Osteomyelitis originating in and around bone infarcts: giant sequestrum phenomena

Imaging Osteomyelitis: An Update

BACKGROUND

 Hematogenous osteomyelitis has increased over the past quarter century in frequency, virulence, and degree of soft-tissue involvement, bringing about changes in clinical manifestations and management of the disease especially in children that should be reflected in the current imaging approach. Likewise, the global disease burden of diabetes has increased greatly in the same period, compounding the problem of ascertaining osteomyelitis in diabetic foot.

METHOD

 This article provides an updated overview of imaging findings in hematogenous and contiguous osteomyelitis based on the literature and our institutional experience, along with salient features of recent recommendations from expert groups on the diagnostic algorithms and reporting terminology.

RESULTS AND CONCLUSION

 Findings on radiography and especially magnetic resonance imaging (MRI) closely reflect pathophysiology in osteomyelitis, whereby the characteristic involvement of the metaphysis or metaphyseal-equivalents, the formation and subperiosteal extension of intramedullary pus collection, and the development of cloaca, sequestrum, and involucrum are all diagnostic clues. Non-enhancing foci within the medullary bone, the penumbra sign, intra- or extramedullary fat globules, and surrounding soft tissue inflammation or abscesses are among key MRI findings. Diabetic foot is a special condition with characteristic pathophysiologic and imaging features that suggest the likelihood of osteomyelitis and the main differential diagnostic consideration of acute on chronic neuropathic osteoarthropathy with or without osteomyelitis.

KEY POINTS

  · Imaging closely reflects pathophysiology in hematogenous osteomyelitis.. · Acute hematogenous osteomyelitis predominantly involves metaphyses and metaphyseal equivalent sites.. · MRI clues for hematogenous osteomyelitis include central marrow non-enhancement, intra- or extramedullary fat globules, and the "penumbra" sign.. · An increased fluid-sensitive MRI bone signal abutting a soft tissue ulcer, abscess, or sinus tract suggests a high probability of contact osteomyelitis..

CITATION FORMAT

· Aydingoz U, Imaging Osteomyelitis: An Update. Fortschr Röntgenstr 2023; DOI: 10.1055/a-1949-7641.

Update on MRI findings of osteomyelitis of long bones in the adult population

OBJECTIVES

To evaluate the usefulness of new and established MRI signs of osteomyelitis in long bones in adults.

METHODS

All patient records over a 9-year period with clinical or MRI suspicion for osteomyelitis were retrospectively reviewed, using strict criteria for proof of infection. Two musculoskeletal radiologists independently reviewed the MRIs of proven osteomyelitis.

RESULTS

Out of 45 MRIs of confirmed osteomyelitis, 2 MRIs (4%) did not show confluent low-signal intensity on T1-weighted images, but all showed confluent high-signal intensity on T2-weighted images. Central hypoenhancing regions of marrow without abscess formation were found in 15-18/35 (43-51%) cases where gadolinium was given. We often found multiple foci of marrow replacement in the same bone. The areas of marrow involvement often had an irregular contour. Penumbra sign, marrow fat globules, and sequestra were uncommon.

CONCLUSION

Multiple foci of bone marrow signal abnormalities, an irregular contour of marrow abnormality, and central marrow hypoenhancement without abscess are common signs of osteomyelitis of long bones in adults. Confluent low T1-signal intensity is not always present.

Strategies to increase access to basic sickle cell disease care in low- and middle-income countries

INTRODUCTION

Sickle cell disease (SCD) is the most common hemoglobinopathy in the world. Over 90% of those born with SCD live in low- and middle-income countries (LMICs), yet individuals in these settings have much poorer outcomes compared to those in high-income countries.

AREAS COVERED

This manuscript provides an in-depth review of the cornerstones of basic SCD care, the barriers to implementing these in LMICs, and strategies to increase access in these regions. Publications in English language, peer-reviewed, and edited from 2000 to 2021 were identified on PubMed. Google search was used for gray literature.

EXPERT OPINION

Outcomes for patients with SCD in high-income countries have improved over the last few decades due to the implementation of universal newborn screening programs and use of routine antimicrobial prophylaxis, increase in therapeutic and curative options, and the adoption of specific measures to decrease risk of stroke. This success has not translated to LMICs due to several reasons including resource constraints. A combination of several strategies is needed to increase access to basic SCD care for patients in these settings.

Bone infarcts: Unsuspected gray areas?

There is agreement to label as bone infarcts avascular necrosis (AVN) occurring in the metaphyses or diaphyses of long bones, the terms AVN or osteonecrosis being used at the epiphyses. One might expect bone infarction to hold no mysteries. Oddly enough, however, scientific evidence about bone infarcts is extraordinarily scant. The prevalence of bone infarcts is unknown. The main sites of involvement are the distal femur, proximal tibia, and distal tibia. In patients without sickle cell disease or Gaucher's disease, involvement of the upper limbs and lesions confined to the diaphysis are so rare as to warrant a reappraisal of the diagnosis. Although widely viewed as a generally silent event, bone infarcts causes symptoms in half the cases. Standard radiographs are normal initially then show typical high-density lesions in the center of the marrow cavity. A periosteal reaction is common and may be the first and only radiographic change. Magnetic resonance imaging consistently shows typical features and therefore, in principle, obviates the need for other investigations. Bone infarcts are multifocal in over half the cases and, when multifocal, are usually accompanied with multiple foci of epiphyseal avascular necrosis. Thus, bone infarcts, whose prognosis is good per se (with the exception of the very low risk of malignant transformation), are usually a marker for systemic avascular necrosis. Consequently, patients with bone infarcts must be investigated both for known risk factors and for other foci of avascular necrosis, which may, in contrast, have function-threatening effects.

The myriad of diseases that present with polyostotic bone lesions

Many diseases result in polyostotic bone lesions including benign entities, benign entities with malignant potential, intermediate entities, and malignant entities. Imaging plays a key role in identifying complications of these disorders, most importantly malignant transformation of a benign lesion. The most common polyostotic bone lesions are reviewed and examples of malignant transformation are highlighted.

Microbiological culture findings of the femoral heads as a prognostic factor in the total hip replacement surgery

Background

In primary total hip replacements (THRs), the dissected femoral heads (FHs) are commonly used to make the bone-chips for the reconstruction in the orthopaedic surgery. The donated FHs are routinely microbiologically cultured to identify and contaminated FHs are discarded. This study examines whether a positive FH culture predicts an infection and prosthetic failure after primary THR.

Methods

The study sampled 274 donated FHs from patients with osteonecrosis (ON), hip joint osteoarthritis (OA), and femoral neck fracture (FNF) in THR to culture the microbes. The FH contamination rates were analyzed for ON, OA, and FNF groups. Proportion of the postoperative infection or prosthetic failure in the group of donors with a positive FH culture were compared to the proportion in the group of donors with a negative FH culture.

Results

The rates of the positive culture in the ON, OA, and FNF groups were 7.1%, 3.8%, and 4.0%, respectively. The infection rate was found to be non-significantly greater in the ON group than in the OA and FNF groups. In the negative culture group, one patient (0.63%) had a postoperative superficial infection, and five patients (3.2%) experienced additional surgeries including a fixation for a periprosthetic fracture, within a minimum follow-up of two years. However, no postoperative infection was encountered, and no revision surgery was required in the positive culture group.

Conclusions

A positive FH culture is not always associated with elevated risks of infection or prosthetic failure after THR. Therefore, such finding cannot be used as a prognostic factor of THR. The FHs that return a positive culture may not lead to the orthopaedic assessment of an infection or other postoperative complication risks in primary THR.

The role of infection in the pathogenesis of vaso-occlusive crisis in patients with sickle cell disease

Sickle cell disease (SCD) is characterized by recurrent vaso-occlusive crisis (VOC). Patients with SCD have impaired immunity and are thus predispose to infections. The vast majority of SCD patients live in underdeveloped nations with high prevalence and transmission rates of infections. This makes the SCD patients prone to infections, which frequently precipitate VOC. We reviewed the role of infection in the pathogenesis of VOC, taking into consideration all potential mechanisms from previous studies and hypothetical perspectives. The potential mechanisms through which infections may lead to VOC involve several pathological changes including pneumonitis, pyrexia, acute phase reaction, hypercoagulability, neutrophilia, eosinophilia, thrombocytosis, bronchospasm, red cell cytopathic and membrane changes, auto-antibodies mediated red cell agglutination and opsonization, diarrhoea and vomiting, which may act singly or in concert to cause red cell sickling. These changes can induce sickling directly or indirectly through their adverse effects on Hb oxygenation and polymerization, hydration, blood viscosity, red cell metabolism, procoagulant activation, intercellular adherence and aggregation, culminating in VOC. There is therefore the need to ameliorate the burden of infection on SCD through immunization, prophylactic and therapeutic use of antimicrobials, barrier protection and vector control in communities with high prevalence of SCD.

The role of microbial biofilms in osteonecrosis of the jaw associated with bisphosphonate therapy

Microbial biofilms have been observed and described in bone specimens of patients with bisphosphonate (BP)-associated osteonecrosis of the jaw (BONJ) and investigators are more recently suggesting that this condition essentially represents an osteomyelitis of the jaw clinically, with greater susceptibility in some patients on BP therapy. This article explains the role of microbial biofilms in BONJ and also discusses associated factors in the disease pathogenesis, which include BP effects on bone remodeling, anti-angiogenesis, matrix necrosis, microcracks, soft tissue toxicity, and inflammation and wound healing. Recent findings suggest a key role for microbial biofilms in the pathogenesis of BONJ; this has important therapeutic implications because biofilm organisms represent a clinical target for prevention and treatment efforts aimed at reducing the significant morbidity and costs associated with this condition.

Simultaneous osteonecrosis and osteomyelitis in a patient with cancer of the breast

Breast cancer is generally managed surgically with adjuvant agents which include hormone therapy, chemotherapy, radiotherapy and bisphosphonate therapy. However, some of these adjuvant therapies may cause adverse events, including wound infection, neutropenia, bone marrow suppression and fever. The simultaneous presentation of osteonecrosis and osteomyelitis has not previously been described in patients with breast cancer undergoing hormone therapy and chemotherapy. We report a patient with breast cancer who developed bone infarcts in both legs as well as osteomyelitis in the right distal tibia after treatment which included a modified radical mastectomy, hormone therapy and chemotherapy. Simultaneous osteonecrosis and osteomyelitis should be considered in patients with breast cancer who are receiving chemotherapy and hormone therapy who present with severe bone pain, especially if there have been infective episodes during treatment.

Imaging of osteomyelitis: current concepts

Osteomyelitis frequently requires more than one imaging technique for an accurate diagnosis. Conventional radiography still remains the first imaging modality. MRI and nuclear medicine are the most sensitive and specific methods for the detection of osteomyelitis. MRI provides more accurate information regarding the extent of the infectious process. Ultrasound represents a noninvasive method to evaluate the involved soft tissues and cortical bone and may provide guidance for diagnostic or therapeutic aspiration, drainage, or tissue biopsy. CT scan can be a useful method to detect early osseous erosion and to document the presence of sequestra. PET and SPECT are highly accurate techniques for the evaluation of chronic osteomyelitis, allowing differentiation from soft tissue infection.

Douleurs osseuses fébriles chez l’enfant drépanocytaire : apport de l’IRM

PURPOSE

The aim of this study was to report the MRI findings that can suggest a vaso-occlusive crisis in cases of febrile osseous pain in children suffering from sickle cell disease.

MATERIALS AND METHODS

MRI (T1 and T2 weighted sequences and T1 weighted sequence with fat saturation before and after gadolinium injection) was performed in 10 children with sickle cell disease, presenting with febrile osseous pain. The diagnosis of vaso-occlusive crisis was made after fast improvement due to symptomatic treatment and negative bacteriological result.

RESULTS

MRI was abnormal in all cases. A multifocal localisation was found in 2 cases. Bone marrow abnormalities were constant. In 10 cases, high T1 and T2 signal and metaphyso-diaphysial lesions were noted. Heterogeneous medullar enhancement with "ink stain" feature was constant. Early periosteal abnormalities were noted in 8 cases with inflammatory or stratified features. Cortical thinning was found in 1 case. Soft tissue abnormalities were observed in 5 cases with inflammatory features in 4.

CONCLUSION

Multifocal synchronous localisation, medullar abnormalities resulting from hemoglobin degradation, heterogeneous enhancement, early periosteal abnormalities and associated soft tissues swelling are MRI findings suggesting acute vaso-occlusive disease.

Multiple avascular necrosis of bone and polyarticular septic arthritis in patients with systemic lupus erythematosus

OBJECTIVE

Avascular necrosis of bone (AVN) and osteoarticular infection share similar risk factors in systemic lupus erythematosus (SLE) patients. However, their coincidental development in SLE has rarely been described. We describe four cases of AVN complicated by Staphylococcus aureus infection in SLE.

METHODS

Patients were identified by retrospectively reviewing an SLE cohort followed between 1979 and 2003. A review of the literature from 1960 until 2003 was also done.

RESULTS

Among 315 SLE patients, four developed joint infection by S. aureus following or coincidentally with AVN. All presented multifocal disease with severe or relapsing course, resulting in severe incapacity. The clinical course suggests that AVN developed first in active SLE patients with positive antiphospholipid (aPL) antibodies treated with high-dose corticosteroids (CS), and subsequent bone infarcts favor infection. Our patients often required prolonged antibiotic therapy and surgical treatment.

CONCLUSIONS

Active SLE patients with aPL antibodies on high-dose CS seem at high risk of developing multiple AVN complicated by infection. Avascular necrosis and bone or joint infection by S. aureus in these patients is a major complication that leads to severe joint destruction and disability.

MR features of tuberculous osteomyelitis

OBJECTIVE

To describe the MR imaging features of tuberculous osteomyelitis.

DESIGN AND PATIENTS

MR imaging features of 11 patients (14-65 years) with proven extra-spinal tuberculous osteomyelitis were reviewed. Osseous and adjacent soft-tissue changes were analyzed.

RESULTS

On the basis of the signal intensity characteristics compared with the normal marrow fat, two kinds of lesions were observed: (a) predominantly intermediate to low signal intensity lesions on T2-weighted images with low signal intensity on T1-weighted images, and (b) lesions which had a discrete peripheral zone of marginally higher signal intensity than the center on T1-weighted images and surrounding edema and lower signal intensity than the fatty bone marrow with variable signal intensity on T2-weighted images. Soft-tissue abscesses and marrow edema were each noted in eight cases. Soft-tissue edema was noted in most cases.

CONCLUSION

An osseous lesion with intermediate to low signal intensity on T2-weighted images and associated soft-tissue abscess may be suggestive of tuberculous osteomyelitis. Lesions with a rim of mildly increased signal intensity on T1-weighted images, a non-specific indicator of an infective process, may also be seen.