Synonyms
artificial hip joint, total hip joint endoprosthesis (HTEP or HTE), hip joint prosthesis, total hip endoprosthesis
Definition
The term total hip joint endoprosthesis stands for “artificial hip joint“. The artificial hip joint is modelled on the human hip joint and therefore consists of the same parts in principle. When a hip prosthesis is implanted, the acetabular cup of the pelvis is replaced by a cup prosthesis (= “artificial cup”). The femoral head and the neck of the femur itself are replaced by the prosthesis stem with the artificial head attached. It is possible to fix these components in the bone either with or without bone cement.
TherapyOperation
Since all prosthesis operations are so-called “elective operations” and the date is therefore known over a long period of time, preparations for the operation can be made early and well thought out. In addition to the procurement of information, the preparations include, for example
- Clarification discussions with the treating, possibly operating doctor.
- Gathering information with regard to the question: Which prosthesis model is suitable for me?
- Procurement of information with regard to the question: Are there specialist clinics?
- Is it possible to donate my own blood?
In short, a hip prosthesis operation involves the removal of surgically damaged bone or cartilage parts of the hip joint and their replacement by artificial parts. The hip joint consists of the thigh bone (= femur), a long tubular bone, which ends with a ball on the upper side.
This “ball” is embedded in the hip socket (= acetabulum) of the pelvis while ensuring a range of motion. This construction ensures maximum freedom of movement in the form of walking, sitting, … , is enabled. Patients who have to consider a hip joint endoprosthesis have lost this maximum freedom of movement or are severely restricted in their ability to perform everyday movements.
The reasons for this will not be discussed here. Rather, we will show how such an operation is performed. As already briefly summarized above, the hip endoprosthesis involves the removal of damaged bone or cartilage, while trying to preserve healthy tissue.
The removed components are replaced by artificial “spare parts”. These artificial parts are on the one hand the acetabulum, the acetabular cup, the hip shaft with the hip prosthesis head (examples see above). The aim of a hip prosthesis operation is to regain maximum quality of life in the form of pain-free movement of the hip joint.
Every operation requires access to the area to be operated on. Within the framework of hip endoprosthetics, this access can be opened anterolaterally (from the front), laterally (from the side) or posteriorly (from behind). The size and thus the length of the access is individually different and varies between 10 and 30 cm.
The surgical team first prepares the area to be operated on, then the surgeon cuts through tissue and muscle layers to allow a free path to the hip joint. Once this is done, the femoral head is dislocated from the acetabulum. After the opening of the operation and the dislocation of the femoral head from the area of the acetabulum, the femoral head is completely removed.
The decisive factor here is the height at which the femoral head is dislocated. This sometimes has a major impact on the course of the operation, but above all on the leg length and thus on the situation after the operation. The acetabulum must also be prepared.
For this purpose – after the acetabulum has been circularly milled out – a cup is inserted into the acetabulum. As already mentioned above, there are various models of such cups. While so-called press-fit cups are “merely” hammered into the acetabulum, there are cups that have to be inserted using antibiotic-containing cement.
In order to allow undisturbed movement, the diameter of the cup is usually about 2 mm larger than the diameter of the head. In order to avoid misalignment of the shell later on, the correct alignment of the shell is checked during the operation with the help of a targeting device and corrected if necessary.If it is determined during such a check that the new components appear to be inadequately fixed, this problem can be counteracted in exceptional cases by means of additional screwing. Under certain circumstances, this can lead to further problems – especially if a change is necessary.
For this purpose, a drill is first used to drill into the medullary canal of the tubular bone. The use of so-called “rasps” makes it possible to prepare an area into which the shaft fits exactly. The exact fit is first tested before the implant – with or without cement – is inserted into the bone.
A femoral head matching the acetabulum is then placed on the stem. All prosthesis components have now been implanted. Of course, it is necessary to check the function of the new hip joint before suturing.
If possible, it should be possible to rule out that the new hip joint tends to dislocate. It can happen that an artificial hip joint tends to dislocate. To counteract such cases, “inlays” have been developed which can be additionally inserted into the socket.
They allow better coverage of the femoral head and can thus prevent the hip joint from dislocating during extreme movements. After “passing” the function test, the surgical site is closed again. This means that the hip joint capsule is first (partially) closed again and any muscle parts that may have been removed are anchored back in the area of their origin.
Finally, the individual skin layers must be closed. For this purpose, the surgeon can use various suturing techniques or even the possibility of “stapling together”. It must be assumed that a hip joint endoprosthesis operation can take between 45 minutes and 2 hours on average, although deviations upwards and downwards are conceivable.
The operation can be performed under general or local anesthesia. At this point, it should be pointed out that rehabilitation measures should generally be followed after the endoprosthetic operation. Which form of rehabilitation can be considered in each individual case should be discussed with the doctor performing the operation.
The motto is: self-help is useful, but too much help, too much ambition can slow down or considerably limit the healing process. The duration of the hip prosthesis operation consists of or can be divided into: 1. the operation itself, in which the prosthesis is inserted, takes one to one and a half hours on average from the induction of anaesthesia to the closure of the wound and the discharge of the anaesthesia. 2. after the operation, the patient is treated on a normal ward for about 7-10 days, provided that no complications have occurred, whereby the length of stay can often vary due to the postoperative, individual course.
3) Directly after the hospital stay an outpatient or even further inpatient rehabilitation measure usually takes place, which on average lasts for a period of three to four weeks. After approx. 3 months, the artificial hip joint is usually completely healed and resilient again, so that no restrictions in everyday life are necessary.
- Duration of the operation
- Duration of hospital stay and
- Duration of the rehabilitation phase afterwards.
In accordance with the prosthesis design, the hip prosthesis shafts anchor more strongly in the upper part of the prosthesis. The remaining part of the prosthesis also contributes to anchoring, but is not as decisive in percentage terms. In any case, it is important that the prosthesis stem is placed as close as possible to the hard part (compakta) of the tubular bone and is accepted by the patient’s own bone in the course of the weeks following the prosthesis operation.
This creates a biological-synthetic bond between the prosthesis and the bone, which remains stable for a lifetime. In particular, bacterial infection or abrasion particles of the sliding pairing of the femoral head with the acetabulum lead to a loosening of the hip prosthesis. With this type of prosthesis, the main part of the prosthesis anchorage is in the middle lower part of the prosthesis.
In percentage terms, the upper part of the stem only contributes less to anchoring in the upper shekel bone. This type of prosthesis is installed in smaller quantities than the type of prosthesis listed above. In the end, various influencing factors – such asB. Bone quality – a role in determining which type of anchorage should be selected.