MRI findings of treated bacterial septic arthritis

MRI in shoulder arthropathies: A short review

Arthropathies are a frequent cause of shoulder pain and comprise of a wide range of clinical entities that may pose a diagnostic challenge. Though history and clinical examination remain vital, imaging plays a pivotal role in accurate diagnosis. Magnetic resonance imaging (MRI) remains an invaluable tool for imaging evaluation of shoulder involvement by various arthropathies. With attention to characteristic imaging features, radiologist may be able to differentiate between various disease processes affecting the shoulder joint. In this article, we have provided a brief review of common and uncommon MRI manifestations of various arthropathies affecting the shoulder joint.

Bone marrow edema of the hip: a narrative review

Bone marrow edema (BME) of the hip is a radiological-clinical condition with symptoms ranging from asymptomatic to severe, and it is characterized by increased interstitial fluid within the bone marrow, usually at the femur. Depending on the etiology it can be classified as primary or secondary. The primary cause of BME is unknown, while the secondary forms include traumatic, degenerative, inflammatory, vascular, infectious, metabolic, iatrogenic, and neoplastic etiologies. BME could be classified as reversible or progressive. Reversible forms include transient BME syndrome and regional migratory BME syndrome. Progressive forms include avascular necrosis of the femoral head (AVNH), subchondral insufficiency fracture, and hip degenerative arthritis. The diagnosis can be difficult, because at the beginning, the outbreak of hip pain, typically acute and disabling without any prior trauma or exceptional physical activity, is poorly supported by radiographic findings. MRI is the gold standard, and it shows an area of intermediate signal on T1-weighted MRI scans and a high signal on T2-weighted scans, usually lacking sharps margins. In the reversible form, BME is typically self-limiting, and it can be managed conservatively by means of pharmacological and physical therapy. Surgery is generally required for progressive forms in patients who failed non-operative treatment, and it ranges from femoral head and neck core decompression to total hip arthroplasty.

Diagnostic use of superb microvascular imaging in evaluating septic arthritis of the manubriosternal joint: A case report

BACKGROUND

Septic arthritis of the manubriosternal joint is a diagnostic challenge due to its rarity and anatomical characteristic. Conventional ultrasound, plain radiographs, and computed tomography are not able to confirm or even suspect arthritis early. Superb microvascular imaging is a new advanced Doppler technique in evaluating low-flow microvascular patterns. The higher sensitivity for increased peri-synovial vascularity helps to suspect septic arthritis and forms a methodical approach to using magnetic resonance imaging (MRI).

CASE SUMMARY

A 34-year-old immunocompetent woman presented with a fever and a dull ache in the chest radiating to the right arm. Traumatic injury and the most common respiratory and cardiac disorders were ruled out. Blood cultures came back positive for Staphylococcus aureus, and sepsis was confirmed. A small lump was noted on the chest during the first week of hospitalization. Superb microvascular imaging was performed and septic arthritis of the manubriosternal joint was detected. MRI confirmed the diagnosis and showed septic arthritis of the manubriosternal joint with several localized abscesses behind the sternum. The patient was treated for three weeks with intravenous antibiotics and the outcome was favorable: Inflammatory markers became normal, and the lump disappeared. Three months later, the patient was examined for a new episode of mild pain in the sternum and was diagnosed with persistent perichondritis by ultrasound in comparison with MRI.

CONCLUSION

Superb microvascular imaging is a useful tool for the early diagnosis of septic arthritis of the manubriosternal joint and following-up.

Septic arthritis of the wrist: a retrospective review of 39 cases

LEVEL OF EVIDENCE

III.

Pediatric Imaging of the Elbow: A Pictorial Review

The elbow is a complex joint, subject to a wide range of traumatic, inflammatory, metabolic and neoplastic insults. The pediatric elbow has several diagnostic pitfalls due to the normal developmental changes in children. Knowledge of these normal variants is essential for both diagnosis and management of their elbow injuries. Radiography remains the first imaging modality of choice. Magnetic resonance imaging is excellent in evaluating lesions within the bone and soft tissues. In this pictorial essay, we provide insights into pediatric elbow imaging, show a range of entities specific to the pediatric elbow, and discuss diagnostic pitfalls that result from normal elbow growth in children.

Osteomyelitis on MR imaging as a key predictor of recurrent septic arthritis of the shoulder

OBJECTIVES

To investigate the clinical and radiologic predictors of postoperative recurrent septic arthritis of the shoulder (SAS) using multivariable analysis.

METHODS

Forty-three patients (mean age, 65 years; 24 women) who underwent surgery for SAS between January 2011 and October 2019 were retrospectively enrolled. An orthopedic surgeon assessed clinical (age, sex, comorbidity, duration from symptom onset to MR imaging and surgery, surgical method, antibiotic usage), laboratory (serum white blood cell [WBC] count, C-reactive protein [CRP] level, synovial cell count), and surgical findings (culture/biopsy results). Two musculoskeletal radiologists evaluated MR imaging findings (bone marrow [reactive bone marrow edema, osteomyelitis, osteochondral erosion] and soft tissue [synovitis, bursitis, muscle edema, abscess] abnormalities). Recurrent SAS was evaluated at ≥ 12 months postoperatively. Univariable and multivariable analyses were performed to determine the best predictor of recurrent SAS.

RESULTS

The overall recurrent SAS rate was 33% (14/43). On univariable analysis, mean age (without recurrence vs. recurrence: 68 vs. 59 years, p = .04), mean duration from symptom onset to surgery (18 vs. 25 days, p = .02), serum WBC count (12,000 vs. 9,000 cells/mL³, p = .04), CRP level (13 vs. 6 mg/L, p = .01), and osteomyelitis on MR imaging (p < .01 for both readers) significantly differed between patients with and without recurrence; on multivariable analysis, only osteomyelitis on MR imaging was significantly associated with recurrent SAS for both readers (p = .02 and .01 for each reader respectively). The inter-reader agreement was good (κ = .62-1.0) for all MR imaging findings, except for muscle edema (fair, κ = .37).

CONCLUSION

Osteomyelitis on MR imaging was the best predictor of recurrent SAS.

KEY POINTS

• Osteomyelitis on preoperative MR imaging was the best predictor associated with recurrent septic arthritis of the shoulder on multivariable analysis including clinical, laboratory, and MR findings. • In multivariable analyses focused on each bone marrow abnormality, with adjustment for clinical and laboratory parameters, the presence of reactive bone marrow edema and osteochondral erosion on MR imaging showed no significant association with recurrent septic arthritis of the shoulder.

MRI nomenclature for musculoskeletal infection

The Society of Skeletal Radiology (SSR) Practice Guidelines and Technical Standards Committee identified musculoskeletal infection as a White Paper topic, and selected a Committee, tasked with developing a consensus on nomenclature for MRI of musculoskeletal infection outside the spine. The objective of the White Paper was to critically assess the literature and propose standardized terminology for imaging findings of infection on MRI, in order to improve both communication with clinical colleagues and patient care.A definition was proposed for each term; debate followed, and the committee reached consensus. Potential controversies were raised, with formulated recommendations. The committee arrived at consensus definitions for cellulitis, soft tissue abscess, and necrotizing infection, while discouraging the nonspecific term phlegmon. For bone infection, the term osteitis is not useful; the panel recommends using terms that describe the likelihood of osteomyelitis in cases where definitive signal changes are lacking. The work was presented virtually to SSR members, who had the opportunity for review and modification prior to submission for publication.

Diagnostic approach and arthroscopic treatment of septic arthritis of the knee, in an infant

A 9-month-old baby presented with sudden inability to stand and unable to move his leg. Clinical examination showed edema and knee effusion. Blood tests and MRI confirmed septic knee arthritis without bone involvement. He was treated with arthroscopic lavage. He had a complete recovery and normal growth.

Role of preoperative magnetic resonance imaging in patients with quiescent septic arthritis undergoing primary total hip arthroplasty

AIM

to evaluate the role of preoperative magnetic resonance imaging (MRI) in assessing patients with a history of quiescent hip septic arthritis undergoing total hip arthroplasty.

MATERIALS AND METHODS

retrospective consecutive study of patients with previous history of septic arthritis who underwent MRI scans of their hips prior to primary hip arthroplasty surgery and who also had minimum 2 years follow up postoperatively. Detailed radiographic examinations were obtained, demographic and microbiological data collected. The primary outcome measure was whether a preoperative MRI scan had influenced the surgical decision-making and planning. Rate of recurrence of infection and complications was also collected at final follow up.

RESULTS

sixteen patients with quiescent hip septic arthritis were included. There were 4 males and 12 females with average age at time of primary hip arthroplasty 51.7 years (range 22-75). Five patients had childhood septic arthritis with no documented microbiology data. Eleven patients had adult onset septic arthritis. In patients with childhood septic arthritis the MRI findings were similar to those with degenerative joint disease and had no added value to the routine surgical work up. MRIs of patients with adult onset septic arthritis showed persistent findings of effusion, marrow oedema and soft tissue oedema and had no added value to the surgical planning. All but one underwent single stage total hip arthroplasty. At final follow up, with average 4.6 years (range 2-8), none had a recurrence of infection.

CONCLUSION

In our experience, preoperative MRI scans did not influence the surgical decision making and are not recommended for routine practice in the surgical work up of quiescent septic arthritis prior to total hip arthroplasty.

2020 French recommendations on the management of septic arthritis in an adult native joint

Septic arthritis (SA) in an adult native joint is a rare condition but a diagnostic emergency due to the morbidity and mortality and the functional risk related to structural damage. Current management varies and the recommendations available are dated. The French Rheumatology Society (SFR) Bone and Joint Infection Working Group, together with the French Language Infectious Diseases Society (SPILF) and the French Orthopaedic and Trauma Surgery Society (SOFCOT) have worked according to the HAS methodology to devise clinical practice recommendations to diagnose and treat SA in an adult native joint. One new focus is on the importance of microbiological documentation (blood cultures and joint aspiration) before starting antibiotic treatment, looking for differential diagnoses (microcrystal detection), the relevance of a joint ultrasound to guide aspiration, and the indication to perform a reference X-ray. A cardiac ultrasound is indicated only in cases of SA involving Staphylococcus aureus, oral streptococci, Streptococcus gallolyticus or Enterococcus faecalis, or when infective endocarditis is clinically suspected. Regarding treatment, we stress the importance of medical and surgical collaboration. Antibiotic therapies (drugs and durations) are presented in the form of didactic tables according to the main bacteria in question (staphylococci, streptococci and gram-negative rods). Probabilistic antibiotic therapy should only be used for patients with serious symptoms. Lastly, non-drug treatments such as joint drainage and early physical therapy are the subject of specific recommendations.

Risk factors for failure of eradicating infection in a single arthroscopic surgical procedure for septic arthritis of the adult native shoulder with a focus on the volume of irrigation

BACKGROUND

Septic arthritis of a native joint is relatively rare but is still a challenging and important orthopedic emergency. Most previous reports have focused on the clinical outcomes rather than the risk factors for failure in arthroscopic surgery.

METHODS

We retrospectively reviewed the records of patients with septic monoarthritis of the shoulder who underwent arthroscopic irrigation and débridement between January 2007 and January 2019. All patients were divided into 2 groups according to recurrence after a single arthroscopic surgical procedure: eradicated group or recurred group. To identify risk factors affecting the recurrence of septic arthritis of the shoulder after arthroscopic surgery, the following parameters were considered: age; sex; involved side; presentation of rotator cuff tear; volume of irrigation; bacterial organism involved; preoperative erythrocyte sedimentation rate, C-reactive protein level, and white blood cell count in blood and joint fluid; diabetes mellitus; and hypertension. We compared the eradicated and recurred groups regarding the presence of potential risk factors.

RESULTS

The study included 97 patients with a mean age of 61 years. Septic arthritis of the shoulder was eradicated completely with a single arthroscopic surgical procedure in 85 patients. However, a second arthroscopic surgical procedure was necessary in 12 patients (12.4%) because of infection recurrence. No significant differences were found between groups except in the volume of irrigation (P < .001).

CONCLUSIONS

Most patients with septic arthritis (87.6%) of native shoulders were effectively treated with a single arthroscopic irrigation and débridement. The amount of irrigation may be the most important factor for preventing the need for additional surgical management.

Imaging musculoskeletal soft tissue infections

Musculoskeletal soft tissue infections are not uncommonly encountered in both the clinic and Emergency Department setting. The clinical diagnosis is not always evident as these infections can have variable presentations depending on the duration and depth of disease extension through the soft-tissue layers. Imaging often plays an important role in diagnosing the infection, defining the extent of involvement, directing tissue sampling, and in monitoring treatment response. After initial radiographs, ultrasound (US) is often the next modality utilized to evaluate patients with suspected soft tissue infections given its low cost, availability, portability, and potential for real-time guidance of fluid aspiration. The widespread use of cross-sectional imaging with magnetic resonance imaging (MRI) and computed tomography (CT) has greatly increased the radiological diagnosis in conditions where US may be limited. In addition, CT and MRI allow a thorough evaluation of disease extension, including assessment of joint spaces, tendons, and osseous changes indicative of bone involvement. This review will focus on the radiological findings of soft tissue infections on US, CT, and MRI.

Osteomyelitis of the pubic symphysis caused by methicillin-resistant Staphylococcus aureus after vaginal delivery: a case report and literature review

BACKGROUND

Osteomyelitis of the pubic symphysis is a rare cause of pelvic pain after delivery, mainly caused by Staphylococcus aureus and Pseudomonas aeruginosa. The clinical context is the same as the more common diastasis of the pubic bone, but the presence of intense local pain in association with fever should prompt further clinical work-up based on blood chemistry, microbiology and diagnostic imaging. We report the first case of methicillin-resistant Staphylococcus aureus osteomyelitis of the pubic symphysis occuring after the delivery.

CASE PRESENTATION

A 39-year-old woman developed pain over the pubic bone 12 h after the delivery. After 72 h fever rose and laboratory examination showed elevation of C-reactive protein and procalcitonin levels. Pelvic x-rays and magnetic resonance showed pubic diastasis, joint effusion, tiny irregularities of articular surfaces and, severe bone edema. The patient was started on broad spectrum intravenous (IV) antibiotics (piperacillin-tazobactam) and then replaced to IV vancomycin and oral levofloxacin based on antibiogram result. She was then discharged with oral antibiotic therapy and fully recovered.

CONCLUSIONS

Due to the rarity of this disease, we compared our experience with the other cases of osteomyelitis of pubic symphysis occurring in peri-postpartum reported in the literature. The course of osteomyelitis was favourable in all patients, and only in one case an additional orthopedic procedure for symphysis fixation was necessary. Knowledge of this rare condition is important to enable prompt diagnosis and treatment.

An Algorithmic Approach to the Suspected Septic Wrist

An acutely painful, erythematous wrist can be due to a variety of pathologic processes, including crystalline arthropathy, infection, trauma, osteoarthritis, and systemic disease. The broad differential diagnosis of the inflamed wrist and nonspecific clinical findings make accurate diagnosis challenging. There is no published clinical or laboratory criterion that reliably differentiates septic wrist arthritis from a sterile inflammatory arthropathy. For septic joint patients, long-term results are notably poorer in patients with a delay in treatment, therefore establishing evidenced-based guidelines deserves attention.After a comprehensive literature review, we present evidenced-based guidelines and an algorithm for the management of the patient with an acutely inflamed wrist concerning for septic arthritis.For determining a diagnosis, systemic blood laboratory results are extremely variable and unreliable. Despite the attention given to the diagnostic potential of synovial fluid tests, the literature consistently demonstrates that diagnostic certainty cannot always be ascertained at the time of presentation based on aspiration fluid samples. Additionally, the investigative work does not necessarily end at the discovery of crystals since concomitant infection is a rare but well reported entity.Relative to larger joints, the wrist is far less likely to be infected and is easier to drain of debris, and therefore the empiric management of an inflamed wrist joint should reflect these differences. For treatment of the suspected or confirmed septic wrist, prompt initiation with appropriate antibiotics and drainage of joint purulence is critical to rapid recovery. However, the best strategy to clear the joint space of infectious material is controversial. Although the traditional standard of care is open drainage of a septic joint, a growing body of literature supports that for a septic wrist joint, a less invasive approach with serial aspiration can be equally efficacious with reduced morbidity and quicker recovery. If the wrist fails to improve with daily aspirations, then arthroscopy or open washout is needed.For patients with suspected wrist joint infection or crystalline arthropathy with probable concomitant infection, a reasonable approach is admission for systemic antibiotics and daily arthrocentesis. If the wrist fails to improve or worsens, then surgical treatment may be pursued. This treatment strategy could potentially avoid the morbidity of surgery while ensuring that no septic wrist goes untreated.

Septic arthritis in children in resource limited and non-resource limited countries: an update on diagnosis and treatment

INTRODUCTION

Septic arthritis (SA) is an orthopedic emergency in childhood. It is uncommon in high resource settings. However, an incidence of 5-20 per 100,000 children has been reported in low-income countries. Area covered: The predictive value of serum markers is still under debate and the proposed diagnostic algorithms for SA are not sufficiently validated in children. Recent data suggest that short-course intravenous treatment, followed by oral therapy, is as effective as traditional long-term treatment. Results from three randomized controlled trials suggest that the addition of systemic steroids may accelerate clinical improvement. Minimally invasive surgical techniques have been proposed for treatment in recent years. Expert commentary: The causes and the epidemiology of septic arthritis will continue to mutate according to the changes in immunization practices, bacterial resistance patterns and the implementation of PCR techniques. Future research should focus on the assessment of appropriate antibiotic regimens and surgical procedures.

Serial MRI evaluation following arthroscopic rotator cuff repair in double-row technique

INTRODUCTION

So far, recurrent rotator cuff defects are described to occur in the early postoperative period after arthroscopic repair. The aim of this study was to evaluate the musculotendinous structure of the supraspinatus, as well as bone marrow edema or osteolysis after arthroscopic double-row repair. Therefore, magnetic resonance (MR) images were performed at defined intervals up to 2 years postoperatively.

STUDY DESIGN

Case series; Level of evidence, 3.

MATERIALS AND METHODS

MR imaging was performed within 7 days, 3, 6, 12, 26, 52 and 108 weeks after surgery. All patients were operated using an arthroscopic modified suture bridge technique. Tendon integrity, tendon retraction ["foot-print-coverage" (FPC)], muscular atrophy and fatty infiltration (signal intensity analysis) were measured at all time points. Furthermore, postoperative bone marrow edema and signs of osteolysis were assessed.

RESULTS

MR images of 13 non-consecutive patients (6f/7m, ∅ age 61.05 ± 7.7 years) could be evaluated at all time points until ∅ 108 weeks postoperatively. 5/6 patients with recurrent defect at final follow-up displayed a time of failure between 12 and 24 months after surgery. Predominant mode of failure was medial cuff failures in 4/6 cases. The initial FPC increased significantly up to 2 years follow-up (p = 0.004). Evaluations of muscular atrophy or fatty infiltration were not significant different comparing the results of all time points (p > 0.05). Postoperative bone marrow edema disappeared completely at 6 months after surgery, whereas signs of osteolysis appeared at 3 months follow-up and increased to final follow-up.

CONCLUSIONS

Recurrent defects after arthroscopic reconstruction of supraspinatus tears in modified suture bridge technique seem to occur between 12 and 24 months after surgery. Serial MRI evaluation shows good muscle structure at all time points. Postoperative bone marrow edema disappears completely several months after surgery. Signs of osteolysis seem to appear caused by bio-absorbable anchor implantations.

Imaging evaluation of inflammation in the musculoskeletal system: current concepts and perspectives

Inflammation is the non-specific stereotyped reaction of the musculoskeletal system to various types of aggression, such as infection, tumor, autoimmune diseases, or trauma. Precise evaluation and, increasingly, reliable quantification of inflammation are now key factors for optimal patient management, as targeted therapies (e.g., anti-angiogenesis, anti-macrophages, anti-cytokines) are emerging as everyday drugs. In current practice, inflammation is evaluated mostly using MRI and US on the basis of its non-specific extracellular component due to the increased volume of free water. Inflamed tissue is described as areas of low T1 signal and high T2 signal on magnetic resonance imaging or as hypoechogenic areas on ultrasound imaging, and the evaluation of the increased tissue vascularity can be performed using gadolinium-enhanced MRI or power Doppler US. Emerging new imaging tools, regrouped under the label "cellular and molecular imaging" and defined as the in vivo characterization and measurement of biologic processes at the cellular and molecular level, demonstrate the possible shift of medical imaging from a macroscopic and non-specific level to a microscopic and targeted scale. Cellular and molecular imaging now allows the investigation of specific pathways involved in inflammation (e.g., angiogenesis, cell proliferation, and recruitment, proteases generation, metabolism, gene expression). PET and SPECT imaging are the most commonly used "molecular" imaging modalities, but recent progress in MR, US, and optical imaging has been made. In the future, those techniques might enable a detection of inflammation at its very early stage, its quantification through the definition of biomarkers, and possibly demonstrate the response to therapy at molecular and cellular levels.

Magnetic resonance imaging of soft tissue infection with iron oxide labeled granulocytes in a rat model

OBJECT

We sought to detect an acute soft tissue infection in rats by magnetic resonance imaging (MRI) using granulocytes, previously labeled with superparamagnetic particles of iron oxide (SPIO).

MATERIALS AND METHODS

Parasternal infection was induced by subcutaneous inoculation of Staphylococcus aureus suspension in rats. Granulocytes isolated from isogenic donor rats were labeled with SPIO. Infected rats were imaged by MRI before, 6 and 12 hours after intravenous injection of SPIO-labeled or unlabeled granulocytes. MR findings were correlated with histological analysis by Prussian blue staining and with re-isolated SPIO-labeled granulocytes from the infectious area by magnetic cell separation.

RESULTS

Susceptibility effects were present in infected sites on post-contrast T2*-weighted MR images in all animals of the experimental group. Regions of decreased signal intensity (SI) in MRI were detected at 6 hours after granulocyte administration and were more pronounced at 12 hours. SPIO-labeled granulocytes were identified by Prussian blue staining in the infected tissue and could be successfully re-isolated from the infected area by magnetic cell separation.

CONCLUSION

The application of SPIO-labeled granulocytes in MRI offers new perspectives in diagnostic specificity and sensitifity to detect early infectious processes.