Osteomylelitis

Question 1

What is it

Answer 1

Infection, typically bacterial, involving bone

Question 2

Most common causative organism

Answer 2

Staphylococcus aureus

Question 3

Most common causative organism in sickle cell patients

Answer 3

Salmonella

Question 4

Haemotogenous causes

Answer 4

Via bloodstream
Usually by seeding of microorganisms from another source
E.g. IV drug users, indwelling devices
More common cause
In adults it leads to vertebral osteomyelitis and in children it affects the metaphysis

Question 5

Non-haemotogenous causes

Answer 5

Trauma e.g. open fracture exposed to pathogens
Surgery
Soft tissue infections/local infections that spread to the bone - contiguous spread
Peripheral neuropathy due to diabetes increases the risk
Vascular insufficiency - prevents wound healing and colonisation of pathogens

Question 6

Pathophysiology of acute

Answer 6

Bacteria enters and proliferate which triggers immune cells
It may resolve and osteoblasts and osteoclasts will repair the bone

Question 7

Pathophysiology of chronic

Answer 7

Bone becomes necrotic and separates from healthy bone - this is a sequestrum
The periosteum (outer layer of the bone) has osteoblasts that may form bone to keep the sequestrum in place and this is called a involucrum
Infection can involve joints, tissue and blood vessels (thrombophlebitis)

Question 8

Risk factors

Answer 8

Haematogenous osteomyelitis is more likely when there is a remote source of infection, such as indwelling vascular catheters or intravenous drug use

Nonhaematogenous osteomyelitis is associated with direct inoculation of the affected tissues via trauma or medical procedures

Associated conditions
Diabetes: poorly controlled diabetes with associated peripheral neuropathy and impairs blood supply can lead to the development of non-healing infected ulcers and secondary nonhaematogenous spread of the associated pathogens to bone
PAD
Sickle cell disease c

Question 9

Clinical features in acute

Answer 9

Symptoms tend to develop gradually over a few days
Pain is the most common symptom, along with warmth, erythema and swelling of the soft tissue surrounding the affected bone
Osteomyelitis of the proximal joints such as the hips or vertebrae may present only with pain
Systemic symptoms such as fever and malaise may be present

Question 10

Clinical features in chronic

Answer 10

Tends to present only with local symptoms such as swelling, erythema and pain
Systemic symptoms such as fever are often absent
A draining sinus tract may be seen - this is pathognomonic of osteomyelitis
Patients with diabetes or vascular insufficiency may develop osteomyelitis subsequent to foot ulcers without the classic symptoms described above
May also present as non-healing fractures

Question 11

Investigations

Answer 11

WCC and CRP raised (WCC may be normal in chronic)
X-ray - periosteal reaction, osteopenia, thickening of the cortical bone and periosteum
MRI is the modality of choice
Biopsy is not generally needed

Question 12

Management - pharmocolgoical

Answer 12

Flucloxacillin (clindamycin if penicillin allergic), with consideration of the addition of fusidic acid or rifampicin for the first two weeks
If MRSA is suspected, vancomycin or teicoplanin is recommended
6 weeks of treatment - parenteral via PICC

Question 13

Surgical options

Answer 13

To remove necrotic bone
Necrotising soft tissue infection or secondary systemic infection from osteomyelitis may need urgent surgical debridement