AMIS technology

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In medicine, the AMIS technology describes a special, minimally invasive approach to the hip joint in order to use artificial hip joints ( hip prosthesis ) with particular care. AMIS stands for Anterior Minimally Invasive Surgery to German minimally invasive surgical technique , the "anterior" stands for "front". The special features are on the one hand access to the hip joint from the front through the so-called Hueter interval , on the other hand the use of special instruments and a special leg holder, with the aim of enabling the safest and most gentle surgical technique possible.

anatomy

In principle, the hip joint can be reached from all directions via surgical access. The so-called Hueter interval (according to Carl Hueter ) represents an access route in which the hip joint is reached from the front (synonyms: direct anterior access , Smith-Petersen access ). This muscle interval is used in the AMIS technique and other anterior approaches such as the "direct anterior approach" (DAA). The anterior access route to the hip joint is anatomically the only access to the hip joint that runs both intermuscularly ("between muscles") and internerval ("between nerves"). This means that individual muscles do not have to be severed, nor do motor nerves cross the surgical area. The hip joint is the deepest large joint in the body and is surrounded by muscles. In the anterior approach via the Hueter interval, the M. tensor fasciae latae is held away to the side (laterally), the M. sartorius and the M. rectus femoris are held away to the middle (medial). All of the adjacent muscles are long and run from the pelvic bone to the middle thigh or knee joint. The length of the muscles means that they can be held apart with little tension, which minimizes the risk of muscle damage in AMIS. The important laterally lying muscle group ( M. gluteus medius and M. gluteus minimus ) is completely supplied by the gluteal nerves, which also run laterally. The central muscle group is supplied by the central femoral nerve . This means that no nerve - which is responsible for the function of a muscle - crosses the operating area.

history

The Hueter interval is traced back to Carl Hueter , who described the access route for operations on the hip joint as early as 1870. In the end, it was the Judet brothers who used the anterior access to the hip joint for the implantation of artificial hip joints. Henri Judet designed a special operating table for this purpose , with which a better overview was achieved. This table was then further developed by other orthopedic surgeons, such as the well-known Parisian orthopedist Émile Letournel . In the early years of hip arthroplasty, Letournel developed the first surgical technique that made it possible to insert hip prostheses without removing or cutting into muscles. In the end, it was Frédéric Laude , a student of Letournel and an orthopedic surgeon in Paris, who further refined both the surgical technique and the design of the instruments and the operating table with colleagues and made a significant contribution to today's AMIS technology.

Surgical technology

The operation is performed in the supine position on an operating table with the help of a special leg holder, which means that an X-ray check can be carried out at all times of the operation. With the AMIS technique, an approx. 8–10 cm long skin incision is made at the front on the side of the hip joint. The muscles are only pushed to the side bluntly and are not severed or nicked. The long course of the adjacent muscles from the pelvis to the knee minimizes the risk of muscle damage, but a good overview can still be achieved. After showing the hip capsule, it is opened in a V-shape and the femoral head - according to the planned prosthesis - separated and removed. A so-called Charnley frame is then clamped into the capsule to keep the hip joint open. The hook position within the hip capsule minimizes the risk of nerve crushing and damage. The surgeon then has an excellent overview of the acetabulum and can insert the socket implant. The leg is then turned outwards using the special leg holder and stretched so that the thighbone is displayed. This allows the stem implant to be introduced and the prosthetic head to be placed on. The artificial hip joint is placed in the socket by lifting the leg and turning it inward. The capsule can be retained and then closed again.

Special properties of the AMIS technology

  • Surgical technique that is gentle on muscles and tissue, resulting in less blood loss and early mobilization
  • Anterior access in the Hueter interval is the only "internerval and intermuscular" access to the hip joint
  • Protection of the side muscles of the abductors , which are important for pelvic stabilization , thereby reducing the risk of limping, side hip pain and chronic bursitis
  • Preservation of the hip capsule with a reduced risk of dislocation
  • At the front, both the muscle mantle and the subcutaneous fat tissue are the least thick, making the access also suitable for obese patients.
  • Special surgical technique that requires practice and requires the surgeon to have good training and experience to avoid complications

Results

The available scientific results so far confirm the expected advantages of the AMIS technology. Significantly less muscle damage compared to lateral accesses could be demonstrated. The muscle-sparing surgical technique is also the cause of the low blood loss and the good early functional results. In spite of the minimally invasive surgical technique, correct implant placement can be achieved with good leg length reconstruction and, associated with this, a very low risk of dislocation.

discussion

The AMIS technique must be differentiated from the other surgical techniques, in which the prosthesis is introduced from the front over the same muscle interval (Hueter interval), but different instruments and the lack of use of the special operating table require a significantly different surgical technique. The "direct anterior approach (DAA)", which is also widespread, should be mentioned here, in which the same muscle interval is approached, but no special leg holder is used. Comparative studies of the various anterior hip approaches are not yet available. For the AMIS technology, a high level of safety with a low complication rate has been demonstrated in more than 150,000 hip prosthesis implantations (as of January 2015). Surgeons experienced in AMIS technology use this technique in particular for complex malpositions, since a good overview is achieved despite gentle access. In particular, an extension of the access on the pelvic side is possible, which is why the AMIS technology is increasingly being used for replacement operations on the socket. The disadvantage of the AMIS technique is that an extension of the access along the thigh is not possible in the same muscle interval, but must take place further back (via a subvastus access). In addition, it is more difficult to insert long-handled thigh implants via the anterior approach, which is why other approaches (anterolateral, lateral or posterior) are usually used for replacement operations on the femoral shaft. Since AMIS is a special surgical technique, longer training of the surgeons is necessary in order to avoid increased complications during the first AMIS operations.

literature