Infections in bone and joints Flashcards
What is osteomyelitis?
A bone infection
What is septic arthritis?
A joint infection
Who is most commonly effected by acute osteomyelitis?
- Children mostly
- Boys >girls
- Those with a history of trauma
- Diabetics
- Rheumatic Arthritis
- Immunocompromised
- Steroid users
- Sickle cell
Acute osteomyelitis, source of infection - Haematogenous spread?
Children and elderly
Acute osteomyelitis, source of infection - Local spread from infection spread?
> Trauma, open fracture
Bone surgery
Joint replacement
Acute osteomyelitis, source of infection?
> Haematogenous
Local from contiguous site of infection
Vascular insufficiency
Acute osteomyelitis, source of infection - in infants?
Infected umbilical cord
Acute osteomyelitis, source of infection - in children?
> Boils
Tonsilitis
Skin abrasions
Acute osteomyelitis, source of infection - in adults?
> UTI
> Arterial line
Acute osteomyelitis, causative organism - In infants, <1 year?
> S aureus
Group B Strep
E. coli
Acute osteomyelitis, causative organism - In older children?
> S aureus
Strep pyogenes
Haemophilus influenzae
Acute osteomyelitis, causative organism - In adults?
> S aureus, most common > Coagulase negative Strep (Prosthesis) > Propionibacterium spp (Prosthesis) > Mycobacterium tuberculosis > Pseudomonas aeroginosa, especially secondary to penetrating foot injuries, IVDAs
Acute osteomyelitis, causative organism - In diabetic foot and pressure sores?
Mixed infection including anaerobes
Acute osteomyelitis, causative organism - In sickle cell disease?
Salmonella spp
Acute osteomyelitis, causative organism - In fishermen, filleter?
Mycobacterium marnum
Acute osteomyelitis, causative organism - In debilitation, HIV, AIDs, other immunocompromised?
Candida
Acute osteomyelitis - where is affected?
Long bones - Metaphysis
- Distal femur
- Proximal tibia
- Proximal humerus
Joints with intra-articular metaphysis:
- Hip
- Elbow (Radial head)
Acute osteomyelitis - Pathology?
1) Start at metaphysis
2) Vascular tasks
3) Acute inflammation
4) Suppuration
5) Release of pressure
6) Necrosis of bone (Sequestrum)
7) New bone formation (Involucrum)
8) Resolution, or not (chronic)
Acute osteomyelitis, clinical features - In infants?
> May be minimal signs, or may be very ill > Failure to thrive > Drowsy or irritable > Metaphyseal tenderness + swelling > Decrease ROM > Positional change > Most common around the knee
Acute osteomyelitis, clinical features - In children?
> 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
Primary acute osteomyelitis, clinical features - In adults?
> Primary OM seen commonly in thoracolumbar spine
Backache
History of UTI or urological procedure
Elderly, diabetic, immunocompromised
Secondary acute osteomyelitis, clinical features - In adults?
> Secondary OM much more common
Often after open fracture, surgery (esp. ORIF)
Mixture of organisms
Causative organism in cellulitis?
Group A Strep
Causative organism in Erysipelas?
Group A Strep
Causative organism in necrotising fasciitis?
- Group A Strep
- Clostridia
Causative organism in gas gangrene?
Clostridium perfringens
Causative organism in toxic shock syndrome?
S aureus
What is cellulitis?
Soft tissue infection - (deep) infection of subcutaneous tissues (Gp A Strep)
What is Erysipelas?
Soft tissue infection - superficial infection with red, raised plaque (Gp A Strep)
What is necrotising fasciitis?
Soft tissue infection - aggressive fascial infection (Gp A Strep, Clostridia)
What is gas gangrene?
Soft tissue infection - grossly contaminated trauma (Clostridium perfringens)
Acute osteomyelitis, diagnosis?
> History and clinical examination (pulse + temp.)
> FBC + diff WBC (neutrophil leucocytosis)
> ESR, CRP
> Blood cultures x3 (at peak of temperature – 60% +ve)
> U&Es – ill, dehydrated
> Aspiration
> Imaging
Acute osteomyelitis, diagnosis - imaging techniques?
> X-ray (normal in the first 10-14 days)
> Ultrasound
> Isotope Bone Scan imaging (Technectium-99 labelled siphosphonate, Gallium-67 citrate delayed)
> Labelled white cell scan (Indium-111)
> MRI
What is seen on radiograph in acute osteomyelitis, early on?
Minimal changes
What is seen on radiograph in acute osteomyelitis, 10-20days?
Periosteal changes
What is seen on radiograph 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 is sequestrum?
Late osteonecrosis
What is involucrum?
Late periosteal new bone formation
When are blood cultures useful in osteomyelitis?
- Heamatogenous osteomyelitis
- Septic arthritis
How do you treat acute osteomyelitis?
> Supportive therapy for pain and dehydration
> Rest and splintage
> Abx:
- Duration = 4-6 weeks, depends on response, monitor ESR
- Choice = Empirical (Fluclox + Benzylpenicillin) whilst waiting for microbiology
> Surgery
Prior to antibiotics what was the mortality in acute osteomyelitis?
70%
What is important in antibiotic choice in acute osteomyelitis?
> Spectrum of activity
Penetration to bone
Safety for long term administration
Why may Abx fail in acute osteomyelitis?
> 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
> MRSA, etc.!!
What are the indications for surgery in acute osteomyelitis?
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
Complications of acute osteomyelitis?
> Septicemia, death > Metastatic infection > Pathological fracture > Septic arthritis > Altered bone growth > Chronic osteomyelitis
Cause of chronic osteomyelitis?
> Acute osteomyelitis
> De novo:
- Following operation
- Following open fracture
- Immunocompromised, diabetics, elderly, drug abusers..
> Repeated breakdown of healed tissue
Chronic osteomyelitis, causative organism?
> Often mixed
Mostly S aureus, E coli, Strep progenes, Proteus
Flare-up usually contains same organism(s)
Chronic osteomyelitis, Pathology?
> Cavities, possibly sinus(es)
Dead bone (retained sequestra)
Involucrum
Histological picture is one of chronic inflammation
Chronic osteomyelitis, complications?
> Chronically discharging sinus + flare-ups
> Ongoing (metastatic) infection (abscesses)
> Pathological fracture
growth disturbance + deformities
> Squamous cell carcinoma (0.07%)
Chronic osteomyelitis, treatment?
> Long-term antibiotics:
- Local (gentamicin cement/beads, collatamp)
- Systemic (orally/ IV/ home AB)
> Eradicate bone infection- surgically
> Treat soft tissue
> Deformity/reconstruction
> Amputation
Acute Septic Arthritis - Route of infection?
> Haematogenous
> Eruption of bone abscess
> Direct invasion:
- Penetrating wound (iatrogenic? – joint injection)
- Intra-articular injury
- Arthroscopy
What can a bone abscess lead to?
1) Acute septic arthritis
2) Acute osteomyelitis
Acute Septic Arthritis -
Organisms?
Common: > Staphylococus aureus > Haemophilus influenzae > Streptococcus pyogenes > E. coli
Acute Septic Arthritis - Pathology?
1) Acute synovitis with purulent joint effusion
2) Articular cartilage attacked by bacterial toxin and cellular enzyme
3) Complete destruction of the articular cartilage
4) then, either:
> Complete recovery
or
> Partial loss of the articular cartilage and subsequent OA
or
> Fibrous or bony ankylosis
End result of acute septic arthritis?
Either:
> Complete recovery
or
> Partial loss of the articular cartilage and subsequent OA
or
> Fibrous or bony ankylosis
Acute Septic Arthritis, clinical presentation - Neonate?
Picture of septicaemia
> irritability
> resistant to movement
> ill
Acute Septic Arthritis, clinical presentation - 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
Most common site(s) of acute septic arthritis in an adults?
Often involves superficial joint - Knee, ankle, wrist
Investigation in acute septic arthritis in an adult?
Investigation: > FBC, WBC, ESR, CRP, blood cultures > X ray > Ultrasound > Aspiration
What is the most common cause of acute septic arthritis in an adult?
Injected joint replacement
- Rare, only 1-1.5%
- Disaster = Amputation, death etc
- S aureus still most common
Differential diagnosis in acute septic arthritis?
> Acute osteomyelitis > Trauma > Irritable joint > Haemophilia > Rheumatic fever > Gout > Gaucher’s disease
Treatment in acute septic arthritis?
> General supportive measures
> Antibiotics (3-4 weeks)
> Surgical drainage & lavage - emergency (“never let the sun set on pus” ); open or arthroscopic lavage;
> Infected joint replacements - one stage revision, two stage revision, antibiotics only?
Classification of tuberculosis in bone and joints?
Classification:
> Extra-articular (epiphyseal / bones with haemodynamic marrow)
> Intra-articular (large joints)
> Vertebral body
Tuberculosis, bone and joints - clinical features?
> Insidious onset & general ill health
> Contact with TB
> Pain (esp. at night), swelling
> Loss of weight
> Low grade pyrexia
> Joint swelling
> Decrease ROM
> Ankylosis
> Deformity
Tuberculosis, bone and joints - pathology?
> Primary complex (in the lung or the gut)
> Secondary spread
> Tuberculous granuloma
> n.b. role of nutrition/ other disease (e.g. HIV AIDS)
Tuberculosis, bone and joints - pathology?
> Primary complex (in the lung or the gut)
> Secondary spread
> Tuberculous granuloma
> n.b. role of nutrition/ other disease (e.g. HIV AIDS)
Tuberculosis, bone and joints - Diagnosis?
> Long history > Involvement of single joint > Marked thickening of the synovium > Marked muscle wasting > Periarticular osteoporosis
Tuberculosis, bone and joints - Investigations?
> 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
Tuberculosis, bone and joints - Differential diagnosis?
> Transient synovitis > Monoarticular RA > Haemorrhagic arthritis > Pyogenic arthritis > Tumour
Tuberculosis, bone and joints - Differential diagnosis?
> Transient synovitis > Monoarticular RA > Haemorrhagic arthritis > Pyogenic arthritis > Tumour
Tuberculosis, bone and joints - Treatment?
chemotherapy 1) Initial: - rifampicin = 8 weeks - isoniazid = 8 weeks - ethambutol = 8 weeks then: - rifampicin and isoniazid for 6-12 months
2) Rest and splintage
3) Operative drainage rarely necessary
Tuberculosis, bone and joints - Treatment, chemotherapy first 8 weeks?
- rifampicin = 8 weeks
- isoniazid = 8 weeks
- ethambutol = 8 weeks
Tuberculosis, bone and joints - Treatment, chemotherapy after the first 8 weeks?
Rifampicin and isoniazid for 6-12 months
When does acute osteomyelitis most commonly occur in adults?
In those immunocompromised, sickle cell, diabetes etc
Where is Propionibacternirm spp found on the body?
In the axilla
If someone was to step on a nail which organism is likely to cause acute osteomyelitis?
Pseudomonas aeroginosa
Which age group is most likely to have acute osteomyelitis caused by H influenzae?
4-8 yrs of age
When do you see acute osteomyelitis caused by fungal infections?
In those who are immunocompromised
If the released into the joint within acute osteomyelitis what is likely to occur?
Septic arthritis
Who is more likely to be affected by multi-site acute osteomyelitis?
Infants
What is the most common site of primary acute osteomyelitis in adults?
The spine
What are the most common organisms which cause acute osteomyelitis in adults?
UTI –> E. coli
What is lost in septic arthritis?
Mobility of the joint
What can viral infection lead to within children?
Transient synovitis (Effusion into the hip)
What can you see if using ultrasound in acute osteomyelitis?
Periosteal swelling from pus
Which imaging modality is more commonly used in acute osteomyelitis now?
MRI
What is the big complication risk of chronic osteomyelitis?
Squamous cell carcinoma
If there is a penetrating wound near a joint how is this managed?
They are taken to theatre and the wound and joint is washed out
What is the risk of a deeper joint being affected by acute septic arthritis?
Deeper joint is harder to recognise and is less tender and often leads to late diagnosis as a consequence
Which organism is more likely to cause acute septic arthritis in an adult who has received a joint replacement?
Staph epidermis
If there is acute inflammation of a joint with a loss of ROM which pathology should be considered?
Acute septic arthritis
How is acute septic arthritis managed?
> Early = Aggressive ABx prior to pus
Once there is pus surgical drainage and lavage is required
Infected joint replacement = One stage/ two stage revisions
Which site is most common in bone/joint related TB?
The vertebral bodies
Which site is most common in intra-articular TB?
The knee
When does pain typically occur in bone/joint TB?
Pain at night
If there is a decreased ROM in bone/joint TB what is this suggestive of?
Fibrosis