Infection in Bone and Joint Presented By: Fadel Naim M.D. Orthopedic Surgeon IUG

Osteomyelitis osteon (bone) myelo (marrow) itis (inflammation) Inflammation and destruction of bone caused by aerobic and anaerobic bacteria, mycobacteria, and fungi The term osteomyelitis does not specify the causative organism or the disease process

Epidemiology Common in young children Common with malnutrition, immunodeficiency - with decreased resistance of the patient Boys> girls History of trauma Decreasing in incidence & severity & mortality with advent of newer antibiotics

Osteomyelitis Classification: Duration Acute, Subacute or Chronic Route of infection Hematogenous or Exogenous Host response Pyogenic or Granulomatous

Acute Pyogenic Osteomyelitis infants Staphylococcus aureus, Streptococcus agalactiae, Escherichia coli children over one year Staphylococcus aureus, Streptococcus pyogenes, and Haemophilus influenzae adults Staphylococcus aureus

Source Of Infection Hematogenous spread Direct inoculation Contiguous focus of infection

The most common site is the rapidly growing and highly vascular metaphysis of growing bones The apparent slowing or sludging of blood flow as the vessels make sharp angles at the distal metaphysis predisposes the vessels to thrombosis the bone itself to localized necrosis and bacterial seeding

The joint is usually spared from infection unless the metaphysis is intracapsular, as is found in the proximal part of: The radius The humerus The femur

Age variation Neonates: Extensive bone necrosis Increased ability to absorb large sequestrum Increased ability to remodel Epiphysio-metaphyseal vascular connection leading to secondary septic arthritis

Age variation Adults: No subperiosteal abscess due to adherent periosteum Soft tissue abscess Vascular connection with the joint leading to secondary septic arthritis

Clinical Pictures Pain, restless Malaise and fever The limb is held still (pseudo paralysis) Sometimes mild or absent (neonates)

Acute Osteomyelitis Diagnosis History and clinical examination CBC, ESR, B.C. X-ray (normal in the first (10-14) days Ultrasound Bone Scan Tc 99, Gallium 67 MRI Aspiration

Radiographic Findings Usually reflect the destructive process but lag at least two weeks behind the process of infection The earliest changes are: Swelling of the soft tissue Periosteal thickening and/or elevation Focal osteopenia At least 50% to 75% of the bone matrix must be destroyed before radiographs show lytic changes

(A) Proximal humerus at day 1 of infection - no visible changes. (B) Proximal humerus at day 12 of infection

Plain-film radiograph showing osteomyelitis of the second metacarpal (arrow). Periosteal elevation, cortical disruption and medullary involvement are present.

The above X-ray of the left ankle of a 10-year-old boy shows lucency in the tibial metaphysis secondary to acute hematogenous osteomyelitis (AHO). The above X-ray of the right ankle of a 10-year-old boy shows lucency in the tibial metaphysis secondary to acute hematogenous osteomyelitis (AHO).

Here is an X-ray of an AHO lesion extending into the growth plate

Show increase activity but it is a non specific sign of inflamation. Radiological studies MRI : Early detection and surgical localization of osteomyelitis. Sensitivity ranges from 90-100%. Radionuclide bone scanning : A 3-phase bone scan with technetium 99m is probably the initial imaging modality of choice Show increase activity but it is a non specific sign of inflamation.

This MRI sagittal section shows the same AHO lesions with the right lesion extending into the growth plate.

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.

Labratory The leukocyte count (WBC), erythrocyte sedimentation rate (ESR), and C-reactive protein level (CRP) should be monitored At the time of admission During treatment During follow-up In all patients with osteomyelitis on a weekly basis

Diagnosis requires 2 of the 4 following criteria: Purulent material on aspiration of affected bone Positive findings of bone tissue or blood culture Localized classic physical findings of bony tenderness, with overlying soft-tissue erythema or edema Positive radiological imaging study

Differential Diagnosis Acute Septic Arthritis Acute monoarticular rheumatoid arthritis Sickle cell crisis Cellulitis Ewing’s Sarcoma

Complications Septicemia & metastatic abscesses Septic arthritis Growth disturbance (children) Pathological fracture Chronic osteomyelitis

Subacute Osteomyelitis

Subacute Osteomyelitis Results from a less virulent Microorganism, or a patient with an elevated resistance. Occurs Mostly at the Distal Femur or Proximal Tibia On X-Ray: Brodie’s Abcess Small and Oval in shape It is surrounded by sclerotic bone May be mistaken for Ostieoid Osteoma

Subacute Osteomyelitis An image depicting subacute osteomyelitis

Chronic Osteomyelitis The coexistence of infected, nonviable tissues and an ineffective host response leads to the chronicity of the disease

Chronic Osteomyelitis Factors responsible for chronicity Local factors: Cavity, Sequestrum, Sinus, Foreign body, Degree of bone necrosis General: Nutritional status of the involved tissues, vascular disease, DM, low immunity Organism: Virulence Treatment: Appropriateness and compliance Risk factors: Penetrating trauma, prosthesis, Animal bite

Pathologic features of chronic osteomyelitis Sequestrum: When both the medullary and the periosteal blood supplies are compromised, large areas of dead bone (sequestra) may be formed Involucrum: New bone forms from the surviving fragments of periosteum and endosteum in the region of the infection to form an encasing sheath of live bone sinus tract: A bone cavity may persist or the space may be filled with fibrous tissue, which may connect with the skin surface by the sinus tract

Sequestrum

Chronic Osteomyelitis Types A complication of acute Osteomyelitis Post traumatic Post operative

Chronic Osteomyelitis Low grade fever, if present ESR usually elevated, reflecting chronic inflammation The blood leukocyte count ( WBC ) is usually normal If a sinus tract becomes obstructed, the patient may present with a localized abscess and/or an acute soft-tissue infection

Chronic Osteomyelitis Organism Usually mixed infection Mostly staph. Aureus E. Coli . strep pyogen, proteus

Treatment of Osteomyelitis A close interaction between various specialists is important to improve the management of this disease Orthopaedic surgeons Plastic and vascular surgeons Infectious disease specialists

Treatment of Osteomyelitis Adequate drainage Thorough débridement Obliteration of dead space Wound protection Specific antimicrobial coverage Correcttion of host defects Improving the nutritional, medical, and vascular status of the patient Good nutrition Smoking cessation Control of specific diseases such as diabetes

                                                   

Bone Stabilization If skeletal instability is present measures must be taken to achieve stability with plates, screws, rods, and/or an external fixator. External fixation is preferred over internal fixation. Ilizarov external fixation: allows reconstruction of segmental defects and difficult infected nonunion. An extended period of treatment with the device, averaging 8.5 months. The sites of the wires or pins usually become infected and the device is painful.

Soft-tissue Coverage Adequate soft-tissue coverage of the bone is necessary to arrest osteomyelitis Small soft-tissue defects may be covered with a split-thickness skin graft For large soft-tissue defects or an inadequate soft-tissue envelope, local muscle flaps and free vascularized muscle flaps may be placed in one or two stages Healing by so-called secondary intention should be discouraged

Septic Arthritis

Septic Arthritis Septic arthritis : Reactive arthritis: Direct invasion of joint space by a variety of microorganisms, including a variety of bacteria, viruses, mycobacteria, and fungi. Reactive arthritis: A sterile inflammatory process, may be the consequence of an infectious process located somewhere else in the body.

Septic Arthritis 50% of cases in children <3 years The hip joint is the common site in <3years, whereas the knee joint is more common in older children.

7.8 cases per 100,000 person-years The incidence of gonococcal arthritis is 2.8 cases per 100,000 person-years Septic arthritis is becoming increasingly common among people who are immunosuppressed and elderly people who have a variety of co-morbid diagnoses

Most of these infections occur in very young and very old people and among people who abuse intravenous drugs The most commonly involved joint: Knee (50%) Hip (20%) Shoulder (8%) Ankle, and wrists (7% each) Elbow, interphalangeal, sternoclavicular, and sacroiliac joints each make up 1-4% of cases

Risk Factors Corticosteroids-33% Existing arthritis-24% Infection elsewhere-22% DM-13% Trauma-12% None-8%

Two major classes : Gonococcal Nongonococcal Neisseria gonorrhoeae remains the most frequent pathogen (75% of cases) among younger sexually active individuals Staphylococcus aureus is the most common cause of the vast majority of cases of acute bacterial arthritis in adults and children older than 2 years

Organisms may invade the joint by: Direct inoculation Contiguous spread from infected periarticular tissue Bacteremia (the most common route)

Acute Septic Arthritis Differential Diagnosis Acute osteomyelitis Trauma Irritable joint Hemophilia Rheumatic fever Gout

Diagnosis History Because joint infections are uncommon, be attentive to features of the patient's history that may indicate an infectious process and not a primary rheumatological or orthopedic process

Inspection Thorough inspection of all joints for signs of inflammation is essential for diagnosing infection : Erythema Swelling (90% of cases) Warmth Tenderness Limitation of both active and passive ROM

Synovial Fluid Examination Leukocyte count Appearance on gram stain Polarizing microscopy examination Culture of the fluid Culture of the synovial fluid or of synovial tissue itself is the only definitive method of diagnosing infective arthritis

Imaging Studies Plain radiographs of some limited value in evaluating a joint for infection Radiographs are most useful in ruling out underlying osteomyelitis or periarticular osteomyelitis resulting from the joint infection itself Periarticular soft tissue swelling is the most common finding Ultrasonography may be used to diagnose effusions

Acute Septic Arthritis Treatment Aspiration Antibiotics Splintage Surgical drainage Treatment of complications

Management of Infective Arthritis Management of infective arthritis focuses on: Adequate and timely drainage of the infected synovial fluid Administration of appropriate antimicrobial therapy Usually, the antibiotic must be administered parenterally for 3-4 weeks, but each case needs to be evaluated individually Immobilization of the joint to control pain

Drainage The choice of the type of drainage, whether percutaneous or surgical, has not been resolved completely Aspirating the joint 2-3 times a day may be necessary during the first few days Surgical drainage is indicated: For the appropriate choice of antibiotics Vigorous percutaneous drainage fails to clear the infection after 5-7 days The infected joints are difficult to aspirate (eg, hip) Adjacent soft tissue is infected

Prognosis 50% of adults with septic arthritis have significant sequelae of decreased ROM or chronic pain after infection poor outcome in the following: Age older than 60 years Infection of the hip or shoulder joints Underlying rheumatoid arthritis Positive findings on synovial fluid cultures after 7 days of appropriate therapy Delay of 7 days or more in instituting therapy

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