5. MSK infection Flashcards
What causes 90% of suppurative (pyogenic) osteomyelitis?
Staphylococcus aureus
What groups of people are at high risk of getting suppurative osteomyelitis?
Immunosuppressive Alcoholic New horns IV drug addicts Diabetic
What is the MC pathway of infection for suppurative osteomyelitis?
Hematogenous
How does suppurative osteomyelitis present in younger patients vs adult patients?
Younger: fever, chills, pain, swelling, loss of limb fxn, ⬆️ ESR and WBC (shift left)
Adult: insidious, chronic, fever, malaise, edema, erythema, pain
Suppurative osteomyelitis is MC in which age group?
2-12 yo
What is mainliner syndrome?
IV drug user
What is the MC cause of mainliner’s syndrome?
Pseudomonas infection (NOT Staph. Aureus)
What location of the body does mainliner syndrome attack?
Axial skeleton “S” joints
- Spine
- SI joint
- Symphysis pubis
- Sternoclavicular
What are the 3 key radiographic features of osteomyelitis?
Seqeustrum
Involucrum
Cloaca
What is the Seqeustrum?
Island of dead bone
What is the involucrum?
Thick layer of periosteal new bone that forms around sequestering
From the Latin “involvere” meaning roll in, envelop.
What is the cloaca?
Opening in an involucrum that drains pus and debris out of infected bone.
There may be a sinus tract that opens to the skin surface.
What is Brodie abscess?
Intraosseous abscess AKA focal osteomyelitis
What Sx of Brodie abscess?
Local pain
Worse at night
Relieved by aspirin
What 2 conditions are relieved by aspirin?
Osteoid Osteoma and
Brodie Abscess
Common location for Brodie abscess?
Metaphyseal
- Distal OR proximal tibia
- Distal femur
- Fibula
- Distal radius
What is septic arthritis?
A destructive, intra-articular infection with pain and decreased ROM that typically is monoarticular
What are MC location sites of septic arthritis?
Knee
Hip
What studies give you the earliest DX for septic arthritis
US
MRI
Aspirate (to identify specific pathogen)
(Radiographs not recommended d/t latent period)
What is Waldenstrom sign?
Increased distance b/w Kohler teardrop to medial femoral head
What is the typical Waldenstrom measurement?
Typical: unilateral <11m or <2mm diff L vs R
Waldenstrom measurement: distance b/w Kohler teardrop to medial femoral head
What are 2 osseous and articular findings for septic arthritis?
1 - Marked and rapid* joint space loss
2 - Loss of subarticular cortical bone AKA bone is becoming extinct
*bc its rapid, you can r/o arthritis. If it was NOT rapid, then DDX arthritis
What is spondylodiscitis?
An infection involving the disc and adjacent vertebral body that typically occurs in younger and older patients
What is the MC location for spondylodiscitis? (Single level? Multiple levels?)
Lumbar spine
Single level 65% of the time
Multiple contiguous levels 20% of the time
What is the MC presenting symptom for spondylodiscitis?
Back pain (fever is less common)
What is the radiographic latent period for spondylodiscitis? (AKA how long will radiographs be normal for?)
2-4 weeks
What is the best imaging for spondylodiscitis?
MRI
Bone scan
What is the Tx for spondylodiscitis?
Surgical drainage and debridement (remove damaged tissue and foreign objects)
What is the cause of non-suppurative infection / tuberculosis?
2˚ to hemotogenous spread from respiratory infection
What is the MC location for TB?
Thoracic and lumbar
What are the symptoms of skeletal tuberculosis?
Insidious onset
Pain is mild
Few remarkable systemic signs
Appendicular Sx: tenderness, swelling, joint effusion, increased skin temp
What is the xray description of 20-60% skeletal TB?
“Pott’s Disease”
Begins at endplate, disc space loss is earliest sign, lytic destruction 2-5 months, paravertebral soft tissue mass
Where does tubercular arthritis MC happen?
Hip and knee 75%
Is tubercular arthritis mono or polyarticular?
Monoarticular
What is phemister triad?
1- Progressive, slow joint space narrowing
2- Juxtaarticular osteoporosis
3- Peripheral erosive defects
What does phemister triad suggest?
Tubercular arthritis
At end stage of tubercular arthritis, what happens?
Fibrous ankylosis
