the potential advantage of preserving the femoral head is often relativized by these more invasive measures.

Why minimally invasive?

Minimally invasive approaches offer:

Faster rehabilitation

Less blood loss

Less postoperative pain

Lower risk of infection

Alternatives to surface replacement: The short stem prosthesis

The short stem prosthesis represents a modern and patient-friendly alternative to surface replacement and is increasingly preferred in hip arthroplasty. In contrast to surface replacement, in which the femoral head is preserved and only its surface is replaced, the short stem prosthesis is characterized by the partial removal of the damaged femoral head, with a short prosthesis stem being introduced into the femur. This technique enables an anatomical reconstruction of the hip joint while preserving a large part of the natural bone substance.

A key advantage of the short stem prosthesis is the possibility of using minimally invasive approaches such as the ALMIS or AMIS method. These approaches are significantly more tissue-friendly, as no complete exposure of the hip joint or dislocation of the femoral head is required. This leads to less tissue trauma, faster mobilisation and a reduced risk of postoperative complications.

The biomechanical properties of the short-stem prosthesis also enable physiological force transmission through the femur, ensuring optimal stability and minimizing the risk of implant failure. In addition, modern short-stem designs offer high adaptability, making them suitable for both younger, active patients and older patients.

Comparing the short stem prosthesis with the surface replacement, it becomes apparent that it is not only less invasive, but also able to demonstrate long-term proven results. While uncertainties regarding new material combinations such as ceramic continue to exist with surface replacement, the short stem prosthesis offers established and proven solutions. These factors make it a clear recommendation in modern endoprosthetics and a sensible alternative for patients who value gentle treatment and rapid recovery.

Advantages of the short stem

The short stem prosthesis has established itself as a popular alternative in modern endoprosthetics. Its advantages are manifold:

Tissue preservation: Minimally invasive approaches preserve the surrounding tissue.

Longer durability: The short stem is ideal for younger patients with a high activity level.

Preservation of bone substance: Compared to a total endoprosthesis, more natural bone substrate is preserved.

Flexibility in revisions: If a revision surgery is necessary, the options are more comprehensive.

Short Stem vs. Surface Replacement

Biological Compatibility: Short stem prostheses are proven and offer low complication rates.

Surgical Method: The implantation perfectly matches minimally invasive approaches.

Long-term data: Established long-term results exist for short stem prostheses.



Conclusion: Why ceramic surface replacement is currently viewed critically

The ceramic surface replacement at the hip may seem like an innovative idea at first glance, but in practice, it shows significant limitations. The more invasive surgical technique means longer healing phases and higher risks for patients. The new material choice offers theoretical advantages, but so far, there are no reliable long-term studies to truly assess safety and efficiency. In comparison, the short stem prosthesis represents a proven, minimally invasive, and long-lasting solution that is the optimal choice for many patients. Until reliable data on ceramic surface prostheses are available, this method remains primarily one thing: an idea with an uncertain future.