WITH ARTIFICIAL JOINTS FOR A BETTER QUALITY OF LIFE

Shoulder joint arthroplasty is possible and conceivable for the following diagnoses:

• Osteoarthritis as a result of degenerative wear and tear
• Rheumatoid arthritis
• Fracture of the humeral head
• Necrosis of the humeral head
• Cufftear arthropathy (secondary arthrosis after major and chronic rotator cuff rupture)

The choice of prosthesis type depends on the degree of remaining shoulder function, the condition of the rotator cuff, the bone substance and the age of the patient.

• Anatomical total shoulder prostheses: These are generally implanted in patients with a still functional rotator cuff. The humeral head and glenoid cavity are replaced. Ceramic or pyrocarbon heads are now also used. The new materials are intended to extend the durability of the prostheses.
• Inverse shoulder prosthesis: The highest growth rates of all implanted joint prostheses in humans are recorded for the inverse shoulder prosthesis. It has shown very good results over the course of more than ten years. An inverse prosthesis should be implanted in patients with a defective rotator cuff, a fractured humeral head, non-functional or failed plate osteosynthesis and larger bone defects.
• Shoulder hemiprosthesis: A complete shoulder joint replacement in which both the head and socket are replaced is not always the ideal measure. Particularly in young patients, the choice of endoprosthesis should also be made in view of the fact that they will still have a long life. Surgeons can achieve good results with partial prostheses by replacing the humeral head. The socket must not yet show any significant signs of osteoarthritis. The less the glenoid is involved in the wear, the better. Caution: An unreplaced glenoid cavity can be problematic in the medium to long term, as it is still exposed to the degenerative process.

After the operation: The more mobile the muscles, tendons and ligaments are, the better the functional result of an arthroplasty reconstruction will be. Patients should therefore not wait too long if joint surfaces in the shoulder are already severely damaged.

The procedure is carried out as part of an inpatient hospital stay, which only lasts a few days. The arm is immobilised in a shoulder abduction cushion for a week, but the joint can be moved again from the very first day after the shoulder operation. Showering or washing hair is possible after about two days. Everyday activities such as eating with the operated arm should be possible again after three days at the latest.

The hospitalisation is followed by outpatient or inpatient rehabilitation. This is agreed with the patient in advance. Physiotherapy treatment is then continued on an outpatient basis. Here too, the quality of the physiotherapy follow-up treatment is decisive for the final result.

It is usually possible to resume everyday activities after six weeks; you should be able to resume more demanding sporting activities such as playing tennis or golf after three months at the latest.

Endoprosthesis models in which an artificial ceramic femoral head is placed on a titanium stem that is clamped in the femur have become established. The artificial hip joint cup is also made of titanium and is implanted “press-fit” into the pelvic bone. An inlay made of ultra-highly cross-linked polyethylene or ceramic is inserted into the cup. Similar to cartilage, ceramic and ultra-highly cross-linked polyethylene have very good sliding properties so that there is hardly any friction between the new joint partners. To summarise, the artificial hip joint consists of four components:

1. A titanium stem, which is anchored in the femur
2. A ceramic head that is attached to the titanium hip stem
3. A titanium cup that is anchored in the pelvic bone
4. A ceramic or ultra-highly cross-linked polyethylene inlay that is inserted into the titanium cup

If the bone quality is poor, for example as a result of osteoporosis, the endoprosthesis stem or cup can be anchored in the femur or pelvic bone with bone cement as an alternative to the press-fit implantation technique. In this case, the stem is made of a cobalt-chrome alloy. The aim of both techniques is to anchor the endoprosthesis so firmly in the bone that you can walk and stand with your full body weight immediately after the operation.

The four approaches to the hip joint:

• The dorsal (posterior) approach
  The dorsal approach leads through the gluteal muscles and through a muscle group that turns the leg outwards (“external rotators”) from behind to the hip joint. This approach provides quick access to the hip and a good overview during the operation. Unfortunately, the gluteal muscles and the external rotators are damaged during the approach. This can lead to muscular weakness and thus delay or impair rehabilitation after the operation. There is also an increased risk of joint dislocation, i.e. dislocation of the artificial femoral head popping out of the acetabulum later on with this approach.
• The lateral approach
  This approach leads through the lateral hip stabiliser muscles (“abductors”) to the hip joint. Similar to the posterior approach, the lateral approach provides quick access to the hip and gives the surgeon a good view of the joint. However, the lateral approach also damages a very important muscle group, namely the abductor group. This means that the lateral approach to the hip has similar disadvantages to the posterior approach. Muscular weakness delays rehabilitation and can favour joint dislocation.
• The anterolateral approach
  This approach does not pass through the muscles, but between muscles to the hip joint. The anterolateral approach is therefore generally gentler than the posterior and lateral approaches.
  However, in order to obtain a good overview of the hip joint, it is necessary to hold the important lateral hip stabiliser muscle (gluteus medius muscle) to the side with hooks. This often causes injury to the muscle, which in turn impairs rehabilitation after the operation. Studies have also shown that the hooks often injure the nerve that innervates the so-called sprinter muscle (tensor fasciae latae muscle), which in turn can lead to partial leg weakness after the operation.
• The anterior approach
  Similar to the anterolateral approach, the anterior approach does not lead through the musculature, but between different muscles to the hip joint. One special feature: no nerves cross the approach. Studies have shown that the anterior approach is associated with the lowest risk of muscle damage and joint dislocation. This makes the anterior approach a particularly gentle approach technique.

The minimally invasive AMIS technique (DAA)

In the context of an artificial hip joint, minimally invasive surgical technique means not only the shortest possible skin incisions, but above all the protection of important functional body structures, in particular the muscles and tendons. The AMIS technique represents a consistent further development of the anterior approach. Recent studies have shown that patients operated on using the AMIS technique suffer less blood loss, can leave hospital earlier, are mobile more quickly and suffer fewer complications such as joint dislocations. You can find out more about the AMIS technique here.

There are basically two types of knee endoprostheses:

• Partial endoprostheses: Here, only a specific area of the knee joint is replaced by the endoprosthesis. Depending on the findings, this may be the medial or lateral part of the knee joint (unicondylar prosthesis) or the area between the kneecap and the femur (patellofemoral joint replacement / PFJ). A partial joint replacement makes sense if only one area of the knee joint is actually affected by osteoarthritis, the ligament structures are intact and there is no excessive bow leg or knock-knee (varus or valgus knee). An older age tends to speak against a partial joint replacement.
• Total endoprosthesis (TEP): In cases where a partial joint replacement is not appropriate, a bicondylar surface replacement prosthesis is implanted. Endoprosthesis models with two metal components and a polyethylene inlay have become established. The metal components are made of a special alloy and serve as a surface replacement for the femur and anchor the polyethylene inlay to the tibial plateau. The polyethylene inlay in turn forms the joint partner of the femoral surface replacement. The prosthesis is firmly anchored in the bone with special bone cement so that you can walk and stand with your full body weight immediately after the operation. The stability of the artificial knee joint – supported by the muscles and joint capsule – is primarily ensured by the body’s own collateral ligaments. In the event of ligament instability or a severe varus or valgus deformity, the stability of the artificial knee joint is achieved by partially or completely ‘coupling’ the femoral and tibial prosthesis components. At the same time, the varus or valgus deformity is corrected by the surgical procedure. If the posterior surface of the patella is also affected by osteoarthritis, it can be replaced with another polyethylene component. Alternatively, the posterior surface of the kneecap is restored to its ‘anatomically correct shape’, i.e. so-called osteophytes are removed.
  Today, an endoprosthesis for the knee joint statistically lasts around 20 years. If it has to be replaced, the reason is usually ‘aseptic loosening’: the joint is no longer stable in the bone. Typical risk factors for a non-infection-related loosening of the artificial knee joint are reduced bone quality and extreme daily stress on the knee joints. A so-called septic loosening, i.e. loosening caused by a bacterial infection, can be caused by dental problems, for example, in which bacteria are transported into the area of the artificial joint via the bloodstream. So be careful with infections of the teeth, but also in the area of the throat, nose and ears as well as with infected wounds.