bone infections and oncology Flashcards
what two factors are needed to differentiate types of infections?
depth of involvement and presence of necrosis
what is osteomyelitis
bone infection characterized by inflammatory destruction and apposition of new bone
what is septic arthritis?
a joint infection
staph (most common), mycobacteria, spirochetes, fungi, virus
what category of infection does necrotizing fasciitis fall under?
soft tissue infections
what are the routes of infection spread?
hematogenous, contiguous (bone/bursa), direct (skin)
what risk factors predispose pts to bone infections?
age diabetes immune state RA Cirrhosis, HIV, CRD malignancy obesity, ETOH/smoking steroids malnutrition surgery vascular insufficiency
what is the mechanism of osteomyelitis spread in peds?
hematogenous seeding of bacteria to metaphyseal region w sluggish flow
why is osteomyelitis more common in the first decade of life?
rich metaphyseal blood supply, immature immune system
what is the molecular result of OM?
pus, osteoblast necrosis, osteoclast activation, inflammatory factors release, thrombosis
where does OM happen in peds?
long bones (femur)
where does OM happen in adults?
vertebrae most common
spine/ribs for dialysis pt
clavicals for IVDU
foot for diabetics
what is the most common organism causing OM?
S. aureus
what is the mainstay of Dx for OM?
bone aspirate/biopsy
high CRP, ESR
MRI for early Dx, XR doesn’t show up for a while
under what circumstances can OM be managed by antibiotics alone?
no pus, acute
chronic, need surgical drainage, debridement and Abx
where does septic arthritis happen in kids?
hip, shoulder, ankle elbow (overlapping joint capsule and metaphysis)
where does SA happen in adults?
knee, then hips
what organisms cause SA?
staph, neisseria
what is seen on XR for SA?
joint space widening/effusion, periarticular osteopenia
what is the Tx for SA?
operative: incision + drainage + IV antibiotics
rarely non-op (except neisseria + gonorrhea, treat w penicillin)
what is the golden period in open wounds?
time after injury that wound can be closed w/o increasing infection risk
what factors indicate a wound that needs the tetanus vaccine and Ig?
unknown/incomplete immunization, >6hrs, irregular, devitalized tissue, gross contamination, >1cm depth, projectile and crush injury, burn/frostbite
what are factors that indicate a wound only needs tetanus vaccine?
immunization to date, no booster in 5 yrs, small wounds
what is necrotizing fasciitis?
rapid progressive infection of deep fascia w secondary necrosis of sc tissue
what organism causes NF?
strep group A
how do you Dx NF?
biopsy for necrosis/microorganisms
how is NF tx?
debridement, broad spec antibiotics, hemodynamic support, amputation if needed
- Pen G for strep/C diff
- Vanco if MRSA
- Imipenem if polymicrobial
- IVIG for strep and TSS
an aggressive bone lesion in >40yo is likely____
an aggressive bone lesion in <40yo is likely___
metastatic carcinoma or myeloma
sarcoma
what tissues can sarcoma originate from?
fat, muscle, cartilage, bone, nerves, blood vessel
connective tissue of mesenchymal origin
what is the order of likely etiology of bone lesions?
benign>carcinoma>soft tissue sarcoma>bone sarcoma
when can a benign lesion become deadly?
if subcapital, can lead to AVN
what is the gold standard for Dx bone sarcoma?
biopsy
where do sarcomas tend to metastasize?
bone and chest
what is the most important predictor of survival in bone sarcoma?
presence of metastases
what are the characteristics of a ewing sarcoma?
sheets of cells (lamellar), moth eaten look, thickening of periosteum to control tumor growth
what is the most common bone sarcoma?
osteosarcoma
where do osteosarcomas tend to occur?
ends of long bones
what population tends to have chondrosarcomas?
40-70
how is chondrosarcoma tx?
surgical (not sensitive to chemo)
how does ewing sarcoma differ from osteo/chondrosarcomas?
cellular proliferation that doesn’t form bone/cartilage
where does ewing sarcoma occur?
diaphysis of long bones, pelvis
where does chondrosarcoma occur?
pelvis
how does ewing sarcoma present?
with systemic signs present
what is the most effective tx for ewing sarcoma?
BM aspirate and radiation
what are the complications associated with expandable prosthesis?
joint contractures, small injuries, infections, failures
what is epiphysiodesis
halt growth of oppositing growth plate in pt with growth plate tumor
what are the types of benign bone lesions?
cysts, cartilage tumors, bone forming tumors, fibrous lesions, infections
what is the most common benign bone lesion?
enchodroma
what benign lesion is often mistaken for ewing?
osteoid osteoma
what benign lesion is most likely to occur at the prox femur/humerus?
bone cysts
why is giant cell tumor of the bone considered aggressive?
can destroy bone (recruit osteoclasts) even though it’s not a tumor (not life threatening)
where do bone lesions metastases from MM tend to form?
spine, ribs, pelvis, femur, humerus
where do lung/breast metastases tend to locate?
knee/elbow
on x rays, benign vs. malignant
Benign bone lesions = well-defined borders, sclerotic rim, septations
Malignant bone lesions = poorly defined borders, periosteal reaction, cortical erosions, ST mass
Tx for sarcoma
chemo, surgical resection
