Osteomyelitis and Septic Arthritis

Question 1

What is Osteomyelitis?

Answer 1

An inflammation or swelling of the bone tissue due to an infection
Can be Acute or Chronic
Can be:
1. Pyogenic (Suppurative)
Producing pus
Typically, bacterial
Acute or Chronic

2. Non-Pyogenic (Non-Suppurative)
   Fungal osteomyelitis
   Skeletal syphilis
   Tuberculous osteomyelitis

Question 1

What is Pyogenic (Suppurative) Osteomyelitis?

Answer 1

Producing pus
Typically, bacterial
Acute or Chronic

Question 2

What is Non-Pyogenic (Non-Suppurative) Osteomyelitis?

Answer 2

Fungal osteomyelitis
Skeletal syphilis
Tuberculous osteomyelitis

Question 3

What may cause Osteomyelitis?

Answer 3

1. A bacterial (Staphylococcus aureus) bloodstream infection
   - M/c in infants and children
   - affects long bones
   - Femur > Tibia > Fibula
   - Distal end > Proximal end
   - In adults it involves the vertebral bones along the spinal column
2. A nearby infection due to
   - a traumatic injury
   - frequent medication injections
   - a surgical procedure
   - Diabetic patients who develop foot ulcers
3. Low immune system
   - e.g Sickle cell disease or HIV
   - immunosuppressive medications (e.g. chemotherapy or steroids)

Question 4

Where abouts in the bone does osteomyelitis affect an infantile?

Answer 4

<8 months
neonates:metaphysis and/or epiphysis

Question 5

Where abouts in the bone does osteomyelitis affect a child?

Answer 5

1 year to closure
metaphysis

Question 6

Where abouts in the bone does osteomyelitis affect a child?

Answer 6

epiphyses and subchondral regions

Question 7

What is the epidemiology of Osteomyelitis?

Answer 7

• M/C in younger children (2 – 12 years old)
• Can occur at any age.
• M/C in males than females

Question 8

What are the signs and symptoms of Osteomyelitis?

Answer 8

• Fever
  - Fatigue
  - Pain and tenderness in the affected area
  - Feeling unwell and irritability in infants who can’t express pain
  - Swelling, warmth and redness of the affected area
  - Difficulty moving joints near the affected area
  - Difficulty bearing weight or walking
  - A new limp
  - Stiffness (with vertebral involvement)

Question 9

What are the DDX of Osteomyelitis?

Answer 9

• Neuropathic osteoarthropathy
  - Aseptic arthritis
  - Acute fracture
  - Recent surgery
  - Ewing’s sarcoma

Question 10

What is treatment and Management for Osteomyelitis?

Answer 10

• Medications
  - Intravenous (IV) or oral antibiotics
  - Monitoring of successive X-rays and blood tests
  - Pain management
  - Bed rest
  - or restricted movement of the affected area
  - Surgery
  - may be necessary to drain infectious fluid, or to remove damaged tissue and bone

Question 11

What are the complications of Osteomyelitis?

Answer 11

Complications:
- In untreated cases, Osteomyelitis becomes chronic with eventual formation of:

1. Sequestrum
   - Devascularisation of a portion of bone with necrosis and resorption of surrounding bone leaving a floating piece (Segment of dead/ necrotic bone)
   - Develops after 30 days
   - In some cases – sequestrum becomes encased in a thick sheath of periosteal new bone (Involucrum)
   - May reside within marrow for long period
2. Involucrum
   - Layer of living bone (bony collar or cloak) around necrotic bone as attempt to wall off infective process
   - Thick sheath of periosteal new bone surrounding a sequestrum
   - Laminated or spiculated periosteal reaction
   - Develops after 20 days
3. Cloaca
   - space in which dead bone resides
   - Associated with chronic osteomyelitis

Complications:
- Other complications of Chronic Osteomyelitis include:

1. Brodie’s Abscess
   - Lucent, well-defined lesion with thick sclerotic rim
   - Lucent tortuous channel extending towards growth plate prior to physeal closure
   - Typically, in metaphysis or diaphysis of long bones:
   - thick and dense cortex
   - sinus tracts to skins
2. Fibrosarcoma
3. Squamous cell carcinoma

Question 12

What are radiological findings of Osteomyelitis?

Answer 12

1. Soft tissue Swelling
   - Earliest Sign
   - Often in metaphyseal region
   - Loss or blurring of normal fat planes
2. Cortical loss
   - Bone destruction (Bony lysis)
3. Periostitis
   - Periosteal reaction or thickening – laminated, solid, codman’s triangle
   - May appear aggressive
4. Endosteal scalloping
5. Loss of trabecular bone architecture
6. Peripheral sclerosis
7. Poss effusion in an adjacent joint
8. Regional Osteopenia

Chronic Osteomyelitis
- Sclerosis
- cortical thickening
- Periosteal new bone formation
- Destruction
- sequestra

Question 13

What is septic arthritis?

Answer 13

A destructive arthropathy caused by an inflammation due to hematogenous seeding of the synovial membrane from an intra-articular infection e.g.
- infected source elsewhere in the body (wound infection)
- direct, contiguous extension from osteomyelitisadjacent to the joint
Early imaging is necessary to:
- detect any joint effusion due to an intra-articular infection
- check for any associated osteomyelitis
Subdivided into:
1. pyogenic (septic) arthritis
- due mostly toStaphylococcalandGonococcalorganisms
- HALLMARK: destruction of the articular cartilage and long, contiguous segments of the adjacent articular cortexfrom proteolytic enzymes released by the inflamed synovium.
2. non-pyogenic arthritis
- due mostly to infection withMycobacterium tuberculosis

Question 14

What is the epidemiology of septic arthritis?

Answer 14

• All age groups
  - 50% <3 yoa
  - M = F

Question 15

What are the clinical findings of septic arthrits?

Answer 15

• M/C affected joint = KNEE
  - Most prone to bacterial infection due to abundant blood supply to the metaphysis
  - Other joints may be affected e.g. shoulder and hip

Question 16

What is the most commonly affected joint for septic arthritis in infants?

Answer 16

Hip

Question 17

What is the most commonly affected joint for septic arthritis in children?

Answer 17

Knee

Question 18

What is the most commonly affected joint for septic arthritis in adults?

Answer 18

Large joints

Question 19

What is the most commonly affected joint for septic arthritis in IVDU?

Answer 19

Sacroiliac joint

Question 20

What are the signs and symptoms of septic arthritis in infants?

Answer 20

Refusal to feed
Irritable
Failure to thrive
High/no fever
Hypothermia
Joint swelling
Decreased active and passive ROM
Deformity at joint

Question 21

What are the signs and symptoms of septic arthritis in children?

Answer 21

Fever
Chills
Rigors
Toxemia
Tachycardia
Tachypnea
Febrile convulsions
Severe pain
Joint swelling
Deformity
Pseudoparalysis with extremely painful ROM

Question 22

What are the signs and symptoms of septic arthritis in adults?

Answer 22

Pre-existing arthritis
RA
Trauma
Fever
Tachycardia
Severe pain
Joint swelling
Deformity
Extremely painful ROM
Muscle spasm

Question 23

What are the causes of septic arthritis?

Answer 23

• Bacterial (staptylococcus aureus, E.Coli, proteus and streptococcus )
  - Viral
  - Fungal

Question 24

What are the risk factors of septic arthritis?

Answer 24

- Advanced age (>80 yoa) - Immunocompromised state - Rheumatoid Arthritis - Intra-articular or steroid injections - Prosthetic joints - Intravenous Drug Abusers - Joint trauma including surgery - AIDS - Diabetes Mellitus

Question 25

What are the DDX of septic arthritis?

Answer 25

1. Osteomyelitis: - may mimic septic arthritis in its presentation - Ultrasonography – helps exclude the presence of joint effusion thus suggesting contiguous septic arthritis - Dx confirmed on a bone scan. 2. Transient synovitis: - benign synovial inflammation with subsequent effusion formation - more common than septic arthritis HOWEVER - septic arthritis is considered as a primary pathology until proven otherwise because of its catastrophic outcomes as compared to transient synovitis, which is a self-limiting condition

Question 26

What is the treatment/management of septic arthritis?

Answer 26

1. Antibiotics 2. Adequate drainage of the joint - Arthroscopic drainage - Open drainage in difficult and deep joints 3. Needle aspiration 4. Monitoring of synovial fluid leukocyte counts and cultures 5. Acute phase of the disease - rest and optimal joint position 6. Following the acute phase - early physical therapy - aggressive mobilization 

Question 27

What are the complications of septic arthritis?

Answer 27

- Bone and cartilage destruction - Osteonecrosis (E.g. Avascular necrosis of the femoral head) - Secondary osteoarthritis - Osteomyelitis - Eventually Ankylosis - Relapses or reinfections - Avascular necrosis of the femoral head

Question 28

What are the radiological findings of septic arthritis?

Answer 28

- Earliest findings: - may be normal in the very early stage of the disease - displaced joint capsule (Waldenstrom’s sign in hip) - Loss of normal subchondral bone (osseous sign) – “white line” - Joint effusion may be seen - Juxta-articular due to hyperaemia  - Joint space narrowing due to cartilage destruction in the acute phase - Medullary, motheaten destruction may occur if process continues - Reactive juxta-articular sclerosis and ankylosis in severe cases - if left untreated Although conventional radiographs are obtained as the initial study, they are relatively insensitive to the early findings of the disease except for soft tissue swelling and osteopenia.

Question 29

What is the advanced modalities for septic arthritis?

Answer 29

1. Computed Tomography (CT) - Delineation of soft tissue extent - Monitoring of percutaneous biopsy - May reveal sequestra, cloaca & soft tissue abscess 2. MRI - Inflammatory response leads to H2O accumulation in marrow -> - Decreased Signal Intensity (SI) on T1 and increased on T2

Question 30

What are the differences between osteomyelitis vs septic arthritis?

Answer 30

Osteomyelitis and septic arthritis both: - rare and serious conditions - usually caused by the bacterium Staphylococcus aureus Osteomyelitis - infection of the bone Septic arthritis - inflammation in the surface of the cartilage that lines the joint and the synovial fluid that lubricates the joint that is caused by an infection.