Bone Infection (Acute, Subacute and Chronic Osteomyelitis, Tuberculous Osteomyelitis) Flashcards
How can bone infections spread?
Can occur from metastatic haematogenous spread (carried in the blood), or from local infeciton. They can also occur 2o to vascular insufficiency.
What organisms most commonly affect infants (<1yr)?
- Staph aureus
- Group B streptococci
- E. coli
What organisms commonly affect older children up to age of 4?
- Staph aureus
- Strep pyogenes
- Haemophilus influenzae
- Kingella kingae
What organisms commonly affect Adults?
- Staph aureus
- Coag negative staphylococci - prostheses
- Propionibacterium spp - prostheses
- Streptococcus pyogenes - infectious arthritis
- Mycobacterium tuberculosis
- Pseudomonas aeroginosa - esp. secondary to penetrating foot injuries, IVDAs
What is the pathogenesis of osteomyelitis?
The classical sequence of changes in osteomyelitis is as follows:
- Transient bacteraemia - e.g. Staphylococcus aureus
- Focus to metaphysis of long bone
- Acute inflammation - increased pressure within haversian canals in cortical bone and under periosteum ⇒ periosteum lifts off and interrupts blood supply to underlying bone
- SEQUESTRUM - Caused by necrosis of bone fragments
- INVOLCURM - New reactive bone formation created by the elevated periostium
-
Outcome ⇒ resolution or chronic osteomyelitis
- If untreated, sinuses form, draining pus to the skin surface via cloacae ⇒ Chronic Osteomyelitis
How do bone Abscesses form?
- Acute inflammatory response ⇒ granulation tissue ‘walls off’ sequestrum
- Bacterial proliferation in dead tissue ⇒ pressure & toxins
- Adjacent healthy bone devascularised, further destruction
- Fibrous membrane forms around abscess
- Reactive bone forms ⇒ involucrum ⇒ Bacteria isolated from host defences!
What is the pathophysiology of Chronic osteomyelitis?
- Cavities, poss. sinus(es)
- Cloacae
- Sequestrum + involcrum + sinus
What is the pathophysiology of Tuberculous Arthritis?
- 2 phases
- Early short lived vascular
- Chronic avascular
- Obliterative endarteritis - poor entry of antibiotics
- Less plasminogen activation - less joint destruction
- Primary complex (in the lung or the gut)
- Secondary spread
- Tuberculous granuloma
What are the clinical features of Acute Osteomyelitis in infants?
May be minimal signs, or may be very ill
- FTT
- Possibly drowsy or irritable
- Metaphyseal tenderness + swelling
- Decreased ROM
*Commonest around the knee
What are the clinical feautrues of Acute Osteomyelitis in children?
Vascular bone most affected - long bone metaphyses, esp. distal femur, upper tibia
- Severe pain - May be tender and inlamed
- Reluctant to move - neighbouring joints held flexed
- Not weight bearing
- Fever (swinging pyrexia) + tachycardia
- Systemic features - Malaise fatigue, nausea, vomiting
What are the clinical features of Acute osteomyelitis in an adult?
Usually gradual/several days
- Localized bone pain - gradual onset over the course of a few days
-
Localised findings
- Overlying tenderness
- Warmth
- Erythema
- Swelling
- Systemic features - fever, malaise, chills
- Slight effusion in neighbouring joints
What is the presentation of subacute osteomyelitis?
- Long history
- Variable symptoms - pain, limp
- Local swelling/warmth, with Tenderness
- Brodie’s abscess - well defined cavity in cancellous bone
What are the clinical features of Chronic Osteomyelitis?
usually following a prior episode of osteomyelitis; may last for months:
- Recurrent Pain
- Fever
- Sequestra - small peice of dead bone separated from live bone
- Sinus suppuration (pathognomic)
- Swelling/redness
-
Risk factors - Diabetic ulcer, Vascular insufficiency
- If bone can be felt on probing ulcer ⇒ CHRONIC OSTEOMYELITIS
What are the clincial featues of Tuberculous Osteomyelitis?
- Insidious onset & general ill health
- Pain - esp. at night
- Swelling
- Weight loss
- Low grade pyrexia
- Decreased ROM
- Ankylosis
- Deformity
What investigations would you do in the context of suspected osteomyelitis?
Clinical Diagnosis, plus
- Bloods - FBC,ESR, CRP, Blood cultures
- Imaging - X-Ray, USS, Isotope Bone Scan, Labelled white cell scan, MRI
- Specific - Biopsy, Tissue swabs, Aspiration
What investigations would you perform if you suspected Tuberculous Osteomyelitis?
Clinical diagnosis
Bloods
- FBC
- ESR
Imaging
- X-ray - Soft tissue swelling, periarticular osteopaenia, articular space narrowing
Other
- Mantoux test
- Sputum/urine culture
- Joint aspiration and biopsy
How would you treat someone with Acute osteomyelitis?
Supportive treatment – general care, analgesia
Rest & splintage
Antibiotics
- Flucloxacillin +/- Rifampicin while waiting for cultures
- IV Vancomycin if MRSA
Surgery
- Aspiration of pus for diagnosis & culture
- Abscess drainage
- Debridement
What are the complications of acute osteomyelitis?
- Septicemia
- Pathological fracture
- Septic arthritis
- Altered bone growth
- Chronic osteomyelitis
How would you manage someone with chronic osteomyelitis?
-
Long-term antibiotics
- Local (gentamicin cement/beads, collatamp)
- Systemic (orally/ IV/ home AB)
-
Surgery
- Soft tissue injury
- Deformity correction
- Massive reconstruction
- Amputation
What are the complications of Chronic osteomyelitis?
- Chronically discharging sinus + flare-ups
- Ongoing (metastatic) infection (abscesses)
- Pathological fracture
- Epithelioma
- Growth disturbance + deformities
- Amyloidosis
- Squamous cell carcinoma (0.07%)
What is the treatment for Tuberculous Bone Infection?
-
6 months
- Rifampicin
- Isoniazid
-
First 2 months
- Ethambutol
- Pyrazinamide
What is the following?
Sinus caused by chronic osteomyelitis
What are the characteristics of an infected joint on examination?
Hot, swollen, tender, erythematous joint with decreased ROM. MAy or may not have a fever
How would you distinguish haemtogenously spread osteomyelitis from exogenous osteomyelitis in terms of number of pathogens?
Haematogenous - often one organism
Exogenous - often multiple organisms
What is the differential diagnosis for someone who is presenting with symptoms of acute osteomyelitis?
- Soft tissue infection - Cellulitis, Erysipelas, Necrotising fasciitis, Gas gangrene, Toxic shock syndrome
- Acute septic arthritis
- Trauma
- Acute inflammatory arthritis
- Transient synovitis (“irritable hip”)
- Rare - sickle cell crisis, Gaucher’s disease, rheumatic fever, haemophilia
What are examples of routes of infection which lead to exogenous osteomyelitis?
- Post-traumatic
- Spread from adjacent issues
What are examples of local risk factors which increase the risk of developing osteomyelitis?
- Poor tissue perfusion
- Open fractures
- Severe soft tissue injury
What are examples of systemic risk factors which increase the risk of developing osteomyelitis?
- Impaired immunocompetence (e.g., immunosuppression, HIV infection, neoplastic diseases)
- Systemic diseases (e.g., diabetes mellitus, atherosclerosis)
- IV drug use
What initial work up would you want to do for someone with suspected osteomyelitis?
- Bloods - FBC, ESR/CRP, BCs
- Imaging - X-rays
Why would you consider MRI for imaging if someone presented with features of osteomyelitis for < 2 weeks?
Early stages (< 2 weeks of symptoms onset): x-rays typically show no pathological findings
What is involved in biopsy for confimation of osteomyelitis?
Bone biopsy: MRI/CT-guided needle or open biopsy + gram staining, culture, and histology
What are indications for surgery in osteomyelitis?
- Refractory to treatment
- Abscess
- Post-traumatic
- Prosthetic involvement
- Revascularisation
