Significance of epiphyseal cartilage enhancement defects in pediatric osteomyelitis identified by MRI with surgical correlation

Pediatric Emergency MRI

There is an overall increase in the use of imaging in the pediatric emergency room setting, which is accompanied by a reduction in computed tomography examinations performed mainly due to the increased awareness of the risks of ionizing radiation. Advances in MRI technology have led to shortened scan time, decreased motion sensitivity, and improved spatial resolution. With increased access to MRI in the emergency room setting, the goal of this article is to review major applications of MR in pediatric emergency room patients.

Magnetic resonance imaging protocols for pediatric acute hematogenous osteomyelitis

Pediatric musculoskeletal infection can be a challenging clinical diagnosis. MRI protocols should be tailored appropriately to diagnose and localize sites of infection, to determine alternative pathologies that could explain the child's presentation, and to identify complications that could alter treatment or lead to devastating consequences in growing bones. In this review, we discuss MRI protocols tailored for suspected acute appendicular musculoskeletal infection in children. These protocols are based on patient age in order to generally reflect the developmental stage of the child, the corresponding relevant anatomy and physiology, and the skeletal maturity-dependent physiopathology of musculoskeletal infections.

Benefits of diffusion-weighted imaging in pediatric acute osteoarticular infections

BACKGROUND

Contrast-enhanced magnetic resonance imaging (MRI) is recommended for the diagnosis of acute osteoarticular infections in children. Diffusion-weighted imaging (DWI) may be an alternative to the injection of gadolinium.

OBJECTIVE

To evaluate unenhanced MRI with DWI in comparison to contrast-enhanced MRI for the diagnostic work-up of acute osteoarticular infections in children.

MATERIALS AND METHODS

This retrospective study included 36 children (age range: 7 months-12 years) with extra-spinal osteoarticular infections and MRI performed within 24 h of admission. MRI protocol included short tau inversion recovery (STIR), water-only T2 Dixon, T1, DWI, and gadolinium-enhanced T1 sequences. Two readers reviewed three sets of images: 1) unenhanced sequences, 2) unenhanced sequences with DWI and 3) unenhanced followed by contrast-enhanced sequences (reference standard). Sensitivity and specificity of sets 1 and 2 were compared to set 3 and assessed to identify osteoarticular infections: osteomyelitis (long bones, metaphyseal equivalents), septic arthritis and abscess (soft tissues, bone).

RESULTS

All 14 cases of osteomyelitis in the metaphyses and diaphyses of long bones and all 27 cases of septic arthritis were identified by unenhanced sequences, but 4/16 abscesses were missed. For the diagnosis of abscess, DWI increased sensitivity to 100%. Among the 18 osteomyelitis in metaphyseal equivalents, 4 femoral head chondroepiphyses were identified by contrast-enhanced sequences only.

CONCLUSION

MRI for suspected pediatric acute osteoarticular infections is the best diagnostic modality to guide patient management. An unenhanced protocol with DWI may be an alternative to a contrast-based protocol, even in the presence of an abscess. However, gadolinium remains necessary to assess for chondroepiphyseal involvement of the femoral head.

ACR Appropriateness Criteria® Osteomyelitis or Septic Arthritis-Child (Excluding Axial Skeleton)

Imaging plays an integral role in the evaluation of suspected musculoskeletal infections in children, not only in the accurate identification of infection such as osteomyelitis or septic arthritis, but also in guiding management. Various diagnostic modalities serve different purposes in the assessment of suspected pediatric musculoskeletal infections. The purpose of this document is to provide imaging guidance in the most frequently encountered clinical scenarios in which osteomyelitis and/or septic arthritis are suspected, outside of the axial skeleton. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion.

Concomitant septic arthritis and osteomyelitis of the hip in young children; a new pathophysiological hypothesis suggested by MRI enhancement pattern

Background

In children, septic arthritis (SA) of the hip is either primary or concomitant with acute haematogenous osteomyelitis (AHO). However, seldom, patients with isolated SA at presentation, may later show osteomyelitis in the metaphysis. The aim of this study was to elaborate a physiopathological hypothesis based on the peculiar MRI findings to explain the onset of AHO after SA.

Methods

Cases of acute infection of the hip admitted between January 2010 and December 2013 were retrospectively reviewed to assess radiographic and MRI features, as well as bacteriological findings. Only children with isolated SA were included in this study, whereas cases of concomitant SA and AHO at presentation were excluded.

Results

Ten patients met the inclusion criteria. Six (1–11 months) demonstrated, on the initial MRI, decreased perfusion on gadolinium enhanced fat-suppressed T1-weighted sequence of the femoral epiphysis and developed one month later metaphyseal AHO. Four (5–14 years) did not show decreased perfusion and did not develop AHO on follow-up. The type of germ involved influenced neither the type of enhancement pattern nor the outcome.

Conclusions

Age under one year and decreased perfusion of the affected femoral epiphysis increases the risk of secondary AHO. Our study is the first report in human medicine supporting the physiopathological hypothesis described by Alderson et al. in an animal model: primary infection can originally affect the joint, then penetrate the epiphyseal cartilage, and finally spread into the metaphyseal region through transphyseal vessels present only in the first 12/18 months of life.

Pediatric osteoarticular infection update

Musculoskeletal infections are a common cause of morbidity in children. A multitude of studies over the past few years have improved our knowledge and understanding of the etiology, diagnosis, and treatment of pediatric osteomyelitis and septic arthritis. Staphylococcus aureus continues to be the most common pathogen; however, new and innovative organism identification techniques are improving the speed and accuracy of diagnosis and increasing the identification of other less common organisms. Improved capability for patient assessment with a combination of advanced imaging studies and timely laboratory tests allow for a more thorough understanding of the disease process and more efficient patient care.

Primary epiphyseal or apophyseal subacute osteomyelitis in the pediatric population: a report of fourteen cases and a systematic review of the literature

BACKGROUND

Primary epiphyseal or apophyseal subacute osteomyelitis (PEASAO) is a rare condition that typically has mild symptoms and lack of a systemic reaction, according to opinions, case reports, and case series. We reviewed fourteen consecutive cases of PEASAO treated at our institution over a thirteen-year period to characterize this disorder.

METHODS

We retrospectively reviewed the medical records of all children and adolescents who had been surgically managed for PEASAO at our institution from January 2000 to December 2012. A systematic review of the literature was also performed to identify trends in causative organisms and formulate evidence-based recommendations for diagnosis and treatment.

RESULTS

Fourteen children (median age, 27.8 months) with PEASAO were included in the study. Fever (rectal temperature, >38°C) was present at admission in two children, C-reactive protein was within the normal range (<10 mg/dL) in eleven, the erythrocyte sedimentation rate was >20 mm/hr in eight, and the white blood-cell count was normal in all. The pathogen was not identified on blood cultures in any child and was identified on classical cultures of bone samples in only one. Use of PCR (polymerase chain reaction) assays allowed the pathogen to be identified in an additional eight children. The pathogen was Kingella kingae in eight and methicillin-sensitive Staphylococcus aureus in one.

DISCUSSION

The use of organism-specific real-time PCR assays markedly improves the detection rate of the pathogen responsible for PEASAO, and K. kingae is the most commonly detected pathogen. The literature highlights a biphasic age distribution of PEASAO in children. The infantile form affects children from one to less than four years of age, accounting for approximately 75% of all PEASAO cases. The second form, in older children, is more likely to be associated with fever and systemic symptoms. The femur and the tibia are the most commonly affected long bones. Laboratory data are usually noncontributory for diagnosing PEASAO, and blood cultures are often sterile. Although K. kingae is the most commonly detected microorganism in children less than four years of age, S. aureus is responsible for most PEASAO in older children. Antibiotic treatment is usually sufficient to eradicate the pathogen.

Can early MRI distinguish between Kingella kingae and Gram-positive cocci in osteoarticular infections in young children?

BACKGROUND

K. kingae is a common causative organism in acute osteoarticular infections (OAIs) in children under 4 years of age. Differentiation between K. kingae and Gram-positive cocci (GPC) is of great interest therapeutically.

OBJECTIVE

Our aim was to identify early distinguishing MRI features of OAIs.

MATERIALS AND METHODS

Thirty-one children younger than 4 years of age with OAI underwent MRI at presentation. Of these, 21 were caused by K. kingae and ten by GPC. Bone and soft tissue reaction, epiphyseal cartilage involvement, bone and subperiosteal abscess formation were compared between the two groups. Interobserver agreement was measured.

RESULTS

Bone reaction was less frequent (P = 0.0066) and soft tissue reaction less severe (P = 0.0087) in the K. kingae group. Epiphysis cartilage abscesses were present only in the K. kingae group (P = 0.0118). No difference was found for bone abscess (P = 0.1411), subperiosteal abscess (P = 1) or joint effusion (P = 0.4414). Interobserver agreement was good for all criteria.

CONCLUSION

MRI is useful in differentiating K. kingae from GPC in OAI. Cartilaginous involvement and modest soft tissue and bone reaction suggest K. kingae.

Infection: musculoskeletal

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.