Infection in bone and joints Flashcards
What is infection in bone known as
Osteomyelitis. Acute or chronic. Specific (e.g. TB) or non-specific (most common)
Who is usually affected with acute osteomyelitis?
Mostly children (different ages). Boys > girls. History of trauma (minor). Other disease/factors: diabetes, RA, immune compromise, long-term steroid treatment, sickle cell.
How is the infection spread in acute osteomyelitis?
Haematogenous spread –children and elderly. Local spread from contiguous site of infection – trauma (open fracture), bone surgery (ORIF: open reduction internal fixation), joint replacement. Secondary to vascular insufficiency.
What may be sources of infection in infants, children and adult in acute osteomyelitis?
Infants: infected umbilical cord. In children: boils, tonsillitis, skin abrasions. In adults: UTI, arterial line.
What organisms are seen in acute osteomyelitis in infants <1 year?
Staph aureus, Group B streptococci, E. coli.
What organisms are seen in acute osteomyelitis in older children?
Staph aureus, Strep pyogenes, haemophilus influenzae
What organisms are seen in acute osteomyelitis in adults?
Staph aureus. Coagulase –ve staphylococci (prostheses), Propionibacterium spp (prostheses). Mycobacterium tuberculosis. Pseudomonas aeruginosa (esp. secondary to penetrating foot injuries, IVDAs)
Where does acute osteomyelitis usually affect?
Long bones – metaphysis: distal femur, proximal tibia, proximal humerus. Joints with intra-articular metaphysis – hip, elbow (radial head).
Describe the pathology of acute osteomyelitis
Starts at metaphysis (maybe role of trauma). Vascular stasis (venous congestion + arterial thrombosis). Acute inflammation – increased pressure. Suppuration. Release of pressure (medulla, sub-periosteal, into joint). Necrosis of bone (sequestrum). New bone formation (involucrum). Resolution – or not (chronic osteomyelitis)
What are the clinical features of AO in infants?
May be minimal signs, or may be very ill. Failure to thrive. Possible drowsiness or irritability. Metaphyseal tenderness + swelling. Decreased ROM. Positional change. Commonest around the knee.
What are the clinical features of AO in children?
Severe pain. Reluctant to move (neighbouring joints held flexed); not weight bearing. May be tender fever (swinging pyrexia) + tachycardia. Malaise (fatigue, nausea, vomiting). Toxaemia.
What are the clinical features of AO in adults?
Primary OM seen commonly in thoracolumbar spine. Backache. History of UTI or urological procedure. Elderly, diabetic, immunocompromised.
Secondary OM much more common. Often after open fracture, surgery (esp. ORIF). Mixture of organisms.
How is acute osteomyelitis diagnosed?
- History and clinical exam (pulse + temp)
- FBC + WBC (neutrophil leucocytosis); ESR, CRP; U&Es (ill, dehydrated)
- Blood cultures x3
- Bone biopsy
- Imaging Ix
What imaging investigations are taken for acute osteomyelitis?
- X-ray (normal in first 10-14 days)
- Ultrasound
- Aspiration
- Isotope Bone scan (Tc-99, Gallium-67)
- Labelled white cell scan (indium-111)
- MRI
How do you manage acute osteomyelitis?
Supportive treatment for pain and dehydration – general care, analgesia. Rest and splintage. Antibiotics – empirical (Flucloxacillin + BenzylPenicillin) while waiting (IV/oral). Surgery.
What are the indications for surgery in acute osteomyelitis?
Aspiration of pus for diagnosis + culture, abscess drainage, debridement of dead/infected/contaminated tissue. Timing, drainage, lavage. Infected joint replacements.
What are the complications of acute osteomyelitis?
Septicaemia, death. Metastatic infection. Pathological fracture. Septic arthritis. Altered bone growth. Chronic osteomyelitis.
How may chronic osteomyelitis result?
May follow acute osteomyelitis (now rare in kids). May start de novo: following operation, open fracture, immunosuppressed, diabetics, elderly, drug abusers etc. Repeated breakdown of “healed” wounds.
What organisms cause chronic osteomyelitis?
Often mixed infection. Usually same organism(s) each flare-up. Mostly Staph. Aureus, E. coli, Strep. Pyogenes, Proteus.
Describe the pathology of chronic osteomyelitis
Cavities, possible sinus(es). Dead bone (retained sequestra). Involucrum (layer of new bone growth). Histological picture is one of chronic inflammation.
What are the possible complications of chronic osteomyelitis?
Chronically discharging sinus + flare-ups. Ongoing (metastatic) infection (abscesses). Pathological fracture. Growth disturbance + deformities. Squamous cell carcinoma (0.07%).
What are the treatment options for chronic osteomyelitis?
- Long term Abx – local (gentamicin cement/beads, collatamp) or systemic (orally/IV/home)
- Eradicate bone infection – surgically (multiple operations)
- Treat soft tissue problems
- Deformity correction; Massive reconstruction; Amputation
What is infection in joint cavity known as?
Septic arthritis
What is the route of infection in acute septic arthritis?
Haematogenous. Eruption of bone abscess. Direct invasion – penetrating wound (poss. iatrogenic, joint injection), intra-articular injury, arthroscopy
What organisms usually cause acute septic arthritis?
Staphylococcus aureus. Haemophilus influenzae. Streptococcus pyogenes. E.coli.
Describe the pathology of acute septic arthritis
Acute synovitis with purulent joint effusion. Articular cartilage attacked by bacterial toxin and cellular enzyme. Complete destruction of the articular cartilage.
What are the outcomes of acute septic arthritis?
Complete recovery
Or
Partial loss of articular cartilage and subsequent OA
Or
Fibrous or bony ankyloses (stiffening/immobility due to fusion of bones)
How does acute septic arthritis present in the neonate?
Picture of septicaemia – irritability, resistant to movement, ill.
How does acute septic arthritis present in the child/adult?
Acute pain in single large joint (common –knee; other superficial – ankle, wrist). Reluctant to any move the joint. Increased temp and pulse, increased tenderness.
Rare in healthy adult, may be delayed diagnosis
What investigations are used for acute septic arthritis?
FBC, WBC, ESR, CRP, blood cultures. X-ray. Ultrasound. Aspiration.
What procedure is the most common cause of septic arthritis in adults?
Infected joint replacement.
How do you treat acute septic arthritis?
General supportive measures. Abx (3-4 weeks).
Surgical drainage + lavage – emergency; open or arthroscopic lavage. Infected joint replacements.
How is tuberculosis bone and joint classified?
Extra-articular (epiphyseal / bones with haemodynamic marrow). Intra-articular (large joints). Vertebral body.
Multiple lesions 1/3 of patient.
What are the clinical features of TB?
Insidious onset + general ill health. Contact with TB (history). Pain (esp. at night), swelling, loss of weight, Low grade pyrexia. Joint swelling, Decrease ROM, Ankylosis, Deformity.
Involvement of a single joint, marked thickening of synovium, marked muscle wasting.
Spinal – little pain, present with abscess or kyphosis.
Describe the pathology of TB
Primary complex (in the lung or the gut). Secondary spread. Tuberculous granuloma. Note – role of nutrition/other disease (e.g. HIV/AIDS)
How do you investigate TB?
- FBC, ESR
- Mantoux test
- Sputum/urine culture
- X –ray – soft tissue swelling, periarticular osteopenia, articular space narrowing.
- Joint aspiration + biopsy: AAFB or culture +ve
What is the treatment of TB?
- Chemotherapy o Initial – 8 weeks ♣ Rifampicin ♣ Isoniazid ♣ Ethambutol o Then – 6-12 months ♣ Rifampicin and isoniazid - Rest and splintage - Operative drainage rarely necessary
