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Osteomyelitis

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Defination of Osteomyelitis

Osteomyelitis is defined as an acute or chronic inflammatory process of bone, bone marrow and its structure secondary to infection with micro organisms.

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CLASSIFICATION

Duration , Mechanism & Host response.

Duration - Acute / Subacute / Chronic

Mechanism - Heamatogenous (tonsil , lungs , ear/ GIT) - Exogenous (injection , open fractures)

Host response - Pyogenic / Granulomatous

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ACUTE OSTEOMYELITIS

Age : Infancy and childhood.Sex : Males predominate 4:1Location : Metaphysis of long

bone.Poor nutrition, unhygienic

surroundings.

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Etiological Agents

Infants < 1 year – Group B streptococci Staph aureus E.coli1- 16 years – S. aureus , S. pyogens , H.

Influenza

> 16 years – S.aureus , S.epidermidis , Gram –ve bacteria

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Pathogenesis

Introduction of bacteria from :

Outside through a wound or continuity from a neighboring soft tissue infection

Hematogenous spread from a pre existing focus (most common route of infection)

PathogenesisPreexisting focus / Exogenous

InfectionInfective embolus enters nutrient arteryTrapped in a vessel of small Caliber(metaphysis) Blocks the vesselActive hyperemia + PMN cells exudate

Hyperemia and immobilization causes decalcification.

Proteolytic enzymes destroy bacteria and medullary elements.The debris increase and intramedullary pressure increases.

Follows paths of least resistance.

Passes through Haversian canal and Volkmann canal.

Local cortical necrosis.

Enter subperiosteal space.Strips periosteum. Perforation of periosteum / reach

joint by piercing capsule.Enters soft tissue and may drain out

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Acute Osteomyelitis Infants

Joint involvement is common

Nutrient metaphyseal capillaries perforate the epiphyseal growth plate, particularly in the hip, shoulder, and knee.

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CLINICAL FEATURES

Fever (High Grade)Child refuses to use limb

(pseudoparalysis)Local redness , swelling , warmth

, oedemaNewborn – failure to thrive ,

drowsy , irritable.

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Laboratory TestsElevations in the peripheral white blood cell

count (WBC), Erythrocyte sedimentation rate (ESR), and C-

reactive protein (CRP) in children with hematogenous osteomyelitis are variable and nonspecific.

Blood culture is positive in half of cases.

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Differential DiagnosisRheumatic fever : Onset is more

gradual, pain and tenderness are less intense. Involvement is polyarticular. Response to salicylates and ACTH is dramatic.

Acute suppurative arthritis : Pain and tenderness are , limted to the joint, joint movements is greatly restricted, muscle spasm is intense, and aspiration reveals purulent synovial fluid.

Management of acute osteomyelitis.

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Drainage technique of acute Hematigenous Osteomyelitis of tibiaUse tourniquet whenever possibe.Make an anteromedial incision 5 – 7.5 cm

long over the affected part of tibia.Incise periosteum longitudinally, gently

elevate the periostum 1.5 cm on each side.

Drill several holes 4mm in diameter through the cortex into the medullary cannal. If pus escapes through these holes, use drill to outline a corticle window 1.3 × 2.5 cm and remove the cortex with osteotome.

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Evavuate the intramedullary pus and remove the necrotic tissue.

Irrigate the cavity with at least 3 L of saline with a pulsatile lavege system.

Close the skin loosely over drains.

Limb is splinted in neutral position.

Generally 6 weeks course of antibiotics is given.

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Complications of acute osteomyelitis

Bone abscessSeptic ArthritisSepticemiaFractureGrowth arrestOverlying soft-tissue cellulitisChronic infection

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Subacute Osteomyelitis

It has an insidious onset, mild symptoms, lack of systemic reaction

Its relative mildness is due to: a) Organism being less virulent OR b) Patient more resistant OR c) (Both)Most common site: Distal femur, Proximal &

Distal Tibia

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Causative Organism

a) Staphyloccocus aureus (30-60%)

b) Others (Streptococcus, Pseudomonas, Haemophilus influenzae)

c) Pseudomonas aeruginosa (IV drug user)

d) Salmonella (patient with sickle cell anaemia)

Gram Positive Staph aureus

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Clinical Features

Pain (several weeks / months)LimpingSwelling & Local tendernessMuscle wastingBody temperature usually normal

(no fever)

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Radiological Finding

Brodie’s abscess A circumscribed, round/oval cavity containing

pus and pieces of dead bone (sequestra) surrounded by sclerosis.

Most commonly seen in tibial / femoral metaphysis.

May occur in epiphysis / cuboidal bone (eg: calcaneum).

Metaphyseal lesion cause no / little periosteal reaction.

Diaphyseal lesion may be associated with periosteal new bone formation and marked cortical thickening.

A circumscribed, oval cavity surrounded by a zone of sclerosis at the proximal tibia (Brodie’s abscess)

This is a lateral view X-ray of left tibia and fibula. There is a marked periosteal reaction at the diaphysis.

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Investigation’s

a) X-ray (may resemble osteoid osteoma / malignant bone tumour)

b) Biopsyc) Fluid aspiration & cultured) ESR raisede) WBC count may be normal

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Treatment

Conservative :a) Immobilizationb) Antibiotics (flucloxacillin + fusidic

acid) for 6weeks

Surgical (if the diagnosis is in doubt / failed conservative treatment) :

c) Open biopsyd) Perform curettage on the lesion

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Chronic OsteomyelitisDefinition: “ A severe, persistent and

incapacitating infection of bone and bone marrow ”

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Aetiological Agents

Usual organisms (with time there is always a mixed infection)

Staph.aureus(commonest)

Staph.pyogenesE.coliPseudomonasStaph.epidermidis(commonest in surgical implant)

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Clinical Features

a) Painb) Pyrexiac) Rednessd) Tendernesse) Discharging

sinus (seropurulent

discharge)

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PathogenesisInadequate treatment of acute

OM /Foreign implant /Open fracture

Inflammatory process continues with time

together with persistent infection by Staphylococcus aureus

Persistent infection in the bone leads to increase in

intramedullary pressure due to inflammatory exudates (pus)

stripping the periosteum

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Pathogenesis (Contd.)

Vascular thrombosis

Bone necrosis (Sequestrum formation)

New bone formation occur (Involucrum)

Multiple openings appear in this

involucrum, through which exudates & debris from the

sequestrum pass via the sinuses

(Sinus formation)

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Staging Of Osteomyelitis:

The Cierny-Mader staging system.

It is determined by the status of the disease process.

It takes into account the state of the bone, the patient's overall condition and factors affecting the development of osteomyelitis.

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The Cierny-Mader Classification

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The Cierny-Mader Classification

1: Medullary Osteomyelitis -

Infection confined to medullary cavity.

2: Superficial Osteomyelitis - Contiguous type of infection. Confined to surface of bone.

3: Localized Osteomyelitis - Full-thickness cortical sequestration which can easily be removed surgically.

4: Diffuse Osteomyelitis -Loss of bone stability, even after surgical debridement.

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Radiographic Findings1) X-ray examination- Usually show bone resorption (patchy loss of

density / osteolytic lesion)- Thickening & sclerosis around the bone- Presence of sequestra- Occasionaly it may present as a Brodie’s abscess

surrounded by vascular tissue and area of sclerosis

2) Radioisotope scintigraphy- Sensitive but not specific- Technetium labelled hydroxymethylene

diphosphonate (99mTc-HDP) may show increased activity in both perfusion phase and bone phase

3) CT scan & MRI- Show the extent of bone destruction, reactive

oedema, hidden abscess and sequestra

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MRI OF OSTEOMYELITIS OF METATARSAL

Active osteomyelitis displays a decreased signal in T1 weighted images and appears bright in T2 weighted images.

AP & lateral view of the left wrist show a lobulated osteolytic lesion with well-defined borders and surrounding sclerosis at the distal radius. Minimal expansion, mild periosteal reaction and soft tissue swelling are present.

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Treatment - Antibiotics

- Chronic infection is seldom eradicated by antibiotics alone.

- Bactericidal drugs are important to:

a) Stop the spread of infection to healthy bone

b) Control acute flares

- Antibiotics used in treating chronic osteomyelitis

(Fusidic acid, Clindamycin, Cefazolin)

- Antibiotic (IV route) is given for 10 days prior to surgery.

- After the major debridement surgery, antibiotic is

continued for another 6 weeks (min) but usually >3months.

[treat until inflammatory parameters (ESR) are normal]

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Surgical Treatment

- After 10 days of antibiotic administration, debridement is

done to remove: a) All the infected

tissue b) Dead /

devitalised bone (Sequestrectomy)

c) Sinus tract

- Wound is left open EXCEPT:

a) Compromised hosts (Class B host); ankle, hand, spine

b) Type II lesions (primary soft tissue reconstruction and/or host alteration)

c) Minimal necrosis osteomyelitis

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- After debridement is done, a large dead space is left in

the bone- Among the methods of

managing dead space: a) Open cancellous

grafting (Papineau technique)

b) Primary closure with local tissue (+/- cancellous grafts)

c) Primary closure with transferred tissues (+/- cancellous grafts)

d) Primary closure over antibiotic impregnated beads

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- Papineau technique: Cavity is packed with small cancellous bone graft (preferably autogenous) mixed with an antibiotic and fibrin sealant- Primary closure with transferred tissue: In muscle flap transfer, a suitable large wad of muscle with its blood supply intact can be mobilized and laid into the cavity. The surface is later closed with a split-skin graft- Primary closure with antibiotic impregnated beads: Porous gentamicin-impregnated beads are used to sterilize the cavity. It is easier but less successful. Furthermore, they are extremely difficult to be removed if not taken out by 2-3 weeks

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Complications1) Pathological Fracture

- This occurs in the bone weakened by chronic osteomyelitis

2) Deformity– In children the focus of osteomyelitis

destroys part of the epiphysis growth plate.

3) Shortening/ lengthening- Destruction of growth plate arrest

growth.- Stimulation of growth plate due to

hyperemia.

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