NHIỄM TRÙNG VIÊM XƯƠNG và VIÊM KHỚP, cơ CHẾ BỆNH SINH (CHẤN THƯƠNG CHỈNH HÌNH)

NHIỄM TRÙNG: VIÊM XƯƠNG & VIÊM KHỚP CƠ CHẾ BỆNH SINH Portals of bacterial entry Vascular anatomy of the metaphysis • Bacteria may accumulate in vascular loops in the metaphysis Traumas with hematoma formation provide good environments for bacterial proliferation Spread to bone and joints • Infection is commonly hematogenous but may occur by local spread or from direct inoculation Natural history of osteomyelitis • The infection starts in the metaphysis Contained by the growth plate, the infection spreads through the metaphysis, and then penetrates the cortex, creating a subperiosteal abscess This may penetrate the periosteum to produce a soft tissue abscess During healing, new bone (involucrum) forms around the devitalized cortical bone This dead bone is called a “sequestrum” Local spread • Infection from metaphyseal osteomyelitis may spread into adjacent joints in the infant Neonatal septic arthritis of the hip • Note the widening of the joint space This is a late finding Transphyseal spread • Transepiphyseal vessels allow spread of infection from the metaphysis into the joint (red arrows) The presence of a physis blocks this spread (yellow arrow) Spread of osteomyelitis by age • Bone structure affects the spread of osteomyelitis (red arrows) In the infant, the absence of an epiphyseal plate may allow spread into a joint In the child, the path of least resistance is through the adjacent cortex to an extramedullary abscess In the mature adolescent, the thick cortex and absence of growth plates allow extension throughout the medullary cavity Abscess protects bacteria from antibiotics • The abscess prevents antibiotic penetration, protecting bacteria 10 Distribution of osteomyelitis • From a series of 66 patients reported by Perlman (2000) 11 Distribution of musculoskeletal tuberculosis 12 Natural history of polymyositis • The natural history of this infection includes cellulitic and suppurative stages 13 Distribution of septic arthritis • From data of Jackson and Nelson (1982) 14 Organisms in septic arthritis • These organisms are listed according to relative frequency 15