Septic Arthritis: Don't Miss This Septic Joint Emergency

1. Sources
   medial clavicle, distal tibia, and distal femur
2. Treatment: symptomatic; resolves spontaneously; NSAIDs help
3. SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis) syndrome
4. Also called acquired hyperostosis syndrome
5. Young to middle-aged adults with bone pain and skin involvement
6. Suspicion that Propionibacterium acnes serves as antigenic trigger
7. Humoral induction of sclerosis and erosions
8. Sternoclavicular region most commonly involved
9. Axial skeleton involvement and unilateral sacroiliitis common
10. Palmopustular psoriasis, acne, or hidradenitis suppurativa
11. Laboratory findings: ESR, CRP moderately elevated
12. Bone scan (gold standard): bull’s head sign, sacroiliac joint uptake
13. MRI: erosion of vertebral body corner
14. Pathology: sterile neutrophilic pseudoabscesses
15. Cultures: occasional P. acnes
16. Treatment: NSAIDs, rheumatology consult, methotrexate, and biologics
17. Hematogenous spread

18. Extension of metaphyseal osteomyelitis at intraarticular physis

19. Proximal femur—most common
20. Proximal humerus, radial neck, distal fibula
21. Direct inoculation—penetrating trauma, iatrogenic complication
22. Diagnosis
23. Progressive development of joint pain, swelling
    (effusion), warmth, redness
24. Progressive loss of function
25. Loading or moving a joint hurts
26. Differential diagnosis of acute monoarthritis
27. Gout/pseudogout—may be history of prior episodes
28. Reactive arthritis—uveitis, urethritis, heel/back pain, colitis, psoriasis
29. Viral arthritis
30. Fever and systemic symptoms more common in younger patients
31. Laboratory findings

32. Elevations of CRP, ESR, WBC

33. Aspiration—best test
34. Cell count: greater than 50,000 WBCs/µL; left shift
35. Gram stain—helpful if positive
36. Cultures: aerobic and anaerobic
37. Crystals
38. S. aureus most common bacteria, but following organisms should also be considered:
39. Group B streptococci (GBS): neonate
40. H. influenza : Unvaccinated children younger than 2 years
41. Kingella kingae: slower progressing or less virulent septic arthritis in young children
42. Toddler (aged 1–4 yr) with painful joint
43. After upper respiratory infection in fall/winter
44. Gram-negative coccobacilli—hard to culture; blood bottles should be used

45. PCR should be considered

46. Group A strep: post-varicella
47. Neisseria gonorrhoeae: sexually active young adults
48. P. acnes
49. Most common cause after mini–open repair of rotator cuff
50. Shoulder replacement (second only to
    S. aureus)
51. Indolent low-grade common contaminant
52. More than one culture needed; grows very slowly (7–10 days)
53. Gram-positive anaerobic rod that fluoresces under ultraviolet light
54. Less sensitive to cefazolin (penicillin, vancomycin, clindamycin)
55. Fungal infections
56. Chronic effusions, synovitis
57. Immunocompromise: especially cellular immunity
58. IV drug abuse
59. Aspiration: 10,000–40,000 WBCs/µL,
    70% PMNs
60. Diagnosis: potassium hydroxide (KOH) versus 6-week culture
61. Treatment
62. I&D
63. IV antibiotics best based on culture results
64. Empiric antibiotics based on Gram stain results:
65. Gram-positive cocci: vancomycin
66. Gram-negative cocci: ceftriaxone
67. Gram-negative rods: ceftazidime, carbapenem, or fluoroquinolone
68. Negative Gram stain: vancomycin and ceftazidime or fluoroquinolone
69. Progress can be monitored with CBC, ESR, CRP (best measure of success)
70. Periprosthetic septic arthritis: see Chapter 5, Adult Reconstruction, for details.

71. Infectious risks of practice

72. HIV infection

73. Obligate intracellular retrovirus
74. Primarily affects lymphocyte and macrophage cell lines

75. Decreases helper cells (CD4 + cells)

76. Approximately 50,000 new cases/year reported by the CDC
77. Increased in: homosexual men, patients with hemophilia, and IV drug abusers
78. One-fifth of those infected know they are HIV positive.
79. AIDS
80. Diagnosis requires an positive HIV test result plus one of the following:
81. Transmission rate
82. One of the opportunistic infections (e.g., pneumocystis)
83. CD4+ cell count of less than 200 cell/ µL (normal, 700–1200 cells/µL)
84. Increases with amount of blood exposed and viral load
85. Decreases with postexposure antiviral prophylaxis

86. From a contaminated needlestick: 0.3%

87. From mucous membrane exposure: 0.09%
88. From a blood transfusion: approximately 1 per 500,000 per unit transfused

89. From frozen bone allograft: less than 1 per 1 million

90. Donor screening—most important factor in preventing viral transmission
91. No cases from fresh frozen bone allograft have been reported since 2001.
92. Most sensitive screen—nucleic acid amplification testing (NAAT)
93. HIV positivity is not a contraindication to performing required surgical procedures.
94. HIV-positive patients more likely to have THA
95. Higher association with liver disease, drug abuse, coagulopathy
96. Development of acute renal failure and postoperative infection more likely
97. Asymptomatic HIV-positive individuals have no significant difference in short-term infection risks.
98. Orthopaedic manifestations more common in later stages
99. Increased infections:
100. Polymyositis: viral muscle infection
101. Pyomyositis: S. aureus
102. TB
103. Bacillary angiomatosis (Bartonella henselae) from cats
104. Reactive arthritis (Reiter syndrome)
105. Non-Hodgkin lymphoma and Kaposi sarcoma
106. 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.
1. Hepatitis
1. Hepatitis B (HB)
1. Blood transmission: bite/sexual/occupational
2. #### Singlestick transmission rate in the unvaccinated: approximately 30%
3. Causes cirrhosis, liver failure, and hepatocellular carcinoma
4. Screening and vaccination have reduced the risk of transmission for health care workers.
1. #### Antibiotics
1. Immune globulin is administered after exposure in unvaccinated persons.
2. Allografts are screened for HB surface antigen and HB core antibody.
3. Hepatitis C (non-A, non-B) (HCV)
1. Blood transmission: two-thirds of U.S. HCV-positive individuals have IV drug abuse history; 2% of cases are occupational
2. #### Single-stick transmission rate ≈3%
3. Advances in screening have decreased the risk of transfusion-associated infection.
4. Most sensitive method to screen and test early:
1. PCR = NAAT
1. Prophylactic treatment of open fractures
1. Gustilo I and II fractures: first-generation cephalosporins the treatment of choice
2. Gustilo IIIA: first-generation cephalosporin plus an aminoglycoside
3. Gustilo IIIB (grossly contaminated): first-generation cephalosporin plus an aminoglycoside plus penicillin
2. Mechanisms of action of antibiotics are summarized in Table 1.35.
3. Antibiotic indications and side effects are listed in Table 1.36.