Diagnosis. Diagnosis of osteomyelitis in the neonate can be challenging and is often delayed, as it is rare in the neonatal period and frequently presents with

Diagnosis of osteomyelitis in the neonate can be challenging and is often delayed, as it is rare in the neonatal period and frequently presents with non-specific signs of illness. Diagnosis is based on clinical signs and symptoms, laboratory findings, radiological and microbiological criteria.

Clinical sings

In general, two distinct clinical syndromes have been postulated to be associated with neonatal osteomyelitis:

1) a benign form, with little or no evidence of infection other than local swelling, and

2) a severe form, with the predominant manifestation of a sepsis-like syndrome with multiple bone sites being noted as manifestations. In neonates, almost half of all cases involve two or more bones.

Clinical symptoms and signs of osteomyelitis in the neonate are at first frequently unspecific and mild. They may include temperature instability, feeding intolerance, irritability or reduced movement, frequently giving rise to the suspicion of secondary sepsis. Fever is a rare condition that could be explained by a rather poorly developed immune system. As the disease progresses, more specific signs may become present, including disability, local swelling or erythema. Focal tenderness over a long bone should catch the physician's attention. In some cases subcutaneous abscess formation prompts the diagnosis of osteomyelitis. Hip, knee and shoulder are most frequently involved.

Laboratory findings

In general, there is no specific laboratory test for osteomyelitis. Neonates with osteomyelitis frequently show normal leukocyte counts and erythrocyte sedimentation rates in the first days. Thus, normal values do not preclude the diagnosis. The CRP is a rapid indicator of systemic inflammation and tissue damage, is useful as acute phase reactant, but not specific for skeletal infection. Procalcitonin has also been described as a potential marker in the diagnosis of osteomyelitis in children, but needs to be investigated in larger trials, especially in newborns. Elevated values of CRP and ESR could be used to monitor response to therapy or identify complications.

Imaging Studies

Radiological investigations confirm the suspicion of neonatal osteomyelitis, define the infection site, differentiate between unifocal and multifocal disease patterns and identify secondary complications. CT, MRI, ultrasound, radiography and bone scintigraphy scanning have been reported to be useful in detecting osteomyelitis. However, awareness of radiation exposure, need for sedation and transfer to another unit must be considered in the selection of technique.

Radiographs should be the first diagnostic assessment to be performed in patients with suspected osteomyelitis, because they may suggest the correct diagnosis and exclude other pathologic conditions. However, the specificity of plain radiographs for detecting osteomyelitis is greater (75% to 83%) than its sensitivity (43% to 75%). Plain radiography can show soft tissue swelling and destroyed fascial planes within days after onset of infection, but may be subtle and not obvious until day 5 to 7 in children. In the neonate even soft tissue swelling may not be present, because subcutaneous fat is lacking and fascial planes are poorly defined. Joint effusions might be suspected if widening of the joint space or bulging of the soft tissues is detected. Additional early changes are as follows: periosteal thickening/elevation, lytic lesions, osteopenia, loss of trabecular architecture, and new bone apposition. Of importance, destructive bone changes do not appear until 7 to 14 days of disease.

Predominately in children, ultrasound can detect features of acute osteomyelitis several days earlier, than radiographs. Even though findings may not be specific and standardized reports for neonates with osteomyelitis are lacking, ultrasound should be taken into account as a useful additional diagnostic tool for the early detection and management of osteomyelitis in neonates as it has many advantages: it is non-invasive, readily accessible, performed bedside, of minimal discomfort for the patient, does not use ionizing radiation and does not need sedation. Even though ultrasound cannot exclude the diagnosis of osteomyelitis, its main value lies in its ability to identify involvement of the adjacent soft tissue (subperiosteal fluid collection or abscess formation), periosteal thickening or elevation, joint effusions and irregularities or interruptions of the cortical bone. Color Doppler imaging further supports the diagnostic assessment, showing coexisting presence of hyperemia surrounding the periost and soft tissue abscess formation. Ultrasound can also be used to image guided-needle aspiration of the subperiosteal fluid for pathogenic organism isolation or subperiosteal abscess drainage. Furthermore, ultrasound has been described as being helpful in differentiating between epiphyseal separation and subluxation following septic arthritis. However, ultrasound cannot exclude the diagnosis of acute osteomyelitis, and thus further imaging diagnostics may be required.

MRI has high specificity (94%) and sensitivity (97%) for the diagnosis of acute osteomyelitis, showing changes as early as day 3 to 5 after the onset of infection. MRI gives excellent tissue characterization and high resolution, showing detailed anatomic presence of the inflammatory process and its complications (abscess formation, physeal involvement, septic arthritis), further allowing the assessment of involvement of the growth plate and epiphysis. MRI has been proven useful in the diagnosis of clinically suspected osteomyelitis in children, but for its use in neonatology it has several limitations: first and foremost the need for sedation and transfer to the MRI unit.

Three-phase bone imaging, using technetium 99m is very sensitive (90%-95%) for the detection of acute osteomyelitis in the early stages of disease and allows detection within 24 to 48 hours after onset of symptoms. Bone scintigraphy is especially useful for detecting multiple foci of infection or if the infection site is poorly localized. Technetium-99 methylene diphosphonate accumulates in areas of increased bone turnover and is for now the preferred agent of choice for radionuclide bone imaging. In neonates bone scintigraphy is the subject of controversy: only a few reports support its use and have shown that sensitivity is much lower, than in older infants because of poor bone mineralization.

Дата добавления: 2014-10-15