Septic Arthritis

Question 1

What is septic arthritis?

Answer 1

Septic arthritis is an infection producing inflammation in a native or prosthetic joint or more than one joint. It can be acute or chronic. Prompt diagnosis and treatment of infectious arthritis can help prevent significant morbidity and mortality. Management is becoming more complex with antibiotic-resistant organisms causing infection.

Question 2

What is the epidemiology of septic arthritis

Answer 2

7.8/100,000 person-years. The incidence of disseminated gonoccal arthritis is 2.8 cases per 100,000 person-years. The disease is becoming increasingly common among the elderly with multiple morbidities and in the immunosupressed.

Question 3

Give some risk factors for septic arthritis

Answer 3

• Increasing age
• Diabetes mellitus
• Rheumatoid arthritis
• Joint surgery
• Hip or knee prosthesis
• Skin infection in combination with joint prosthesis
• Infection with HIV

Question 4

What is the presentation of septic arthritis

Answer 4

Classic picture is swollen joint with pain on active or passive movement. The knee is involved in about 50% of the cases, but wrists, ankles and hips are also commonly affected. Fevers and rigors are present in the majority of cases, but absence does not exclude diagnosis.
Joint is swollen, warm, tender and exquisitely painful on movement. Effusion may be obvious. Prosthetic joint infections show few signs untila drainage sinus develops. OCassionaly an abscess around the joint or loosening of the implant is indicated by pain.

Question 5

What are the three SA red flags in children?

Answer 5

• Fever
• Refusal to use a joint
• ESR (erythrocyte sedimentation rate common marker of inflammation) and CRP elevated

Question 6

What are two coniditions SA can be mistaken for in children?

Answer 6

Transient synovitis

Trauma

Question 7

What is the bacterial aeitology of SA?

Answer 7

Staphylococcus aureus is the most common cause of polyartiicular arthritis. Other causes include gonoccal disease, group B strep (sternocalvicular, sacroiliac joint), lyme disease.

Question 8

Give five investigations for SA?

Answer 8

• FBC
• Joint aspiration – Leukocyte count, gram staining, culture
• Synovial tissue culture
• Blood culture
• PCR

Question 9

Give two imaging techniques for SA

Answer 9

Ct and MRI scanning

Question 10

How is AB therapy handled in SA?

Answer 10

Treatment should be started empirically, but the onus should be placed on identifying the causative organism. Gram stain, the clinic picture and the background of the patient will inform this decision – if gram stain fails to show anything then age and level of sexual activity become major determinants as to the likelihood of gonnocal infection.
Staph aureus and strep should be covered by the anti-microbials.

Question 11

Give two treatment methods other than AB

Answer 11

Joint drainage

Splinting

Question 12

HOw should you treat infected joints

Answer 12

Treatment should be started empirically, but the onus should be placed on identifying the causative organism. Gram stain, the clinic picture and the background of the patient will inform this decision – if gram stain fails to show anything then age and level of sexual activity become major determinants as to the likelihood of gonnocal infection.
Staph aureus and strep should be covered by the anti-microbials.

Question 13

What is the prognosis of SA?

Answer 13

• Current mortality rates of bacterial arthritis range from 10 to 20 percent, depending on the presence of comorbid conditions, such as older age, co-existing renal or cardiac disease, and concurrent immunosuppression.
• Factors associated with death include age 65 years or older, and infection in the shoulder, elbow, or at multiple sites.
• After completing antimicrobial therapy, patients with S. aureus septic arthritis regain 45-50% of baseline joint function.
• Morbidity occurs in 1/3rd of patients with bacterial arthritis