Bone and Joint Infection

Mike Uglow

David G Little

Osteomyelitis

• Acute

• Chronic

– Sequel to Acute

– Specific

• TB, fungal

– Non-specific

• Metaphyseal / Epiphyseal Cavities

• Chronic multifocal osteomyelitis

– Post Trauma

Bacteria

• Staph aureus

• Streptococcus

• E coli (neonates)

• H Influenzae

• Gram negatives (open

fractures, spine)

• Pseudomonas

• Salmonella

Host Defence

• Humoral

• Cell Mediated

– Osteoblasts

– Osteoclasts

– Inflammatory cells

Pathogenesis of Acute

Osteomyelitis

• Metaphysis

• Epiphysis

• Synovial Joints

Pathogenesis

• Bacteraemia common in childhood

– 50% incidence after brushing teeth

• Initiating / compounding factors

– Trauma

– Immunocompromised host

Bacterial adherence

• Blood flow ? stasis

• Relative immonodeficiency of metaphysis

• Minor trauma

– Dead bone

• Attraction for staph aureus to hyaline

cartilage

Immune response

• Inflammatory exudate

– increased intramedullary pressure

– worsening blood flow

– ischaemia / necrosis

• Tissue destruction

– proteolytic enzyme release

– increased phagocytosis (osteoclasts)

Outcome

• Resolution

– Intervention aborts process with minimal tissue

destruction

• Chronicity

– sequestrum (dead bone) formation

– subperiosteal / intramedullary abscess

– sinus formation

– secondary joint infection

Sequelae

• Bone destruction

– regeneration unless blood supply destroyed

• Cartilage / Growth plate destruction

– repair (scarring)

– loss of function

• structural loss

• growth disturbance

• joint dysfunction

Treatment Goals in AHO

• Minimise tissue destruction

– Early diagnosis

– Effective therapy

• antibiotics

• surgery

AHO presentation

• Febrile, unwell, unhappy child

• Acute signs of inflammation in metaphysis

– redness

– warmth

– swelling

– point bony tenderness

– loss of nearby joint function

AHO Workup

• FBC, ESR, CRP

• Blood cultures

• Plain X ray

• TC99 bone scan*

*initiate empiric treatment prior to scan

after cultures

AHO treatment

• Appropriate IV bacteriocidal antibiotics

targeted at likely organism

– Flucloxacillin 200 mg / kg / day

– Cephotaxime 150 mg / kg / day

• Modify antibiotics once organism known

• Convert to oral antibiotics (age > 1) once

fever and CRP settled

• Total therapy three weeks

AHO treatment

• Observation / Investigation for abscess

formation

– Failure of fever / acute phase reactants to

resolve

– Ultrasound

– MRI

Surgery in AHO

• Drain subperiosteal abscess

• Drain joint sepsis

• Debride dead tissue

Neonates

• Immunocompromised

• Septicaemia

• Absent / minimal local signs

• Often multifocal, growth plate and joint

involvement

• Mostly staph, can be Group B strep, gram

negatives

• As joints largely cartilaginous, quickly

destroyed

Childhood

• Staph still common

• H influenzae now less common

• Refusal to walk / limp

• Any odd presentation - subacute forms

• Discitis

Subacute Osteomyelitis

• Metaphyseal /

epiphyseal cavities

• Diaphyseal

osteomyelitis

• Chronic multifocal

osteomyelitis

• Differential diagnosis

includes neoplasia

Subacute Osteomyelitis

• At least as common as acute osteomyelitis

• Mostly still staph Aureus

• Only recover organism in 30% of biopsies

• ? changing virulence pattern

• ? partially treated forms

Subacute Osteomyelitis

• Treatment

– Unlikely infection itself will cause growth

disturbance, surgery may do so

– Trial of antibiotics alone may be successful

– 3 to 6 months oral therapy

– Monitor therapeutic drug level and LFT’s

– Surgery for recalcitrant cases

Discitis

• Vertebral osteomyelitis spreads across disc

to contiguous vertebrae

• May present with bizarre gait, refusal to

walk

• Subacute presentation

– may be afebrile

Discitis

• Decreased spinal movement

• Disc space narrowing

• ESR / CRP likely to be elevated

• TC99 bone scan / Gallium scan positive

• MR may be helpful

• Treat with flucloxacillin

Septic Arthritis

• Emergency

– Joint poor immune defence

– Tissue destruction = loss of function

– Thick capsule does not allow spontaneous

drainage

– Proteolytic enzymes destroy hyaline cartilage in

24 - 48 hours

Septic Arthritis

• Clinical picture

– Usually febrile and unwell

– Unable to ambulate

– Severe restriction of joint motion

• Investigations

– Ultrasound documents hip effusion, not

infection

– Aspiration

Septic Arthritis

• Treatment

– Rapid surgical drainage

– IV antibiotics as for AHO

– Oral antibiotics for total 3 week course

• Sequelae

– Late cases = joint destruction

shortening

deformity

Chronic Osteomyelitis

• Long term disturbance of bone architecture

– pathological weakness / fracture

– ischaemia decreases antibiotic penetration

– dead bone harbours organisms

• adherence

• glycocalyx

• Treatment must be directed at these

deficiencies

Chronic Osteomyelitis

• Chronic from the onset

– Tuberculosis

– Fungal infection

– Parasitic infection

– ? Viral infection

Important Points

• Acute musculoskeletal sepsis relatively easy

to diagnose and treat

• Subacute forms now common

• Differential diagnosis

– Trauma

– Tumour

• Eosinophilic granuloma, chondroblastoma

• Ewings, osteosarcoma

• Leukaemia