BONE and JOINT INFECTIONS Flashcards
What is osteomyelitis?
Inflammatory process of bone secondary to bacterial infection
May involve periosteum, medullary cavity, compact, cancellous bone
What are the common routes of infection for osteomyelitis?
- Haematogenous spread
- Exogenous (direct or contiguous)
Most common in children is haematogenous; often polymicrobial in adults
What is the most common route of infection?
Haematogenous (most common in children)
Why is Haematogenous most common in children?
Due to vascular stasis at growth plates
- monomicrobial
What is involved in the exogenous route of infection?
Direct (Entry to bone from fracture ect.)
Contiguous (Spread from local infection)
- polymicrobial
Haemotagenous and exogenous are most susceptible to?
Gram-negatives, E. coli, S. aureus
What is the most common bacterial cause of osteomyelitis in children?
S. aureus
Responsible for 90% of infections in children
What is the treatment for S. Aureus
Flucloaxacillin unless MRSA then Vancomycin
What is the typical site of osteomyelitis infection in children?
Metaphysis of long bones
In adults, common in foot bones (especially diabetics) and vertebrae & pelvis
What diagnostic methods are used for osteomyelitis?
- Culture & Gram stain of pus aspirates
- Bone biopsy
- Imaging (X-ray, CT, MRI)
- Blood culture
Blood culture useful in haematogenous infection
What is the initial treatment duration for osteomyelitis?
4-6 weeks IV + 2-4 weeks oral
Empiric treatment is adjusted once sensitivities are known
What is septic arthritis?
Invasion of joint by infectious agent causing arthritis
Can be caused by bacteria, viruses, or fungi
What is the most common cause of septic arthritis?
S. aureus
(60-80%)
Neisseria gonorrhoeae is also a significant cause in young sexually active individuals
What are the risk factors for septic arthritis?
- Previously damaged joints
- Joint replacement surgery
- IDU
- Immunosuppression
- Male
- Age (>65 years old)
56% of infections occur in males
What are the clinical symptoms of septic arthritis?
- Acute onset of inflammation & swelling
- Loss of joint mobility
- Arthralgia
Knee is the most common site in adults
What is the typical treatment for septic arthritis?
- IV empirical therapy
- Change when sensitivities known
- 2-4 weeks IV + 1-2 weeks oral
Surgical aspiration/drainage may be required
What is the most common complication of osteomyelitis?
Septic arthritis
Other complications include DVT, sepsis, and chronic/recurrent osteomyelitis
What are the classifications of osteomyelitis based on duration?
- Acute
- Subacute
- Chronic
Classification helps in understanding the disease progression
What is Brodie’s abscess?
Localized osteomyelitis with few clinical signs
Often presents with little to no pain and may persist for years
What is the significance of imaging studies in diagnosing osteomyelitis?
X-rays may initially appear normal; changes visible after 10-14 days
MRI is useful for early diagnosis
What is the role of Gram stain in the diagnosis of osteomyelitis?
Provides direct empiric antimicrobial guidance
Culture may be negative in 25% of cases
What is the treatment for MRSA in osteomyelitis?
Vancomycin
Flucloxacillin is used for S. aureus
What is the most common cause of septic arthritis in younger sexually active individuals?
Neisseria gonorrhoeae
Accounts for a significant percentage of cases in this demographic
What are biofilms in the context of septic arthritis?
A layer of microorganisms that can form on joint prostheses
They complicate infections and are associated with S. aureus and S. epidermidis
What is the typical appearance of synovial fluid in septic arthritis?
Turbid, yellow, decreased viscosity
Indicates infection and inflammation in the joint
What is the recommended empirical treatment for septic arthritis caused by S. aureus?
Flucloxacillin
Treatment may vary based on the patient’s history and infection type
What is the common presentation of osteomyelitis in children?
Severe pain, oedema, erythema, fever, malaise
Infants may show less dramatic symptoms
What factors contribute to the pathogenesis of osteomyelitis?
- Inflammation
- Ischaemia & necrosis
- Osteolysis
- Suppuration
These factors contribute to bone damage and infection progression
What is Sequestrum?
Devitalised bone
What is supperation?
Pus formation in bone
What is osteomyelitis?
Inflammatory process of bone due to infection, may involve periosteum, medullary cavity, compact, and cancellous bone.
Classification includes acute, subacute, and chronic based on duration.
What are the two main routes of infection for osteomyelitis?
- Haematogenous
- Exogenous
Haematogenous is most common in children, while exogenous involves direct inoculation of bone.
Which bacteria are most commonly associated with haematogenous osteomyelitis in children?
- S. aureus
- S. pyogenes
- S. pneumoniae
- E. coli
Neonates are also affected by S. aureus, S. agalactiae, and E. coli.
What are some risk factors for osteomyelitis?
- Immunosuppression
- Diabetes
- Steroids
- Cancer
- Asplenia
- Age (children & elderly)
- PVD
- Smoking
- IDU
- Chronic joint disease
- Recent bone surgery/joint replacement/bone trauma
IDU refers to intravenous drug use.
What are common clinical symptoms of osteomyelitis in children?
- Severe pain
- Oedema
- Erythema
- Pseudoparalysis
- Fever
- Malaise
- Nausea
- Vomiting
Symptoms may be less dramatic in infants.
What is the most common cause of septic arthritis?
S. aureus, accounting for 60-80% of cases.
Other causes include S. epidermidis, streptococci, Neisseria gonorrhoeae, and gram-negative bacteria.
True or False: Septic arthritis can be caused by bacteria, fungi, or viruses.
True
The disease can be acute or chronic, focusing on acute bacterial infections.
What is the treatment duration for osteomyelitis?
IV (4-6 weeks) followed by oral (2-4 weeks) therapy.
Treatment may change when sensitivities are known.
What diagnostic methods are used for osteomyelitis?
- Aspiration of pus from bone
- Gram stain
- Culture
- Bone biopsy
- Imaging studies (X-ray, CT, MRI)
- Raised CRP
~50% of blood cultures are positive in haematogenous osteomyelitis.
What is a common complication of osteomyelitis?
- Septic arthritis
- DVT
- Sepsis
- Metastatic infection
- Chronic/recurrent osteomyelitis
- Altered bone growth
- Pathological fracture
These complications can arise due to the progression of the infection.
Fill in the blank: The most common site for septic arthritis in adults is the _______.
Knee
The hip is the most common site in children.
What are the common imaging studies used for diagnosing osteomyelitis?
- X-ray
- CT
- MRI
- Bone scans
X-rays may take 10-14 days to show changes.
What is Brodie’s abscess?
Localized osteomyelitis with few clinical signs and little to no pain, may persist for years.
It is often associated with S. aureus.
What is the typical treatment for septic arthritis?
- IV empirical therapy
- Change when sensitivities known
- Surgical aspiration/drainage
- Removal of prosthesis/debridement
Treatment is similar to that of osteomyelitis.
What is the role of Gram stain in diagnosing septic arthritis?
Direct empiric antimicrobials based on the appearance of the aspirate.
Non-Neisseria cases are usually culture positive unless antibiotics were administered beforehand.
What is the typical clinical presentation of septic arthritis?
- Acute onset of inflammation and swelling
- Joint effusion
- Loss of joint mobility
- Arthralgia
Knee and hip are the most affected joints.
What are the common pathogens involved in chronic osteomyelitis?
- S. aureus
- S. epidermidis
- Streptococci
- Gram-negatives
- Anaerobes
Granulomatous infections can also occur with pathogens like TB and syphilis.
What is the significance of biofilms in septic arthritis?
S. aureus forms biofilms in early-onset infections (within 3 months post-implant), while S. epidermidis is associated with late-onset infections.
Biofilms contribute to the increasing incidence of septic arthritis after joint surgery.
