Infection: musculoskeletal

Abstract

The imaging approach to osteomyelitis has evolved in the past two decades. Advances in MRI allow for whole body imaging, decreasing the need for scintigraphy when symptoms are not localized or the disease may be multifocal. There is an increasing clinical need for depiction of abscesses in the soft tissues and subperiosteal space, particularly because methicillin-resistant Staphylococcus aureus infections constitute more than one-third of all the infections. The increasing emphasis on radiation dose reduction has also led away from scintigraphy and computed tomography. MR imaging has become the advanced imaging modality of choice in osteomyelitis. There is an increasing understanding of the appropriate role for gadolinium enhancement, which is not indicated when the pre-gadolinium images are normal. Other related infections, including pyomyositis, are best imaged with MRI.Keywords Infection . Musculoskeletal . Children . MRI EpidemiologyAcute hematogenous osteomyelitis is the most common form of musculoskeletal infection [1]. Its incidence is difficult to determine, but it has been reported to be 1 per 5,000 [2]. There is conflicting data regarding the change of the disease over time. A study in 1998 found that the incidence in Norway ranged between 70 and 160 per million and that the incidence had remained stable between 1965 and 1994 [3]. An American study, however, found that in the last 20 years the incidence of osteomyelitis had increased 2.8-fold, whereas that of septic arthritis was stable. Methicillin-resistant Staphylococcus aureus (MRSA) was the causative organism in 30% of the children [4]. More than half of the cases occur before 5 years of age, and it appears to be more frequent in boys. Approximately 70% of infections involve the lower extremities and onethird affect the knee [2]. PathophysiologyHematogenous osteomyelitis results from the seeding of bacteria, usually Staphylococcus aureus (S. aureus) in the metaphysis of a long bone (Fig. 1) or in the metaphyseal equivalents of the axial skeleton (Fig. 2). S. aureus bacteria, which are present in the skin or mucosal membranes, enter the bloodstream and lodge in the bone, usually at sites where blood flow is abundant and slow. The metaphyses are richly vascularized and the valveless sinusoidal loops of the metaphyseal venules have sluggish flow and discontinuous endothelium which facilitates bacterial invasion. During childhood, the metaphyses that grow the fastest, such as those around the knee, are the most richly vascularized in order to produce new bone at a rapid rate. These rapidly growing metaphyses also tend to be affected more frequently by infection. S. aureus has the capacity to attach to the bony matrix and produce proteolytic enzymes that destroy the surrounding tissues, allowing the spread of the infection. From the bone, the infection extends through the porous metaphyseal cortex into the subperiosteal space. The periosteum in children is loosely attached to the bone and separates easily from it, creating a space that allows ...

Ekstremitenin Travmatik Olmayan Acilleri

“…Bunlardan en sık görülen hematojen yolla bulaştır ve genelde etken mikroorganizma S. aureus'dur [4]. Osteomiyelitin akut, subakut ve kronik dönemleri vardır.…”

“…İnfantlarda (<18 ay) transfizyel damarlar aracılığı ile eriş-kinlerde ise epifiz plağının kapanmış olması nedeniyle enfeksiyon metafizden epifize ve hatta eklem aralığına ulaşabilir [4]. Bakteriler metafiz içerisinde kemik içi basınç artışına ve kanlanmanın bozulmasına neden olarak nekroz meydana getirirler.…”

“…Daha sonra kortekste oluşan harabiyet, pürülan koleksiyonun periostun altında birikmesi ile periostu kaldırır. Periostun harabiyeti ise enfeksiyonun kemikten yumuşak dokuya uzanmasına neden olur [4].…”

“…Direkt grafi ve BT'nin ikisi de erken dönem-de normal olabilir [2,4]. Günümüzde kemik iliği ve yumuşak dokudaki anormalliklerin değerlendirilmesinde en duyarlı yöntem MRG'dir [4].…”

“…Günümüzde kemik iliği ve yumuşak dokudaki anormalliklerin değerlendirilmesinde en duyarlı yöntem MRG'dir [4]. Akut osteomiyelit, MRG'de kemik iliğinde ödem benzeri sinyal değişiklikleri ve kontrast parlaklaşması ile kendini gösterir (Resim 1).…”