The concept of joint replacement in the form of surface replacement of the hip (synonyms: hip resurfacing; resurfacing arthroplasty) is a therapeutic surgical procedure in orthopedics that is used to correct debilitating damage to the hip joint. It can be used to maintain mobility and freedom from pain for as long as possible. Unlike the conventional stem-anchored prosthesis, in which the prosthesis is secured in the middle to upper portion of the femur, the surface replacement of the hip joint does not involve anchoring the implant in the stem of the femur (thigh bone). Instead, an endoprosthetic replacement is implanted that is limited to the degeneratively altered articular surface without further stem anchorage. This isolated replacement is not only intended to be gentler on the patient, but instead it is also intended to achieve a longer life and thus retention time of the implant, especially in patients under 55 years of age, through the use of the procedural technique. The surgical replacement of the hip joint can often hardly be prevented despite optimal and time-consuming conservative therapy measures, such as physiotherapy or through orthopedic technical aids. Even the use of various joint-preserving surgical methods, which are not accompanied by implantation of a new hip joint, do not show any relevant improvement of the patient’s problem in many cases, so that if surgery without joint replacement is not adequately successful, joint implantation is preferred. It should also be noted that the lack of success of many surgical procedures without joint replacement, such as hip arthroscopy, means that the use of such procedures is of no apparent benefit. Moreover, the use of surface replacement of the hip joint, compared with conventional total hip arthroplasty, should ensure that a more precise fit of the implant to the shape of the joint can be achieved, so that the stress on the prosthesis is reduced and the life of the implant can be significantly extended. As mentioned earlier, implantation of the surface replacement is a viable option especially for patients below senior age, since in this group of patients, unlike the older generation, a conventional stem-anchored prosthesis rarely provides desirable function until the end of life without replacement. Based on many different clinical studies with different designs (methods), it can be seen that the durability of conventional socket prostheses is usually significantly shortened in young and active patients. As a rule, the surface replacement is implanted in the presence of arthrosis (joint degeneration). If this condition is present in a younger patient and implantation of a conventional prosthesis is performed, this may result in loosening of the prosthesis, which would result in further bone loss during initial implantation.
Indications (areas of application)
- To date, there are no clear indications for surface replacement. However, according to the National Institute for Clinical Excellence from the United Kingdom, performing resurfacing can be used in all patients with advanced osteoarthritis (age-related wear of the joint) for whom implantation of a stem-anchored total hip arthroplasty (hip TEP) would be an indication. Furthermore, this procedure should be performed when the patient’s mean life expectancy exceeds the mean length of stay of the hip TEP.
Contraindications
- Osteoporosis – the presence of this primarily hormonal condition is a contraindication, as the loss of bone strength leads to a higher risk of femoral neck fractures.
- Deformities of the hip joint – if there is a clear malformation of a compartment of the hip joint, this is to be considered a clear contraindication to the implementation of a surface replacement.
- Femoral head necrosis – in the presence of this symptomatology, it has not been possible to determine whether a surface replacement can be performed. In the meantime, it is assumed that implantation should be performed only in the presence of sufficient vital bone tissue.
- Acute septic inflammatory event – the surgical procedure should not be used under any circumstances in the presence of an acute inflammatory reaction in the hip joint.
Before the operation
- It is critical that various measures be taken before implantation of the hip prosthesis to evaluate (assess) both the indication (indication for therapy) and other therapeutic options for the patient. The criterion of greatest importance for ensuring a satisfactory therapeutic outcome is the adaptation of the implanted prosthesis to the physiological and anatomical conditions. Only if the prosthesis then permits physiological function can secondary postural damage with further secondary symptoms be effectively prevented. Based on this, a sketch should be made to improve planning. For the preparation of this planning sketch, a computer-assisted system is used, which allows the creation and elaboration of a digital X-ray.
- From an infectious disease point of view, it is considered particularly important to minimize the patient’s lying time before surgery to minimize the risk of infection. Although implantation of the surface replacement is primarily in patients younger than 55 years with a reduced susceptibility to infection compared with seniors, there is still a risk of serious wound infection, which, in addition to the retention time of the implant, can also potentially lead to a reduction in the life expectancy of the patient due to complications.
- Although surface replacement does not involve removal or destruction of the femoral head, it is still important that the patient improves personal fitness status before the operations and loses weight if necessary to reduce the load on the prosthesis. This is complicated, however, by the fact that those affected often have difficulty losing weight due to mobility limitations.
- In addition to the reduction of body weight, it is also essential that the attending specialist is informed both about the medication and chronic diseases such as diabetes mellitus or cardiovascular disease. The same applies to existing allergies or acute infections.
- In many cases, medications that inhibit blood clotting, such as ASA, must be discontinued before surgery.
The surgical procedure
The surgical methods for implantation of a conventional prosthesis and surface replacement of the hip joint differ significantly. Unlike the conventional prosthesis, the head of the femur is not removed during surface replacement of the hip joint. Instead, the femoral head is slightly adjusted so that a metal plate can subsequently be placed on the machined femoral head. The result of this implantation technique is complete preservation of the femoral neck. The procedure
- To begin the surgical procedure, a skin incision must first be made in the area of the femoral head, allowing further exposure of the hip joint. Subsequently, the diseased cartilage and bone parts of the femoral head are removed and replaced by the metal components of the surface replacement.
- In the further course, the so-called press-fit procedure is performed, in which the socket of the hip joint, which is composed of three bone parts, is clamped in the pelvic bone without the use of bone cement. In contrast, to increase the stability of the implanted surface replacement, the surface of the femoral head is fixed with bone cement. By preserving a large portion of the femoral bone, it is possible to significantly shorten the period of immobility so that the ability to walk is fully restored within one to two days after surgery. In order to additionally improve stability in addition to fixation by bone cement, there should be no loading of the operated hip joint immediately after surgery. However, in order not to suffer from prolonged loss of function, patients should begin with passive exercise, which is performed under the supervision of a physiotherapist.
- Only when weight-bearing capacity improves can more intensive exercises be performed with the hip joint. In addition to faster recovery of function, early physiotherapeutic measures can prevent complications such as thrombosis and possibly pulmonary embolism.
After surgery
- As mentioned above, after surgery there is a short period of reduced stress on the joint, during which only passive training is possible.Later, training or rehabilitation is carried out by using active and intensive movement procedures. Rapid use of the operated joint reduces the risk of thrombosis by shortening immobility.
Possible complications
- Anesthesia – since the procedure is performed under general anesthesia or after spinal anesthesia is performed, this already poses various risks. General anesthesia can cause nausea and vomiting, dental damage, and possibly cardiac arrhythmias. Circulatory instability is also a feared complication of general anesthesia. Nevertheless, general anesthesia is considered a procedure with few complications. Spinal anesthesia is also relatively low in complications, but complications can occur with this method as well. Injury to tissue, such as nerve fibers, could lead to a long-lasting impairment of quality of life.
- Infections – the likelihood of bacterial infections occurring is dependent on several factors, such as preoperative bed length and age. Infections can cause far-reaching complications that can lead to sepsis (blood poisoning).
- Blood loss – despite relatively gentle surgical techniques, there is a risk of having to compensate for relatively heavy blood loss.
- Blood vessel injury
- Wound healing disorders – this symptom can be associated with many factors, so that an exact derivation of the symptomatology is difficult to achieve.
- Abscesses – this inflammatory reaction is characterized by the presence of a solid capsule, which massively complicates conservative therapy using antibiotics. Due to this, surgical removal of the abscess is usually considered.
