Basic Sciences 2023, Jan, 25 | 12:00 am

Septic arthritis

  • Sources

medial clavicle, distal tibia, and distal femur

  • Treatment: symptomatic; resolves spontaneously; NSAIDs help

  • SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis) syndrome

    • Also called acquired hyperostosis syndrome

    • Young to middle-aged adults with bone pain and skin involvement

    • Suspicion that Propionibacterium acnes serves as antigenic trigger

    • Humoral induction of sclerosis and erosions

    • Sternoclavicular region most commonly involved

    • Axial skeleton involvement and unilateral sacroiliitis common

    • Palmopustular psoriasis, acne, or hidradenitis suppurativa

    • Laboratory findings: ESR, CRP moderately elevated

    • Bone scan (gold standard): bull’s head sign, sacroiliac joint uptake

    • MRI: erosion of vertebral body corner

    • Pathology: sterile neutrophilic pseudoabscesses

    • Cultures: occasional P. acnes

    • Treatment: NSAIDs, rheumatology consult, methotrexate, and biologics

       

  • Hematogenous spread

  • Extension of metaphyseal osteomyelitis at intraarticular physis

    • Proximal femur—most common

    • Proximal humerus, radial neck, distal fibula

  • Direct inoculation—penetrating trauma, iatrogenic complication

    • Diagnosis

      • Progressive development of joint pain, swelling

        (effusion), warmth, redness

      • Progressive loss of function

      • Loading or moving a joint hurts

    • Differential diagnosis of acute monoarthritis

      • Gout/pseudogout—may be history of prior episodes

      • Reactive arthritis—uveitis, urethritis, heel/back pain, colitis, psoriasis

      • Viral arthritis

      • Fever and systemic symptoms more common in younger patients

      • Laboratory findings

        • Elevations of CRP, ESR, WBC

        • Aspiration—best test

          • Cell count: greater than 50,000 WBCs/µL; left shift

          • Gram stain—helpful if positive

          • Cultures: aerobic and anaerobic

          • Crystals

    • S. aureus most common bacteria, but following organisms should also be considered:

      • Group B streptococci (GBS): neonate

      • H. influenza: Unvaccinated children younger than 2 years

      • Kingella kingae: slower progressing or less virulent septic arthritis in young children

        • Toddler (aged 1–4 yr) with painful joint

        • After upper respiratory infection in fall/winter

        • Gram-negative coccobacilli—hard to culture; blood bottles should be used

        • PCR should be considered

      • Group A strep: post-varicella

      • Neisseria gonorrhoeae: sexually active young adults

      • P. acnes

        • Most common cause after mini–open repair of rotator cuff

        • Shoulder replacement (second only to

          S. aureus)

        • Indolent low-grade common contaminant

        • More than one culture needed; grows very slowly (7–10 days)

        • Gram-positive anaerobic rod that fluoresces under ultraviolet light

        • Less sensitive to cefazolin (penicillin, vancomycin, clindamycin)

      • Fungal infections

        • Chronic effusions, synovitis

        • Immunocompromise: especially cellular immunity

        • IV drug abuse

        • Aspiration: 10,000–40,000 WBCs/µL,

          70% PMNs

        • Diagnosis: potassium hydroxide (KOH) versus 6-week culture

    • Treatment

      • I&D

      • IV antibiotics best based on culture results

      • Empiric antibiotics based on Gram stain results:

        • Gram-positive cocci: vancomycin

        • Gram-negative cocci: ceftriaxone

        • Gram-negative rods: ceftazidime, carbapenem, or fluoroquinolone

        • Negative Gram stain: vancomycin and ceftazidime or fluoroquinolone

      • Progress can be monitored with CBC, ESR, CRP (best measure of success)

  • Periprosthetic septic arthritis: see Chapter 5, Adult Reconstruction, for details.

  • Infectious risks of practice

    • HIV infection

      • Obligate intracellular retrovirus

      • Primarily affects lymphocyte and macrophage cell lines

      • Decreases helper cells (CD4 + cells)

      • Approximately 50,000 new cases/year reported by the CDC

      • Increased in: homosexual men, patients with hemophilia, and IV drug abusers

      • One-fifth of those infected know they are HIV positive.

      • AIDS

        • Diagnosis requires an positive HIV test result plus one of the following:

           

      • Transmission rate

  • One of the opportunistic infections (e.g., pneumocystis)

  • CD4+ cell count of less than 200 cell/ µL (normal, 700–1200 cells/µL)

    • Increases with amount of blood exposed and viral load

    • Decreases with postexposure antiviral prophylaxis

    • From a contaminated needlestick: 0.3%

    • From mucous membrane exposure: 0.09%

    • From a blood transfusion: approximately 1 per 500,000 per unit transfused

    • From frozen bone allograft: less than 1 per 1 million

      • Donor screening—most important factor in preventing viral transmission

      • No cases from fresh frozen bone allograft have been reported since 2001.

      • Most sensitive screen—nucleic acid amplification testing (NAAT)

      • HIV positivity is not a contraindication to performing required surgical procedures.

        • HIV-positive patients more likely to have THA

        • Higher association with liver disease, drug abuse, coagulopathy

        • Development of acute renal failure and postoperative infection more likely

        • Asymptomatic HIV-positive individuals have no significant difference in short-term infection risks.

      • Orthopaedic manifestations more common in later stages

        • Increased infections:

          • Polymyositis: viral muscle infection

          • Pyomyositis: S. aureus

          • TB

          • Bacillary angiomatosis (Bartonella henselae) from cats

        • Reactive arthritis (Reiter syndrome)

        • Non-Hodgkin lymphoma and Kaposi sarcoma

        • Osteonecrosis

 

Table 1.35

 

Mechanism of Action of Antibiotics

 

 

Class of Examples Mechanism of Action Antibiotic

β-Lactam

antibiotics

Penicillin, cephalosporins

Inhibit cross-linking of polysaccharides in the cell wall by blocking transpeptidase enzyme

Aminoglycosides

Gentamicin, tobramycin

Inhibit protein synthesis (the mechanism is through binding to cytoplasmic 30S-ribosomal subunit)

Clindamycin and macrolides

Clindamycin, erythromycin, clarithromycin, azithromycin

Inhibit the dissociation of peptidyl-transfer RNA from ribosomes during translocation (the mechanism is through binding to 50S-ribosomal subunit)

Tetracyclines

 

Inhibit protein synthesis (binds to 50S-ribosomal subunit)

Glycopeptides

Vancomycin, teicoplanin

Interfere with the insertion of glycan subunits into the cell wall

Rifampin

 

Inhibits RNA polymerase F

Quinolones

Ciprofloxacin, levofloxacin ofloxacin

Inhibit DNA gyrase

Oxazolidinones

Linezolid

Inhibit protein synthesis (binds to 50S-ribosomal subunits)

 

 

 

Table 1.36

 

Antibiotic Indications and Side Effects

 

 

Antibiotics Sensitive Complications/Other Information Organisms

Aminoglycosides

G−, PM

Auditory (most common) and vestibular damage is caused by destruction of the cochlear and vestibular sensory cells from drug accumulation in the perilymph and endolymph

Renal toxicity Neuromuscular blockade

Amphotericin

Fungi

Nephrotoxic

Aztreonam

G−

Ineffective against anaerobes

Carbenicillin/ticarcillin/piperacillin

Better against G− than G+

Platelet dysfunction, increased bleeding times

Cephalosporins:

 

Nausea, vomiting, diarrhea

 

Prophylaxis (surgical)

Cefazolin is the drug of choice

First generation

 

 

Second generation

Some G+, some G−

 

Third generation

G−, fewer G+

Hemolytic anemia (bleeding diathesis [moxalactam])

Chloramphenicol

Haemophilus influenzae, anaerobes

Bone marrow aplasia

Ciprofloxacin

G−, MRSA

Tendon ruptures; cartilage erosion in children; antacids reduce absorption of ciprofloxacin; theophylline increases serum concentrations of ciprofloxacin

Clindamycin

G+, anaerobes

Pseudomembranous enterocolitis

Daptomycin

G+, MRSA

Muscle toxicity

Erythromycin

G+

In cases of PCN allergy Ototoxic

Imipenem

G+, some G−

Resistance, seizure

Methicillin/oxacillin/nafcillin

Penicillinase resistant

Same as penicillin; nephritis (methicillin); subcutaneous skin slough (nafcillin)

Penicillin

Streptococcal, G+

Hypersensitivity/resistance; hemolytic

Polymyxin/nystatin

GU

Nephrotoxic

Sulfonamides

GU

Hemolytic anemia

Tetracycline

G+

In cases of PCN allergy

Stains teeth/bone (contraindicated up to age 8 yr)

Vancomycin

MRSA,

Clostridium difficile

Ototoxic; erythema with rapid IV delivery

G − , Gram-negative; G+, gram-positive; GU, genitourinary; PCN, penicillin; PM, polymicrobial.

  • Hepatitis

    • Hepatitis B (HB)

      • Blood transmission: bite/sexual/occupational

      • Singlestick transmission rate in the unvaccinated: approximately 30%

      • Causes cirrhosis, liver failure, and hepatocellular carcinoma

      • Screening and vaccination have reduced the risk of transmission for health care workers.

 

  • Antibiotics

    • Immune globulin is administered after exposure in unvaccinated persons.

    • Allografts are screened for HB surface antigen and HB core antibody.

    • Hepatitis C (non-A, non-B) (HCV)

      • Blood transmission: two-thirds of U.S. HCV-positive individuals have IV drug abuse history; 2% of cases are occupational

      • Single-stick transmission rate ≈3%

      • Advances in screening have decreased the risk of transfusion-associated infection.

      • Most sensitive method to screen and test early: