Septic arthritis Inflammation of a joint caused by a bacterial infection

Septic arthritis is also called infectious arthritis

Septic arthritis is diagnosed by identifying infected joint fluid

Epidemiology Incidence: General population 2-5/100,000/yr Children 5.5 - 12/100,000/yr RA 28 - 38/100,000/yr Prosthetic joint 40 - 68/100,000/yr Monoarticular (<20% more than one joint) Large joints>small joints Knee (>50%), ankle, wrist, hip, …

The most common joints to become infected are the knee In infants under the age of three, septic arthritis usually affects the hip

Epidemiology: Tow peaks in the age related incidence children < 5 years adult > 64 years > 75% of childhood SA previously healthy > 75% of adult onset SA predisposing factor

Etiology Gonococcal Non gonococcal Gram-positive cocci (75-80%) Staphylococcus aureus (most common) Staphylococcus epidermidis Immuncompromise, joint surgery β-Hemolytic Streptococci Streptococcus pneumoniae (polyarticular, bacteremia) Hemophilia,Sickle cell disease Older age, comorbidity

Microbiology : Every bacterium has been reported to cause SA. Staph. aureus 40-60% Streptococcus 9.5-28% S. pneumoniae 5.5-9.7% gram negative bacilli 9-19% Anaerobes 1.2-6%

Etiology Gram-negative bacilli (15-20%) Anaerobes (5-7%) E-coli Pseudomonas IV drug abuse, immuncompromise Older age, Comorbidity, UTI Salmonella Proteus SLE Anaerobes (5-7%) Trauma, joint surgery

Clinical presentation: Acute onset of pain and swelling in a single joint. The pain is typically severe and occurs at rest. Large joints (knee, hip, ankle, shoulder) Fever 60-80% (mild) Chills (unusual) Warmth, tenderness, effusion and limited active and passive range of motion

Polyarticular septic arthritis: 10-15% Two or more joints S. aureus is the most common pathogen More common in s. pneumoniae (36%) Streptococci, H-influenza, salmonella, gonorrhoeae, anaerobes Many have comorbidity (RA, IVDA) Mortality

Risk factors : Prosthetic joint Underlying joint diseases ( RA , OA ) Age > 80 years Recent joint surgery Previous SA Diabetes mellitus, hemodialysis, advanced hepatic disease, malignancy, hemophilia, sickle cell disease, hypogammaglobulinemia, IV drug abuse, AIDS Low social economic status Skin infection

Bacterial colonization Pathogenesis Bacterial colonization host immune response Joint damage

Pathogenesis Hematogenous seeding Direct inoculation Most common Abundant vascular supply of synovium and lack of a limiting basement membrane Direct inoculation Trauma Joint surgery Arthroscopy (<0.5%) Joint aspiration and injection (0.0002%) Osteomyelitis, cellulitis, or septic bursitis

Source of infection : Hematogenous seeding (bacteremia): skin, lung, urinary tract, oral cavity, IV catheter Direct inoculation : joint aspiration and injection (0.0002 %) arthroscopic surgery (0.5 %) Spread from adjacent soft tissue infection or osteomyelitis (hip and shoulder)

Pathogenesis Microbial factors: virulence Attach to host tissue within joint Evade host defenses Host factors: Immune response Opsonization Phagocytosis cytokines

Clinical manifestations Monoarticular, knee Febrile Acute onset of pain and swelling Warmth and tenderness, joint effusion, redness and limited active and passive ROM

How is it diagnosed?

Diagnosis History PH/E Arthrocentesis Imaging

Diagnosis Arthrocentesis Normal synovial fluid: Small amount Clear Highly viscous Few WBCs (<200) Protein concentration is one third of plasma Glucose concentration is similar to plasma

Diagnosis Septic joint: Purulent Decreased viscosity WBC > 50,000/mm³, PMN predominance Glucose less than half the serum glucose

The normal joint fluid is sterile and, if removed and cultured in the laboratory, no microbes will be detected.

Organisms in septic arthritis Gram -positive cocci S. aureus S. pyogenes S. pneumoniae S. viridans group Gram-negative cocci N. gonorrhoeae and meningitidis H. influenzae Gram-negative bacilli E. coli Salmonella Pseudomonas species Mycobacteria and Fungi Organisms in septic arthritis #9218010 Copyright © 1972-2004 American College of Rheumatology Slide Collection. All rights reserved.

Diagnosis Culture: 70% - 90% Blood culture: 40% - 50% Definite diagnosis: Gram-stained smear and culture of synovial fluid Smear: Gram-positive cocci: 50% - 75% Gram-negative bacilli: <50% Culture: 70% - 90% Blood culture: 40% - 50% Extraarticular site of infection

Diagnosis Plain radiographs Imaging: Early stages: normal, soft tissue swelling Advanced infection: periosteal reaction, marginal or central erosions, destruction of subchondral bone, Bony ankylosis Baseline films should be obtained to look for evidence of other disease and osteomyelitis

Staphylococcal arthritis: wrists (radiograph) The septic arthritis of the wrist on the right is caused by a staphylococcal infection. The carpus and adjacent bones reveal soft-tissue swelling and localized osteopenia. There is narrowing of multiple joints and irregularity of adjacent bony margins. The left wrist is normal. #9518090 Copyright © 1972-2004 American College of Rheumatology Slide Collection. All rights reserved.

Septic arthritis: early and late changes, hip (radiographs) Left, The anteroposterior view of the hip shows narrowing of the joint space without reactive bone change or osteopenia. Right, Destruction and flattening of the weight-bearing surface of the femoral head have occurred. Some osteopenia is also present. Diffuse loss of cortex (rather than focal erosion) is characteristic of septic arthritis, as demonstrated in both the femoral head and the acetabulum. #9518130 Copyright © 1972-2004 American College of Rheumatology Slide Collection. All rights reserved.

Septic arthritis: sternoclavicular joint (technetium radioisotope scan) The technetium radioisotope scan demonstrates increased uptake in the medial aspect of the left clavicle (arrow) and medial aspect of the anterior left first rib (short arrow). The two sites are separated more than usual, indicative of a soft-tissue lesion, which, in this case, was secondary to a joint-space infection caused by Staphylococcus aureus. #9518070 Copyright © 1972-2004 American College of Rheumatology Slide Collection. All rights reserved.

Differential diagnosis Crystal induced arthritis RA Reactive arthritis Trauma ………………..

If septic arthritis is left untreated

Treatment: septic arthritis is suspected blood and synovial fluid sample empiric parenteral antibiotics based on gram stain joint drainage adjust antibiotics based on culture and sensitivity results

Treatment Immediate treatment after clinical evaluation and cultures Appropriate antibiotics and adequate drainage Initial treatment is IV

Treatment Gram-positive cocci 1gr IV q12h Gram-negative bacilli MSSA Nafcillin/Oxacillin 2gr IV q4h MRSA Vancomycin 1gr IV q12h Gram-negative bacilli Ceftriaxone/Cefotaxime 2gr IV q24h/ 2gr IV q8h Pseudomonas Piperacillin/Ceftazidime + AG 3gr IV q6h/ 2gr IVq8h

Treatment Ceftriaxone or Cefotaxime No organism Healthy, sexually active patient with community-acquired septic arthritis Ceftriaxone or Cefotaxime Elderly debilitated patient Antistaphylococcal + Antipseudomonal + AG Polymicrobial Nafcillin/oxacillin + ceftriaxone/cefotaxime

Prognosis Disability: 25-50% Mortality: 5-20% Patients receiving immunosuppressive therapy Serious underlying comorbidities (liver, kidney, or heart diseases) Juxta-articular osteomyelitis Disability: 25-50% Mortality: 5-20%

Septic olecranon bursa Marked tenderness, swelling, and erythema are present over the olecranon bursa. A purulent serosanguinous drainage is seen exuding from the bursa after needle puncture. Staphylococcus aureus was cultured from the drainage. #9118040 Copyright © 1972-2004 American College of Rheumatology Slide Collection. All rights reserved.

There are more than 150 bursae in the human body. Superficial Deep

Gonococcal arthritis Neisseria gonorrhea Clinical presentation: Disseminated gonococcal infection (DGI) Gonococcal septic arthritis Most common cause of acute monoarthritis in sexually active healthy young adults DGI is more common in women than men (3/1)

Gonococcal arthritis Clinical features DGI septic arthritis Women/men: 3/1 Intrauterine devices, menstruation, pregnancy, and pelvic operation Fever, shaking chills, skin lesions (vesiculopustular, hemmorhagic), tenosynovitis (wrist, fingers, ankle, and toes), polyarthralgias, and arthritis septic arthritis knee, wrist, ankle, or more than one joint

Gonococcal arthritis Diagnosis DGI: Septic arthritis: DNA-PCR Skin lesion culture: negative SF culture: often negative Blood culture: 50% positive Culture from genital, rectal, and pharyngeal sites Septic arthritis: SF culture: 50% positive Blood culture: often negative DNA-PCR

Gonococcal arthritis Treatment DGI: Septic arthritis: Ceftriaxone/cefotaxime 7-10 days Doxycycline Septic arthritis: Ceftriaxone/cefotaxime 7-14 days drainage

Prosthetic joints infection Epidemiology Knee: 1-2% Hip: 0.5-1% Shoulder: <1%

Prosthetic joints infection Clinical manifestations Depend on the timing of infection: Early (<3 m) Acquired during implantation Virulent pathogens such as S. aureus or gram-negative bacilli Joint pain, and effusion, wound drainage, fever, implant site erythema, induration or edema, sinus tract

Prosthetic joints infection  Delayed (3 - 24 m) Acquired during implantation Less virulent pathogens such as S. epidermidis, P. acnes Persistent joint pain, with or without implant loosening, fever< 50% and leukocytosis<10  Late (>24 m) Hematogenous S. aureus Joint pain, tenderness and swelling, fever, leukocytosis

Prosthetic joints infection Treatment Medical and surgical Organisms within biofilms are resistant to antibiotics: