| The Septic Joint | | Counselor, The septic joint, otherwise known as septic arthritis is inflammation of a synovial membrane with purulent effusion into the joint capsule, usually due to bacterial infection. This disease entity also is referred to in the literature as bacterial, suppurative, purulent, or infectious arthritis. Septic arthritis is a relatively common disease that typically affects monoarticular joints. The age range of those affected is broad, from the neonatal period to advanced age. Treatment consists of a combined medical and surgical approach. Septic arthritis usually is divided into gonococcal and nongonococcal arthritis, as clinical and treatment regimens differ. In adults, septic arthritis most commonly affects the knee; in children, infection into the hip joint predominates. Despite advances in diagnostic studies, powerful antibiotics, and early drainage, significant joint destruction often occurs if diagnosis and treatment are delayed. We value all your comments, so, if you have a suggestion for a newsletter subject but haven't submitted it yet, or if you have already submitted one but think of another, please take a minute to let us know by clicking on your "Reply" button and dropping us a note. To learn more about AMFS, Inc., the organization run by Physicians and Attorneys that provides medical experts and case review services nationwide, and has produced the following informational newsletter to aid you in understanding complex medical issues, please click here - www.medicalexperts.com. |
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| How Serious is Septic Arthritis? Septic arthritis can quickly destroy a joint and can cause many complications, including osteomyelitis, bony erosions, fibrous ankylosis, sepsis, and even death. Barriers to successful management include lack of clinical suspicion in the early phase of presentation, delay in definitive diagnostic needle aspiration, and failure to provide adequate drainage of the joint. In addition, septic arthritis in neonates and infants can be especially treacherous as a result of blunted inflammatory signals and/or confounding infection at a distant site (eg, ear, umbilical catheter site). |
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| Frequency: Of all the forms of arthritis, septic arthritis is the most aggressive at quickly destroying a joint. The frequency of septic arthritis is approximately 2-10 cases per 100,000 in the general population. In patients with immunologic disorders (eg, rheumatoid arthritis, systemic lupus erythematosus), the occurrence is approximately 30-70 cases per 100,000. The incidence in patients with joint prosthesis is similar to that of patients with immunologic disorders. In gonococcal arthritis, women are approximately 3 times as likely as men to develop this disease. Approximately 20,000 cases of suppurative arthritis occur in the United States each year. |
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| | Etiology: The 2 major classes of bacterial/suppurative arthritis are gonococcal and nongonococcal. Overall, although Neisseria gonorrhoeae remains the most frequent pathogen (75% of cases) among younger sexually active individuals, Staphylococcus aureus is the most common cause of the vast majority of cases of acute bacterial arthritis in adults and in children older than 2 years. This pathogen is the cause in 80% of infected joints affected by rheumatoid arthritis. Streptococcal species, such as Streptococcus viridans, Streptococcus pneumoniae, and group B streptococci, account for 20% of cases. Aerobic gram-negative rods are involved in 20-25% of cases. Most of these infections occur in people who are very young, who are very old, who are immunosuppressed, and who abuse intravenous drugs. |
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| | Pathophysiology: Various sources of infection exist for the joint space. Bacteria may enter the joint directly as with trauma. Infection may enter hematogenously (eg, intravenous [IV] drug injection). Infection may enter from osteomyelitis that is adjacent to the capsule. Infection also may enter from soft tissue infections (eg, cellulitis, abscess, bursitis, tenosynovitis). According to Orthopaedic Pathology, the knee accounts for approximately 40-50% of infections, and the hip accounts for 20-25% of infections. However, in infants and very young children, hip involvement is the most common joint infection. Shoulders, ankles, and elbows account for approximately 10-15% of infections. Finally, septic arthritis of the wrist occurs in 10% of cases. |
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| |  History/Physical: Septic arthritis can be difficult to diagnose in the early stages of progression, so it is imperative that a clinician maintain a high index of suspicion for the condition. Once purulence has developed and a bulging effusion is noted, diagnosis is made easily. Typically, the patient initially presents with fever and a joint that is hot, red, painful, distended, and has a markedly decreased range of motion. Restriction of movement occurs to active and passive attempts, and there is usually significant pain. In young sexually active patients with fever, tenosynovitis, migratory polyarthralgia, and dermatitis, suspect N gonorrhoeae. The rash may appear as papules over the trunk and extensor surfaces of distal extremities that eventually can turn into hemorrhagic pustules. Women are more likely to develop gonococcal arthritis than are men. In infants and children, diagnosis can be very difficult. Neonates and infants often have blunted inflammatory signals and cannot give the clinician feedback. Symptoms such as fever, decreased appetite, and irritability without obvious joint involvement can easily lead to an incorrect diagnosis. Aside from obvious open fractures, foreign object, and trauma, searching for distant infections is very important. Clinical presentation in the older child will be similar to that in the adult. However, the child may not allow the affected joint to be touched. Additional confounding symptoms may be present, including nausea, vomiting, headache, sore throat, and abdominal pain. Ear infections are the most common source of bacteria leading to septic arthritis in children. Also, it is important to distinguish benign transient synovitis from septic arthritis. Four independent variables have been found useful as clinical predictors for septic arthritis, including the following: history of fever, nonweightbearing, erythrocyte sedimentation higher than 40 mm/h, and WBC count higher than 12,000/?L. |
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| | Lab Studies: CBC with differential - Often reveals leukocytosis with a left shift. Erythrocyte sedimentation rate and C-reactive protein are helpful in monitoring treatment course. Blood cultures should be obtained, and Synovial fluid should be analyzed – Gram stain, culture, cell counts, and crystal analysis in order to confirm a bacterial infection. Imaging studies include plain x-rays, which are often normal, but can also demonstrate soft tissue swelling and widening of the joint space, and in later stages, bony erosion. Ultrasound is very sensitive in detecting joint effusions and can help guide further evaluation and treatment. |
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| | Diagnostic Procedures: Needle aspiration of the joint space is the initial best diagnostic procedure. Fluid can be obtained for analysis and the joint space can be drained and decompressed. |
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| | Medical Treatment: In addition to drainage of the septic joint, rapid administration of IV antibiotics is essential. It is important to obtain the synovial sample and blood cultures prior to commencement of IV antibiotic treatment. Pending gram stains and/or cultures should not preclude treatment. With this in mind, most patients respond to IV oxacillin or nafcillin in combination with IV ceftriaxone, cefotaxime, or ceftizoxime. Special situations warrant modification of this antibiotic treatment. For example, in patients who are hospitalized with suspected methicillin-resistant S aureus (MRSA), IV Vancomycin would be an appropriate regimen. In patients with suspected Pseudomonas (eg, IV drug users), an IV aminoglycoside in combination with an antipseudomonal cephalosporin (eg, IV ceftazidime, cefepime, cefoperazone) will adequately treat this organism. Patients with prosthetic joints or intraarticular injected and subsequently infected joints are highly susceptible to MRSA and methicillin-resistant Staphylococcus epidermidis (MRSE), as well as Enterobacteriaceae and Pseudomonas. In this case, IV vancomycin and IV ciprofloxacin are appropriate choices. In young sexually active patients with suspected gonococcal arthritis, IV ceftriaxone (1 g q24h) is recommended almost universally in most studies. In neonates and children, IV nafcillin or oxacillin in combination with a third-generation cephalosporin will properly treat most cases. The duration of treatment varies depending on organism and patient response to medical and surgical drainage. Management of prosthetic infected joints is varied, depending largely on whether or not the prosthesis is removed. Conservative treatment warrants removal of the prosthesis and treatment for approximately 6 weeks with antibiotics. For stable prosthetic joints, several regimens have shown very high success rates, including initial IV antibiotics with oxacillin/nafcillin or vancomycin followed by oral ciprofloxacin and oral rifampin for 6 months for knees and 3 months for hips. Joints infected with S aureus generally are treated with 4 weeks of antibiotics. Pseudomonal infections are treated for at least 3 weeks, whereas streptococcal infections and H influenzae are treated for approximately 2 weeks. Joints infected with N gonorrhoeae respond well to 1 week of IV Rocephin. If the patient responds quickly, a full 7-day regimen can be completed with oral antibiotics, such as ciprofloxacin 500 mg twice a day. |
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| | Surgical Treatment: Adequate drainage of a septic joint is the cornerstone of successful treatment. As Staph aureus is the most prevalent and most virulent organism involved, rapid destruction of the joint proceeds quickly without drainage. Needle aspiration can serve as the initial diagnostic and therapeutic intervention in many cases. However, if rapid improvement is not achieved, open drainage and lavage (arthroscopically or via arthrotomy) is strongly recommended. Arthroscopic drainage and lavage can be used as an initial procedure or after needle decompression fails to provide relief of infection. It is a useful procedure for decompression of elbows, knees, and ankles. Arthrotomy is the best procedure for bacteria deeply embedded in a joint and for loculations. It is especially helpful for drainage of shoulders and hips. |
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| | Complications and Medical/Legal Concerns: Despite medical and surgical treatment, sometimes irreversible destruction of the joint occurs in a large percentage of patients. Major complications of septic arthritis include degenerative joint disease, soft tissue injury, osteomyelitis, fibrous plus bony ankylosis, sepsis, and death. Failure to recognize an infected joint and to promptly institute appropriate therapy in a timely manner poses a significant malpractice risk. |
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