Osteomyelitis, Septic Arthritis and Prosthetics Flashcards
What is osteomyelitis?
Bone inflammation that is secondary to infection
What is the epidemiology and main causes of osteomyelitis?
e: ^ Incidence of chronic OM with bimodal age distribution
Causes: S aureus, CNeg staph, aerobic gram -ve bacilli and mycobacterium TB
What are 2 predisposing conditions that can lead on to osteomyelitis?
1) Diabetes
2) PVD
What are the 3 methods of Osteomyelitis travelling into the bone?
1) Basic: Inoculation of infection into bone e.g. trauma/open wound
2) Slightly easy: Contiguous spread of infection from adjacent tissues to bone
3) Difficult: Haematogenous seeding (e.g. cannula infection)
Which bones does Haematogenous seeding affect and why?
Adults: Vertebrae as ^ vasculature in age so bacterial seeding is ^ likely
Children: Long bones as metaphysis of bones has high blood flow and bacteria can move to bone from blood as BM absent
Which group of people are at risk of haematogenous osteomyelitis?
IVDU and other groups at risk from bacteraemia
What are 4 host factors affecting pathogenesis of osteomyelitis?
1) Behavioural: Risk of trauma
2) Vascular Supply: Arterial disease
3) Pre-existing bone/joint problems e.g. RA
4) Immune deficiency
What changes would histologically be seen in Acute osteomyelitis?
1) Inflammatory cells
2) Oedema
3) Vascular congestion
What changes would histologically be seen in Chronic osteomyelitis?
1) Necrotic bone “sequestra”
2) New bone formation
3) Neutrophil exudates
(Seq and new bone as inflammatory exudate ruptures periosteum –> blood supply impaired –> necrosis –> sequestra –> new bone forms)
What are the main signs of osteomyelitis?
Fever, Rigor, Sweats, Malaise, Tenderness, Warmth, Swelling and Erythema
(Chronic –> Sinus formation)
What would the investigations and DD be for osteomyelitis?
Inv: Bloods, Radiographs/MRI, Bone biopsy and blood cultures
DD: Cellulitis, avascular necrosis and gout
What is the usual treatment?
1) Large dosage of IV antibiotics tailored to culture findings (Flucloxacillin)
2) Surgical Treatment: Debridement
How does TB OM differ from the other types?
1) Slower onset
2) Different epidemiology
3) Longer treatment
4) Biopsy essential –> Caseating granuloma
What is the most common cause of septic arthritis?
Staphylococcus aureus
What are 3 main causes of septic arthritis?
1) Staph. aureus
2) Streptococci
3) Neisseria
(Clinical context of patient)
