Infection is one of the most serious complications after artificial joint replacement, which not only brings multiple surgical blows to patients, but also consumes huge medical resources. Over the past 10 years, the infection rate after artificial joint replacement has decreased significantly, but the current growth rate of patients undergoing artificial joint replacement has far exceeded the rate of decrease of infection rate, so the problem of postoperative infection should not be ignored.
I. Causes of morbidity
Post-artificial joint replacement infections should be considered as hospital-acquired infections with drug-resistant causative organisms. The most common is staphylococcus, accounting for 70% to 80%, gram-negative bacilli, anaerobes and non-A group streptococci are also common.
II Pathogenesis
Infections are divided into two categories: one is early infection and the other is late infection or called late-onset infection. Early infections are caused by direct entry of bacteria into the joint during surgery and are commonly Staphylococcus epidermidis. Late-onset infections are caused by blood-borne transmission and are most often Staphylococcus aureus. Joints that have been operated on are more likely to become infected. For example, there is a 10% infection rate in cases of revision after artificial joint replacement, and the infection rate is also higher in people who have had joint replacement for rheumatoid arthritis.
Most of the infections occur within a few months after the operation, the earliest can appear in the first two weeks after the operation, but also as late as a few years before the emergence of the early main manifestations of acute joint swelling, pain and fever, fever symptoms must be differentiated from other complications, such as postoperative pneumonia, urinary tract infections and so on.
In the case of early infection, the body temperature not only does not recover, but rises three days after surgery. Joint pain not only does not gradually reduce, but gradually aggravate, and there is throbbing pain at rest. There is abnormal oozing or secretion from the incision. This should be carefully examined, and the fever should not be easily attributed to postoperative infections in other parts of the body such as the lungs or urinary tract. It is also important not to simply dismiss incisional oozing as the usual common oozing such as fat liquefaction. It is also important to identify whether the infection is located in superficial tissues or deep around the prosthesis.
In patients with advanced infections, most of whom have left the hospital, joint swelling, pain, and fever may not be severe. Half of the patients may have no fever. Staphylococcus epidermidis can cause a painless infection with an increased white blood cell count in only 10% of patients. Elevated blood sedimentation is more common but again not specific. Pain is sometimes misdiagnosed as prosthetic loosening, the latter being pain associated with movement that should be relieved by rest, and inflammatory pain that is not relieved by rest. However, it has been suggested that the main cause of prosthesis loosening is delayed chronic infection.
III. Diagnosis
1. Haematological examination:
Mainly include white blood cell count plus classification, interleukin 6 (IL-6), C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). The advantages of haematological examination are simple and easy to carry out, and the results can be obtained quickly; ESR and CRP have low specificity; IL-6 is of great value in determining the periprosthetic infection in the early postoperative period.
2.Imaging examination:
X-ray film: neither sensitive nor specific for the diagnosis of infection.
X-ray film of knee replacement infection
Arthrography: the main representative performance in the diagnosis of infection is the outflow of synovial fluid and abscess.
CT: visualisation of joint effusion, sinus tracts, soft tissue abscesses, bone erosion, periprosthetic bone resorption.
MRI: highly sensitive for the early detection of joint fluid and abscesses, not widely used in the diagnosis of periprosthetic infections.
Ultrasound: fluid accumulation.
3.Nuclear medicine
Technetium-99 bone scan has a sensitivity of 33% and a specificity of 86% for the diagnosis of periprosthetic infections after arthroplasty, and indium-111 labelled leukocyte scan is more valuable for the diagnosis of periprosthetic infections, with a sensitivity of 77% and a specificity of 86%. When the two scans are used together for the examination of periprosthetic infections after arthroplasty, a higher sensitivity, specificity and accuracy can be achieved. This test is still the gold standard in nuclear medicine for the diagnosis of periprosthetic infections. Fluorodeoxyglucose-positron emission tomography (FDG-PET). It detects inflammatory cells with increased glucose uptake in the infected area.
4. Molecular biology techniques
PCR: high sensitivity, false positives
Gene chip technology: research stage.
5. Arthrocentesis:
Cytological examination of joint fluid, bacterial culture and drug sensitivity test.
This method is simple, fast and accurate
In hip infections, a joint fluid leucocyte count > 3,000/m l in combination with increased ESR and CRP is the best criterion for the presence of periprosthetic infection.
6. Intraoperative rapid frozen section histopathology
Rapid intraoperative frozen section of periprosthetic tissue is the most commonly used intraoperative method for histopathological examination. Feldman's diagnostic criteria, i.e., greater than or equal to 5 neutrophils per high magnification (400x) in at least 5 separate microscopic fields, are often applied to frozen sections. It has been shown that the sensitivity and specificity of this method will exceed 80% and 90%, respectively. This method is currently the gold standard for intraoperative diagnosis.
7. Bacterial culture of pathological tissue
Bacterial culture of periprosthetic tissues has high specificity for diagnosing infection and has been regarded as the gold standard for diagnosing periprosthetic infections, and it can also be used for drug sensitivity test.
IV. Differential diagnosis
Painless prosthetic joint infections caused by Staphylococcus epidermidis are more difficult to differentiate from prosthetic loosening. It must be confirmed by X-rays and other tests.
V. Treatment
1. Simple antibiotic conservative treatment
Tsakaysma and se,gawa classified post arthroplasty infections into four types, type I asymptomatic type, the patient is only in the revision surgery tissue culture found to have bacterial growth, and at least two specimens cultured with the same bacteria; type II is an early infection, which occurs within one month of surgery; type IIl is a delayed chronic infection; and type IV is an acute haematogenous infection. The principle of antibiotic treatment is sensitive, adequate amount and time. And preoperative joint cavity puncture and intraoperative tissue culture are of great significance for the correct selection of antibiotics. If the bacterial culture is positive for type I infection, simple application of sensitive antibiotics for 6 weeks can achieve good results.
2. Prosthesis retention, debridement and drainage, tube irrigation surgery
The premise of adopting the premise of trauma retaining prosthesis treatment is that the prosthesis is stable and acute infection. The infecting organism is clear, the bacterial virulence is low and sensitive antibiotics are available, and the liner or spacer can be replaced during debridement. Cure rates of only 6% with antibiotics alone and 27% with antibiotics plus debridement and prosthesis preservation have been reported in the literature.
It is suitable for early stage infection or acute haematogenous infection with good prosthesis fixation; also, it is clear that the infection is a low virulence bacterial infection that is sensitive to antimicrobial therapy. The approach consists of thorough debridement, antimicrobial flushing and drainage (duration 6 weeks), and postoperative systemic intravenous antimicrobials (duration 6 weeks to 6 months). Disadvantages: high failure rate (up to 45%), long treatment period.
3. One stage revision surgery
It has the advantages of less trauma, shorter hospital stay, lower medical cost, less wound scar and joint stiffness, which is conducive to the recovery of joint function after surgery. This method is mainly suitable for the treatment of early infection and acute haematogenous infection.
One-stage replacement, i.e., the one-step method, is limited to low-toxicity infections, thorough debridement, antibiotic bone cement, and the availability of sensitive antibiotics. Based on the results of intraoperative tissue frozen section, if there are less than 5 leukocytes/high magnification field. It is suggestive of a low-toxicity infection. After thorough debridement a one stage arthroplasty was performed and there was no recurrence of infection postoperatively.
After thorough debridement, the prosthesis is immediately replaced without the need for an open procedure. It has the advantages of small trauma, short treatment period and low cost, but the recurrence rate of postoperative infection is higher, which is about 23%~73% according to the statistics. One-stage prosthesis replacement is mainly suitable for elderly patients, without combining any of the following: (1) history of multiple surgeries on the replacement joint; (2) sinus tract formation; (3) severe infection (e.g. septic), ischemia and scarring of the surrounding tissues; (4) incomplete debridement of trauma with partial cement remaining; (5) X-ray suggestive of osteomyelitis; (6) bone defects requiring bone grafting; (7) mixed infections or highly virulent bacteria (e.g. Streptococcus D, Gram-negative bacteria); (8) bone loss requiring bone grafting; (9) bone loss requiring bone grafting; and (10) bone grafts requiring bone grafting. Streptococcus D, Gram-negative bacteria, especially Pseudomonas, etc.), or fungal infection, mycobacterial infection; (8) Bacterial culture is not clear.
4. Second-stage revision surgery
It has been favoured by surgeons over the past 20 years because of its wide range of indications (sufficient bone mass, rich periarticular soft tissues) and the high rate of eradication of infection.
Spacers, antibiotic carriers, antibiotics
Regardless of the spacer technique used, cemented fixation with antibiotics is necessary to increase the concentration of antibiotics in the joint and increase the cure rate of infection. Commonly used antibiotics are tobramycin, gentamicin and vancomycin.
The international orthopaedic community has recognised the most effective treatment for deep infection after arthroplasty. The approach consists of thorough debridement, removal of the prosthesis and foreign body, placement of a joint spacer, continued use of intravenous sensitive antimicrobials for at least 6 weeks, and finally, after effective control of the infection, reimplantation of the prosthesis.
Advantages:
Sufficient time to identify the bacterial species and sensitive antimicrobial agents, which can be used effectively before revision surgery.
The combination of other systemic foci of infection can be treated in a timely manner.
There are two opportunities for debridement to remove necrotic tissue and foreign bodies more thoroughly, which significantly reduces the rate of recurrence of postoperative infections.
Disadvantages:
Re-anaesthesia and surgery increase the risk.
Prolonged treatment period and higher medical cost.
Postoperative functional recovery is poor and slow.
Arthroplasty: Suitable for persistent infections that do not respond to treatment, or for large bone defects; patient's condition limits reoperation and reconstruction failure. Residual postoperative pain, the need for long-term use of braces to assist mobility, poor joint stability, limb shortening, functional impact, the scope of application is limited.
Arthroplasty: the traditional treatment for postoperative infections, with good postoperative stability and pain relief. Disadvantages include shortening of the limb, gait disorders and loss of joint mobility.
Amputation: It is the last resort for the treatment of postoperative deep infection. Suitable for: (1) irreparable serious bone loss, soft tissue defects; (2) strong bacterial virulence, mixed infections, antimicrobial treatment is ineffective, resulting in systemic toxicity, life-threatening; (3) has a history of multiple failure of revision surgery of chronic infected patients.
VI. Prevention
1. Preoperative factors:
Optimise the patient's preoperative condition and all existing infections should be cured preoperatively. The most common blood borne infections are those from the skin, urinary tract, and respiratory tract. In hip or knee arthroplasty, the skin of the lower extremities should remain unbroken. Asymptomatic bacteriuria, which is common in elderly patients, does not need to be treated preoperatively; once symptoms occur they must be treated promptly. Patients with tonsillitis, upper respiratory tract infections, and tinea pedis should have local foci of infection eliminated. Larger dental operations are a potential source of bloodstream infection, and although avoided, if dental operations are necessary, it is recommended that such procedures be performed prior to arthroplasty. Patients with poor general conditions such as anaemia, hypoproteinaemia, combined diabetes and chronic urinary tract infections should be treated aggressively and early for the primary disease to improve the systemic condition.
2. Intraoperative management:
(1) Completely aseptic techniques and tools should also be employed in the routine therapeutic approach to arthroplasty.
(2) Preoperative hospitalisation should be minimised to reduce the risk that the patient's skin may colonise with hospital-acquired bacterial strains, and routine treatment should be carried out on the day of surgery.
(3) The preoperative area should be properly prepared for skin preparation.
(4) Surgical gowns, masks, hats, and laminar flow operating theatres are effective in reducing airborne bacteria in the operating theatre. Wearing double gloves can reduce the risk of hand contact between surgeon and patient and can be recommended.
(5) It has been clinically proven that the use of more restrictive, especially hinged, prosthesis has a higher risk of infection than non-restrictive total knee arthroplasty due to abrasive metal debris that reduces phagocytosis activity, and should therefore be avoided in prosthesis selection.
(6) Improve the surgical technique of the operator and shorten the duration of the operation (<2.5 h if possible). The shortening of surgical duration can reduce the time of exposure to air, which in turn can reduce the time of tourniquet use. Avoid rough operation during surgery, the wound can be repeatedly irrigated (pulsed irrigating gun is best), and iodine-vapor immersion can be taken for incisions suspected to be contaminated.
3. Postoperative factors:
(1) Surgical blows induce insulin resistance, which can lead to hyperglycaemia, a phenomenon that can persist for several weeks postoperatively and predispose the patient to wound-related complications, and which, moreover, occurs in non-diabetic patients as well. Therefore, clinical postoperative blood glucose monitoring is equally important.
(2) Deep vein thrombosis increases the risk of haematoma and consequent wound-related problems. A case-control study found that postoperative application of low molecular heparin to prevent deep vein thrombosis was beneficial in reducing the probability of infection.
(3) Closed drainage is a potential portal of entry for infection, but its relationship to wound infection rates has not been specifically studied. Preliminary results suggest that intra-articular catheters used as postoperative administration of analgesics may also be susceptible to wound infection.
4. Antibiotic prophylaxis:
Currently, routine clinical application of prophylactic doses of antibiotics systemically administered intravenously before and after surgery reduces the risk of postoperative infection. Cephalosporins are mostly used clinically as the antibiotic of choice, and there is a U-shaped curve relationship between the timing of antibiotic use and the rate of surgical site infections, with a higher risk of infection both before and after the optimal time frame for antibiotic use. A recent large study found that antibiotics used within 30 to 60 min before incision had the lowest infection rate. In contrast, another major study of total hip arthroplasty showed the lowest rate of infection with antibiotics administered within the first 30 min of incision. Therefore the time of administration is generally considered to be 30 min before the operation, with the best results during the induction of anaesthesia. Another prophylactic dose of antibiotics is given after surgery. In Europe and the United States, antibiotics are usually used until the third postoperative day, but in China, it is reported that they are usually used continuously for 1 to 2 weeks. However, the general consensus is that long-term use of potent broad-spectrum antibiotics should be avoided unless there are special circumstances, and if prolonged use of antibiotics is necessary, it is advisable to use antifungal drugs in conjunction with antibiotics to prevent fungal infections. Vancomycin has been shown to be effective in high-risk patients carrying methicillin-resistant Staphylococcus aureus. Higher doses of antibiotics should be used for prolonged surgeries, including bilateral surgeries, especially when the antibiotic half-life is short.
5. Use of antibiotics in combination with bone cement:
Antibiotic-infused cement was also first used in arthroplasty in Norway, where initially a Norwegian Arthroplasty Registry study showed that the use of a combination of antibiotic IV and cement (combined antibiotic prosthesis) infusion reduced the rate of deep infection more effectively than either method alone. This finding was confirmed in a series of large studies over the next 16 years. A Finnish study and the Australian Orthopaedic Association 2009 reached similar conclusions about the role of antibiotic-infused cement in first-time and revision knee arthroplasty. It has also been shown that the biomechanical properties of bone cement are not affected when antibiotic powder is added in doses not exceeding 2 g per 40 g of bone cement. However, not all antibiotics can be added to bone cement. Antibiotics that can be added to bone cement should have the following conditions: safety, thermal stability, hypoallergenicity, good aqueous solubility, broad antimicrobial spectrum, and powdered material. Currently, vancomycin and gentamicin are more commonly used in clinical practice. It was thought that antibiotic injection into cement would increase the risk of allergic reactions, the emergence of resistant strains, and aseptic loosening of the prosthesis, but so far there is no evidence to support these concerns.
VII. Summary
Making a prompt and accurate diagnosis through history, physical examination and ancillary tests is a prerequisite for successful treatment of joint infections. Eradication of the infection and restoration of a pain-free, well-functioning artificial joint is the basic principle in the treatment of joint infections. Although antibiotic treatment of joint infection is simple and inexpensive, the eradication of joint infection mostly requires a combination of surgical methods. The key to choosing surgical treatment is to consider the problem of prosthesis removal, which is the core aspect of dealing with joint infections. At present, the combined application of antibiotics, debridement and arthroplasty has become a comprehensive treatment for most complex joint infections. However, it still needs to be improved and perfected.
Post time: May-06-2024
