Bone and Soft tissue infection Flashcards
What is a bone infection called?
Osteomyelitis
What is a joint infection called?
Septic arthritis
Classes of osteomyelitis
Acute
Chronic
Specific (E.g. TB)
Non-specific (most common)
Most common type of osteomyelitis
Non-specific
Who does acute osteomyelitis mostly affect?
Children (different ages)
Do boys or girls get acute osteomyelitis more?
Boys > girls
Associations/things likely in the history with acute osteomyelitis
History of minor trauma Diabetes Rheumatoid arthritis Immunocompromised Long term steroid treatment Sickle cell
Source of infection in acute osteomyelitis
Haematogenous spread (elderly and children) Local spread from contiguous site of infection e.g. - trauma - bone surgery (ORIF) - joint replacement Secondary to vascular insufficiency Infected umbilical cord in infants In children - boils - tonsillitis - skin abrasions Adults - UTI - Urinary catheter - arterial line
Most common source of infection in acute osteomyelitis
Haematogenous spread
Causative organisms of acute osteomyelitis
Infants < 1 year - E coli ( most common ) - Staph aureus - group B streptococci Older children - Staph aureus ( most common ) - Strep pyogenes - haemophilus influenzae Adults - staph aureus ( most common ) - protheses; coagulase -ve streptococci - mycobacterium TB - pseudomonas aeruginosa (esp. 2ndry to penetrating foot injuries, IVDAs) Diabetic foot and pressure sores - mixed infection including anaerobes Sickle cell disease - salmonella Fishermans and filleters - mycobacterium marinum Candida - debilitating illness - HIV AIDs
Pathology of acute osteomyelitis
- starts of metaphysis (possible role of trauma - bruising/damage)
- Vascular stasis (venous congestion + arterial thrombosis)
- Acute inflammation - increased pressure
- Suppuration - a lot of pus
- Release of pressure - put breaks out (medulla, sub-periosteal, into joint)
- Necrosis of bone (sequestrum)
- New bone formation (involucrum)
- Resolution (or not - chronic osteomyelitis)
Causes of chronic osteomyelitis
Following acute osteomyelitis
Following operation
Following open fracture (possibly many years earlier)
Risk factors for chronic osteomyelitis
Acute osteomyelitis Surgery Open fracture Immunosuppressed Diabetes Elderly Drug abusers
Organisms that cause chronic osteomyelitis
Often mixed infection with the same organisms causing each flare up (usually) Staph aureus E. coli Strep pyogenes Proteus
Pathology of chronic osteomyelitis
Cavities, possible sinus(es)
Dead bone (retained sequestra)
Involucrum
Histological picture of chronic inflammation
Route of infection of septic arthritis
Haematogenous Eruption of bone abscess Direct invasion - penetrating wound - intra-articular injury - arthroscopy - infected joint replacement Metaphyseal septic focus
Most common cause of septic arthritis in adults
Infected joint replacement
Causative organisms of septic arthritis
Staph aureus
Haemophilus influenzae
Strep pyogenes
E. coli
Pathology of septic arthritis
Acute synovitis with purulent joint effusion
Articular cartilage attacked by bacterial toxin and cellular enzyme
Completed destruction of articular cartilage (result of acute septic arthritis)
What happens after septic arthritis?
Complete recovery
OR
Partial loss of articular cartilage and subsequent OA OR
Fibrous or bony ankylosis
Classification of bone and joint TB
Extra-articular (epiphyeal/bones with haemodynamic marrow)
Intra-articular (large joints)
Vertebral body
How many bone and joint TB infections have multiple lesions?
1/3rd
Pathology of bone and joint TB
Primary complex (in lung or gut)
Secondary spread
TB granuloma
Note role of nutrition/other disease e.g. AIDs
Presentation of acute osteomyelitis in infants
Minimal signs or very ill Failure to thrive Drowsy/irritable Metaphyseal tenderness and swelling decreased ROM - tough to know if small baby Positional change Commonest around knees
Meaning of ROM
Range of movement
Commonest site of acute osteomyelitis in infants
Around the knee
Presentation of acute osteomyelitis in a child
Severe pain Reluctant to move Neighbouring joints held flexed Not weight bearing Tender fever (swinging pyrexia) Tachycardia Malaise Fatigue Nausea, vomiting Toxaemia
Where in adults is primary osteomyelitis most commonly seen?
Thoracolumbar spine
When does secondary osteomyelitis occur in adults?
Iatrogenic (especially ORIF)
Open fracture
Presentation of acute osteomyelitis in adults
Backache
Temperature
History of UTI/urological procedure
Acute primary osteomyelitis in adults Is commonly seen in who?
Elderly
Diabetic
Immunocompromised
Presentation of acute septic arthritis in the neonate
Picture of septicaemia
- irritability
- resistant to movement
- ill
Presentation of child/adult acute septic arthritis
Acute pain in a single large joint
Reluctant to move joint - ANY movement
Increased temp and pulse
Increased tenderness
What joints are usually affected in adult septic arthritis?
Superficial joints (knee, ankle, wrist)
How common is septic arthritis in a healthy adult?
Rare
Presentation of bone and joint TB
Insidious onset with general ill health Contact with TB Presentation (especially at night) Swelling Loss of weight Low grade pyrexia Decreased ROM Ankylosis Spinal (little pain, present with abscess or kyphosis)
Definition of ankylosis
Abnormal stiffening and immobility of a joint due to fusion of bones
Investigations of acute osteomyelitis
FBC and different WCC (neutrophil leucocytes) Raised ESR and CRP Blood cultures (x3) if haematogenous osteomyelitis and septic arthritis U and Es Imaging - Xray - USS - Aspiration - isotope bone scan - labelled white cell scan - MRI Bone biopsy Tissue or swabs from up to 5 sites around the implant at debridement in prostetic infections
Differential diagnosis of acute osteomyelitis
Acute septic arthritis
Acute inflammatory arthritis
Trauma (fracture, dislocation)
Transient synovitis in children (“irritable hip”)
Soft tissue infection
- cellulitis, erysipelas, necrotising fasciitis, gas gangrene, TSS
Rare - haemophilia, sickle cell crisis, rheumatic fever
What is gas gangrene?
Grossly contaminated trauma
What Is gas gangrene caused by?
Clostridium perfringes
Investigations of acute septic arthritis
FBC, WBC, ESR, CRP, blood cultures
X ray
USS
aspiration
Differential diagnosis for acute septic arthritis
Acute osteomyelitis Trauma Irritable joint Haemophilia Rheumatic fever Gout Gaucher's disease
Bone and joint TB investigations
Long history Involvement of a single joint Marked muscle wasting FBC, ESR Mantoux test Sputum/urine culture Xray Joint aspiration and biopsy
Bones and joint TB differential diagnosis
Transient synovitis Monoarticular RA Haemorrhagic arthritis Pyogenic arthritis Tumour
Treatment of acute osteomyelitis
Supportive treatment for pain and dehydration (general care and analgesia)
Rest and splintage
Antibiotics (very high dose) for 4-6 weeks depending on response - flucloxacillin and benzylpenicillin
Surgery
Why do antibiotics 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
Treatment of chronic osteomyelitis
Long term antibiotics Eradicate bone infection surgically Treat soft tissue problems Deformity correction Amputation
Treatment of acute septic arthritis
General supportive measures
Antibiotics 3-4 weeks
Surgical drainage and lavage
What responds better to antibiotics, joints or bones?
Joints
Treatment of bone and joint TB
Initial for 8 weeks - rifampicin - isoniazid - ethambutol Then for 6-12 months - rifampicin and isoniazid Rest and splintage Operative drainage - rarely needed
Complications of acute osteomyelitis
Septicaemia leading to death
Metastatic infection
Pathological fracture (due to weakened bones)
Septic arthritis
Chronic osteomyelitis
Altered bone growth (especially in children)
Complications of chronic osteomyelitis
Chronically discharging sinus plus flare ups ongoing metastatic infection (abscesses) pathological fracture Growth disturbance and deformities Squamous cell carcinoma (0.07%)
