OSTEOMYELITIS

ACUTE OSSTEOMYELITISCHRONIC OSTEOMYELITIS

OSTEOMYELITISDEFINITION : inflammation of the boneOsteo= bone, myelitis= inflammation of the marrow

• Bone becomes infected either through1. haematogenous spread of organisms, or,2. secondary to a contiguous focus of infection. (invasion from a

skin puncture, operation or open fracture)

Contiguous-focus osteomyelitis:• bone infection with relatively normal vascularity and • bone infection with generalized vascular insufficiency (eg:

diabetic foot)

• Acute or chronic.

Anatomy of the bone

EPIDEMIOLOGY• Osteomyelitis affects about 2 in 10,000 people.• In children long bones • In adults vertebrae, feet, and the pelvis• Risk factors are recent trauma diabetes Hemodialysis IV drug abuse People who had splenectomy.

SKIN ABRASION, BOIL, SEPTIC TOOTH

HEMATOGENOUS SPREAD OF

ORGANISMIMPLANTED AT BONE

INFECTION OF ADJACENT

JOINT/SOFT TISSUEEXTENSIO

N TO THE BONE

PENETRATING WOUND, OPEN FRACTURE,

SURGERY TRAUMATIC AND IATROGHENIC

IMPLANTATION

SOURCES OF INFECTIONS

ACUTE HEMATOGENOUS OMPATHOGENESIS

• Bloodstream is invaded, perhaps from minor skin abrasion or boil or in the newborn from an infected umbilical cord

• In adults source of infection – arterial line or dirty needle and syringe

MICROBIAL INVASION

Organism usually settles in the metaphysis possibly because of – highly vascular hairpin arrangement of capillaries slows down the rate of blood flow (sluggish blood flow) has relatively fewer phagocytic cells than the physis or diaphysis thin cortex

• Terminal branches of metaphyseal artery form

loops at growth plate and enter irregular

afferent venous sinusoid. Blood flow

slowed and turbulent, predispose to bacterial seeding plus, lining cell

have little/no phagocytic action made it

favourable for bacteria.

Epiphysis

Looped capillary

Venous sinusoid

Metaphyseal artery

Foci of osteomyelitis

MICROBIAL INVASION

1)TRIGGER ACUTE INFLAMMATION

•Vascular congestion•Fluid exudation•PMN leukocyte infiltration

INCREASE INTRAOSSEOUS PRESSURE

intense pain and obstruction of blood flow

Growth plate

periosteum

2)SUPPURATION(2ND DAY)

Pus appears in the medulla and spread along Volkmann’s canals and elevate periosteum to forms a sub-periosteal abscess then spread along shaft• The pus can spread from here back into the bone, into an adjacent joint or into the soft tissues.

In infants, infxn often extends into epiphysis and thence into the joint. In older children the physis is a barrier to direct spread but where metaphysis is partly intracapsular (e.g. hip, shoulder, or elbow) pus may discharge through periosteum into the joint.

3)NECROSIS (END OF WEEK)

Rising intraosseous pressure, vascular stasis, infective thrombosis and periosteal stripping compromise the blood supply to the bone resulting in bone death and formation of a sequestrum.

4)NEW BONE FORMATION

At 10-14 days new bone forms from the deep layer of the stripped periosteum. With time, new bone thickens to form involucrum enclosing infected tissue and sequestra.

sequestrum

involucrum

Medullary cavity

5)RESOLUTION

if infection is controlled and intraosseous pressure released, the bone will heal

If infection persist, pus may discharge through

perforation in involucrum and track by sinus to the skin surface.

The condition is now established as a chronic

osteomyelitis

Over 90% of acute osteomyelitis cases are caused by Staphylococcus aureus but Streptococcus pyogenes and Haemophilus influenzae may also cause acute infection of the bone although infection with Haemophilus inflenzae is rare following the widespread use of the Hib vaccine. Pseudomonas aeruginosa is often isolated from intravenous drug abusers with vertebral osteomyelitis.

Aetiological agents

ACUTE HEMATOGENOUS OM

CLINICAL FEATURES

• In child, presented withpain, malaise and feverH/o preceding skin lesion, injury, sore throatLimb is held stillRestricted joint movementLocal redness, swelling, warmth and edema-

presence of pus

• In infant,Fails to thrive, drowsy and irritableh/o birth difficulties or umbilical artery

cathetherizationMetaphyseal tenderness and resistance to

joint movementLook for other sites – multiple infections

In adult, commonest site of hematogenous spread is spine – backache, mild fever

INVESTIGATIONBLOOD• FBC – leucocytosis• ESR AND CRP – elevated (CRP is a measurement of the acute phase response and is

especially useful in monitoring the course of treatment of acute osteomyelitis because it normalizes much sooner than the ESR.)

• Blood C&S

ASPIRATION AND BIOPSY aspiration of pus from subperiosteal abscess or the adjacent

joint send for bacteriological examination and sensitivity to antibiotics

IMAGING

1)Plain Radiograph or tomography (changes may lag by 10-14 days) – Early changes

• soft tissue swelling, blurring of fat plane and periosteal reaction – Intermediate changes

• bone destruction (ill defined lytic lesion)• Cloaca• Osteopenia

– Late Changes • Sequestrum formation • Involucrum and bony sclerosis

2. Nuclear medicine – Bone scan – can be confirmed earlier (48 hours)

• Technitium 99m-labeled phosphonate• Galium 67-labeled citrate• Indium-labeled leucocyte

– Increased uptake of tracer in bone scans and white cell scans.

– High sensitivity but other processes such as arthritis and soft tissue infection can appear similar. (lower specificity)

Increased uptake of radiopharmaceutical in the right femur just above the knee joint. Plain film reveals a large lytic area

Acute Osteomyelitis

Bone scan Radiograph of knee

Bone scans, both anterior (A) and lateral (B), showing the accumulation of radioactive tracer at the right ankle (arrow). This focal accumulation is characteristic of osteomyelitis.

Acute Osteomyelitis

Bone Scan of the foot

3. Magnetic Resonance Imaging (MR) – Demonstrate OM as early as isotope scanning– High sensitivity but other processes such as

fractures and tumors can be similar in appearance. – Excellent for demonstrating associated soft tissue

infection4. Computed Tomography

– Demostrate change in subacute and chronic OM• Sequestra• Cloacae• Periostitis• Soft tissue masses

5. Culture of fluoroscopically or CT guided aspirate • Confirm infection• Determine which organism is causing the infection • When the organism is isolated, then treat the patient with the

single appropriate antibiotic. – Lesion must first be visible with some form of imaging – Failure to grow an organism is common, especially if

patient has been treated with antibiotics – A positive culture gives a definitive diagnosis and identifies

organism and sensitivities

Complications

• Chronic OM • Bone abscess (pocket of pus) • Bone necrosis (bone death) • Spread of infection to the joint-septic arthritis other bones – metastatic osteomyelitis• Inflammation of soft tissue (cellulitis) • Growth disturbance if physis is damaged- leads to

shortening, deformity• Sepsis

TREATMENT

• PRINCIPLES OF TREATMENTProvide analgesia and general supportive

measuresTo rest the affected partTo initiate antibiotic treatmentTo undertake surgical eradication of pus and

necrotic tissue

1)ANTIBIOTICSInitially the choice of antibiotics based on examination and

best guess at the most likely pathogenMore appropriate drug can be subtitued once organism is

identify

Older children and previously fits adultProbably have staphylococcal infectionAntibiotic -intravenous flucloxacillin and fusidic acid ( may be

changed once results of sensitivity are known) -continued until there is clinical and laboratory evidence

of improvement (usually for 1-2 weeks) - followed by oral antibiotic for another 2-3 weeks

• Children under 4 years oldHigh incidence of haemophilus infectionAntibiotic: third generation cephalosporin 2)ANALGESICS- paracetamol3) SPLINTAGE Complete bed rest is essential.Splint could be used but should not conceal

affected area.

4)DRAINAGEIf antibiotics given early, drainage may not be

necessaryIf subperiosteal abscess can be detected, or if pyrexia

and local tenderness persists >24 hr after tretment with adequate antibiotics, the pus should be let out.

About 30% of patient with confirmed OM are likely to need an operation

5)FOLLOW UPOnce infection subsided, movement are encouragedto look for recurrence of infection