Basic Science Flashcards
Give an example of an osteoconductive, osteoinductive and osteogenic bone graft:
Osteoconductive: demineralized bone matrix
Osteoinductive: bone morphogenetic protein
Osteogenic: fresh autograft, bone marrow aspirate
What are the properties of bone graft?
- Osteoconductive: provides scaffolding for bone growth
- Osteoinductive: provides factors that stimulate osteogenesis and induction of stem cells down a bone forming lineage
- Osteogenic: directly osteogenic. Material directly provides cells that will produce bone including primitive mesenchymal stem cells, osteoblasts, and
What are the different types of bone graft? Give an example of each type:
Autograft: cancellous, cortical, vascularized bone graft
Allograft: fresh, fresh frozen, freeze dried (croutons)
Demineralized bone matrix:
Synthetics: silicate, calcium sulfate/phosphate, corraline
Bone growth factor: BMP, TGF-B, IGF-2, PDGF
What is the only bone graft with osteoinductive, osteoconductive and osteogenic properties?
Autologous bone graft
What are the major risks of iliac crest bone grafting? Which approach has a higher complication rate?
2% to 36% complication rate: anterior > posterior for complications
- Blood loss and hematoma
- Nerve injury: lateral femoral cutaneous or cluneal nerves
- Hernia formation
- Infection
- Fracture
- Cosmetic defect
- Chronic pain
Name the different types of necrotizing soft tissue infections:
Necrotizing cellulitis, myositis and fasciitis
What are the different microbiological types of necrotizing soft tissue infections?
Type 1: Polymicrobial
- At least 1 anaerobic species (Bacteroides, clostridium or peptostreptococcus) in combination with one or more facultative anaerobic streptococci (other than GAS), and members of enterobacteriaceae (E.coli, enterobacter, klebsiella or proteus)
Type 2: GAS or B-hemolytic strep aka hemolytic streptococcal gangrene
- GAS or other beta-emolytic streptococci are isolated alone or in combination with other species, most commonly staph aureus
Name 5 risk factors for necrotizing fasciitis:
Diabetes Drug use (IVDU) Obesity Immunosuppression Recent surgery Traumatic wounds
What is the pathological difference between necrotizing cellulitis, fasciitis and myositis?
Cellulitis: infection of superficial soft tissue, sparing the fascia and deep muscles
Fasciitis: deep infection of subcutaneous tissue with destruction of fascia and fat
Myositis: aggressive infection of skeletal muscle
Describe clinical signs of necrotizing cellulitis?
- Thin, dark wound drainage and gas formation in the skin.
- Gradual onset, but may later progress rapidly
- Pain, swelling and systemic toxicity NOT prominent features
Describe the clinical signs of necrotizing fasciitis?
- Erythematous area without sharp margins
- Swollen, warm, shiny and very tender
- Rapidly progressive over days
- Skin changes from red-purple to blue-grey
- May have bullae with skin breakdown
- Frank cutaneous gangrene may be present in 3-5 days
- High fever and systemic toxicity in advanced infection
Describe the clinical signs of necrotizing myositis?
- Fever, exquisite pain, swelling of muscle with induration
- Erythema, warmth, petechiae, bullae, and vesicles may develop over skin
- However, may be uninvolved initially
- Systemic toxicity may develop, with Streptococcal TSS
What is the diagnosis of necrotizing soft tissue infections?
Clinical/Surgical diagnosis
- Can only be truly diagnosed through surgery by seeing what planes it involves
When type of necrotizing soft tissue infections causes gas in the soft tissue?
Type 1 necrotizing fasciitis or gas gangrene caused by clostridia
What is the best way to radiographically detect gas in the soft tissue?
Non-contrast CT scan
What type of necrotizing soft tissue infection does the presence of anasthesia and skin necrosis suggest?
Necrotizing fasciitis (as opposed to cellulitis or myositis)
What is the definitive management of necrotizing infection?
Surgical debridement (antibiotics alone has a mortality rate of almost 100%)
When is surgery indicated in necrotizing infection?
Progressive soft tissue infection, severe pain, toxicity, fever, elevated serum CK
What are goals of initial debridement of necrotizing infections/
- Debride tissue until viable (bleeding) tissue is reached
- Send tissue for gram stain and culture
- Do not close definitively as will need repeat in 24hrs
What is the antibiotic therapy of choice in necrotizing infections?
Coverage of G+, G-, anaerobic species.
- Regimen: carbapenem or beta/lactam/lactamase inhibitor + clindamycin (for its antitoxin effects) + Vancomycin/daptomycin or linezolid (for MRSA)
IVIG may be used for GAS infection
Hyperbaric oxygen
When does C-Reactive Protein (CRP) levels start and peak?
Start at 6hrs and peak 2-3 days. Comes down 5-21 days
So POD 5, CRP should be coming down, if not, then it’s a sign of infection/continuing inflammation
When does Erythrocyte sedimentation rate (ESR) levels start and peak?
Peak 4-11 days
What is the most sensitive measurement of post-op infection or inflammation?
CRP
What are the characteristic lab findings of renal osteodystrophy?
Bone mineralization deficiency b/c of lack of minerals: Decreased Ca Increased serum Phosphate Increased alkaline phosphate Increased PTH - Secondary hyperparathyroidism