Bone and Soft Tissue Infection Flashcards by Andrew Hay

What is the epidaemiology of acute haematogenous osteomyelitis?

(Who is it more common in? What is it associated with?)

Haematogenous spread is mostly children (different ages)

boys > girls

Associated with diabetes, rheumatoid arthritis, immune compromise, long-term steroid treatment, sickel cell

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What should you look for in a history when you suspect acute haematogenous osteomyelitis?

History of trauma (minor)

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What can be a source of infection in acute osteomyelitis?

3 general sources + Infants, children and adults

Haematogenous spread - children and elderly

Local spread from contaguous site of infection - trauma (open fracture), bone surgery (ORIF), joint replacement

Secondary to vascular insufficiency

In infants: infected umbilican cord

In children: boils, tonsilitis, skin abrasions

In adults: UTI, arterial line

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What organisms cause acute osteomyelitis in infants?

under 1 year

Staph aureus
Group B streptococci
E. coli

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What organisms cause acute osteomyelitis in older children?

Staph aureua
Strep pyogenes
Haemophilus influenzae

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What organisms cause acute osteomyelitis in Adults?

Staph aureua

Coagulase negative staphylococci (prostheses)

Propionibacterium spp (prosthesus)

Streptococci pyogenes (infectious arthritis)

Mycobacterium tuberculosis

Pseudomonas aeroginosa (esp secondary to penetrating foot injuries, IVDAs)

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Acute osteomyelitis in butchers may be caused by what organism?

Brucella

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Acute osteomyelitis in fishermen, filleters may be caused by what organism?

Mycobacterium marinum

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When may candida cause acute osteomyelitis?

Debilitating illness,
HIV AIDS,
long term antibiotic treatment,
extensive GI surgery,
malignancy

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What 2 special cases may cause mixed infection acute osteomyelitis?

Diabetic foot (mixed infection including anaerobes)

Pressure sores

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What organisms can cause vertebral and sternal acute osteomyelitis?

Vertebral

S. aureus
TB

Sternal:
-Coagulase negative staphylococci post cardiac surgery

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What two conditions can result in acute osteomyelitis caused by salmonella spp and gonococcus?

Sickle cell disease -> salmonella spp

STD - gonococcus

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Describe the pathology of osteomyelitis

Starts at metaphysis - role of trauma?

Vascular stasis
(venous congestion + arterial thrombus)

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)

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Give 3 examples of long bones with their metaphysis outside the joint

Distal femur
Proximal tibia
Proximal humerus

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Give two examples of joints with intra-articular metaphysis

Hip

Elbow (radial head)

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What is involucrum?

An involucrum (plural involucra) is a layer of new bone growth outside existing bone seen in pyogenic osteomyelitis. It results from the stripping off of the periosteum by the accumulation of pus within the bone, and new bone growing from the periosteum.

It can be seen radiographically (i.e., with x-rays), although it is seen rarely in developed countries, given that osteomyelitis is rarely left untreated there.

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What is a sequestrum?

A sequestrum (plural: sequestra) is a piece of dead bone that has become separated during the process of necrosis from normal or sound bone.

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Describe the pathological process of sequestrum

Infection in the bone leads to an increase in intramedullary pressure due to inflammatory exudates
The periosteum becomes stripped from the osteum, leading to vascular thrombosis (granulation tissue “walls off” sequestrum)
Bone necrosis follows due to lack of blood supply (adjacent healthy bone is devascularised, causing further destruction)
Sequestra are formed

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What are the clinical features of acute osteomyelitis in a child?

Severe pain

Reluctant to move (neighbouring joints held flexed); not weight bearing

May be tender and inflammed

Fever (swinging pyrexia) + tachycardia

malaise (fatigue, N+V - “Nae weel”)

Toxaemia

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What are the clinical features of acute osteomyelitis in an infant?

May be minimal signs, or may be very ill

Failure to thrive

Possibly drowsy or irritable

Metaphyseal tenderness + swelling

Decreased ROM

Positional change

Commonest around knee

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What are the clinical features of an adult with acute osteomyelitis?

Both primary and secondary

Primary OM seen commonly in thoracolumbar spine fever

Backache
History of UTI or urological procedure
Old, diabetic, immunocompromised

Secondary OM much more common

Often after open fracture, surgery (esp. ORIF)
Mixture of organisms

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How do you diagnose acute osteomyelitis?

list the diagnostic tests -> bloods, imaging etc

History and clinical examination (pulse and temp)

FBC + diff WBC (neutrophil leucocytosis)

ESR, CRP

Blood cultures x3 (at peak temp -> 60% positive)

U+Es- ill, dehydrated

X-ray (normal in first 10-14 days)

USS

Aspiration

Isotope bone scan (Tc-99, Gallium-67)

Labelled white cell scan (Indium-111)

MRI

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How can you make a microbiological diagnosis in acute osteomyelitis?

Blood cultures in haematogenous ostemyelitis 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)

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What is the differential diagnosis of acute osteomyelitis?

Acute septic arthritis

Trauma (fracture, dislocation etc)

Acute inflammatory arthritis

Transient synovitis (“irritable hip”)

Rare:

Sickle cell crisis
Gaucher’s disease
Rheumatic fever
Haemophilia

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How do you treat acute osteomyelitis?

Supportive treatment for pain and dehydration -general care, analgesia Rest and splintage Antibiotics - Route (IV/oral switch - 7-10 days?) - Duration (4-6 wks - depends on response, ESR) - Choice - empirical (Fluclox + BenylPen) while waiting

Give some reasons for antibiotic "failure"

Drug resistance - e.g. lactamases Bacterial persistence - "dormant" bacteria in dead bone Poor host defences - IDDM, alcoholism... Poor drug absorption Drug inactivation by host flora Poor tissue penetration

Give 4 indications for surgery in acute osteomyelitis

Aspiration of pus for diagnosis and culture Abscess drainage (multiple drill-holes, primary closure to avoid sinus) Debridement of dead/ infected/ contaminated tissue Refractory to non-operative Rx >24-48hrs

Give some complications of acute osteomyelitis

Septicaemia, death Metastatic infection Pathological fracture Septic arthritis Altered bone growth Chronic osteomyelitis

Give 3 reasons why subacute osteomyelitis may occur over acute osteomyelitis

Increased host resistance Lower bacterial virulence Antibiotic usage

What are the clinical features of subacute osteomyelitis?

Long history (weeks, months) Variable symptoms (pain, limp) Local swelling/ warmth occasionally Tenderness

What is the differential diagnosis for subacute osteomyelitis?

Tumour - Ewing's sarcoma, osteoid osteoma TB

What is Brodie's abscess? (What is it? Who does it occur in? What are its features?

A well defined cavity in cancellous bone A Brodie abscess is a type subacute osteomyelitis Older children Painful limp, no systemic features Radiographic lucency in long bone metaphysis

What is the differential diagnosis of Brodie's abscess?

Ewing's sarcoma

What is the treatment for Brodie's abscess?

Curettage

What are the investigations for subacute osteomyelitis?

X-ray Bone scan Biopsy (50% +ve) grow oragism

What is the treatment for subacute osteomyelitis?

Prolonged course of antibiotics Surgery - curettage

What can cause chronic osteomyelitis?

May follow acute osteomyelitis (now much rarer in children) May start de novo - Following operation - Following open fracture (possibly many years later) - Immunosuppressed, diabetes, elderly, drug abusers etc) Repeated breakdown of "healed" wounds

What is the definition of chronic osteomyelitis?

Chronically discharging sinus fixed to the underlying bone containing sequestrum surrounded by infected granulation tissue and involucrum

What organisms usually cause 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? | What 3 features can it be boiled down to?

Sequestrum + involucrum + sinus

What is the treatment for 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?

What are the complications of chronic osteomyelitis?

Chronic discharging sinus + flare ups Ongoing (metastatic) infection (abscesses) pathological fracture Epithelioma Growth disturbance + deformities Amyloidosis Squamous cell carcinoma (0.07%)

What is the route of infection in acute septic arthritis?

Direct invasion - Penetrating wound (iatrogenic? - joint injection) - I/A injury - Arthroscopy Eruption of bone abscess Haematogenous Metaphyseal septic focus

What are the two outcomes of a metaphyseal septic focus?

Spread into either joint cavity -> septic arthritis OR Spread into periosteum -> osteomyelitis

What are the common oragnisms of acute septic arthritis?

Staphylococcus aureus Haemophilus influenzae Streptococcus pyogenes E. Coli

What is the pathology of acute septic arthritis?

Acute synovitis with purulent joint effusion Articular cartilage attacked by bacterial toxin and cellular enzyme Complete destruction of the articular cartilage

What are the sequelae of acute septic arthritis? | outcomes

Complete recovery OR partial loss of the articular cartilage and subsequent OA OR Fibrous or bony ankylosis

What are the clinical features of acute septic arthritis in a neonate?

Picture of septicaemia - Irritability - Resistant to movement - Ill

What are the clinical features of acute septic arthritis in a child?

Acute pain in a single large joint - Reluctant to move the joint (ANY movement- c.f. bursitis where RoM ok) - Increased temp and pulse - Increased tenderness

What are the clinical features of acute septic arthritis in an adult?

Often involves superficial joint (knee, ankle, wrist) Rare in healthy adult

What are the investigations for acute septic arthritis?

FBC, WBC, ESR, CRP, blood cultures X-ray USS Aspiration

What is the most common cause of acute septic arthritis in adults? Wat can it result in?

Infected joint replacement Rare (1-1.5%) but disaster (death, amputation, removal of arthroplasty Changing picture of organisms, but Staph still most common

What is the differential diagnosis of acute septic arthritis?

``` Acute osteomyelitis Trauma Irritable joint Hemophilia Rheumatic fever Gout Gaucher's disease ```

How do you classify tuberculosis of the bone and joint?

Extra-articular (epiphyseal/ bones with haemodynamic marrow) Intra-articular (large joints) vertebral body

Does bone and joint TB involve single or multiple lesions?

Multiple lesions in 1/3 of patients So 2/3 have single

What are the clinical features of tuberculosis of the bone and joint?

Insidious onset and general ill health Contact with TB Pain (esp. at night), swelling, loss of weight low grade pyrexia Joint swelling Decrease ROM Ankylosis Deformity

Why is there poor entry of antibiotics in bone and joint TB?

Obliterative endarteritis

What are the 2 stages of bone and joint TB?

Early short lived vascular Chronic avascular

How do you diagnose bone and joint TB?

Long history Involvement of single joint Marked thickening of the synovium Marked muscle wasting Periarticular osteoporosis

What are the investigations for TB?

FBC, ESR Mantoux test Sputum/ Urine culture X-ray - Soft tissue swelling - Periarticular osteopaenia - Articular space narrowing Joint aspiration and biopsy - AAFB identified in 10-20% - Culture +ve in 50% of cases

What is the differential diagnosis of bone and joint TB?

Transient synovitis Monoarticular RA Haemorrhagic arthritis Pyogenic arthritis

Bone and Soft Tissue Infection Flashcards

(61 cards)