Chapter 1 suppurative infection of bone and joint

Section 1 osteomyelitis Osteomyelitis is an inflammation of bone caused by an infecting organism. Stapbylococus aureus is the most common cause of osteomyelitis,about 75%; group B streptococcus organisms and gram-negtive coliforms also are common

classification 1.The mechanism of infection  Hematogenous form  Exogenous form :by trauma or surgery (iatrogenic) infection  Contiguous infection

classification 2.the duration and type of symptoms Acute,subacute,or chronic

acute hematogenous osteomyelitis Acute hematogenous oateomyelitis is the most common type of acute suppurative osteomyelitis.about 80% in children younger than 12 years old,male:female 4:1. the metaphyses of rapidily growing long bone are most frequently involved.

Pathology 1 The infection causes an inflammatory reaction,local ischemic necrosis of the marrow and then bone,and subsequent abscess formation. As the abscess increases in size,intramedullary pressure inceases ;this causes more bone to become ischemic,and eventually purulent material escapes through the cortex into the subperiosteal space and forms a subperiosteal abscess. If inadequately treated,this eventually results in extensive sequestration of bone and chronic osteomyelitis.

Pathology 2 In children younger than 2 years old,some vessels cross the physis and may allow the spread of infection into the epiphsis. The metaphsis has relatively fewer phagocytic cells,allowing infection to occour in this area.The inflammatory responses from the diaphysis and phsis effectively block Infection. The resultant abscess breaks through the thin metaphseal cortex and forms a subperiosteal abscess.

Pathology 3 In children older than 2 years of age,the metaphysreal cortex is thicker,and if inflammatory responses does not prevent the spresd of infection onto the diaphysis,the endosteal blood supply to bone will be jeopardized. This process results in extensive sequestrum formation and chronic osteomyelitis when both the endosteal ang pteriosreal blood supplies are destroyed.

Pathology 4 Spread of infection to a contiguous joint also affected by the patient ’ s age.The physis of the proximal femur is within the hip joint capsule. The epiphyses of the proximal humerus, radial neck,and distal fibula are also intraarticular,and infection in these areas can cause septic arthtitis.

Clinical presentation  Signs and symotoms vary considerably.  Systemic signs such as fever and malaise.  Pain and localized tenderness over the mataphysis of a long bone or to percussion of the spine.  In infants, elderly patients,or immunocompromised patients,the signs and symptoms may be minimal.

Diagnosis 1.Fever,pain, limited movement,tenderness over the metapysis of long bone; 2. WBC count,ERS andC-reactivprotein(CRP) 3.Roetgenograms :soft tissue w\swelling,skeletal changes(such as localized destruction of bone or periosteal reaction) 4.ECT bone scan:Technetium 99m bone scan can confirm the diagnosis as eraly hours after onset. 5.MRI:shows changes in the marrow and soft tissue from an inflammatory response.

Diagnosis  6.blood cultures  7.bone and marrow aspiration if an abscess is present.

Differentiation  1.acute cellulitis  2.suppurative arthritis  3.Eving ’ s tumor

Treatment  1.general supportive measures  2.antibiotic treatment  3.drain any abscess cavity and remove all dead or necrotic material.  4.splint is applied to keep limbs in position

Chronic osteomyelitis  Chronic osteomyelitis is difficult to eradicate completely.  Systemic symptoms usually subside,but one or more foci in the bone may still contain purulent material,infected granulation tissue,or a sequestrum.  Acute exacerbations may occur intermittently for years.  The hallmak of chronic osteomyelitis is infected dead bone and sinus tract formed.

Chronic osteomyelitis  The infected foci within the bone are surrounded by sclerotic,relatively avascular bone;the haversian canals became sealed off by scar tissue and proteinaceous material,and this is covered by scared,thicked periosteum and scarred muscle and subcutanous tissue.  In this situation,systemic antibiotics that require tissue perfusion to be effective have limited value.  In chronic osteomyelitis secodary infections are common.

Treatment  Surgery for chronic osteomyelitis consists of sequestrectomy and resection of scarred and infected bone and soft tissue.  Radical debridement may be required to achieve a viable and vascular environment to eradicate the infection.

Treatment  Sequestrectomy and curettage  Eliminate this dead space are bone grafting with primary or secodery closure.  Closed suction drains  Systemic antibiotic treatment

Brodie ’ s abscess  A Brodie abscess is a localized form of chronic osteomylitis that occurs most often in the long bones of lower extremities of youny adults.  Before epiphseal closure,it most commonly occurs in the metaphysis.In adults,the metaphyseal-epiphyseal area is involved.

Brodie ’ s abscess  Intermittent pain of long duration is the presenting complaint,along with local tenderness over the affected area.  roentgenograms show a markedly varied appearance,and an abscess may be easily mistaken for various neoplasms.  The lesion is thought to be caused by organiams of low virulence.  It often requires a biopsy to make the diagnosis of a Brodie abscess.  It is treated by curettage of the lesion and administration of antibiotics.  The wound should be loosely closed over drains.

Sclerosing osteomyelitis Sclerosing osteomylitis is a chronic form of disease in which the bone is thickend and distended and sequestra is absent. The disease affects children and young adults.Its cause is unknown,but it is thought to be an infection caused by a low-grade,possibly anaerobic bacteria.

Sclerosing osteomyelitis  Patients complain of intermittent pain of moderate intensity,usually of long duration.  Swelling and tenderness over the affected bone may be found.Roentgenograms show an expanded bone with generalized sclerosis.The ESR usually is slightly elevated.Biopsy shows only chronic,low-grade,nonspecific osteomyelitis,and culture usually are negative.  No treatment has been predictably helpful,but fenestration of the sclerotic bone and antibiotics are advisable.

Setion 2 suppurative arthritis  Acute suppurative arthritis results from bacterial invasion of a joint space.  It can occur through hematogenous spread,direct inoculation from trauma or surgery,or contiguous spread from an adjacent site of oateomyelitis or cellulitis

Suppurative arthritis  In neotnates,Streptococcus is the most common causative organism. Haemopbilus influenzate type B may be the cause of septic arthritis in children under 2 years of age. In adults,Neisseria gonorrboeae is the most infecting organism.

Diagnosis 1.Fever,pain,limited motion,swelling,erythema 2.WBC,ERS,C-reactive protein 3.Aspiration:Gram staining,culture,cell counts,and crystal analysis. 4.Roetgenograms :soft tissue swelling,skeletal changes 5.MRI:shows changes in the joint space and soft tissue from an inflammatory response.

Managenment The essiential priciples in the management of acute suppurative aithritis : (1)the joint must be adequately deained (2)antibiootics must be given to diminish the systemic effects of sepsis, (3)the joint must be rested in a stable position.