Lobna Al Juffali, Mscfall 2010

Osteomyelitis

osteomyelitis

Osteomyelitis represents an acute or chronic infection of the bone.

Osteo refers to bone, myelo refers to the marrow cavity, both of which are involved in this disease. 20 cases per 100,000 The annual incidence :

in sickle cell patients is 0.36%. foot puncture 16%patients with Diabetes 30-40%

Introduction Osteomyelitis is an inflammation of the bone

marrow and surrounding bone caused by an infecting organism.

It can occur in any bone of the body and often leads to serious morbidity, even with early diagnosis and treatment.

Despite the continued refinement of diagnostic procedures advances in antimicrobial therapy, and the use of prophylactic antibiotics before orthopedic procedures, osteomyelitis continues to be a serious problem from both a diagnostic and therapeutic standpoint.

Introduction Osetomylitis may be caused by a wide variety of

microorganisms introduced during injury, during operative procedures, or from the bloodstream.

Once localized in bone, the microorganisms proliferate, produce cell death, and spread within the bone shaft, inciting a chronic inflammatory response with further destruction of bone.

Bone Anatomy

The bone is divided into three sections: the epiphysis, located at the end of the bone; the metaphysis The diaphysis.

Epiphyseal growth plate is the rapidly growing area of the bone that separate the epiphysis and metaphysis

Surrounding most of the bone is a fibrous and cellular envelope. Periosteum is The external portion of this envelope Endosteum is the internal portion

Bone Anatomy

The difference in bone structure regarding to age : Variations exist in the vasculature of bone in

different age groups, leading to different forms of osteomyelitis.

In neonates and adults, vascular communications are present between the epiphysis and metaphysis, which may allow infection to spread from the metaphysis to the epiphysis and the adjacent joint.

However, during childhood, this area often is protected from infection because the epiphyseal plate separates the vascular supply for these two regions.

Classification of osteomyelitis depending on severity

Osteomyelitis can occur as1. an acute evolves over several days or weeks.2. Subacute3. chronic condition evolve over months or even

years .

Microbiology

bacteria viruses Parasites fungi, but infections caused by certain pyogenic

bacteria and mycobacteria are the most common.

Most common Bacteria

Staphylococcus aureus is the most common cause

Escherichia coli, Neisseria gonorrhoeae Haemophilus influenzae, Salmonella species are also seen.

S. aureus has two characteristics that favor its ability to produce osteomyelitis:

(1) it has the ability to produce a collagen-binding adhesion molecule that allows it to adhere to the connective tissue elements of bone

(2) it has the ability to be internalized and survive in osteoblasts, making the microorganism more resistant to antimicrobial therapy

Microorganism depending on site of infection

Microorganism depending on age

Likely etiology Host

Staphylococcus aureusGroup B streptococciGram-negative bacilli

Neonate

S. aureusHaemophilus influenzae type b <3 yr

S. Aureus≥3 yr

P. aeruginosa After puncture wound through shoe

S. AureusSalmonella sp

Child with sickle cell

Classification

•seeding through the bloodstream

•Childhood disease

Hematogenous Spread

•skin infections in persons with vascular insufficiency.

Vascular insufficiency

•Spread of bacteria from adjacent tissue infection or by direct inoculation

Contiguous Spread

Hematogenous Osteomyelitis

Hematogenous osteomyelitis originates with infectious organisms that reach the bone through the bloodstream.

Acute hematogenous osteomyelitis occurs predominantly in children.

In adults in debilitated persons those with a history of chronic skin infections, chronic urinary tract infections intravenous drug use Immunocomprimised patients

Intravenous drug users are at risk for infections with Streptococcus and Pseudomonas

Pathogenesis. In children

In children, the infection usually affects the long bones of the appendicular skeleton.

In children 1 year of age and younger, the adjacent joint is often involved because the periosteum is not firmly attached to the cortex.

From 1 year of age to puberty, subperiosteal abscesses are more common

Pathophysiology

Infectious organisms reach the metaphysis through a nutrient blood vessel .

Bacterial growth results in bone destruction and abscess formation. From the abscess cavity, the infection spreads between the

trabeculae into the medullary cavity of compact bone and then through the cortex to the outside .

The purulent exudate finds its way beneath the periosteum, due to the rigid structure of the bone shearing off the perforating arteries that

supply the cortex with blood, thereby leading to necrosis of cortical bone and formation of devascularized fragments, called sequestra.

Eventually, the purulent drainage may penetrate the periosteum and skin to form a draining sinus.

Pathopysiology

sequestrum necrotic bone, often denser than surroundings may be resorbed, discharged thru a sinus

tract, or persist as a focus of continued infection

involucrum bone formed beneath elevated periosteum surrounds sequestrum

Manifestations.

The signs and symptoms of acute hematogenous osteomyelitis are those of bacteremia accompanied by symptoms referable to the site of the bone lesion.

Bacteremia is characterized by chills, fever, and malaise.

There often is pain on movement of the affected extremity

loss of movement, and local tenderness followed by redness and swelling

Treatment.

The treatment of hematogenous osteomyelitis begins with identification of the causative organism through blood and bone aspiration cultures.

Antimicrobial agents are given first parenterally and then orally.

The length of time the affected limb needs to be rested and pain control measures used is based on the person's symptoms. Debridement and surgical drainage also may be necessary.

Direct Penetration and Contiguous Spread Osteomyelitis Direct penetration or extension of

bacteria from an outside (exogenous) source is now the most common cause of osteomyelitis in the United States.

Bacteria may be introduced directly into the bone

by a penetrating wound an open fracture surgery.

Risk factors

The following increase the bone's susceptibility to infection.

Inadequate irrigation or debridement introduction of foreign material into the

wound extensive tissue injury

Microorganisms

Staphylococci and streptococci are still commonly implicated,

but in 25% of postoperative infections, gram-negative organisms are detected.

Measures to prevent these infections

preparation of the skin to reduce bacterial growth before surgery or insertion of traction devices or wires;

strict operating room protocols; prophylactic use of antibiotics immediately before and for 24 hours after surgery and as a topical wound irrigation;

maintenance of sterile technique after surgery when working with drainage tubes and dressing changes.

Manifestations. Osteomyelitis after trauma or bone surgery

usually is associated with persistent or recurrent fever,

increased pain at the operative or trauma site,

poor incisional healing, which often is accompanied by continued wound drainage and wound separation.

Prosthetic joint infections often present with joint pain, fever, and cutaneous drainage.

Osteomyelitis With Vascular Insufficiency

In persons with vascular insufficiency, osteomyelitis may develop from a skin lesion.

It is most commonly associated with chronic or ischemic foot ulcers in persons with long-standing diabetes.

Neuropathy causes a loss of protective reflexes, and impaired arterial circulation and repetitive trauma are the major contributors to skin fissure and ulcer formation.

Microorganism

S. aureus coagulase-negative staphylococci Gram-negative anaerobic organisms usually mixed infection

Manifestations Persons with vascular insufficiency osteomyelitis often

present with seemingly unrelated problems such as ingrown toenails cellulitis, a perforating foot ulcer making diagnosis difficult. pain is often muted by peripheral neuropathy.

Osteomyelitis is confirmed when bone is exposed in the ulcer bed or after debridement. Radiologic evidence is a late sign.

Treatment Treatment depends on the oxygen tension of the

involved tissues. Debridement and antibiotic therapy may benefit

persons who have good oxygen tension in the infected site.

Hyperbaric oxygen therapy may be used as an adjunctive treatment.

Amputation may be indicated when oxygen tension is inadequate.

Chronic Osteomyelitis

Chronic osteomyelitis usually occurs in adults. Generally, these infections occur secondary to an

open wound, most often to the bone or surrounding tissue.

it is a long-standing infection that evolves over months or even years, characterised by the persistence of microorganisms, low-grade inflammation, and the presence of dead bone (sequestrum)

Chronic osteomyelitis It may be the result of delayed or inadequate

treatment of acute hematogenous osteomyelitis or osteomyelitis caused by direct contamination of bone by exogenous organisms.

Relapses in the same area and with accompanying fever are a clear sign of chronic osteomyelitis.

Clinical signs persisting for longer than 10 days are associated with the development of necrotic bone and chronic osteomyelitis.

Chronic osteomyelitis The hallmark feature of chronic osteomyelitis is the

presence of infected dead bone, a sequestrum, that has separated from the living bone.

A sheath of new bone, called the involucrum, forms around the dead bone.

Diagnostic test for chronic osteomyelitis Radiologic techniques such as x-ray films, bone

scans, and sinograms are used to identify the infected site.

Chronic osteomyelitis or infection around a total joint prosthesis can be difficult to diagnose because the classic signs of infection are not apparent and the blood leukocyte count may not be elevated.

A subclinical infection may exist for years.

Bone scans are used with bone biopsy for a definitive diagnosis.

Diagnosis

Laboratory tests WBCESRC-Reactive ProteinBone biopsy

Diagnostic testsRadiographs findings of chronic osteomyelitis Magnetic resonance imaging (MRI) is the best

modality Computed tomography (CT) Nuclear imaging

General treatment consideration

Antibiotics used should have good penetration to the bone.

High doses should be used Parental therapy in the first two weeks then

depending on patient condition change it to oral. Duration of therapyAcute osteomylitis

- 4-6 wks

Chronic osteomylitis- 6-8 wks of parentral therapy- 3-12 months of oral therapy

Characteristic of osteomyelitisVascular insufficiency

Contiguous Spread Hematogenous spread

Infection results from insufficient blood supply to fight the bacteria

Spread of bacteria from adjacent tissue infection or by direct inoculation

Spread of bacteria through the blood stream from a distant site

Definition

Adults >50Feet

Adults from 25-50 yrsFemur, tibia, Skull

Children< 16 yrs and >50 yrs Femur, tibia, humerus ,vertebrae

Patient Population

•DM•Pulmonary Vasculary disease•Post CABG (Sternum)

• Open reduction of fractures

• Gun shot wound• Dental/Sinus

infections• Soft tissue infections

•Bacteriemia•Sickle cell anemia

Predisposing factors

•Pain, swelling, drainage, ulcer formation

• Fever, warmth, swelling unstable joint

•Fever, chills, local tenderness, swelling; limitation of motion

Clinical findings

Usually polymicrobial–S.Aureus–S.Epidermidis–Streptococcus –Gram –ve bacilliAnerobicBacteroides fragilis gp

•Infected prosthesis–S.Aureus–S.Epidermidis

Usually mixed Infection–S.Aureus–S.Epidermidis–Streptococcus –Gram –ve bacilliAnerobic

Usually monomicrobialChildren•S.Aureus,S.Epidermidis ,S.Pyogenes•H.Influenzae ,P.auerginosa ,Enterobacter, Ecoli•Adults

–S.Aureus–Gram –ve bacilli

Sickle cell anemia salmonella ,S.pneumoniae

Common pathogens