Bone and Tissue Infections Flashcards
Common background for acute osteomyelitis
Children - boys
History of trauma
Other long term disease
Source of infection for acute OM
Haematogenous spread
Local spread from contiguous site of infection (open fracture, bone surgery, joint replacement)
Secondary to vascular insufficiency
Infants = infected umbilical cord
Children = boils, tonsillitis, skin abrasions
Adults = UTI, arterial line
Common organisms of acute OM
Infants - E. coli Older - staph aureus Prostheses - coagulase -ve strep Infectious arthritis - strep pyogenes Secondary to penetrating foot injury - pseudomonas aeruginosa Sickle cell disease - salmonella Butchers - Brucella Candida - HIV, long term Abx, malignancy Vertebral OM - s. aureus, TB STD - gonococcus
- Group B strep
- Strep pyogenes
- Haemophilus influenzae
- Proteus / Klebsiella
- Mycobacteria tuberculosis
Pathology of acute OM - order of events
- Starts at metaphysis (role of trauma)
- Vascular stasis - venous congestion + arterial thrombosis
- Acute inflammation causes increased pressure
- Pus forms
- Release of pressure
- Necrosis of bone
- New bone formation
- Resolution or not - chronic OM
Clinical features of acute OM in infants
Failure to thrive Drowsy Irritable Metaphyseal tenderness + swelling Positional change Decreased ROM esp knee
Clinical features of acute OM in children
Severe pain Reluctant pain Fever + tachycardia Malaise Toxaemia
Clinical features of acute OM in adults
Primary OM common in thoracolumbar spine
- Back ache
- UTI Hx
- Elderly, diabetic
Secondary OM more common
- open fracture, surgery
- mixture of organisms
Diagnosis of acute OM
H&E FBC + WCC (neutrophil leucocytosis) ESR, CRP rise Blood cultures x3 (+ve in60%) U&Es - dehydrated X-Ray (normal in first 10-14 days) MRI - preferred Isotope bone scan sometimes required i.e. in presence of prostheses)
USS
Aspiration
Labelled white cell scan
Differential diagnosis of acute OM
Acute septic arthritis Acute inflammatory arthritis Trauma Transient synovitis Soft Tissue Infection
What does x-ray of acute OM show
Good disc = tumour (bad)
Bad disc = infection (good)
Nothing for 10-14 days
Then haziness + loss of density
Then subperiosteal reaction
Later see sequestrum (late osteonecrosis) and Involucrum (late periosteal new bone)
Microbiological diagnosis
Blood cultures
Bone biopsy
Tissue swabs from up to 5 sites around implant in prosthetic infections
Treatment of acute OM
Supportive for pain and dehydration
Rest and splint age
Abx (High dose IV 6 weeks)
- empirical flucloxacillin and Benzylpenicillin while waiting for organism and sensitivities)
- switch to oral 7-10 days
Indications for surgery in acute OM
Aspiration of pus for diagnosis and culture
Drain abscess and remove sequestra
Debridement of dead or infected or contaminated tissue
Refractory to non-surgical treatment >24-48hrs
Complications of acute OM
Septicaemia Metastatic infection Pathological fracture Septic Arthritis Altered bone growth Chronic OM
Common presentation of chronic OM
Follow acute OM
Following operation
Following open fracture
Long-term conditions
Common organism in chronic OM
Often mixed
- s aureus, E. coli, strep pyogenes, proteus
Treatment of chronic OM
Radical excision of sequestra
Skeletal stabilisation
Dead-space management - reconstruction
Abx - local gentamicin cement, beads or systemic oral / IV
Complications of chronic OM
Amyloid
Squamous cell carcinoma development in sinus track
Pathological fracture
Ongoing infection
Risk factors for OM
Diabetes Vascular disease Impaired immunity Sickle cell disease Surgical prostheses Open fractures
Patterns of infection of OM
In adults, cancellous bone is typically affected.
In children, vascular bone is commonly affected (i.e. long bone metaphases - esp. distal femur, upper tibia)
This leads to cortex erosion with holes (cloacae). The pus lifts up the periosteum causing death of the original bone (sequestrum). Continued bone formation by the elevated periosteum forms an involucrum. Pus may discharge into joint spaces or via sinuses to the skin.
Route of infection in acute septic arthritis
Direct invasion - penetrating wound, injury
Eruption of bone abscess
Haematogenous
Metaphysial Septic Focus
Organisms in acute septic arthritis
Staph aureus
Haem influenzae
Strep pyogenes
E. coli
Pathology of ASA
acute synovitis and purulent joint effusion causing destruction of the articular cartilage
Sequelae of ASA
Complete recovery
OR partial loss of the articular cartilage and OA
OR fibrous or bony ankylosis
Presentation of ASA in neonate
irritability
resistant to movement
ill
Presentation of ASA in child
Acute pain in single large joint
Reluctant to move
Increased temp and pulse and tenderness
Presentation of ASA in Adult
Common in superficial joints (knee, ankle, wrist)
Rare in healthy adult
Investigations of ASA
FBC, WBC, ESR, CRP Blood cultures X-ray USS Aspiration
Most common cause of ASA in adult
Infected joint replacement
Ddx of ASA
Acute OM Trauma Irrritable joint Haemophilia Rheumatic fever Gout Gaucher's disease
Treatment of ASA
Abx 4 weeks
Surgical drainage and lavage
Classification of bone TB
Extra-articular - epiphyseal / bones with haemodynamic marrow Intra-articular - large joints Vertebral body (Pott's disease)
How does TB spread to bones
Haematogenous or via nearby nodes
Clinical features of bone TB
Pain esp at night Swelling Cold abscess formation \+/- joint formation Joint pain on movement Decreased ROM Muscle wasting Weight loss Malaise, fever, lethargy Insidious onset
Pathology of bone TB
Primary complex (in lung or gut). Then secondary spread causing a tuberculous granuloma
How does spinal TB present
Little pain
Abscess
Kyphosis
Diagnosis of bone TB
Long history Involvement of single joint Marked thickening of synovium Marked muscle wasting Periarticular osteoporosis
Investigations for bone TB
FBC ESR - elevated Matoux test = +ve Sputum / Urine culture X-ray MRI Joint aspiration and biopsy
Findings on x-ray in bone TB
Periarticular osteopenia
Articular space narrowing
Soft tissue swelling (MRI)
findings on joint aspiration and biopsy in bone TB
AAFB in 20%
Culture +ve in 50%
Ddx for bone TB
Transient synovitis Monoarticular RA Haemorrhagic / Pyogenic arthritis Malignancy Gout
Treatment for bone TB
Chemotherapy
- Rifampicin, Isoniazid, Ethambutol for 8 weeks
- Rifampicin, Isoniazid for 6-12 months
Rest and splintage
Operative drainage rarely needed
