History

MicroHip is a minimally invasive technique of total hip replacement surgery developed by Doctors Markus C. Michel and Pierre Witschger of the OZM Orthopaedic Centre in Münsingen. As the name would imply, minimally invasive is the least intrusive way to perform the surgery.

We are often asked how it is possible to perform hip replacement surgery through such a small incision and why the method wasn't used years ago.

"The history of MicroHip begins with an anecdote", says Dr. Markus C. Michel: My first mentor was the world-renowned surgeon Dr. Maurice E. Müller, one of the key pioneers in the development of modern hip surgery. One day, he showed us his new approach to the hip joint for hip surgery—the transgluteal approach. This novel approach required the cutting of much fewer tendons than other approaches used at that time. "Great!", I said, then a young assistant, "But wouldn't it be much better if you didn't have to cut any muscles and tendons at all? That always causes permanent damage".

The great mentor smiled at me patiently and answered: "Better, yes, but unfortunately impossible."

However, the thought never left me. After I finished my initial Orthopaedic Specialist training and had gained more experience in performing hip surgery, I soon realised that most postoperative complications were not related to the hip implant itself, but rather to the tendons and muscles. That rekindled my interest.

If you read up on the history of hip replacement surgery, you will soon discover that hip implants were not developed primarily to restore the function of the hip joint, but rather, to alleviate the pain of arthritis. Anyone who suffers from the pain of hip arthritis knows what I'm talking about: The hip pain can sometimes be so terrible that nothing else matters! Since hip joint function was secondary to the developers of hip replacement surgery, the tendons and muscles were also secondary.

"If only the pain would go away, then it would certainly be nice to be able to do a bit of walking ..." Back in those days, no one dreamed of doing sports or strenuous work after hip replacement surgery.

The situation today is completely different. Now, patients expect that a good hip implant will allow them to do EVERYTHING they could do before. Therefore, the preservation of tendons and muscles is extremely important. You could say: What good is the most beautiful Ferrari without an engine? One of our patients even made a film showing that people who undergo hip replacement surgery today can return to sports or even climb the North Face of the Eiger (Johann Eiger film).

Our project for development of the most tissue-sparing hip replacement procedure possible, that is, to develop a procedure using a truly minimally invasive approach to the hip joint, was launched in 1998. As is always the case in such a research project, our first task was to study the international literature on hip implant surgery. In this regard, we Swiss have a great linguistic advantage: We can not only read all the literature in English, but also have no problem understanding the articles in German and French. This was a tremendous advantage in our research. However, our research soon revealed that, of all of the more recent publications available on the Internet, hardly any contained any major stimulus for new surgical approaches. We had to resort to the original literature, some of which dates back to the beginning of the 20th century and, of course, was not available in English. We had to order copies of the original articles from large international libraries.

After reading several hundred articles, what we learned was astonishing. The standard approaches used to the hip in German and English-speaking countries started on the side of the hip (lateral approach) or back of the hip (posterior approach).

The problem with all posterior approaches is that the gluteus maximus (largest muscle of the buttocks) must be cut and that at least some fibres of the lesser rotator muscles, which are important for fine control of hip movement, must be detached. In addition, all posterior approaches have a high risk of hip dislocation.

All of the lateral approaches, on the other hand, go through the muscles that stabilize the pelvis (the abductor muscles). When these approaches are used, there is a risk of damaging muscles and tendons, which could result in variably severe and permanent limping.

Specifically, this means that a posterior approach results in a 20% loss of muscle strength for outward rotation, and the lateral approach results in a significant and often painful loss of abductor muscle strength in more than 80% of cases.

Things got interesting in the French literature, where several references were made to anterior (front) approaches to the hip joint. Some of the problems involved are described in "MicroHip – Technique".

We then proceeded to the Step 2 of the project: I travelled around the world to see surgeons and take a closer look at their techniques of hip joint replacement.

The most interesting procedure I had seen at that time was that of Jean-Pierre Vidalin in Annecy. However, his technique had two main problems: First, it posed a severe risk to a nerve (the superior branch of the superior gluteus nerve). Secondly, the patient positioning procedure was rather complicated: A surgical nurse had to sit on the floor during the entire operation to hold the patient's leg in position. Surgical staff who like to sit on the floor for hours are definitely hard to find!

However, we were sure that any "new" approach had to be anterior approach because entering the hip from the front caused the least damage to tendons and muscles.

Step 3 consisted of anatomic research—first, in anatomic atlases and, afterwards, during many nights at the Anatomic Institute. This enabled us to see even the finest and most discrete anatomic structures, some of which are not even mentioned in an anatomic atlas.

After a while, we focused mainly on the Smith-Peterson approach—the only way to reach the hip joint via an internervous plane, that is, an area with no nerve fibres crossing through it. The use of an internervous plane means that there is no risk of damaging small but important nerve fibres during surgery.