Imaging of musculoskeletal infections

Approach to imaging modalities in the setting of suspected infection

Imaging plays an important role in the workup of musculoskeletal infection, in conjunction with clinical history and physical exam. There are multiple imaging modalities that can be of clinical utility in the setting of suspected infection, each with their own benefits and limitations. Radiography is a low-cost, accessible modality providing a broad osseous overview, but can be insensitive for early osteomyelitis. Ultrasound plays a more limited role in the workup of musculoskeletal infection, but can be useful in the pediatric population or for real-time guidance for joint and soft tissue aspirations. Computed tomography (CT) plays an important role in the timely and accurate diagnosis of critically ill patients in the emergency setting. Its superior soft tissue characterization allows for diagnosis of abscesses, and it can help confirm the clinical diagnosis of necrotizing fasciitis when soft tissue gas is present. Magnetic resonance imaging (MRI) is often the modality of choice in the diagnosis of infection, as its superior contrast resolution allows for clear delineation of the presence and extent of both soft tissue infection and osteomyelitis. Additionally, the use of intravenous contrast and advanced imaging sequences such as diffusion weighted imaging (DWI) further increases the diagnostic utility of MRI in the assessment for infection. Familiarity with the diagnostic utility of each imaging modality will allow the radiologist to appropriately guide imaging workup in the setting of clinically suspected infection.

Hybrid imaging of Diabetic Foot Infections

Diabetic foot infections, a common but diagnostically challenging clinical presentation, requires the difficult differentiation between soft tissue-only infection, diabetic neuropathic osteoarthropathy, osteomyelitis or a combination of these pathological processes. While there are clinical predictors for osteomyelitis and simple bedside tests available, imaging is often required for accurate diagnosis. A variety of anatomic and molecular imaging tests are in clinical use, each with its advantages and disadvantages. This review will provide an overview of the different available imaging modalities and their diagnostic criteria, emphasizing the role of hybrid imaging for the accurate diagnosis of osteomyelitis.

Coronal STIR MRI sequences in unexplained limping in children under 6 years old: A single-center retrospective study of 130 cases

INTRODUCTION

Limping is a common presenting symptom in young children. Clinical examination backed up by laboratory analysis, standard radiography, and/or ultrasound may fail to determine the diagnosis, and limping may prove persistent, requiring repeated consultation. Magnetic resonance imaging (MRI) can suggest the etiology or provide welcome reassurance when normal. We advocate the use of MRI in cases of persistent unexplained limping in young children. The study hypothesis was that coronal short TI inversion recovery (STIR) MRI has good negative predictive value (NPV) in unexplained limping in children under 6 years of age.

MATERIAL AND METHOD

Coronal STIR MRI sequences were analyzed in 130 children younger than 6 years (84 boys, 46 girls) during the period April 2007 to May 2017. They extended from the lower thoracic spine down to the feet. Agreement was analyzed between the radiologist's initially suggested diagnosis and the pediatric orthopedic specialist's final diagnosis.

RESULTS

Overall, 49 scans were normal (37.7%) and 81 abnormal (62.3%). The mean age at MRI was 32.3 months. Coronal STIR MRI had 98% NPV. There was 99.2% agreement between the radiologist's diagnosis and the final diagnosis.

DISCUSSION

The recently reported contribution of STIR MRI in bone and joint infections was extended to unexplained limping.

CONCLUSION

First-line MRI with coronal STIR sequences improved the diagnostic efficacy, thanks to its speed and relative lack of movement artifacts.

Microbiological, Clinical and Radiological Aspects of Diabetic Foot Ulcers Infected with Methicillin-Resistant and -Sensitive Staphylococcus aureus

Diabetic foot ulcer (DFU) is one of the most common chronic complications of diabetes. This study aimed to assess the factors with an impact on the infection of diabetic foot ulcers by methicillin-resistant S. aureus and to evaluate the influence of methicillin resistance on the frequency of osteitis (based on classic X-ray images). A total of 863 patients suffering from DFU were analyzed during the study period. Out of 201 isolated S. aureus cases, 31 (15.4%) were methicillin-resistant (MRSA). MRSA infections were associated with a higher incidence of osteitis compared to MSSA infections (p << 0.0001), both the occurrence of smaller (<50%)) and greater (>50%) inflammatory bone changes (p << 0.0001). Furthermore, MRSA occurred significantly more frequently in men than in women (p < 0.01) and more often among patients with type 2 diabetes than among patients with type 1 diabetes (p < 0.05). MRSA were isolated statistically less often in overweight patients than in patients with normal BMI (p < 0.05). DFUs infected with MRSA were significantly more frequently associated with the presence of Pseudomonas sp. and other non-fermenting bacilli than those infected with MSSA (p < 0.05). To conclude, osteitis incidence is related to MRSA infection in patients with diabetic foot ulcers; thus, patients infected by S. aureus should be closely monitored in the course of using antibiotics and treated with narrow-spectrum antibiotics.

Acute septic arthritis of the acromioclavicular joint caused by Staphylococcus aureus with marked soft tissue collection towards posterior medial aspect of the AC joint: A rare clinical presentation

Primary septic arthritis of the Acromioclavicular joint is an unusual disorder and is seldom seen even in an immunocompromised person. We report a case of primary septic arthritis of the acromioclavicular (A-C) joint caused by Staphylococcus aureus. The patient was admitted with pain in the left shoulder, restricted movements and fever. Laboratory parameters showed elevated C-reactive protein, raised erythrocyte sedimentation rate and leukocytosis. Ultrasound revealed a 32 mm collection at the acromioclavicular joint. Patient underwent incision and drainage of abscess. Culture and sensitivity revealed moderate growth of Staphylococcus-aureus. Patient was started on appropriate intravenous antibiotics. Magnetic resonance imaging (MRI) done after 2 weeks revealed marked erosion in the lateral end of clavicle with soft tissue collection along the posteromedial aspect A-C joint. The patient had to undergo repeat drainage of the abscess along with the decompression of lateral end of clavicle. The patient was successfully treated with 8 weeks of appropriate antibiotics with complete resolution of infection.

Imaging update on musculoskeletal infections

The clinical diagnosis of musculoskeletal infections can be challenging due to non-specific signs and symptoms on presentation. These infections include infectious myositis, necrotising fasciitis, septic arthritis, septic bursitis, suppurative tenosynovitis, osteomyelitis, spondylodiscitis and periprosthetic infections. Diagnostic imaging is routinely employed as part of the investigative pathway to characterise the underlying infectious disease pattern, allowing expedited and customised patient management plans to optimise outcomes. This article provides an update on the various imaging modalities comprising of radiography, computed tomography, ultrasonography, magnetic resonance imaging and radionuclide procedures, and incorporates representative images of key findings in the different forms of musculoskeletal infections.

Acute Pyogenic Osteomyelitis of the Pubic Bone in a Patient with Systemic Lupus Erythematosus Mimicking Fracture of the Pubic Bone and Periprosthetic Joint Infection of the Hip

Introduction

Pubic bone osteomyelitis is atypical, and the diagnosis is often overlooked. It may present as osteitis pubis, fracture, or noninfectious inflammation of the pubic symphysis. Case Report. We report a case of a 65-year-old lady who has systemic lupus erythematosus with acute pyogenic osteomyelitis of the pubic bone who presented initially with a suspicious healing pubic rami fracture and periprosthetic infection of the hip joint.

Conclusion

Acute osteomyelitis of the pubic bone has often an infrequent and delayed presentation. Clinical awareness, early diagnosis, and appropriate treatment including surgical debridement and long-term antibiotics can prevent ongoing morbidities such as chronic osteomyelitis, pain, and deformities of pelvic bone and joints.

Frequency of Multifocal Disease and Pyogenic Arthritis of the Hip in Infants with Osteoarticular Infection in Three Neonatal Intensive Care Units

OBJECTIVE

To describe the clinical features of osteoarticular infection in infants cared for in neonatal intensive care units (NICUs) and to assess the presence of multifocal infection.

STUDY DESIGN

Retrospective medical record review with structured data abstraction of infants with osteomyelitis or pyogenic arthritis or both in NICUs at 3 children's hospitals over a 29-year period.

RESULTS

Of the 45 cases identified, 87% occurred in prematurely born infants, with a median gestational age of 27.4 weeks (IQR, 26, 31 weeks). Median postnatal age at diagnosis of infection was 33 days (IQR, 20, 50 days). Osteomyelitis was present without joint involvement in 53% and with joint involvement in 44% of cases. Methicillin-susceptible Staphylococcus aureus (71%) was the predominant pathogen, despite prevalent methicillin-resistant S aureus in community-associated infections. More than 1 bone was infected in 34% of cases. The femur (in 50% of patients) was the most frequently involved bone and the hip (in 20% of patients) was the most frequently involved joint. Bacteremia persisted for 4 or more days in 54% of patients with a positive blood culture despite active antimicrobial therapy.

CONCLUSIONS

Among infants with osteoarticular infection in NICUs, multifocal disease is common and frequently is unsuspected. Search for additional sites of infection including the hip is warranted following the diagnosis of osteoarticular infection at a single site. Involvement of contiguous joints should be suspected in cases of osteomyelitis; conversely the presence of pyogenic arthritis usually indicates extant osteomyelitis in a contiguous bone.

Imaging and Laboratory Workup for Hand Infections

Hand infections can lead to significant morbidity if not treated promptly. Most of these infections, such as abscesses, tenosynovitis, cellulitis, and necrotizing fasciitis, can be diagnosed clinically. Laboratory values, such as white blood cell count, erythrocyte sedimentation rate, C-reactive protein, and recently, procalcitonin and interleukin-6, are helpful in supporting the diagnosis and trending disease progression. Radiographs should be obtained in all cases of infection. Ultrasound is a dynamic study that can provide quick evaluation of deeper structures but is operator dependent. Computed tomographic and MRI studies are useful for evaluating deep space or bony infections and preoperative surgical planning.

A new sequential animal model for infection-related non-unions with segmental bone defect

BACKGROUND

The treatment of fracture-related infections (FRI) is still a challenge for orthopedic surgeons. The prevalence of FRI is particularly high in open fractures with extensive soft-tissue damage. This study aimed to develop a new two-step animal model for non-unions with segmental bone defects, which could be used to evaluate new innovative bone substitutes to improve the therapeutic options in humans with FRI and bone defects.

METHODS

After randomization to infected or non-infected groups, 30 Sprague-Dawley rats underwent a transverse osteotomy of the mid-shaft femur with a 5 mm defect. Additionally, the periosteum at the fracture zone was cauterized at both sides. After intramedullary inoculation with 10³ CFU Staphylococcus aureus (infected group) or PBS (non-infected group), a fracture stabilization was done by intramedullary K-wires. After 5 weeks, the bone healing process was evaluated, and revision surgery was performed in order to obtain increased bone healing. The initial K-wires were removed, and debridement of the osteotomy-gap was done followed by a more stable re-osteosynthesis with an angle-stable plate. After further 8 weeks all rats were euthanized and the bone consolidation was tested biomechanically and the callus formation quantitatively by micro-CT analysis.

RESULTS

We developed and presented a new two-stage non-union animal model through a targeted S. aureus infection. After 5 weeks, all animals showed a non-union irrespective of assignment to the infected and non-infected group. Lane and Sandhu score showed a higher callus formation in the infected group. In all infected animals, the inoculated S. aureus strain was detected in the revision surgery. The second surgery did not improve bone healing, as shown by the Lane Sandhu score and in the μ-CT analysis. Similarly, biomechanical testing showed in both groups a significantly lower maximum torque as compared to the contralateral side (p < 0.0001).

CONCLUSIONS

We were able to successfully develop a new two-stage non-union animal model, which reflects a genuine clinical situation of an infection-related non-union model with segmental bone defects. This model could be used to evaluate various therapeutic anti-infectious and osteoinductive strategies in FRIs.

Development of a Novel and Rapid Antibody-Based Diagnostic for Chronic Staphylococcus aureus Infections Based on Biofilm Antigens

Prosthetic joint infections are difficult to diagnose and treat due to biofilm formation by the causative pathogens. Pathogen identification relies on microbial culture that requires days to weeks, and in the case of chronic biofilm infections, lacks sensitivity. Diagnosis of infection is often delayed past the point of effective treatment such that only the removal of the implant is curative. Early diagnosis of an infection based on antibody detection might lead to less invasive, early interventions. Our study examined antibody-based assays against the Staphylococcus aureus biofilm-upregulated antigens SAOCOL0486 (a lipoprotein), glucosaminidase (a domain of SACOL1062), and SACOL0688 (the manganese transporter MntC) for detection of chronic S. aureus infection. We evaluated these antigens by enzyme-linked immunosorbent assay (ELISA) using sera from naive rabbits and rabbits with S. aureus-mediated osteomyelitis, and then we validated a proof of concept for the lateral flow assay (LFA). The SACOL0688 LFA demonstrated 100% specificity and 100% sensitivity. We demonstrated the clinical diagnostic utility of the SACOL0688 antigen using synovial fluid (SF) from humans with orthopedic implant infections. Elevated antibody levels to SACOL0688 in clinical SF specimens correlated with 91% sensitivity and 100% specificity for the diagnosis of S. aureus infection by ELISA. We found measuring antibodies levels to SACOL0688 in SF using ELISA or LFA provides a tool for the sensitive and specific diagnosis of S. aureus prosthetic joint infection. Development of the LFA diagnostic modality is a desirable, cost-effective option, potentially providing rapid readout in minutes for chronic biofilm infections.

Impact of Bacterial Infections on Osteogenesis: Evidence From In Vivo Studies

The clinical impact of bacterial infections on bone regeneration has been incompletely quantified and documented. As a result, controversy exists about the optimal treatment strategy to maximize healing of a contaminated defect. Animal models are extremely useful in this respect, as they can elucidate how a bacterial burden influences quantitative healing of various types of defects relative to non-infected controls. Moreover, they may demonstrate how antibacterial treatment and/or bone grafting techniques facilitate the osteogenic response in the harsh environment of a bacterial infection. Finally, it a well-known contradiction that osteomyelitis is characterized by uncontrolled bone remodeling and bone loss, but at the same time, it can be associated with excessive new bone apposition. Animal studies can provide a better understanding of how osteolytic and osteogenic responses are related to each other during infection. This review discusses the in vivo impact of bacterial infection on osteogenesis by addressing the following questions (i) How does osteomyelitis affect the radiographic bone appearance? (ii) What is the influence of bacterial infection on histological bone healing? (iii) How do bacterial infections affect quantitative bone healing? (iv) What is the effect of antibacterial treatment on the healing outcome during infection? (v) What is the efficacy of osteoinductive proteins in infected bones? (vi) What is the balance between the osteoclastic and osteoblastic response during bacterial infections? (vii) What is the mechanism of the observed pro-osteogenic response as observed in osteomyelitis? © 2019 The Authors. Journal of Orthopaedic Research^© published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 37:2067-2076, 2019.

An infective cause for the limping child

A 7-year-old girl presented with left hip pain and a limp, in the absence of any other systemic features, having recently been treated for a urinary tract infection. Examination revealed limited active hip movements on the left, with a tendency to weight bear on the contralateral side. Biochemical investigations were significant for raised inflammatory markers, and subsequent MRI imaging revealed osteomyelitis of the left pubis and ischium with an associated large soft tissue collection. Treatment was bimodal with surgical drainage and long-term antibiotics. The patient consequently recovered, without significant effect on either growth or mobility.

Clinical analysis of 17 cases of neonatal osteomyelitis: A retrospective study

Although acute osteomyelitis is rare in neonates, it might result in severe sequelae such as joint destruction and growth failure if it is not diagnosed and treated early. However, few studies have focused on the clinical features and treatment of this disease.A retrospective review of 17 cases of neonatal osteomyelitis, for which the patients underwent medical treatment alone or combined with surgery at the Children's Hospital of Zhejiang University School of Medicine between January 2009 and September 2016, was conducted. Medical treatment included the use of antibiotics and supportive care. Surgery was performed in cases with subperiosteal abscess (>1 cm) or clinical deterioration despite antibiotic therapy.All of the patients (11 men and 6 women) were term neonates. The main complaints were redness or swelling around the affected bone and fever. The most common sites were the femur (29.4%) and humerus (23.5%). There were 14 (82.35%) cases with positive cultures: Staphylococcus accounted for 71.43% (n = 10), followed by Salmonella (n = 1), Streptococcus pneumoniae (n = 1), Klebsiella pneumoniae (n = 1), and Escherichia coli (n = 1). X-rays (n = 14), ultrasound (n = 6), computed tomography (CT) (n = 5), or magnetic resonance imaging (MRI) (n = 7) were performed. Three of 14 x-rays were not pathological at the onset of the disease, while the positive rate of MRI in detecting osteomyelitis was 100%. Eleven of 17 cases underwent surgical drainage, and higher white blood cell (WBC) counts were found in patients requiring surgery (P < .05). The prognosis for all patients was good without severe sequelae with a mean follow-up period of 49.47 ± 23.43 months.In conclusion, the prognosis of neonatal osteomyelitis with early active treatment is good. MRI is advocated for detecting early osteomyelitis. Additionally, neonates with higher WBC count together with osteomyelitis have an increased risk for surgery.

Reevaluating Magnetic Resonance Imaging in Radiographically Suspected Osteomyelitis of the Toe

BACKGROUND:

Magnetic resonance imaging (MRI) is both sensitive and specific in the diagnosis of osteomyelitis, and it is an important imaging modality in preoperative planning of resection of infected bone. In many cases, however, the extent of osseous infection is evident on plain radiographs, and little additional information is gained from the MRI. The goal of this study was to assess the accuracy of radiographs against MRIs in assessing the spread of suspected osteomyelitis from one phalanx to another or to a metatarsal.

METHODS:

A medical record review was performed, and 14 patients with 16 toes confirmed to have osteomyelitis involving one or more phalanges were included in the study. An investigator blinded to the MRI findings interpreted the extent of osseous involvement based solely on the radiographic and clinical presentation. The accuracy of the radiographic interpretation was then calculated against the MRI findings.

RESULTS:

In 14 of the 16 toes (87.5%), whether osteomyelitis had spread from one bone to another was determined based on the radiographic and clinical presentation. In one toe, the radiograph did not adequately depict osteomyelitis in adjacent infected bone. In one more toe, the radiograph depicted features of osteomyelitis in uninfected bone.

CONCLUSIONS:

In a large percentage of patients, the phalanges affected by osteomyelitis had visible findings on the radiograph, and operative planning could have been based on the radiograph alone.

Salmonella osteomyelitis in a previously healthy neonate: a case report and review of the literature

Background

Acute osteomyelitis, which is uncommon in neonates, needs to be quickly diagnosed and treated to avoid devastating sequelae. Therefore, it is important to maintain a high index of suspicion and be aware of the evolving epidemiology and of the emergence of antibiotic resistant and aggressive strains requiring careful monitoring and targeted therapy. The most frequently isolated bacterium in neonates with osteomyelitis is Staphylococcus aureus, while Salmonella is an unusual organism causing osteomyelitis and is exceedingly rare in non-sickle cell disease children.

Case presentation

We report an extremely rare case of neonatal osteomyelitis caused by Salmonella in a neonate, who was previously healthy. We report this case because it was caused by a rare pathogenic germ in newborns and by its non-specific presentation.

Conclusions

Salmonella should be kept in mind in the differential diagnosis of neonatal osteomyelitis. It is important to start antibiotic therapy as soon as possible and to adjust therapy in relation to the susceptibility of the bacterial strain.

A Comprehensive Review of Skull Base Osteomyelitis: Diagnostic and Therapeutic Challenges among Various Presentations

Skull base osteomyelitis (SBO) is a complex and fatal clinical entity that is often misdiagnosed for malignancy. SBO is commonly a direct complication of otogenic, sinogenic, odontogenic, and rhinogenic infections and can present as central, atypical, or pediatric clival SBO. This review describes the clinical profile, investigational approach, and management techniques for these variants. A comprehensive literature review was performed in PubMed, MEDLINE, Research Gate, EMBASE, Wiley Online Library, and various Neurosurgical and Neurology journals with the keywords including: SBO, central or atypical SBO, fungal osteomyelitis, malignant otitis externa, temporal bone osteomyelitis, and clival osteomyelitis. Each manuscript's reference list was reviewed for potentially relevant articles. The search yielded a total of 153 articles. It was found that with early and aggressive culture guided long-term intravenous broad-spectrum antibiotic therapy decreases post-infection complications. In cases of widespread soft tissue involvement, an early aggressive surgical removal of infectious sequestra with preferentially Hyperbaric Oxygen (HBO) therapy is associated with better prognosis of disease, less neurologic sequelae and mortality rate. Complete resolution of the SBO cases may take several months. Since early treatment can improve mortality rates, it is paramount that the reporting radiologists and treating clinicians are aware of the cardinal diagnostic signs to improve clinical outcomes of the disease. It will decrease delayed diagnosis and under treatment of the condition. However, due to rarity of the condition, complete prognostic factors have not fully been analyzed and discussed in the literature.

Prolonged infection at the tibial bone tunnel after anterior cruciate ligament reconstruction

A 24-year-old man with severe atopic dermatitis underwent anterior cruciate ligament (ACL) reconstruction of the right knee seven years earlier but developed a surgical site infection. The infection did not heal after removal of the metal implants, and a fistula eventually developed. This condition was left untreated for six years before he was referred to our hospital. Magnetic resonance imaging showed fluid in the tibial bone tunnel and extensive bone marrow edema surrounding the bone tunnel. Based on these findings, abscess formation within the tibial bone tunnel and osteomyelitis spreading to the proximal tibia were suspected. During the surgery, a portion of artificial ligament and non-absorbable suture were observed in the bone tunnel, and the infection healed immediately after removal of this complex. When surgical site infection occurs after ACL reconstruction, it is important to completely remove all artificial materials as early as possible.

Postoperative Foot and Ankle MR Imaging

MR imaging has an important role in the evaluation of the postoperative foot and ankle. In this article, a variety of operative techniques and postoperative findings in the foot and ankle are described, including tendon and ligament reconstruction, as well as the treatment of tarsal coalition and Morton neuroma. The role of MR imaging in the assessment of complications of foot and ankle surgery is also detailed.

Accuracy of diagnostic imaging modalities for peripheral post-traumatic osteomyelitis - a systematic review of the recent literature

AIMS

Post-traumatic osteomyelitis (PTO) is difficult to diagnose and there is no consensus on the best imaging strategy. The aim of this study is to present a systematic review of the recent literature on diagnostic imaging of PTO.

METHODS

A literature search of the EMBASE and PubMed databases of the last 16 years (2000-2016) was performed. Studies that evaluated the accuracy of magnetic resonance imaging (MRI), three-phase bone scintigraphy (TPBS), white blood cell (WBC) or antigranulocyte antibody (AGA) scintigraphy, fluorodeoxyglucose positron emission tomography (FDG-PET) and plain computed tomography (CT) in diagnosing PTO were considered for inclusion. The review was conducted using the PRISMA statement and QUADAS-2 criteria.

RESULTS

The literature search identified 3358 original records, of which 10 articles could be included in this review. Four of these studies had a comparative design which made it possible to report the results of, in total, 17 patient series. WBC (or AGA) scintigraphy and FDG-PET exhibit good accuracy for diagnosing PTO (sensitivity ranged from 50-100%, specificity ranged from 40-97% versus 83-100% and 51%-100%, respectively). The accuracy of both modalities improved when a hybrid imaging technique (SPECT/CT & FDG-PET/CT) was performed. For FDG-PET/CT, sensitivity ranged between 86 and 94% and specificity between 76 and 100%. For WBC scintigraphy + SPECT/CT, this is 100% and 89-97%, respectively.

CONCLUSIONS

Based on the best available evidence of the last 16 years, both WBC (or AGA) scintigraphy combined with SPECT/CT or FDG-PET combined with CT have the best diagnostic accuracy for diagnosing peripheral PTO.

Role of Diffusion Weighted Imaging in Musculoskeletal Infections: Current Perspectives

Accurate diagnosis and prompt therapy of musculoskeletal infections are important prognostic factors. In most cases, clinical history, examination and laboratory findings help one make the diagnosis, and routine magnetic resonance imaging (MRI) is useful to identify the extent of the disease process. However, in many situations, a routine MRI may not be specific enough especially if the patient cannot receive contrast intravenously, thereby delaying the appropriate treatment. Diffusion-weighted imaging (DWI) can help in many such situations by providing additional information, accurate characterization and defining the extent of the disease, so that prompt treatment can be initiated. In this article, we illustrate the imaging findings of the spectrum of musculoskeletal infections, emphasizing the role of DWI in this domain.

KEY POINTS

• Abscess in background cellulitis is detected on DWI. • Infectious tenosynovitis shows diffusion restriction as compared to mechanical tenosynovitis. • Pyomyositis with abscess can be differentiated from diabetic myonecrosis on DWI. • Intraosseous abscess is bright on DWI versus devitalized tissue, sequestrum and air. • DWI can be used to differentiate spine infection from simple Modic changes.

Novel developments in the prevention, diagnosis, and treatment of periprosthetic joint infections

Periprosthetic joint infection (PJI) is one of the most challenging complications compromising the outcome of an otherwise successful operation. Considerable efforts have been invested in the recent years to address paradigm shifts in our understanding of the complex microbiological phenomena that contribute to the pathophysiology of PJI, such as microbial adherence, biofilm formation, and resistance to antibiotics. This article is an introduction to some of the recent advancements in the prevention, diagnosis, and treatment of PJI. It describes how industry, academic researchers, and government are increasing collaboration to address PJI through development of novel technologies, therapeutic strategies, and regulatory science that specifically target the unique biofilm-associated aspects of its pathogenesis.

Alendronate-coated long-circulating liposomes containing 99mtechnetium-ceftizoxime used to identify osteomyelitis

Osteomyelitis is a progressive destruction of bones caused by microorganisms. Inadequate or absent treatment increases the risk of bone growth inhibition, fractures, and sepsis. Among the diagnostic techniques, functional images are the most sensitive in detecting osteomyelitis in its early stages. However, these techniques do not have adequate specificity. By contrast, radiolabeled antibiotics could improve selectivity, since they are specifically recognized by the bacteria. The incorporation of these radiopharmaceuticals in drug-delivery systems with high affinity for bones could improve the overall uptake. In this work, long-circulating and alendronate-coated liposomes containing ^99mtechnetium-radiolabeled ceftizoxime were prepared and their ability to identify infectious foci (osteomyelitis) in animal models was evaluated. The effect of the presence of PEGylated lipids and surface-attached alendronate was evaluated. The bone-targeted long-circulating liposomal ^99mtechnetium–ceftizoxime showed higher uptake in regions of septic inflammation than did the non-long-circulating and/or alendronate-non-coated liposomes, showing that both the presence of PEGylated lipids and alendronate coating are important to optimize the bone targeting. Scintigraphic images of septic or aseptic inflammation-bearing Wistar rats, as well as healthy rats, were acquired at different time intervals after the intravenous administration of these liposomes. The target-to-non-target ratio proved to be significantly higher in the osteomyelitis-bearing animals for all investigated time intervals. Biodistribution studies were also performed after the intravenous administration of the formulation in osteomyelitis-bearing animals. A significant amount of liposomes were taken up by the organs of the mononuclear phagocyte system (liver and spleen). Intense renal excretion was also observed during the entire experiment period. Moreover, the liposome uptake by the infectious focus was significantly high. These results show that long-circulating and alendronate-coated liposomes containing ^99mtechnetium-radiolabeled ceftizoxime have a tropism for infectious foci.

Acute osteomyelitis as cause of late sepsis in a nigerian neonate

Neonatal osteomyelitis (NO) is said to be rare and uncommonly reported in the sub-region. Although this may be true, either because the cases are under-diagnosed, unreported or under-reported. The diagnosis is clinical and supported with blood culture or the aspiration of pus with radiological findings. We report a case of a neonate with acute osteomyelitis of the right femur, diagnosed at 10(th) day of life, which was confirmed with blood culture and radiogram findings of the right upper thigh of the baby. To the best of our knowledge, this is the first documented reported case of NO from the south-eastern Nigeria. It is imperative to recognize the clinical presentation necessary to raise the suspicion of NO and other focal infection in the newborn. With thorough examination and selected investigation the focus of infection in the neonate can be detected.

Necrotizing fasciitis: an urgent diagnosis

Necrotizing fasciitis (NF) is a rare, life-threatening soft-tissue infection and a medical and surgical emergency, with increasing incidence in the last few years. It is characterized by a rapidly spreading, progressive necrosis of the deep fascia and subcutaneous tissue. Necrotizing fasciitis is often underestimated because of the lack of specific clinical findings in the initial stages of the disease. Many adjuncts such as laboratory findings, bedside tests--e.g., the "finger test" or biopsy--and imaging tests have been described as being helpful in the early recognition of the disease. Imaging is very useful to confirm the diagnosis, but also to assess the extent of the disorder, the potential surgical planning, and the detection of underlying etiologies. The presence of gas within the necrotized fasciae is characteristic, but may be lacking. The main finding is thickening of the deep fasciae due to fluid accumulation and reactive hyperemia, best seen on magnetic resonance imaging.

[Acute limping in children between 1 and 4 years old]

Recent limping in children aged between 1 and 4 years old are often a diagnostic problem because the young child may not be able to show the area of pain. Dominated by the traumatic causes like hairline fracture, the physician should eliminate the most severe, including infectious etiologies that require urgent treatment. The clinical examination is fundamental and simple complementary investigations like standard X-rays and biology (blood count cell, C reactive protein) looking for increased inflammatory parameters will help to find the cause in the majority of cases. The persistence of a limp beyond a week involves the realization of bone scan or MRI imaging.

Magnetic resonance imaging of the immature skeleton

Magnetic resonance (MR) is unique in its ability to allow assessment of bone marrow, epiphyseal, physeal, and articular cartilage as well as tendons and ligaments. An understanding of skeletal maturation and the accompanying changes on MR is of utmost importance in pediatric radiology. In particular, it is important to recognize the normal spectrum related to ossification and marrow transformation. This review will include a brief description of main indications and common pitfalls in musculoskeletal MR in children. Also, we will focus on the MR appearance of the growing pediatric skeleton on the most commonly used sequences.

[Acute osteomyelitis: epidemiology, clinical manifestations, diagnosis and treatment]

BACKGROUND AND AIMS

The present study focuses on the epidemiology, clinical and laboratory data, and management of osteomyelitis in a pediatric third level hospital.

METHODOLOGY

All cases of children under 15 years-old admitted with osteomyelitis between 2000 and 2011 were retrospectively reviewed until July 2006, then prospectively from then until 2011.

RESULTS

A total of 50 patients were identified (52% males) with median age at diagnosis of 2 years. Principal onset manifestations were pain (94%), functional impairment (90%) and fever (72%). The femur (32%), fibula (28%) and calcaneus (22%) were most affected bones. Leucocytosis > 12.000/μl was found in 56%, elevated ESR > 20 mm/h in 26%, and elevated CRP > 20 mg/L in 64%. Blood culture was positive in 20%, with group A streptococcus being the most frequently isolated bacteria (11%). All diagnoses were confirmed by a (99)Tc scintigraphy bone scan. Antibiotic therapy was initially intravenously (mean time of administration: 10 days ± 3 SD), followed by oral medication (mean time of administration: 18 days ± 6 SD). Surgery was necessary in 3 patients. Evolution of all cases was excellent, despite 3 exceptions that resolved over time.

CONCLUSIONS

The current short-term intravenous therapy led to shorter hospitalizations. There were no statistically significant differences between time from clinical onset or in CRP levels at discharge compared to long-term therapies prior to 2006.

Magnetic resonance imaging of musculoskeletal infections: systematic diagnostic assessment and key points

Prompt diagnosis and treatment are essential in preventing the complications of musculoskeletal infection. In this context, imaging is often used to confirm clinically suspected diagnoses, define the extent of infection, and ensure appropriate management. Because of its superior soft-tissue contrast resolution, magnetic resonance imaging (MRI) is the modality of choice for evaluating musculoskeletal infections. This article describes the MRI features along the full spectrum of musculoskeletal infections and provides several illustrative case examples.

Pediatric osteomyelitis: a scintigraphic case-based review

This review presents techniques to optimize bone scintigraphy for evaluation of the spectrum of abnormalities associated with pediatric osteomyelitis, with an emphasis on the approaches to patient preparation and positioning and to interpretation. The diagnosis of pediatric osteomyelitis can be challenging for several different reasons. Bone scintigraphy is especially useful when the site of osteomyelitis is unclear. Other imaging modalities, including radiography, ultrasonography, and magnetic resonance imaging, all have advantages and may have a role in evaluating the condition of the child with osteomyelitis. Pathophysiologic considerations unique to children contribute to a different clinical presentation of osteomyelitis in the pediatric population than that seen in adults. In addition, patient movement degrades image quality substantially, which is an important consideration for imaging children. Neonates have a higher incidence of multifocal osteomyelitis, and they represent a unique subset of the pediatric population with separate considerations. Several examples illustrate techniques to optimize imaging, as well as show the spectrum of abnormalities associated with pediatric osteomyelitis. Careful attention to bone scintigraphic technique ensures that high-quality images can be obtained, which will allow confident diagnosis of pediatric osteomyelitis.

Chronic multifocal osteomyelitis: is infectious causation a moot point?

Chronic multifocal osteomyelitis (CMO) is an uncommon disease entity with descriptions possibly emanating from the medical literature over one century ago, and there are numerous disease entities which have been historically detailed and which are probably synonymous. The illness is one of chronicity with exacerbating and remitting focal bony lesions. The differential diagnosis for a bony lesion which ultimately proves to be CMO is initially quite broad. There is no absolute pathognomonic clinical finding, and the diagnosis is highly dependent on clinical course, histopathology, and an absence of microbial infection. Recent studies have focused on immune dysfunction or dysregulation, and there are now many other diseases which are inflammatory in nature and which have been diagnosed among patients with CMO. Despite the aforementioned, the potential for direct infectious causation or indirect causation by infectious stimulation of immunity cannot be entirely excluded. Infection as a mechanism for pathogenesis must continue to be entertained. Multi-centre studies are key to future research.

Functional imaging of infection: conventional nuclear medicine agents and the expanding role of 18-F-FDG PET

A growing body of literature suggests that 18-fluorine fluorodeoxyglucose positron emission tomography ((18)F-FDG PET), particularly when combined with CT, is a useful tool for the detection of infectious and inflammatory disease processes. This article will briefly review the data to date on the use of FDG PET in diagnosing musculoskeletal infections and fever of unknown origin, comparing it to conventional scintigraphic techniques in both adults and, when available, in children.

Imaging of musculoskeletal soft tissue infections

Prompt and appropriate imaging work-up of the various musculoskeletal soft tissue infections aids early diagnosis and treatment and decreases the risk of complications resulting from misdiagnosis or delayed diagnosis. The signs and symptoms of musculoskeletal soft tissue infections can be nonspecific, making it clinically difficult to distinguish between disease processes and the extent of disease. Magnetic resonance imaging (MRI) is the imaging modality of choice in the evaluation of soft tissue infections. Computed tomography (CT), ultrasound, radiography and nuclear medicine studies are considered ancillary. This manuscript illustrates representative images of superficial and deep soft tissue infections such as infectious cellulitis, superficial and deep fasciitis, including the necrotizing fasciitis, pyomyositis/soft tissue abscess, septic bursitis and tenosynovitis on different imaging modalities, with emphasis on MRI. Typical histopathologic findings of soft tissue infections are also presented. The imaging approach described in the manuscript is based on relevant literature and authors' personal experience and everyday practice.