Joint and Bone Infections
·
Presentation: systemic illness
with fever, usually one joint (knee most common), swelling, effusion, warmth,
markedly reduced movement of the affected joint, and very painful to move (cf
adjacent osteomyelitis ® some pain only). Hip and shoulder have less swelling
·
In neonates, may overlap with
acute haematogenous osteomyelitis
·
Risk factors: diabetes, recurrent
steroid injections, systemic steroids, alcoholic liver disease,
immunosuppression
·
Differential:
o Gout and pseudogout
o Haemarthrosis
o Acute osteomyelitis
o Acute traumatic arthritis
·
Pathogenesis:
o From haematogenous spread or extension of osteomyelitis, often following
distant infection. Also following penetrating injury
o WBC enzymes rapidly erode articular cartilage ® surgical
emergency: empiric antibiotics and rapid drainage. Urgent – can destroy a joint
in 24 hours. In neonates/kids can damage growth plate ® growth
disturbance
o S. Aureus, also S pneumoniae and S pyogenes. In high-risk groups, M Tb
and Candida. Neonates consider S agalactiae, Haemophilus and N gonorrhoea (did
they have bacterial conjunctivitis soon after birth?). Pseudomonas from foot
wound.
o Tb arthritis: usually haematogenous spread from lungs to hips (kids),
knees (adults) or spine. X-ray shows marginal erosions and destruction of
sub-chondral bone (like Rheumatoid – but different distribution). Have
granulomas (except in AIDS). Histology: Granulomas are pink, cf lymphoid
aggregates in Rheumatoid that are blue
·
Investigations:
o Joint aspiration (arthrocentesis: opaque fluid with WBC > 50,000/ml)
o FBC, ESR, CRP, blood cultures,
plain Xray, US (for detection effusion)
o Xray delays rather than establishes the diagnosis
·
Management:
o Flucloxacillin: for staph aureus, but also covers S pneumonia, S
pyogenes, S agalactiae
o If neonate:
§ And unimmunised consider H. Influenzae: cefuroxime or cefotaxime
§ Consider G –ive: gentamycin
o Arthroscopic washout
o Initial splinting for pain relief, but then encourage mobility
o If there is a joint prosthesis, revision may be necessary
·
Complications due to delayed
diagnosis:
o Joint degeneration, joint dislocation
o Damage to the growth plate ® growth arrest
·
Common in low socio-economic and
warmer weather
·
May follow minor trauma with or
without infection elsewhere in body
·
Acute haematogenous
osteomyelitis:
o Presentation:
§ Early: short, febrile illness, bone pain, metaphyseal tenderness (point
tenderness)
§ Late: Swelling/erythema (suggest abscess). Cellulitis. Adjacent joints
sore but some movement still possible
§ Vascular supply to bone is compromised and infection spreads to
surrounding soft tissue
o Differential diagnosis:
§ Septic arthritis
§ Cellulitis
§ Trauma (Facture)
§ Tumour
o Aetiology:
§ Trauma/surgery ® direct introduction of bacteria
§ Direct extension from infective site: eg dental infection ® jaw,
diabetic foot ® bones of foot
§ Haematogenous seeding:
·
Commonest site in children is
metaphysis of the long bones. Femur and tibia account for > ½ all cases (especially
around knee joint). Epiphyseal growth plate acts as a barrier to the spread of
infection to the joint. May spread through Haversian and Volkmann‟s canal
system to form a subperiosteal abscess (requires drainage)
·
In adults, haematological spread
less common. Tends to affect subperiosteal corticies of long bones. Also
cancellous bone of vertebral bodies, may ® compression fracture
·
Eg: sluggish blood flow ® easy
thrombosis following trauma ® predisposes to infection (esp staph aureus)
o Pathology: Inflammatory response ® oedema ®
compromise vascular supply ® necrosis ® spread of infection through cortices ® pus
under periosteum ® shearing of periosteum ® further disruption to blood vessels
o Causative organisms:
§ Under one year: staph aureus, strep agalactiae, E coli. May be non-specific illness
§ Children: staph aureus, strep pyogenes, H influenzae
§ Adults: staph aureus, staph epidermis and G negatives (E coli,
salmonella and pseudomonas from foot wounds)
§ M. Tb and Candida in high risk groups
o Complications:
§ Spread of infection ® septicaemia, joint infection
§ Fracture, abscess formation
§ ® Chronic
osteomyelitis in 5 – 20% of cases
·
Subacute osteomyelitis: Focal
rather than systemic response to infection. Xray shows bone destruction.
Differential includes bone tumour and stress fracture
·
Chronic osteomyelitis:
o Usually delayed or inadequate treatment.
o Pain, swelling +/- discharging sinuses.
o Xray: destruction, with sequestrum (areas if necrotic bone which can‟t be resorbed) harbouring bacteria and involucrum (formed from periosteum raised over an abscess). Brodie‟s abscess: abscess surrounded by sclerotic bone due to organisms of low virulence
o Treatment: sequestrum must be removed, may require repeated surgery.
Poor penetration of antibiotics
o Complications:
§ Persistently discharging sinus
§ Chronic ill health
§ Pathological fractures/deformities
§ Malignant change ® SCC
·
Investigations:
o Blood: FBC, ESR, CRP, Blood cultures (+ive in 50%)
o Imagining:
§ Plain films: no changes until day 10
§ US: subperiosteal abscesses
§ Bone scan: very sensitive but not specific
§ MRI: very sensitive but expensive
§ CT: good for detecting degree of bone destruction
· Treatment:
o High dose IV antibiotics for at least 2 – 4 days (for children, Flucloxacillin 50 mg/kg/6 hourly, max 2 g), followed by 3 – 4 weeks of oral therapy
o Surgery to decompress and remove necrotic bone if late or failed medical
treatment, or subperiosteal abscess drainage
·
Specific presentations:
o Osteomyelitis of the calcaneum: infection 5 – 10 days after puncture
wound. P aeruginosa
o Discitis: inflammation of the lumber disc, usually < 8 years
o Pelvic osteomyelitis: pain referred to the abdomen, buttock or leg. S aureus.
Bone scan diagnostic
o Tb Osteomyelitis: rare in developed world. Occurs in 1-3% of patients with pulmonary Tb.
o Insidious. After months: pain on movement, fever, night sweats, weight
loss. Destructive. If lumber or thoracic vertebrae may ®
hunchback deformity
·
Usually history of trauma
·
Paronychia: common infection of
periungual tissues, usually by Staph Aureus
·
Felon: deep infection of the pad
of the finger. Usually Staph aureus
following puncture wound
·
Cellulitis: Strep Pyogenes
infection
·
Suppurative flexor tenosynovitis:
o Infection of flexor tendon sheaths
o Presentation: Swollen finger with painful motion. Symmetrical swelling,
tenderness, erythema along tendon sheath. Semi flexed posture and severe pain
on passive extension of DIP joint
o Signs: crepitus, erythema, vesicle formation, colour, pain, puss
o Tests:
§ Culture of puss, blood culture, FBC
§ X-ray to rule out foreign body, air in tissue or joint, associated
fracture
o Treatment: irrigate, leave wound open and dress after swelling has
decreased, antibiotics, splint
·
Atypical infections:
o Herpes infections of the thumb and fingers (eg Whitlow‟s lesions)
o Fungal infections: more indolent. Sporotrichosis common
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