Septic arthritis

Septic arthritis is a rapidly progressing infectious disease of the joints caused by the direct entry of pyogenic microorganisms into the joint cavity.

ICD-10 code

• M00.0-M00.9 Septic arthritis.
• A.54.4 Gonococcal infection of the musculoskeletal system.
• 184.5 Infection and inflammatory reaction due to endoprosthetics.

Epidemiology

Septic arthritis and prosthetic joint infection are common. They account for 0.2-0.7% of all hospitalizations. Children and older people are most often affected. The incidence of septic arthritis is 2-10 per 100,000 population, among patients with RA - 30-40 cases per 100,000. The prevalence of prosthetic joint infection is 0.5-2.0% of all cases of prosthetics per year.

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What causes septic arthritis?

All known bacteria can cause septic arthritis. The most common etiologic agent of septic arthritis is Staphylococcus aureus (37-56%), which accounts for up to 80% of joint infections in patients with RA and diabetes mellitus. S. aureus is also considered the main etiologic factor in infectious coxitis and polyarticular variants of septic arthritis. Streptococci are the second most common bacteria found in people with septic arthritis (10-28%). Joint inflammation caused by streptococci is usually associated with underlying autoimmune diseases, chronic skin infection, and previous trauma. Gram-negative rods (10-16%) cause septic arthritis in the elderly, intravenous drug addicts, and immunocompromised patients. Septic arthritis caused by Neisseria gonorrhoeae (0.6-12%) is usually detected within the framework of disseminated gonococcal infection. Anaerobes as pathogens (1.4-3.0%) appear in recipients of joint prostheses, in individuals with deep soft tissue infections and in patients with diabetes mellitus.

Structure of pathogens causing infection of the prosthetic joint:

• gram-positive aerobes – 64-82%, including Staphylococcus epidermidis – 29-42%;
• Staphylococcus aureus – 17-22%$
• Streptococcus spp. - 8-10%;
• Enterococcus spр. - 4-5%;
• diphtheroids - 2%;
• gram-negative aerobes - 9-23%;
• anaerobes - 8-16%;
• fungal and mixed flora - 2-5%.

Early forms of prosthetic joint infection (up to 3 months after implantation of the prosthesis) are caused primarily by Staphylococcus epidermidis. Colonization of the endoprosthesis by staphylococci occurs by contact with infected skin, subcutaneous fat, muscles, or from a postoperative hematoma. Late forms of prosthetic joint infection occur as a result of infection with other microorganisms, which occurs primarily by the hematogenous route.

How does septic arthritis develop?

Normally, joint tissues are sterile, which is ensured by the successful functioning of phagocytes of the synovial membrane and synovial fluid. For the development of septic arthritis, a number of "risk factors" are necessary. The most significant include the weakening of the natural defenses of the macroorganism, caused by old age, severe concomitant diseases (diabetes mellitus, liver cirrhosis, chronic renal failure, cancer, etc.), as well as the presence of primary foci of infection (pneumonia, pyelonephritis, pyoderma, etc.). No less important are considered background joint pathology (hemarthrosis, osteoarthritis), the presence of joint prostheses, as well as the therapy carried out in this regard and its possible complications. Hematogenous spread of pathogens is significantly facilitated by various manipulations, including intravenous administration of drugs (including narcotics), catheterization of central veins, as well as penetrating stab wounds and bites. Congenital disorders of phagocytosis associated with complement deficiency and impaired chemotaxis can play a significant role in the development of septic arthritis.

The pathogen enters the joint by the hematogenous route during the period of transient or persistent bacteremia, by the lymphogenous route - from the foci of infection closest to the joint, as well as with direct penetration caused by medical manipulations (arthrocentesis, arthroscopy) and penetrating injuries.

The penetration of bacteria into the joint causes an immune response, accompanied by the release of proinflammatory cytokines and immunocompetent cells into the joint cavity. Their accumulation leads to inhibition of the process of cartilage tissue reparation and its degradation with subsequent destruction of cartilage and bone tissue and the formation of bone ankylosis.

How does septic arthritis manifest itself?

Septic arthritis is characterized by an acute onset with intense pain and other symptoms. In most cases (60-80%), patients are bothered by fever. However, body temperature may be subfebrile and even normal, which is more common with damage to the hip and sacroiliac joints, against the background of active anti-inflammatory therapy for the underlying disease, as well as in elderly patients. In 80-90% of cases, a single joint is affected, most often the knee or hip. The development of the infectious process in the hands is mostly of traumatic genesis (penetrating stab wounds or bites). Oligoarticular or polyarticular type of lesion is more often observed in the development of septic arthritis in patients with systemic diseases of connective tissue, as well as in drug addicts who inject drugs intravenously. In addition, in "intravenous" drug addicts, septic arthritis is characterized by a slower onset, a long course and frequent damage to the sacroiliac and sternoclavicular joints, pubic symphysis.

When septic arthritis develops as part of disseminated gonococcal infection, clinical symptoms develop within 2-3 days from the onset of the disease and include general malaise, fever, skin rashes, and teposynovitis.

The onset of a prosthetic joint infection may be acute or subacute depending on the virulence of the pathogen. Pain (95%), fever (43%), swelling (38%) appear, and purulent discharge is obtained during drainage or puncture (32%).

How to recognize septic arthritis?

The main attention is paid to the presence of "risk factors" predisposing to the development of septic arthritis. One of the most significant components of the occurrence of septic arthritis is considered to be the weakening of the body's natural defenses, caused by concomitant diseases, immunosuppressive therapy, and the elderly age of patients. Significant importance is attached to the background pathology of the musculoskeletal system, as well as possible complications of its treatment.

Predisposing factors for gonococcal septic arthritis in women include menstruation, pregnancy, the postpartum period, and chronic asymptomatic endocervical infection. For men, homosexuality may be a risk factor. For both sexes, there are several predisposing factors (extragenital gonococcal infection, promiscuous sexual relations, low socioeconomic and educational status, drug use, HIV infection, congenital deficiency of complement components C3 and C4).

The main risk factors for infection of a prosthetic joint include immunodeficiency states, repeated and long-term surgical interventions, and prosthetics of superficial joints (elbow, shoulder, ankle).

Physical examination

Along with intense pain syndrome, swelling, hyperemia of the skin and hyperthermia of the affected joint are detected. When the process is localized in the hip or sacroiliac joints, pain in the lower back, buttocks and on the anterior surface of the thigh is often noted. In such situations, special tests can be useful: in particular, the Patrick test or the FABERE symptom (the initial letters of the Latin words flexio, abductio, externa rotatio, extensio) helps to identify pathology of the hip joint. When performing this test, the patient lying on his back bends one leg at the hip and knee and touches the lateral ankle to the patella of the other extended leg. Pressure on the knee of the bent leg in case of damage causes pain in the hip joint. A positive Henslen symptom (pain in the sacroiliac joint area with maximum flexion of the leg joints on the same side and maximum extension on the other side) indicates the presence of sacroiliitis.

In young children, the only manifestation of bacterial coxitis may be sharp pain during movement with fixation of the hip joint in a position of flexion and external rotation.

Gonococcal septic arthritis is often accompanied by lesions of the skin and periarticular soft tissues. Gonococcal dermatitis develops in 66-75% of patients with disseminated gonococcal infection and is characterized by painless hemorrhagic papular or pustular rashes with a diameter of 1 to 3 mm localized on the distal parts of the extremities. Formation of blisters with hemorrhagic contents is possible. In typical cases, a pustule is formed with a hemorrhagic or necrotic center surrounded by a purple halo. As a rule, the rash undergoes regression within 4-5 days and leaves behind unstable pigmentation. Tenosynovitis develops in 2/3 of patients with disseminated gonococcal infection, has an asymmetrical nature, mainly affects the tendon sheaths of the hands and feet and occurs in parallel with skin changes. As part of disseminated gonococcal infection, hepatitis, myopericarditis, and, very rarely, endocarditis, meningitis, perihepatitis (Fitz-Hugh-Curtis syndrome), adult respiratory distress syndrome, and osteomyelitis may develop.

Laboratory diagnostics of septic arthritis

When analyzing peripheral blood in patients with septic arthritis, leukocytosis with a shift in the leukocyte formula to the left and a significant increase in ESR are detected. However, in 50% of patients with septic arthritis that developed against the background of RA and treatment with glucocorticoids, the number of leukocytes may be within normal limits.

The basis for diagnosing septic arthritis is a comprehensive analysis of synovial fluid (including microbiological testing) obtained by puncturing the affected area. Immediately after synovial fluid is collected, it is sown (at the patient's bedside) on nutrient media for aerobic and anaerobic pathogens. To obtain preliminary information about the pathogen and prescribe empirical antibiotic therapy, synovial fluid smears must be stained according to Gram, preferably with preliminary centrifugation of the synovial fluid. In this case, the diagnostic information content of the method is 75% and 50% for infection with gram-positive cocci and gram-negative rods, respectively. Visually, synovial fluid in septic arthritis has a purulent character, grayish-yellow or bloody color, turbid, thick, with a large amorphous sediment. The white blood cell count in synovial fluid is often higher than in other inflammatory diseases, being more than 50,000/mm3 and often more than 100,000/mm3 with a predominance of neutrophils (>85%). Synovial fluid also has low glucose levels, less than half of the serum glucose level, and high lactic acid levels. Blood cultures show growth of microflora in 50% of cases.

If gonococcal etiology of septic arthritis is suspected, bacteriological examination of discharge from the urethra (in men) or cervix (in women) is indicated. In order to suppress saprophytic flora, cultures are performed on selective media with the addition of antibiotics (Thayer-Martin medium). In the case of gonococcal infection, a positive result with a single millet is obtained in 80-90% of cases. Given the possibility of associated infection, all patients with gonococcal infection are recommended to be examined for chlamydia and other sexually transmitted diseases (syphilis, HIV infection, etc.).

In patients with infection of the prosthetic joint, a histological and microbiological examination of a bone tissue biopsy taken near the junction of the cement with the prosthesis is performed to verify the diagnosis and monitor treatment.

Instrumental research

X-ray examination of the joint is one of the primary diagnostic measures, since it allows to exclude concomitant osteomyelitis and determine the further tactics of examination and treatment of the patient. However, it should be noted that distinct and imputed on X-ray images in septic arthritis (osteoporosis, narrowing of the joint space, marginal erosions) appear approximately on the 2nd week from the onset of the disease.

Radioisotope scanning with technetium, gallium or indium is especially important in cases where the joint being examined is located deep in the tissues or is difficult to palpate (hip, sacroiliac). These methods help to identify changes characteristic of septic arthritis (accumulation of radiopharmaceutical indicating active synovitis) and the early stages of the process, i.e. during the first two days, when there are no radiographic changes yet.

CT allows to detect destructive changes in bone tissue much earlier than radiography. This method is most informative in case of damage to the sacroiliac and sternoclavicular joints.

MRI allows detecting soft tissue swelling and effusion into the joint cavity, as well as osteomyelitis, in the early stages of the disease.

Differential diagnostics

Septic arthritis should be differentiated from the following diseases that manifest as acute monoarthritis: acute gout attack, pyrophosphate arthropathy (pseudogout), RA, seronegative spondyloarthritis, Lyme borreliosis. Infection is considered one of the few emergency situations in rheumatology that require rapid diagnosis and intensive treatment to avoid irreversible structural changes. Therefore, there is a rule that every acute monoarthritis should be considered infectious until proven otherwise.

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Example of diagnosis formulation

• Acute bacterial coxarthritis of staphylococcal (Staphylococcus aureus) etiology.
• Acute staphylococcal (Staphylococcus epidermidis) infection of a hip replacement.

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Treatment of septic arthritis

Non-drug treatment

The infected joint is drained (sometimes several times a day) by closed aspiration through a needle. The maximum possible amount of effusion is removed. To assess the effectiveness of the treatment, a leukocyte count, Gram staining and synovial fluid cultures are performed each time. The joint is immobilized for the first two days. Passive movements are performed starting from the third day of the disease; loads and active movements are carried out after the disappearance of arthralgia.

Medicinal cookies

Antibacterial therapy is carried out for two days empirically, taking into account the patient's age, the clinical picture of the disease and the results of staining of synovial fluid smears according to Gram, and later - taking into account the isolated pathogen and its antibiotic resistance. Antibiotics should be administered primarily parenterally; their intra-articular use is inappropriate.

The absence of positive dynamics after two days of treatment dictates the need to change the antibiotic. Persistent elevated ESR serves as an indication for prolonging the treatment period, which is on average 3-4 weeks (sometimes up to 6 weeks), but not less than two weeks after the elimination of all signs of the disease.

In patients with prosthetic joint infection, antibiotic therapy is prescribed based on microbiological examination of bone biopsy and is administered for at least 6 weeks according to the following regimens: oxacillin + rifampicin, nancomycin + rifampicin, cefene/ceftazidime + ciprofloxacin.

The antibiotics of choice for the treatment of gonococcal septic arthritis are third-generation cephalosporins - ceftriaxone (1-2 g/day intravenously) or cefotaxime (3 g/day in 3 intravenous doses), prescribed for 7-10 days. Subsequently, oral therapy is carried out with ciprofloxacin (1 g/day in 2 doses) or ofloxacin (800 mg/day in 2 doses). Persons under 18 years of age and patients with intolerance to fluoroquinolones are prescribed cefixime (800 mg/day orally in 2 doses),

The duration of antibacterial therapy for gonococcal septic arthritis should be at least two weeks after the elimination of all signs of the disease. Given the high probability of concomitant chlamydial infection, the above treatment regimens are supplemented with azithromycin (1 g orally once) or doxycycline (200 mg/day orally in 2 doses for 7 days).

In addition to antimicrobial therapy, analgesics and NSAIDs are prescribed (diclofenac 150 mg/day, ketoprofen 150 mg/day, nimesulide 200 mg/day, etc.).

Surgical treatment

Open surgical drainage of septic arthritis is performed in the presence of the following indications: infection of the hip and, possibly, shoulder joint; osteomyelitis of the vertebrae, accompanied by compression of the spinal cord; anatomical features that complicate joint drainage (for example, sternoclavicular joint): impossibility of removing pus with closed drainage through a needle due to increased viscosity of the contents or adhesions in the joint cavity; ineffectiveness of closed aspiration (persistence of the pathogen or lack of decrease in leukocytosis in the synovial fluid): prosthetic joints; concomitant osteomyelitis requiring surgical drainage; septic arthritis that developed due to the ingress of a foreign body into the joint cavity; late initiation of therapy (more than 7 days).

Surgical treatment of prosthetic joint infection is carried out in the following ways.

• One-stage arthroplasty with excision of infected tissues, installation of a new prosthesis and subsequent treatment with antibiotics. In this case, the duration of the course of antibiotic therapy should be at least 4 or 6 months if the process is localized in the hip or knee joint, respectively.
• Excision of prosthetic components, contaminated skin and soft tissue areas followed by antimicrobial therapy for 6 days. Then a tissue biopsy is performed from the affected joint area, and antibiotic treatment is stopped for two weeks until the results of histological and microbiological studies are obtained, after which reimplantation is performed. If there are no inflammatory changes or microbial growth in the biopsy specimens, antibiotic therapy is not resumed. Otherwise, antibiotic treatment is continued for 3 or (> months).

Indications for consultation with other specialists

All patients with septic arthritis are examined by an orthopedic surgeon to clarify the indications for open drainage, as well as prosthetics (or re-prosthetics) of the infected joint. In case of gonococcal etiology of septic arthritis, it is advisable to consult a dermatovenerologist to agree on the treatment tactics and further observation of the patient and his sexual partner.

Further management

Treatment of the underlying disease in recipients of joint prostheses: use of antibacterial prophylaxis as indicated. It is also recommended to give patients a memo indicating the principles of preventing bacterial arthritis and infection of the prosthetic joint.

How to prevent septic arthritis?

There is no data on the prevention of septic arthritis. The probability of infection of the prosthetic joint increases significantly during the period of bacteremia that occurs during dental and urological manipulations. In this regard, experts from the American Academy of Orthopedic Surgery, the American Dental Association and the American Urological Association have developed antibacterial prophylaxis regimens for individuals with a high risk of developing endoprosthesis infection.

Prevention of prosthetic joint infection should be performed in all recipients of joint prostheses during the first two years after surgery; in patients with immunodeficiency caused by drug or radiation therapy; in patients who have previously suffered from infection of the joint prosthesis. Prevention should also be performed in individuals with concomitant pathology (hemophilia, HIV infection, type 1 diabetes mellitus, malignant neoplasms) when performing dental interventions that exclude tooth extraction, periodontal manipulations, implant placement, etc. The above categories of patients should receive antibacterial agents during various manipulations associated with a possible violation of the integrity of the mucous membrane of the urinary tract (lithotripsy, endoscopy, transrectal prostate biopsy, etc.)

What is the prognosis for septic arthritis?

In the absence of serious underlying diseases and timely adequate antibiotic therapy, the prognosis is favorable. Irreversible loss of joint function develops in 25-50% of patients. Mortality in septic arthritis depends on the age of the patient, the presence of concomitant pathology (for example, cardiovascular, renal diseases, diabetes mellitus) and the severity of immunosuppression. The frequency of fatal outcomes in such a disease as septic arthritis has not changed significantly over the past 25 years and is 5-15%.