Bone And Soft Tissue Infection

Question 1

What is the bacteriological and pathological basis of bone infections?

Answer 1

Bone infections are known as osteomyelitis and can be acute or chronic, specific or non specific.

Acute
Most common organism in <1y is staph aureus, group B strep or E. coli, in older child it is staph aureus, strep pyogenes or haemophilus influenzae, in adults it is staph aureus.
Pathology: starts at metaphysis, vascular stasis, acute inflammation, suppuration, release of pressure, necrosis of bone, new bone formation, and resolution (or not).

Chronic
Most common organism: often mixed infection but same organism each flare up. Staph aureus, E. coli, strep pyogenes, proteus.
Pathology: cavities, possibly sinus, dead bone within, new bone formation and histological picture of chronic inflammation

Septic arthritis
Bacterial: staph aureus, h. influenzae, strep pyogenes, E. coli
Pathology: acute synovitis with purulent joint effusion, articulate cartilage is attacked by bacterial toxin and cellular enzyme, complete destruction of articular cartilage, complete recovery / partial loss / fibrous or bony ankylosis

Question 2

What is acute, subacute and chronic osteomyelitis?

Answer 2

Acute is mostly children with a history of minor trauma and possibility other disease. The source of infection can be haematogenous, local spread or secondary to vascular insufficiency.

Chronic may follow acute OM or may start de novo, following operation, open fracture, immunosuppressed, diabetes etc. It is the repeated breakdown of “healed” wounds

Question 3

What are the clinical features of and differential diagnosis of a patient with osteomyelitis, septic arthritis or soft tissue infection?

Answer 3

OM
Features:
- infant: failure to thrive, minimal signs, drowsy, irritable, metaphyseal tenderness + swelling, decreased ROM, positional change
- child: severe pain, reluctant to move, may have swinging lyre in, tachycardia, malaise (fatigue, N+V), toxaemia
- adult: primary = backache, history of UTI or urological procedure, may be elderly, diabetic, immunocompromised, secondary = history of fracture, surgery

DD: soft tissue infection eg cellulitis, necrotising fasciitis, TSS, acute septic arthritis, acute inflammatory arthritis, trauma, transient synovitis

Septic arthritis
Features:
- neonate: irritability, resistant to movement, I’ll
- child/adult: acute pain in single large joint, reluctant to move joint or any movement, increased temp and pulse, increased tenderness
- adult: often involves superficial joint

DD: acute OM, trauma, irritable joint, haemophilia, rheumatic fever, gout, Gaucher’s disease

Tuberculosis
Features:
- insidious onset, general ill health, contact with TB, pain, swelling, weight loss, low grade pyrexia, joint swelling, decreased ROM, ankylosis, deformity

DD: transient synovitis, monoarticular RA, haemorrhagic arthritis, pyogenic arthritis, tumour

Question 4

What are the investigations for osteomyelitis, septic arthritis or soft tissue infection and what are the expected results?

Answer 4

OM investigations: x ray, ultrasound, aspiration, isotope bone scan, labelled white cell scan, MRI

Septic arthritis: FBC, WBC, ESR, CRP, blood cultures, x ray, USS, aspiration

Tuberculosis: FBC, ESR, Mantoux test, sputum/urine culture, x ray, joint aspiration and biopsy

Question 5

What are the principles of management for bone and soft tissue infections?

Answer 5

Acute OM management: supportive treatment for pain and dehydration, rest + splint, antibiotics, surgery

Chronic OM: long term antibiotics, eradication of bone infection via multiple surgeries, treat soft tissue problems

Septic arthritis: general supportive measures, 3-4wks antibiotics, surgical drainage and lavage

TB: rifampicin, isoniazid, ethambutol 8 weeks then rifampicin + isoniazid for 6-12 months. Rest + splint

Question 6

What are the possible complications of bone and soft tissue infections?

Answer 6

Acute OM: septicaemia, death, metastatic infection, pathological fracture, septic arthritis, altered bone growth, chronic OM

Chronic OM: chronically discharging sinus + flare ups, ongoing infection (abscesses), pathological fracture, growth disturbance + deformities, squamous cell carcinoma