Osteomyelitis Flashcards
What type of bone is most likely to get infected in adults?
Cancellous (spongy) bone
Any bone can be affected
Where is the most common site for osteomyelitis in children?
Distal femur and proximal tibia
Through what structures can infection spread from spongy bone to compact bone?
Via haversian canals
How is osteomyelitis classified?
Haematogenous
Contiguous (direct)
How does haematogenous osteomyelitis arise?
Bacteria spread to the bone via bloodstream from a distant source e.g. Infected urinary catheter
How does direct osteomyelitis arise?
Direct contact of infected tissue with bone e.g. Trauma, orthopaedic surgery
Define chronic osteomyelitis
Infection for >6 month
Briefly outline the pathophysiology of osteomyelitis
Local infection lead to:
Cortex erosions, leading to cloacae
Exudation of pus, causing separation of the periosteum from the underlying cortical bone, leading to sequestra and involcrum formation
What are cloacae?
Holes in the cortex due to erosion by the infection
What are sequestra and how to they form?
Necrotic fragments of bone
Forms due to loss of blood supply to the area of bone as the periosteum is lifted away due to pus exudation
What is an involcrum and how does it form?
Area of new bone formation
New bone is laid down when the periosteum is lifted
What does the presence of sequestra indicate?
Chronic osteomyelitis
What are the risk factors for osteomyelitis?
Diabetes Peripheral vascular disease Immunosuppression e.g. HIV, long term steroid use Sickle cell disease Surgical prosthesis Open fractures Orthopaedic surgery IVDU
What is the most common organism that causes osteomyelitis?
Staph. aureus
How does acute osteomyelitis typically present?
Pain Tenderness Warmth Erythema Immobile limb Systemic symptoms - fever, malaise
Briefly describe some atypical presentations of osteomyelitis
Mild symptoms with history of blunt trauma to the area e.g. bumping shin on hard surface
Non specific malaise
Vertebral infection - chronic back pain
What investigations would you do if you suspected osteomyelitis?
Bloods: FBC, ESR/CRP, cultures
X-ray
MRI
For acute osteomyelitis, would you do MRI or X-ray, and why?
MRI
Shows soft tissue changes better
more sensitive in acute infections because X-ray changes can take up to 14 days to become apparent
What would you see on X-ray in a) acute and b) chronic osteomyelitis?
A) Haziness
Loss of bone density
Subperiosteal reaction
B) sequestra
Involcrum (deformed bone)
Roughly what percentage of blood cultures come back positive?
60%
What is the gold standard investigation for diagnosing osteomyelitis?
Bone biopsy and culture
Not usually required in acute cases
How would you manage osteomyelitis?
Drain any abscesses Open surgery to remove sequestra (send for mc&s) Empirical antibiotics Analgesia Limb splinting
Which antibiotics would you give empirically?
Flucloxacillin + ciprofloxacin
If pen allergic: clindamycin + ciprofloxacin
If MRSA: vancomycin + ciprofloxacin
How long should the antibiotic therapy last in a) acute and b) chronic cases?
A) 4-6 weeks
B) 12 weeks
How would you treat chronic osteomyelitis?
Delay antibiotics until culture and sensitivities are back UNLESS the pt is very unwell, in which case start empirical therapy
Surgical debridement
What must you be aware of in diabetic patients with foot ulcers?
Peripheral neuropathy means they may not feel pain in their foot so osteomyelitis may be missed
What particular complication are diabetics more at risk of?
Amputation
What are the complications of osteomyelitis?
Progression to chronic osteomyelitis, leading to deformity Abcess formation Sinus formation (due to abcess rupture) Septicaemia Fractures Septic arthritis Nonunion of fractures Loosening of prosthesis
What is the staging system for osteomyelitis and what factors does it consider?
Cierny-Mader staging
Anatomical state of bone
General condition of the patient
Factors affecting immunity, metabolism and local vascularity
