MSK Infections Flashcards
What is osteomyelitis?
Inflammation of bone and medullary cavity, usually located in one of the long bones
How can osteomyelitis be classified?
Acute or chronic, contiguous or haematogenous, host status
What is needed for a bone to become infected?
Only with necrosis +/- high inoculum
What are the principles of surgery for osteomyelitis?
Remove infected tissue, drain and debride (may recur after treatment)
When should antimicrobials be given before culture results have been obtained?
Sepsis syndrome or soft tissue infection
What are some appropriate cultures?
Percutaneous aspirate or deep surgical cultures
When are sinus/drain cultures useful?
If they yield staph. or resistant organisms
What are some antibiotics active against staph. aureus?
Flucloxacillin (MSSA only), doxycycline, vancomycin, cotrimoxazole, teicoplanin, linezolid, daptomycin, clindamycin
What are some causes and classes of osteomyelitis?
Open fracture, diabetes/vascular insufficiency, haematogenous, vertebral, prosthetic joint infections
What are some features of osteomyelitis caused by open fractures?
Polymicrobial, contiguous infection, staph. aureus and aerobic gram negative bacteria, symptoms are non-union and poor wound healing
How is open fracture osteomyelitis treated?
Early management is key = aggressive debridement, fixation, soft tissue cover
What are some features of osteomyelitis caused by diabetes/venous insufficiency?
Polymicrobial, diagnosed by a probe to the bone, treated by debridement and antimicrobials
What is the gram positive cover used to treat diabetes-linked osteomyelitis?
Flucloxacillin = IV, for staph (and strep) Vancomycin = people with penicillin allergy (can't take fluclox) Doxycycline = oral switch, excellent bone penetration
What is the gram negative cover for diabetic osteomyelitis?
Gentamicin/aztreonam IV if severe
Oral cotrimoxazole/doxycycline if able to use oral route
Only if needed
What antibiotic is used to treat anaerobic organisms that may cause osteomyelitis in diabetics?
Metronidazole
What are significant causative organisms of osteomyelitis in patients with diabetes?
Staph. aureus, Groups A-C strep, Milleri group, anaerobes
What colonisers may be present in an osteomyelitis infection in a diabetic?
P. aeruginosa, E.coli, proteus, klebsiella, Enterobacter, bacillus sp, coagulase negative staph
May be present on culture but not causing infection = only prescribe antibiotics if signs of infection in patient
What patient groups get haematogenous osteomyelitis?
Prepubertal children, people who inject drugs, central lines/dialysis/elderly
What are some features of haematogenous osteomyelitis?
Caused by presence of bacteria in blood, acute onset illness
What are some features of haematogenous osteomyelitis in IV drug users?
Spread = haematogenous, contiguous, direct inoculation
Unusual sites = SCJ, SChoJ, SIJ, pubic symphysis
What organisms cause haematogenous osteomyelitis in IV drug users?
Most commonly staph. and strep
Less commonly pseudomonas, candida, eikenella corrodens (needle lickers) and myobacterium tuberculosis
What are some features of haematogenous osteomyelitis in dialysis patients?
7% with tunnelled line, high staph. colonisation rates, peripheral vascular disease and diabetes are risk factors, staph. aureus is most common cause, sometimes gram negative organisms are the cause
What are some examples of unusual site osteomyelitis?
Osteitis pubis and Clavicle osteomyelitis
What are some features of osteitis pubis?
Predisposed by urogenital procedures
Aseptic osteitis pubis = triggered by surgery, can be up to 18 months later, athletes get it
What are some features of clavicle osteomyelitis?
3% of osteomyelitis cases
Risk factors = neck surgery, subclavian vein catheterisation
What are some unusual patient groups that get osteomyelitis?
Sickle cell osteomyelitis, Gaucher’s disease, SAPHO/CRMO
What are some features of sickle cell osteomyelitis?
Most commonly salmonella, also staph. aureus, occurs in 12% of homozygotes, acute long bone osteomyelitis
Differentials = bone infarction, septic arthritis
What are some features of Gaucher’s disease?
Lysosomal storage disorder, may mimic bone crisis, often affects tibia, staph. aureus if infected
What do SAPHO and CRMO stand for?
Synovitis Acne Pustolosis Hyperostosis Oseitis = adults
Chronic Recurrent Multifocal Osteomyelitis = children
What are needed to exclude osteomyelitis when considering SAPHO/CRMO?
History plus culture samples crucial
What are some features of SAPHO/CRMO?
Raised inflammatory markers, lytic lesions on x-ray, fever, weight loss, generalised malaise, multi focal osteitis, self-limiting, exacerbations and remissions, genetics and propionbacterium play a role
Where are some sites affected by SAPHO/CRMO?
63% chest, 40% pelvis, 33% spine, 6% lower limb
5 or so active lesions per patient
What are some examples of vertebral osteomyelitis?
Spondylodiscitis and disc space infection
How is vertebral osteomyelitis spread?
Haematogenous spread
What are some associations and comorbidities of vertebral osteomyelitis?
May be associated with epidural or psoas abscesses
Comorbidities = IV drug use, IV site infections, GU infections, SSTI, post-operative
What are the symptoms of vertebral osteomyelitis?
Fever, insidious pain and tenderness, neurological signs, raised inflammatory markers, abnormal plain film and raised white cell count may be present
What investigations are done for vertebral osteomyelitis?
MRI, Ga-67 scan (FDG-PET)
What is the treatment for vertebral osteomyelitis?
Drainage of large paravertebral/epidural abscesses
Antimicrobials for 6 weeks minimum (pathogen specific)
Expect >50% decrease in ESR
Duration extended in complicated cases
When should MRIs be repeated for vertebral osteomyelitis?
Only if unexplained increase in inflammatory markers, increasing pain or new anatomically related signs/symptoms
What is the gold standard investigation for osteomyelitis?
Bone biopsy
