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The surgeon’s task during primary hip or knee replacement is to return the patient to a full life as soon as possible. By restoring the anatomical shape and physiological mobility of the joint using artificial components, the surgeon tries to ensure long and reliable service of the installed structure. It is very important to comply with all the requirements of surgical technique and sterility in order to avoid the need for repeated revision surgery in the future. Repeated replacement of a previously installed endoprosthesis is a more complex, lengthy and statistically less successful procedure, which has its own risks and complications. Unfortunately, with the growing number of operations for the primary installation of endoprostheses performed in the world, the number of complications requiring revisions is also growing. During repeated operations, surgeons are often faced with the problem of a postoperative defect (lack of bone mass), primarily in the area of the acetabulum of the pelvis and the articular end of the femur.
The main indication for revision surgery is the functional failure of the installed prosthesis. As a result of inadequate fixation of the installed components of the prosthesis to the bone structures, a “looseness” of the joint occurs, which does not allow it to perform the full range of movements. As a result of pathological mobility of the internal elements of the joint, the process of chronic destruction of its bone part and the formation of fibrous tissue around the endoprosthesis begins.
The causes of instability and loosening of the endoprosthesis (loosening), with the exception of technical errors during the operation, can be: a) aseptic or germ-free, sterile process (aseptic loosening) as a result of the inflammatory reaction of the periarticular tissues to microdust (debris) resulting from mechanical friction of the parts prosthesis during movement; b) septic or microbial process as a result of chronic infection in the joint area (septic loosening).
Aseptic loosening of the endoprosthesis
High-strength artificial materials of the endoprosthesis, despite their durability, are not capable of self-healing, like the regeneration of tissue of living organisms. Over time, the rubbing contact surfaces of the components “wear out”, forming microdispersed dust. Microdust penetrates into the tissue surrounding the joint and causes reactive inflammation, destruction and melting of the bone elements of the joint, followed by their replacement with fibrous tissue.
The rate of development of the process according to the type of aseptic loosening directly depends on the level of mechanical load on the joint, the degree of physical activity of the person and the material of the friction pair in the installed endoprosthesis. A friction pair is the two contact parts of a joint that ensure the process of its movement. The friction pair material that is least resistant to mechanical stress is polyethylene, which has a high abrasion coefficient. However, modern technology for the production of polyethylene with reinforced fiber bonds (highly crosslink polyethilene) has made it possible to significantly improve its strength characteristics. Metal-ceramics have the highest wear resistance in a friction pair.
Anatomy
The hip joint is a ball and socket joint. The concave part of the joint is called the acetabular cavity and is a regular, deep cup-shaped depression in which the head of the femur is located. The hip joint is surrounded by powerful gluteal muscles at the back and thigh muscles at the front. The head of the femur is located in the articular cavity and is covered with articular cartilage. The thickness of the articular cartilage of the hip joint is 5-7 mm, which is comparatively greater than that of other joints. Articular cartilage normally has a very smooth, slippery surface, which reduces friction during joint movements between the articular ends of the bones.
Septic loosening of the endoprosthesis
Infection of the surgical wound and prosthesis is a serious postoperative complication. Therefore, the requirements for sterility during endoprosthetics operations are the highest in orthopedic surgery. The principles of preventing purulent complications must be strictly observed by operating personnel. Despite all the precautions taken, according to world statistics, infection accounts for 1% to 5% of endoprosthetics complications. Infectious complications are divided into acute and chronic.
Damage to the implant
Among all damages to the endoprosthesis, wear of the tibial polyethylene liner is the most common. The problem can usually be resolved by open debridement. The essence of the operation is arthrotomy, surgical treatment of the articular cavity and replacement of the liner.
Result of injury or fall.
Revision arthroplasty should be done in case of repeated dislocations or fracture of one or more components of the prosthesis.
Acute infection or suppuration of a surgical wound
Acute infection, as a rule, develops in the superficial soft tissues of the surgical wound without penetration into the deeper layers and without involving the installed endoprosthesis in the infectious process. Its development becomes possible when the patient’s immunity is weakened and infection prevention measures are not followed, sterility is violated and microbial contamination of the wound surface. Staphylococcus aureus (Staphylococcus aureus) is usually cultured from wound discharge. After determining the sensitivity of microbes to antibiotics, an intravenous course of antibiotic therapy is prescribed. The duration of treatment takes from several days to a month.
If antibiotic therapy is ineffective, surgical cleansing of the wound is performed, necrotic tissue is removed, while the endoprosthesis remains in place. At the same time, a new antibiotic or their combination is selected. If the treatment tactics are chosen correctly, the infection is completely eliminated and the endoprosthesis is preserved. If treatment is unsuccessful, an acute infection can become chronic.
Contraindications to revision endoprosthetics
All contraindications to reoperation are divided into absolute and relative. If the former are present, surgical intervention is prohibited, as this can lead to serious complications.
Absolute contraindications:
- the patient's inability to move independently;
- hemiparesis on the side of the planned surgical intervention;
- acute or worsened thrombophlebitis;
- severe chronic diseases of the cardiovascular system;
- respiratory failure stage 3;
- the presence of unsanitized foci of chronic infection in the body;
- severe osteopenia;
- serious mental or neuromuscular disorders;
- absence of the medullary canal of the femur.
Relative contraindications include liver failure, severe chronic decompensated diseases, hormonal osteopathy and HIV-associated immunodeficiency conditions.
Chronic infection
The appearance of signs of local chronic infection in the area of the operation is the most severe infectious complication that occurs after endoprosthetics. It can develop as an independent primary form of the disease or as a consequence of ineffective treatment of the acute phase of infection. The causative agent of the primary form of chronic infection most often becomes epidermal staphylococcus (staphylococcus epidermidis). Colonies of staphylococci grow on the metal components of the endoprosthesis and, with the help of glycocalyx molecules, protect themselves from destruction by cells of the immune system and antibiotics. As microbes with a low degree of pathogenicity, staphylococci, when entering a surgical wound, do not cause a pronounced immune response and the classic picture of suppuration. Therefore, in the early postoperative period, a chronic infection does not show itself and is not diagnosed. Subsequently, it manifests itself in the presence of constant pain in the joint area. Relatively quickly, from one to two years after surgery, the infection destroys the bone around the endoprosthesis. At this time, symptoms of instability of its components progress. The diagnosis is established by examining the patient, assessing his complaints, x-rays and laboratory tests. Identified chronic infection is a direct indication for revision of the endoprosthesis. To reliably get rid of a chronic infection, the infected endoprosthesis is removed. For this purpose, there are two types of revision operations - one-stage and two-stage replacement of the endoprosthesis.
Diagnostics
Diagnosis is carried out not only by detecting symptoms of aseptic instability of endoprostheses. An experienced traumatology or surgical orthopedics doctor will definitely prescribe a series of preventive diagnostic procedures in the near future after installation.
In general, the program for detecting the first signs of endoprosthesis instability includes:
- X-ray;
- 2-energy X-ray absorptiometry (densitometry or DXA) with monitoring of bone density in seven Gruen zones;
- checking bone metabolic markers.
The first diagnosis is usually carried out in the coming months after surgery. The higher the risk of developing aseptic instability of the endoprosthesis (for example, the patient had osteoporosis before treatment), the sooner the doctor will conduct a follow-up examination.
Two-stage audit
At the first stage, the infected endoprosthesis is removed, and after cleaning the wound, a temporary articular spacer is installed in its place. The latter is similar to the primary endoprosthesis, but is encased in a shell of acrylic cement with a high concentration of antibiotic. Cement allows you to fill all bone defects and creates a high local concentration of the antibiotic. This allows you to reduce the course dose of postoperative intravenous antibiotic therapy. The use of an articular spacer helps to restore the patient's walking function with full load on the joint. After 3-6 or more months, in the absence of clinical and laboratory signs of infection, the second stage of the operation is performed - removing the spacer and replacing it with a revision endoprosthesis. When using two-stage revision tactics, the success rate increases to 90% of cases.
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Treatment
The symptoms of aseptic instability of the hip endoprosthesis largely replicate ANFH, which makes it possible to use proven courses of therapy for necrosis of the femoral head for its treatment. The program includes:
- vitamin therapy;
- unloading of the limbs (the patient moves for some time with the help of crutches);
- drug treatment (selected individually, taking into account the age, general condition of the patient, clinical picture before and after implantation);
- therapeutic diet (including those with the addition of bioactive complexes);
- a set of special exercises to prevent instability of the hip joint endoprosthesis ;
- electrical stimulation of areas of the legs or pelvis.
To visualize progress in the complex treatment of aseptic instability of endoprostheses, patients are required to keep a daily diary of their well-being. As a rule, this is enough for successful rehabilitation, normalization of the processes of resorption (destruction of bone tissue cells) and bone formation, and normal implant healing. In some cases, a new surgical procedure (revision endoprosthetics) is performed.
Rehabilitation in the postoperative period
In the first days after surgery, the patient undergoes careful prevention of thromboembolic complications. For this purpose, his legs are bandaged with elastic bandages or stockings. At the same time, the patient is given a set of exercises to restore normal joint mobility. Note that in the first days, the medical staff practically teaches a person to move, walk, and climb stairs.
At first, the seam is securely hidden.
In the later recovery period, the patient needs therapeutic exercises, physiotherapy and some other rehabilitation measures. They help restore the functional activity of the knee and return the patient to a full life. The lack of full rehabilitation increases the risk of complications and often leads to unsatisfactory results of revision arthroplasty.
Examination before surgery
Before repeat joint replacement, the patient must undergo an examination. In addition to general clinical examinations, he is prescribed radiography of the knee joint in 2 projections, CT, MRI, densitometry and ultrasound examination of the veins of the lower extremities. The patient also undergoes a detailed coagulogram and echocardiography.
Tests, instrumental research methods and consultations with specialists help assess the general condition of the patient and the tactics of revision arthroplasty. This makes it possible to avoid unforeseen complications and make surgery successful.
When performing revision endoprosthetics, the correct selection of the implant is of great importance. Therefore, the hospital where surgery is performed must have a full line of endoprostheses available.