Hip resurfacing (cap prosthesis, hip cap, McMinn, resurfacing) has long been considered a promising method that should offer an alternative to the classic total hip endoprosthesis, especially for younger and active patients. So far, this type of implant has not been able to establish itself due to many serious complications.

In recent years, modern materials such as ceramics have brought the approach back into focus. But despite the potential, there are still serious challenges 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 the current use of ceramic materials. We also highlight the disadvantages of the more invasive surgical technique compared to modern minimally invasive approaches and present the short-shaft prosthesis as a progressive alternative.

What is hip resurfacing?

Functionality and objectives

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

Target group of resurfacing

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

Difference to short shaft

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

Review of resurfacing: past experiences

Failure of metallic surface replacements

The first generation of resurfacing failed on several fronts. Metallic materials in particular had significant disadvantages:

Wear 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: Compared to THA, surface replacements had to be revised more frequently due to complications.

Technically demanding: Correct placement of the implants was complex and error-prone.

Loss of image and current developments

The disproportionate number of complications led to surface replacement almost completely disappearing from the market. A revival is now being sought through the use of new materials such as ceramics. Nevertheless, skepticism remains.

New approaches to surface replacement with ceramics – can that work?

Advantages of ceramic as a material

Ceramic materials have excellent properties:

High biocompatibility: Ceramic does not cause toxic reactions.

Minimal abrasion: Significantly less abrasion occurs compared to metal.

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

Current restrictions

Despite the advantages, there are serious problems:

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

Mechanical challenges: Ceramics are more brittle than metal, increasing the risk of fractures or material failure.

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

The surgical technique of surface replacement:

A step backwards in minimally invasive surgery

Comparison of resurfacing vs. minimally invasive techniques

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

However, dislocation of the femoral head requires extensive manipulation and stretching of soft tissues and muscles. In particular, the outer rotator muscles 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 much gentler because they do not dislocate the femoral head and largely preserve the integral structures of the hip joint. The less invasive technique ensures faster mobilization and less postoperative pain, making it the preferred choice, especially in modern endoprosthetics. This shows that surface replacement represents a significant step backwards in terms of surgical technique and the potential advantage of preserving the femoral head is often put into perspective by these more invasive measures.

Why minimally invasive?

Minimally invasive approaches offer:

Faster rehabilitation

Lower blood loss

Less postoperative pain

Lower risks of infection

Alternatives to surface replacement: The short-shaft prosthesis

The short-shaft 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 left in place and only its surface is replaced, the short-shaft prosthesis is characterized by the partial removal of the damaged femoral head, with a short prosthetic shaft being inserted into the femur. This technique enables anatomical reconstruction of the hip joint while preserving a large part of the natural bone substance.

A decisive advantage of the short-shaft prosthesis is the possibility of using minimally invasive approaches such as the ALMIS or AMIS method. These approaches are significantly gentler on the soft tissue because they do not require complete exposure of the hip joint or dislocation of the femoral head. This results in less tissue trauma, faster mobilization 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 to suit both younger, active patients and older patients.

If you compare the short-shaft prosthesis with the surface replacement, you will notice that it is not only less invasive, but also has long-term proven results. While there are still uncertainties regarding new material combinations such as ceramics when it comes to surface replacement, the short-shaft prosthesis offers established and proven solutions. These factors make them a clear recommendation in modern endoprosthetics and a sensible alternative for patients who value gentle treatment and a quick recovery.

Advantages of the short shaft

The short-shaft prosthesis has established itself as a popular alternative in modern endoprosthetics. Your advantages are diverse:

Soft tissue protection: Minimally invasive approaches protect the surrounding tissue.

Longer durability: The short shaft 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 for revisions: If revision surgery is necessary, the options are more extensive.

Short stem vs. resurfacing

Biological compatibility: Short-shaft prostheses have been tried and tested and offer low complication rates.

Surgical method: The implantation fits perfectly with minimally invasive approaches.

Long-term data: There are established long-term results for short-shaft prostheses.



Conclusion: Why ceramic surface replacement is currently viewed critically

Ceramic hip resurfacing may seem like an innovative idea at first glance, but practice shows significant limitations. The more invasive surgical technique means longer healing phases and higher risks for patients. The new choice of material offers theoretical advantages, but so far there is a lack of reliable long-term studies to really assess safety and efficiency. In comparison, the short-shaft prosthesis is a tried-and-tested, 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 one thing above all: an idea with an uncertain future.