Bone and Soft Tissue Infection Flashcards
what is Osteomyelitis?
Infection in bone
what are the different types of Osteomyelitis?
acute
chronic
specific (e.g. TB)
non-specific (most common)
who gets Acute Osteomyelitis?
- mostly children (different ages)
- boys > girls
- history of trauma (minor)
- Adults - other disease: diabetes, rheum arthritis, immune compromise, long-term steroid treatment, sickle cell
what is often the source of infection in Acute Osteomyelitis?
- haematogenous spread – children and elderly
- local spread from contiguous site of infection – trauma (open fracture), bone surgery (ORIF), joint replacement
- secondary to vascular insufficiency
what is the most common source of infection in Acute Osteomyelitis?
haematogenous spread
what are exampels of source of infection in an infant
infected umbilical cord
what are exampels of source of infection in children?
boils, tonsilitis, skin abrasions
what are exampels of source of infection in adults?
UTI, arterial line
what organisms are responsible for Acute Osteomyelitis in infants <1 year
Staph aureus, Group B streptococci, E. coli
what organisms are responsible for Acute Osteomyelitis in older children
Staph aureus, Strep pyogenes, Haemophilus influenzae (immunisation significantly reduced)
what organisms are responsible for Acute Osteomyelitis in adults?
• Staph aureus
−coagulase negative staphylococci (prostheses), Propionibacterium spp (prostheses)
− Mycobacterium tuberculosis
− Pseudomonas aeroginosa (esp. secondary to penetrating foot injuries, IVDAs)
What are examples of organisms responsible for Acute Osteomyelitis in special cases?
- Diabetic foot and Pressure sores - mixed infection including anaerobes
- Vertebral osteomyelitis – S. aureus, TB
- Sickle cell disease – Salmonella spp
What are examples of other organisms responsible for Acute Osteomyelitis?
- Brucella (butchers)
- Mycobacterium marinum (fishermen, filleters)
- Proteus mirabilis
- Candida (debilitating illness, HIV AIDS) (long-term antibiotic treatment, extensive GI surgery, malignancy)
pathology - where does Acute Osteomyelitis occur?
• long bones – metaphysis:
- distal femur
- proximal tibia
- proximal humerus
•j oints with intra-articular metaphysis:
- hip
- elbow (radial head)
what is the pathology of actue oesteomyelitis?
starts at metaphysis – role of trauma?
vascular stasis (venous congestion + arterial thrombosis)
acute inflammation – increased pressure
suppuration
release of pressure (medulla, sub-periosteal, into joint)
necrosis of bone (sequestrum)
new bone formation (involucrum)
resolution - or not (chronic osteomyelitis)
what are the clinical features of osteomyelitis in infants?
may be minimal signs, or may be very ill
failure to thrive
poss. drowsy or irritable
metaphyseal tenderness + swelling
decrease range of motion
positional change
commonest around the knee
Often multiple sites
what are the clinical features of osteomyelitis in a child?
severe pain
reluctant to move (neighbouring joints held flexed); not weight bearing, may be tender
fever (swinging pyrexia) + tachycardia
malaise (fatigue, nausea, vomiting – “nae weel” - fretful
toxaemia
what are the clinical features of osteomyelitis in a adult?
Primary OM seen commonly in thoracolumbar spine
backache
history of UTI or urological procedure
elderly, diabetic, immunocompromised
- Secondary OM much more common
- often after open fracture, surgery (esp. ORIF)
- mixture of organisms
how is the diagnosis of acute osteomyelitis made?
history and clinical examination (pulse + temp.)
FBC + diff WBC (neutrophil leucocytosis)
ESR, CRP (both should be elevated)
blood cultures x3 (at peak of temperature - 60% +ve)
U&Es - ill, dehydrated
what imaging techniques may be used in the diagnosis of osteomyelitis?
X-ray (normal in the first 10-14 days)
ultrasound
aspiration
Isotope Bone Scan (Tc-99, Gallium-67)
labelled white cell scan (Indium-111)
MRI
how may radiographs appear in acute osteomyelitis?
early radiographs minimal changes
10-20 days early periosteal changes
medullary changes - lytic areas
late osteonecrosis - sequestrum
late periosteal new bone - involucrum
what scans may be used in Acute Osteomyelitis?
Technetium-99m labelled diphosphonate
Gallium 67 citrate delayed imaging
Indium-111 labelled WBC scan
MRI
Technetium scan- early and late phases
Growth plates light up as active but on the left leg it is abnormally active
what are some differential diagnosis for Acute Osteomyelitis?
lacute septic arthritis
acute inflammatory arthritis
trauma (fracture, dislocation, etc.)
transient synovitis (“irritable hip”)
rare:
- sickle cell crisis
- Gaucher’s disease
- rheumatic fever
- haemophilia
what are some soft tissue infections that may be a differential diagnosis for acute ostemoyelitis?
cellulitis - (deep) infection of subcutaneous tissues (Gp A Strep)
erysipelas - superficial infection with red, raised plaque (Gp A Strep)
necrotising fasciitis - aggressive fascial infection (Gp A Strep, Clostridia)
gas gangrene - grossly contaminated trauma (Clostridium perfringens)
toxic shock syndrome - secondary wound colonisation (Staph aureus)
How is a Microbiological diagnosis of Acute Osteomyelitis done?
- blood cultures in haematogenous osteomyelitis and septic arthritis
- bone biopsy
- tissue or swabs from up to 5 sites around implant at debridement in prosthetic infections
- sinus tract and superficial swab results may be misleading (skin contaminants)
what is the treatment of osteomyelitis?
supportive treatment for pain and dehydration – general care, analgesia
rest & splintage
antibiotics:
- route (IV/oral switch – 7-10 days?)
- duration (4-6 wks – depends on response, ESR)
- choice - empirical (Fluclox + BenzylPen) while waiting
when giving antibiotics to treat osteomyelitis, what needs to be thought about?
- spectrum of activity
- penetration to bone
- safety for long term administration
when treating acute osteomyelitis with antibitcs, why may they fail?
- drug resistance – e.g. b lactamases
- bacterial persistence - ‘dormant’ bacteria in dead bone
- poor host defences - IDDM, alcoholism…
- poor drug absorption
- drug inactivation by host flora
- poor tissue penetration
- MRSA, etc.!!
how is surgery used to treat acute osetomyelitis and what are indications ofr surgery?
indications:
- aspiration of pus for diagnosis & culture
- abscess drainage (multiple drill-holes, primary closure to avoid sinus)
- debridement of dead/infected/contaminated tissue
- refractory to non-operative Rx >24..48 hrs
timing, drainage, lavage
infected joint replacements - one stage revision/two stage revision/antibiotics only?
if pus is present why remove it
as antibiotics cant reacha pus filled cavity
whata re some complications of Acute Osteomyelitis?
septicemia, death
metastatic infection
pathological fracture
septic arthritis
altered bone growth
chronic osteomyelitis
how may Chronic Osteomyelitis develop?
may follow acute osteomyelitis (now much rarer in children)
may start de novo - following operation, following open # (poss. many years earlier), immunosuppressed, diabetics, elderly, drug abusers, etc.
repeated breakdown of “healed” wounds
what organism is usually resopnsible for Chronic Osteomyelitis?
often mixed infection
usually same organism(s) each flare-up
mostly Staph. Aureus, E. Coli, Strep. pyogenes, Proteus
what is the pathology of Chronic Osteomyelitis?
cavities, poss. sinus(es)
dead bone (retained sequestra)
involucrum
histological picture is one of chronic inflammation
what is the treatment of chronic osteomyelitis?
- long-term antibiotics? - local (gentamicin cement/beads, collatamp), systemic (orally/ IV/ home AB)
- eradicate bone infection - surgically (multiple operations)
- treat soft tissue problems
- deformity correction?
- massive reconstruction?
- amputation? (how many operations/years later?)
what are some complications of chronic osteomyelitis?
- chronically discharging sinus + flare-ups
- ongoing (metastatic) infection (abscesses)
- pathological fracture (infected bones are weaker)
- growth disturbance + deformities - Acute and chronic infection near a growth plate can cause growth disturbance and can cause significant deformities
- squamous cell carcinoma (0.07%)
“Chronic osteomyelitis is a time bomb which ticks for the patient’s lifetime.”
Once its established it never goes away
You can supress it but tends to reoccur
Discharging sinus
Acute Septic Arthritis
what is the route of infection in Acute Septic Arthritis?
haematogenous (most common)
eruption of bone abscess
direct invasion - penetrating wound (iatrogenic? – joint injection), intra-articular injury, arthroscopy (a minimally invasive surgical procedure on a joint in which an examination and sometimes treatment of damage is performed using an arthroscope, an endoscope that is inserted into the joint through a small incision)
metaphyseal septic focus
it can lead to what 2 things?
either septic arthritis
or osteomyelitis
what organisms are responsible for causing acute septic arthritis?
Staphylococus aureus (most common)
Haemophilus influenzae
Streptococcus pyogenes
E. coli
what is the pathology of Acute Septic Arthritis?
acute synovitis (synovial membrane becomes inflamed) with purulent joint effusion
articular cartilage attacked by bacterial toxin and cellular enzyme
complete destruction of the articular cartilage
what may the result of Acute Septic Arthritis be?
complete recovery
or
partial loss of the articular cartilage and subsequent OA (osteoarthritis)
or
fibrous or bony ankylosis (abnormal stiffening and immobility of a joint due to fusion of the bones)
how would Acute Septic Arthritis present in a Neonate?
Picture of septicaemia
irritability
resistant to movement
ill
how does Acute Septic Arthritis present in a Child/Adult?
Acute pain in single large joint
reluctant to move the joint (any movement – c.f. bursitis where RoM OK)
increase temp. and pulse
increase tenderness
Swelling – seen in superficial joint
NOT erythema – unless superficial and later
how does Acute Septic Arthritis present in a Adult?
often involves superficial joint (knee, ankle, wrist)
rare in healthy adult
May be delayed diagnosis
Anyone with a temperature and joint that is sore to move
what investigations would you do for Acute Septic Arthritis present in a Adult?
FBC, WBC, ESR, CRP, blood cultures
X ray
ultrasound
Aspiration - Aspirate joint and culture the aspirate
MRI
Acute Septic Arthritis may occur in an Adult during Infected Joint Replacement, how?
now most common cause of septic arthritis in adult
rare (1-1.5%) but very significant:
- Death
- Amputation
- removal of arthroplasty
- Recurrent operation
changing picture of organisms, but Staph epidermidis/aureus still most common
what is the differential diagnosis of Acute Septic Arthritis?
acute osteomyelitis
trauma
irritable joint
haemophilia
rheumatic fever
gout
Gaucher’s disease
what is the treatment of acute septic arthiritis?
general supportive measures
antibiotics (3-4 weeks)
surgical drainage & lavage - emergency (“never let the sun set on pus” ); open or arthroscopic lavage;
linfected joint replacements - one stage revision, two stage revision, antibiotics only?
Tuberculosis Bone and Joint is often called the great mimic, why?
Mimics other conditions, e.g. bone cancer
Rare in UK
what are the different classifications of Tuberculosis Bone and Joint?
Classification:
- extra-articular (epiphyseal / bones with haemodynamic marrow)
- intra-articular (large joints)
- vertebral body
Can multiple lesions be seen in patiants with TB in bones and joints?
multiple lesions in 1/3 of patient
what are the lcinical features of TB in bones or joints?
insidious onset & general ill health
contact with TB
pain (esp. at night) (may confuse it with bone cancer), swelling, loss of weight
low grade pyrexia
joint swelling (may be seen depending on site)
decrease ROM (range of motion)
ankylosis (Join will fail to move and stick together eventually)
deformity
what is the pathology of TB?
primary complex (in the lung or the gut)
secondary spread
tuberculous granuloma (at the site)
n.b. role of nutrition/other disease (e.g. HIV AIDS) - associated with other conditions
how does spinal TB present?
little pain
present with abscess or kyphosis
Spinal TB is the commonest
(Collapse of vertebral bodies at the top and bony destruction)
what should be done and looked for when making a diagnosis of TB?
long history
involvement of single joint
marked thickening of the synovium
marked muscle wasting
periarticular osteoporosis
Bone around the joint is effected and becomes extremely osteoporotic and osteopenic (lose bone mass and your bones get weaker)
what investigations can be done for TB?
FBC , ESR
Mantoux test
Sputum/urine culture
Xray - soft tissue swelling, periarticular osteopaenia, articular space narrowing
Joint aspiration and biopsy - AAFB identified in 10-20%, culture +ve in 50% of cases
what are some differential diagnosis of TB?
transient synovitis
monoarticular RA
haemorrhagic arthritis
pyogenic arthritis
Tumour
what is the treamtent of TB (it is constantly changing)?
chemotherapy
initial - rifampicin, isoniazid 8 weeks, ethambutol
then - rifampicin and isoniazid 6-12 month
rest and splintage
operative drainage/fusion of spine or affected joint rarely necessary
