**5. Imaging studies**

Imaging (computed tomography (CT) scan, radiography, bone scan, US and/or MRI) is used to identify the site of an infection, the presence of liquid collections for diagnostic aspira‐ tion and/or biopsy, to differentiate a unifocal from multifocal disease and to identify pres‐ ent or impending complications, such as joint or extradural involvement. Montgomery et al. [32] showed that the use of advanced imaging (CT scan, bone scan, and/or MRI) in infants younger than 4 months of age may shorten hospital stays, decrease the number of operative procedures required, and possibly limit infection‐related sequelae. MRI has become the gold standard to evaluate musculoskeletal infection. It has the capability of assessing the osseous, articular and muscular structures simultaneously and does not require ionizing radiation. In particular MRI plays an important role in defining the extent of soft tissue involvement, defin‐ ing drainable fluid collections and bone biopsy sites pre‐operatively and thereby decreasing the need for repeating the surgery. Increased marrow intensity with surrounding inflamma‐ tion are the most suggestive signs of OM. MRI of the spine is useful in children not responding to therapy and/or to detect complications, such as extradural and paraspinal collections that will require surgical treatment because of causing spinal cord compression. The enhanced uptake of the radioisotope, distinguishes OM from deep cellulitis Gadolinium‐enhanced fat‐ saturated T1‐weighted sequences increase the confidence of the diagnosis of OM and may help also to distinguish edema from an abscess [33] and allows one to see the isolated involve‐ ment of the epiphyseal growth cartilage that is occult on radiographs and bone scintigraphy because of the paucity of growth cartilage ossification. The finding of hypo‐enhancing foci in the growth cartilage suggests cartilage ischemia, necrosis or abscess as a consequence of infectious chondritis or septic thrombosis [34]. MRI may not be appropriate for monitoring the evolution of the lesions. Technetium bone scanning has a false‐negative rate of as much as 20%, particularly in the first few days of illness. Indium‐labeled leukocytes have limitations in newborns. Gallium scanning is not recommended because of lower specificity and expo‐ sure to higher levels of radiation. Ultrasonography: Although ultrasonography is an operator dependant technique with an inability to differentiate infectious fluid from traumatic ones, in able hands, it allows the detection of changes of acute OM as early as 48 h after the onset of infection. In the early stages ultrasound document deep soft tissue swelling (1–3 d), then the elevation of the periosteum by a thin layer of fluid, a definite subperiosteal collection, joint effusion and finally cortical erosion (2–4 w). In this last case it is used to guide needle drain‐ age aspiration if necessary. Ultrasound images normalize by 4 weeks in the case of response to treatment [35]. Doppler venous ultrasonography is the first imaging study indicated in the case of clinical suspicion for deep vein thrombosis in patients with OM caused by CA‐MRSA. A normal ultrasound scan does not exclude OM. Radiography is usually the first radiological investigation in a neonate with suspected OM, although it is reported that only 20% of the radiographs are abnormal at 10–14 days [36, 37]. Despite the low prevalence of abnormal fea‐ tures at presentation, it allows the exclusion of fractures and is useful to show long‐term fol‐ low‐up of complications. Initially it may reveal normal results, after 10–15 days signs of bone destruction, osteopenia, lytic lesions, and periosteal changes. Metaphyseal irregularities and periostitis (both non‐specific) may be documented [37]. It has low sensitivity toward detec‐ tion of a joint effusion or deep soft tissue swelling; the diagnosis of suspicion may include widening of the joint space with or without subluxation and soft tissues protruding that can be detected as early as 48 h after the onset of infection. Radiography may detect bone destruc‐ tion when at least one‐third of the matrix has been involved. Findings related to the spine may be limited to a loss of the normal lumbar lordosis, disc space narrowing, end plate ero‐ sions, pressure erosion of the superior and inferior margins of the adjacent vertebral body if the infection prolonged. Normally, other imaging tests are required. A bone scan is reserved for the cases in which radiographs and/or ultrasound are unclear, for suspected multifocal infection, chronic multifocal OM, and discitis. Bone scintigraphy is highly sensitive to the detection of OM in the early stages of the disease. In the first week of the disease, techne‐ tium (99mTc)‐labeled bone scans revealed positive in 87% of the cases as compared with 42% diagnosed with radiography. Scintigraphy is useful for detecting multifocal diseases that are more common in neonates. A 99mTc‐labeled phosphonate complex is the most used isotope. Scintigraphic study, even if non‐specific, is useful to document through increased uptake of

all three phases: perfusion, blood pool activity and bone metabolism. Cold spots occur as a result of decreased blood flow secondary to edema and subperiosteal or articular infection. It may be a discriminating diagnosis in secondary bone infection in the case of persisting coagu‐ lase negative staphylococcus (CONS) bacteremia [38]. Computed tomography (CT) scan use is limited in the neonate. It is superior to MRI in chronic OM with cortical destruction, air and sequestra. It may also be used to guide aspiration and biopsy, especially when the spine and

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If signs and symptoms do not begin to resolve within 48–72 h of initiation of appropriate antimicrobial treatment, bone aspiration may be necessary to identify the pathogen and to drain the pus in accordance with the orthopedic surgeon. Bone and/or joint fluid aspirate for

It is a necessary antibiotic treatment, as soon as possible, in order to prevent the potentially adverse anatomic and functional consequences, preferably after obtaining blood and bone aspirates for culture. As cultures may be negative or difficult to obtain, empirical treatment is based on the local prevalence of organisms, resistance patterns taking account of the change over the years of the spectrum of organisms causing OM. The choice of an agent is generally either a penicillin‐ ase‐resistant penicillin (e.g. nafcillin, oxacillin, flucloxacillin), which will be effective against S. aureus but may be of limited value against other organisms, or a broad‐spectrum cephalosporin, which could have reduced the activity against *S. aureus.* Antibiotics against methicillin‐sensitive *S. aureus* (MRSA) and streptococci (a penicillinase‐resistant penicillin, first generation cephalo‐ sporin or clindamycin) must be incorporated into any empiric regimen for OM because *S. aureus*, *group A Streptococci* and group B streptococcus (GBS) and *S. pneuomoniae* together account for more than 90% of the cases of osteoarthritis in neonates [39]. Immunization rates worldwide have obviated the need to use antibiotics against Hib in many countries. Cefuroxime, a sec‐ ond‐generation cephalosporin can be used as a single agent against both methicillin‐sensitive *S. aureus* (MSSA) and Hib, if they are the suspected pathogens. The increasing incidence of peni‐ cillin‐resistant S pneumoniae warrants the use of a clindamycin and cefotaxime/ceftriaxone com‐ bination. When treating neonatal OM, consider nafcillin and tobramycin or vancomycin and gentamicin combinations to provide coverage of bacteria from the Enterobacteriaceae family, in addition to group B streptococci and *S. aureus*. Vancomycin is preferred for proven or suspected MRSA‐related septicaemia or known multi‐drug resistant MRSA infection. The suspicion of enteric organisms justify additional therapy with an aminoglycoside, such as gentamicin, tobra‐ mycin or amikacin or an extended‐spectrum, a Pseudomonas‐active agent, such as cefepime [40]. In the case of acquired MRSA infections should be started vancomycin, rather than a peni‐ cillin antibiotic [5]. Daptomycin, Linezolid, and Quinupristin‐dalfopristin have not been fully

culture, can be bactericidal. Bone biopsy is necessary in the suspicion of tumors.

paraspinal soft tissues are involved [9].

**6. Procedures**

**7. Management**

all three phases: perfusion, blood pool activity and bone metabolism. Cold spots occur as a result of decreased blood flow secondary to edema and subperiosteal or articular infection. It may be a discriminating diagnosis in secondary bone infection in the case of persisting coagu‐ lase negative staphylococcus (CONS) bacteremia [38]. Computed tomography (CT) scan use is limited in the neonate. It is superior to MRI in chronic OM with cortical destruction, air and sequestra. It may also be used to guide aspiration and biopsy, especially when the spine and paraspinal soft tissues are involved [9].
